Less-Common Carbon Nanostructures

Kharisov, Boris Ildusovich; Kharissova, Oxana Vasilievna

doi:10.1007/978-3-030-03505-1_4

Boris Ildusovich Kharisov³ &
Oxana Vasilievna Kharissova³

1595 Accesses
1 Citations

Abstract

When the area of nanotechnology began to develop intensively as an independent field in the frontiers of physics, chemistry, materials chemistry and physics, medicine, biology, and other disciplines two decades ago, terms such as “nanoparticle,” “nanopowder,” “nanotube,” and “nanoplate,” and other terms related to shape rapidly became very common. At the same time, during the last years, efforts of researchers have led to reports of a large number of the nanostructure types mentioned earlier and the discovery of rarer species, such as “nanodumbbells,” “nanoflowers,” “nanorices,” “nanolines,” “nanotowers,” “nanoshuttles,” “nanobowlings,” “nanowheels,” “nanofans,” “nanopencils,” “nanotrees,” “nanoarrows,” “nanonails,” “nanobottles,” and “nanovolcanoes,” among many others.

Reproduced with permission of the Elsevier Science (Inorganica Chimica Acta, 2017, 468, 67–76).

Access provided by Autonomous University of Puebla. Download chapter PDF

Keywords

When the area of nanotechnology began to develop intensively as an independent field in the frontiers of physics, chemistry, materials chemistry and physics, medicine, biology, and other disciplines two decades ago, terms such as “nanoparticle,” “nanopowder,” “nanotube,” and “nanoplate,” and other terms related to shape rapidly became very common. At the same time, during the last years, efforts of researchers have led to reports of a large number of the nanostructure types mentioned earlier and the discovery of rarer species, such as “nanodumbbells,” “nanoflowers,” “nanorices,” “nanolines,” “nanotowers,” “nanoshuttles,” “nanobowlings,” “nanowheels,” “nanofans,” “nanopencils,” “nanotrees,” “nanoarrows,” “nanonails,” “nanobottles,” and “nanovolcanoes,” among many others. The naming of a discovered rare nanoform is commonly left to the imagination of researchers. Since any novel nanoform/nanostructure could, theoretically, have useful, unexpected, and unpredictable applications (e.g., famous graphene, discovered not long ago), each new achievement, reproducible or not, is welcome due to the importance of nanotechnology in current and future applications. Without a good understanding of the reasons for shape formation, approaches to the synthesis of nanostructures can be hard to carry out.

According to the available literature, there is no universal generalization of rare and common nanostructures. Several existing classifications are related to dimensionality of the nanostructure itself and its components (for instance, 0D clusters and particles, 1D nanotubes and nanowires, 2D nanoplates and layers, 3D core–shell nanoparticles, or self-assembled massive, intermediate dimensional nanostructures as fractals or dendrimers) or based on the triad symmetry group-shell composition-structural formula of the shell (here nanostructures are divided into branches, classes, and subclasses determined by the symmetry group of a shell and the sets of the quantum numbers of a structure). In our book on less-common nanostructures [1] of 2012, we presented a nonformal classification, which is not directly related to dimensionality and chemical composition of nanostructure-forming compounds or composites and is based mainly on the less-common nanostructures. In this classification, in addition to classic carbon-based and non-carbon nanostructures (carbon nanotubes, fullerenes, nanodiamonds, graphene, and graphane, simple and core–shell nanoparticles, non-carbon nanotubes, nano-metals, nanowires, nanorings, nanobelts, nanopowders, nanocrystals, nanoclusters, nanofibers, and nanodots/quantum dots), a series of relatively rare nanostructures have been described:

Simple linear 1D, 2D, and 3D nanostructures
Nanolines, nanopencils, nanodumbbells, nanopins, nanoshuttles, nanopeapods, nanochains, nanobelts, nanowicks, nanobars, and nanopillars

Various elongated 3D nanostructures
Nanobricks, nanocones, nanoarrows, nanospears, nanospikes, nanonails, nanobowlings, nanobones, nanobottles, nanotowers, nanoarmors, and nanopins

Circle- and ball-type nanostructures
Nanowheels, nanorings, nanoballs, nanoeggs, nanograins, nanorices, and nanospheres

Nanocage-type structures
Nanocages, nanoboxes, and nanocapsules

“Nanovegetation” world
Nanotrees, nanopines, nanopalms, nanobushes, nanograsses, nanoacorns, nanokelps, nanomushrooms, nanoflowers, nanobouquets, nanoforests, nanocorns, nanoleaves, nanobroccoli, nanomulberry, nanocactus, nanospines, nanosheaves, nanoonions, and nanodewdrops

“Nanoanimal” world
Nano-urchins, nanoworms, nanolarvae, and nanosquamae

“Nanohome” objects
Nanobrushes, nanobrooms, nanocombs, nanocarpets, nanofans, nanowebs, nanospoons, nanoforks, nanobowls, nanotroughs, nanocups, nanospindles, and nanofuns

“Nanotechnical” structures and devices
Nanosaws, nanosprings (nanocoils/nanospirals), nanoairplanes, nanopropellers, nanowindmills, nanoboats, nanobridges, nanocars, nanobatteries, nanotweezers, nanomeshes, nanofoams, nanobalances, nanojunctions, nanopaper, nanorobots, nanothermometers, E-nose, E-tongue, E-eye, and NEMS

Nanostructures classified as polyhedra
Nanotriangles, nanotetrahedra, nanosquares, nanorectangles, nanocubes, nanopyramids, nanooctahedra, nanoicosahedra, nanododecahedra, nanocubes, nanoprisms, and nanocuboctahedra

Other rare nanostructures
Nano–New York, nanopaper, nanovolcanoes, nanosponges, nanostars, nanoglasses, and nanodrugs

A certain part of these rare nanostructures (not all) correspond to carbon-based ones. In this section, we examine carbon less-common nanostructures (i.e., published mainly in the range of 1 ÷ 100 reports each one) that correspond to the shapes mentioned earlier. Such structures, as will be shown later, possess unusual shapes and high surface area, which make them very useful for catalytic, medical, electronic, and many other applications.

4.1 Atomic, Dotted, and Chain Molecular Carbon Forms

Reproduced with permission of the Royal Society of Chemistry (Nanoscale, 2016, 8, 4414–4435).

4.1.1 Atomic and Diatomic Carbon

The data on these two carbon allotropes are scarce [2, 3]. Atomic [C] and diatomic [C=C] carbons are unstable molecules existing in gaseous phase only above 3642 °C and forming fullerene or graphite at lower temperatures. They were observed in carbon vapor (electric arcs), blue hydrocarbon flames, comets, stellar atmospheres, and the interstellar medium [4]. Their some features are as follows:

C₁:

Atomic carbon is created by passing a large current through two adjacent carbon rods, generating an electric arc.
Atomic carbon is highly reactive; its most reactions are highly exothermic (carried out in the gas phase at 77 K).
Atomic carbon is generated in the thermolysis of 5-diazotetrazole (CN₆ =:C: + 3N₂) [5].
Atomic carbon can also be fabricated by decomposition of tantalum carbide [6].

C₂:

Bond order of 2 (a double bond between the two carbons in a C₂ molecule should exist).
Bond length 1.24 Å.
A quadruple bond could exist in C₂ [7, 8] (Fig. 4.1) and its isoelectronic molecules CN⁺, BN, and CB⁻ (each having eight valence electrons). In contrast, the analogues of C₂ that contain higher-row elements, such as Si₂ and Ge₂, exhibit only double bonding.
Fig. 4.1
(a) Molecular orbital diagram. The shapes of the 2σ_u and 3σ_g molecular orbitals, as determined from FCI calculations, are also represented together with their respective energy levels; (b) three simplified bonding cartoons. (Reproduced with permission of Nature)
Full size image
Carbon vapor is around 28% diatomic, but theoretically this depends on the temperature and pressure [9].

4.1.2 Carbon Nanodots^, and Graphene Quantum Dots

Carbon nanodots (CDs), a class of carbon nanomaterials with sizes below 10 nm, were first discovered in 2004 during purification of SWCNTs. Graphene quantum dots (GQDs) consist of a single or a few layers of small graphene fragments. CDs have a much more comprehensive definition compared to GQDs. Carbon nanodots (CDs) (or carbon quantum dots, CQDs), graphene quantum dots (GQDs), doped C-dots/GQDs, carbon nitride dots, and C-dots/GQDs nanocomposites are members of the same family [10]. Main features of CDs and GQDs are as follows:

CDs are conjugated systems: C atoms are sp² hybridized with no saturated sp³ carbon atoms.
C-dots hold a discrete and quasispherical structure, usually containing oxygen/nitrogen organic functional groups [11, 12].
CDs are quasispherical carbon nanoparticles with amorphous to nanocrystalline cores with a diameter of less than 10 nm.
Due to their strong luminescence, in contrast to macroscopic carbon, CDs are also referred to as nanolights or fluorescent carbon [13, 14].
The electrochemical, microwave, and hydrothermal methods are common for CD and GQD synthesis, among others.
CNDs possess high stability, good conductivity, low toxicity, and environmental friendliness.
CNDs can be synthesized physically, chemically, or electrochemically, by “top-down” (from other carbons) or “bottom-up” (from organic precursors) methods, as well as by “greener” techniques.
CDs prepared from organic matter such as used tea and ginger possess a great inhibitory effect on the growth of cancer cells [15].
CNDs can be functionalized and this way dispersed in water and solvents.
CNDs can be surface-passivated getting new properties.
Compared to traditional semiconductor quantum dots (QDs), the photoluminescent CDs are superior in terms of high aqueous solubility, robust chemical inertness, easy functionalization, and good biocompatibility.
CDs with unique properties have great potential applications in bioimaging, biomedicine, optoelectronics , solar cells, supercapacitors, sensors, detection of metal ions, SERS, drug delivery, and photocatalysis, among other uses.

Synthesis

A variety of methods for CD synthesis have been offered. In whole, CDs can be prepared (Fig. 4.2) by (1) top-down methods from carbon structures (amorphous carbon (candle soot and carbon black) and regular sp² carbon layers (graphite (Fig. 4.3) and carbon nanotubes) by arc discharge, laser ablation, electrochemical oxidation, and nitric acid/sulfuric acid oxidation or (2) bottom-up methods from small molecules (citric acid, glycerol, amino acid, ascorbic acid, carbohydrates, and other molecules with abundant hydroxyl, carboxyl, and amine groups) by dehydration and carbonization/calcination (pyrolysis), in particular by hydrothermal and microwave treatment. Thus, highly luminescent carbon nanodots were fabricated by employing a hydrothermal method with citric acid as the carbon source and ethylenediamine as the nitrogen source, together with adding moderate ammonia water to achieve both appropriate inner structure and excellent N passivation [18]. The photoluminescence quantum yield of the resultant C-dots reached as high as 84.8%, which is of 10.56% higher than that of the C-dots synthesized in the absence of ammonia in the reaction precursors. Hydrothermal method was used also for preparation of the 3D GQDs/rGO composites with different ratios of GQDs versus GO (Figs. 4.4 and 4.5) [19]. These GQDs/rGO composites showed improved catalytic activities for the reduction of nitroarene compared with GQDs, 3D rGO, and some metal catalysts; the high catalytic activity of the 3D GQDs/rGO was found to be directly related to the GQDs-to-rGO ratio.

Natural precursors for CDs are chitosan [20], grape and orange juice, pepper, strawberry, banana juice, watermelon and pomelo peel, soy milk, grass, tea, coffee, and various leaves, among others. For instance, sweet potatoes as carbon source, used for hydrothermal green synthesis, led to fluorescent carbon nanodots ranging from 1 to 3 nm [21]. Such CDs were found to be a very effective fluorescent probe for label-free, sensitive, and selective detection of Hg²⁺ with a detection limit as low as 1 nM. Green microwave-assisted rapid green synthesis of photoluminescent carbon nanodots (C-dots) with diameters in the range of 1–4 nm using flour as the carbon source was decribed in [22]. These C-dots exhibited high sensitivity and selectivity toward Hg²⁺ with detection limit as low as 0.5 nM and a linear range of 0.0005–0.01 M. Also, highly luminescent ultrasmall CDs were prepared by one-step microwave-assisted pyrolysis and functionalized with fluorescein photosensitizer by a diazo-bond [23]. Thus obtained water-soluble yellow-emitting [fluorescein–N═N–CDs]Ru²⁺ showed absorbance maximum the same as CDs but do not contain a mixture of blue- and blue–green-emitting nanoparticles; it was considered as a powerful alternative to cadmium-based toxic quantum dots. A microwave reactor for CDs preparation was also offered [24].

Electrochemical methods are also available for synthesis of CDs (Fig. 4.6) and their study [26]. Among other techniques, fluorescent CDs (5–20 nm in size) were obtained by the laser ablation (laser pulses of 1064, 532, and 355 nm under different irradiation times) of a carbon solid target in liquid environment (acetone) [27]. It was observed that the use of a short-wavelength UV laser source can yield carbon quantum dot-like structure whereas changing the laser ablation to the longer wavelength especially at 1064 nm results in agglomeration. MOFs are rarely used for CDs fabrication. Thus, highly photoluminescent CNDs were synthesized (Fig. 4.7) from metal–organic framework (MOF, ZIF-8) nanoparticles at a mild temperature (500 °C). Possessing stable fluorescence (maximum emission wavelength is independent on the excitation wavelength in the range of 300–400 nm) and non-toxic characteristics, these carbon nanodots could potentially be used in biosafe color patterning [28].

Aqueous arc-discharge process [29] (Fig. 4.8) was also developed to produce the blue-luminescent graphene quantum dots (bGQDs). The resulting bGQDs were found to be ~15 nm in diameter, and the amount of oxygen-including functional groups can be controlled to 27.4% and 30.8% at 1 and 4 A of a current level, respectively.

The production of CDs can be scaled-up; the synthetic methods for CDs in a macroscale manner are described (Fig. 4.9) [30]. As an example, a scalable synthesis of water-dispersible fluorescent carbon nanodots based on the hydrothermal method (180 °C for 6 h) of kitchen wastes (grape peel) is known [31]. The as-prepared nanodots have high selectivity for Fe³⁺ ions based on fluorescence quenching.

Functionalization, Grafting, and Doping

As an example of chemical functionalization of CDs, the functionalization of CDs with a bis-amino-modified silicone reagent enhanced their fluorescence properties [32]. Further treatment with a poly(ethylene glycol)–phospholipid surfactant increased the water dispersibility and promoted the nanoassembly of the silicone-modified CNDs. The synthesized nanocomposites were found to be biologically compatible and useful for cellular fluorescence imaging. Gd(III)-doped carbon dots (3–4 nm in size) can be used as dual fluorescence-MRI probes for biomedical applications [33]. The derived Gd(III)-doped carbon dots showed uniform particle size (3–4 nm) and gadolinium distribution and form stable dispersions in water. Exhibiting bright fluorescence, strong T1-weighted MRI contrast, and low cytotoxicity, they can be used in biomedical research for multimodal imaging. In addition, CDs, grafted onto the surface of TiO₂ nanotubes, can enhance the photocatalytic properties degrading organic pollutants [34], increasing light absorption, trap and shuttle photo-generated electrons, and enhance the pollutant adsorptivity. Under xenon lamp illumination, irradiation not only induces electrons and holes but also can heat the CDs-TiO₂ at local spots because of the photothermal effect.

Applications

CDs have great potential applications mentioned above; we present here some selected examples. For instance, a sensitive and selective detection approach for tetracycline in complex water samples was developed by preparing blue photoluminescent europium-doped carbon quantum dots (Eu-CQDs) through a rapid carbonization method operating at 200 °C for 5 min [35]. The fluorescence of the Eu-CQDs can be quenched efficiently by tetracycline, based on the strong inner filter effect mechanism between Eu-CQDs and tetracycline. Also, CD functional composites with MOFs, combining the advantages of both MOFs and nanoparticles, may exhibit unprecedented properties, for instance, for H₂ storage. Due to the interactions between polar functional groups at the surface of the CDs and H₂ molecules, such systems efficiently enhanced H₂ storage capacity and allowed the sensitive fluorescent sensing for nitroaromatic explosives [36]. In addition, dual-emission CDs can serve as dual-mode nanosensors with both fluorometric and colorimetric output for the selective detection of H₂O₂ [37]. For the case of GQDs, luminescent graphene quantum dots or graphene quantum disks have their future and potential development in bioimaging, in electrochemical biosensors and catalysis, and specifically in photovoltaic devices that can solve increasingly serious energy problems [38, 39].

4.1.3 Carbyne^, ^,

Carbyne [40, 41], an infinite carbon chain with pure sp¹ hybridization, has attracted much interest and significant controversy since the 1960s, after the first claims of detection. It was first proposed in 1885 by Adolf von Baeyer, who described the existence of linear acetylenic carbon. In 1995, the several reports on the preparation of carbyne chains with over 300 carbons or indeterminate length were published, until great success in 2016, when its linear chains of up to 6000 sp-hybridized carbon atoms were prepared (see below). These chains were grown inside DWCNTs and are highly stable protected by their hosts. Main features of carbyne are as follows:

Carbyne, similar to graphene, is just one atom thick, having an extremely large surface area (a single gram of graphene has a surface area of roughly five tennis courts).
Carbyne is not a novel substance (carbyne was earlier detected in shock-compressed graphite, interstellar dust, and meteorites).
The carbyne, made up of a chain of carbon atoms linked by alternate triple and single bonds (−C ≡ C−)_n, is actually twice as strong as graphene.
1D chain of the cumulene is known to undergo a Peierls transition into the polyyne form. This instability shows an energy difference of 2 meV per atom in favor of the polyyne structure over cumulene.
Carbyne has beat out graphene as the world’s strongest material.
Carbyne Young’s modulus is 32.7 TPa – 40 times that of diamond.
Stretching it by as little as 10% significantly alters its bandgap.
A 90-degree end-to-end rotation transforms it into a magnetic semiconductor.
Chains of carbyne can take on side molecules making energy storage possible.
Carbyne may be stable at high temperatures (3000 K).
In several articles, the carbynes are determined as “1D chain-like structures [(-C≡C-)_n/(=C=C=)_n] with sp¹ carbon-carbon hybridization,” but it is accepted nowadays that the (−C ≡ C−)_n formula corresponds to carbyne and the (=C=C=)_n – to cumulene. Formation of π-electron delocalization in carbyne is shown in Fig. 4.10.
Fig. 4.10
Formation of π-electron delocalization in carbyne. (a) Process of atomic orbital sp hybridization. (b) Existence of extensive π-electron delocalization in carbyne. (Reproduced with permission of the Royal Society of Chemistry. J. Mater. Chem. C, 2016, 4, 4692–4698.)
Full size image
Carbyne exhibited a large nonlinear absorption coefficient β and a refractive index n₂ of 3.53 × 10⁻¹³ m W⁻¹ and −1.40 × 10⁻¹³ esu at 800 nm excitation, respectively [42].

The following report is currently considered as most important in the area of carbyne synthesis. Thus, a method for the bulk production of carbyne protected by thin double-walled CNTs by very high temperature and high vacuum (HTHV) was offered, establishing a route for the bulk production of exceptionally long and stable chains composed of more than 6000 carbon atoms [43]. Direct observations of the long linear carbon chains (LLCCs) by aberration-corrected HRTEM and STEM are summarized in Fig. 4.11. The HRTEM micrograph in Fig. 4.11a shows a long, bent DWCNT encapsulating a carbon chain.

Other techniques also can lead to carbynes with different lengths and capping groups. Thus, the synthesis of carbyne (Figs. 4.12, 4.13, and 4.14) with finite length, which is clearly composed of alternating single bonds and triple bonds capped by hydrogen, using a process involving laser ablation in liquid, was reported [44]. The combination of gold and alcohol was found to be crucial to carbyne formation. Structure information and binding energy of formed carbyne is shown in Table 4.1. In addition to the hexagonal crystal structure data in this table, we note for comparison that the crystal structure of a perfect carbyne was also calculated by the molecular mechanics methods showing a difference with the above [45]. It was established that the carbyne crystals should consist of polycumulene chains arranged in hexagonal bundles. The unit cell of the perfect carbyne crystal is here trigonal and contains one carbon atom. The unit cell parameters are as follows: a = b = c = 0.3580 nm, α = β = γ =118.5°, and space group P3m1. Another synthesis approach was based on the fact that the removal of Ti atoms from the TiC surface surpasses that of C atoms, leading to enrichment of the TiC surface with carbon [46] (see also the section on carbide-derived carbons for more details). Formed carbon-based films contain carbynes (50–100 nm thick) in the form of nanorod-like clusters (lengths 5–100 nm). Also, metalated carbyne chains were recently synthesized by dehydrogenative coupling of ethyne molecules and copper atoms on a Cu(110) surface under ultrahigh-vacuum conditions (Figs. 4.15 and 4.16) [47]. The length of the fabricated metalated carbyne chains was found to extend to the submicron scale (with the longest ones up to ∼120 nm).

Table 4.1 Structure information and binding energy: carbyne crystal versus graphite and diamond

Full size table

The mechanical properties of carbyne were calculated obtained by first-principles-based ReaxFF molecular simulation [48]. The intrinsic thermal transport was determined in two abovementioned carbon sp¹ allotropes, carbyne (polyyne, (−C ≡ C−)_n, Fig. 4.17a) and cumulene ((=C = C=)_n, Fig. 4.17b), using equilibrium MD simulations and the Green–Kubo approach and knowing that cumulene is less stable than carbyne [49]. Their thermal conductivities at the quantum-corrected room temperature can exceed 54 and 148 kW/m/K, respectively, much higher than that for graphene, being attributed to high phonon energies and group velocities, as well as reduced scattering from non-overlapped acoustic and optical phonon modes. The strength of carbyne equals 251 GPa at T = 77 K [50]. This value is close to the strength 7.85 nN (250 GPa) of contact atomic bond between carbyne and graphene sheet, from which the monatomic chain is pulled. Carbyne exhibited a large nonlinear absorption coefficient β and a refractive index n₂ of 3.53 × 10⁻¹³ m W⁻¹ and − 1.40 × 10⁻¹³ esu at 800 nm excitation, respectively [42].

Although potential applications of carbyne are still under discussion, several uses of carbyne are already clear. Several researchers speculate that the unusual mechanical and electronic properties of carbyne may have great potential for applications in nanomechanics, nanoelectronic/spintronic devices, and MEMS. Decorating a carbyne chain with calcium atoms, which suck up hydrogen molecules, creates a high-density, reversible hydrogen storage device. Carbyne polysulfide (having a sp² hybrid carbon skeleton with polysulfide attached on it) was found to serve as a cathode material for rechargeable magnesium batteries [51]. Carbyne can be a precursor of fullerenes; thus, laser ablation of targets of carbonaceous matter containing carbyne nanodomains (the sp-hybridized carbon chains) or targets of C₆₀ photopolymer produced carbon clusters C₇₄-C₁₂₄ or larger cages with odd number up to C₁₆₂ [52]. Also, carbyne-based nanodevices, consisting of two graphene sheets connected by ten-atom carbyne chain, in the unloaded state has a level of thermal stability, sufficient for application up to the temperatures of order 1200–1400 K [53].

4.1.4 Carbon-Atom Wires

Carbon-atom wires (CAWs) and carbynes are indeed “two sides of the same medal.” Linear strings of sp-hybridized carbon atoms are considered as a possible phase of carbon since decades [54]. Nowadays, the occurrence of sp-hybridized carbon has been suggested in many carbon-based materials and structures; in carbon–metal moieties, embedded in matrices, after laser irradiation of polymers; in free carbon clusters; in pure sp–sp² systems; and in liquids, inside CNTs and connecting graphene sheets. Long, stable, and freestanding linear atomic carbon wires, CAWs, can be considered as extremely narrow graphene nanoribbons or extremely thin carbon nanotubes [55]. Carbon-atom wires can represent a novel nanostructure with tunable functionality. Their peculiarities are as follows:

The nature of the sp bonding along the chain is nontrivial, since in most cases C–C bonds cannot be classified as either purely double or a pure sequence of single–triple bonds.
Calculations on carbon chains are facilitated by the fact that chains consist of typically ten atoms only and constitute very small systems as compared to 2- or 3D nanomaterials.
CAWs can be produced in different forms (isolated structures, in liquids, in solid matrices, and in thin films).
CAWs can be fabricated by a bottom-up approach (production of a carbon vapor followed by a rapid quenching in gas or liquid phase), including the submerged arc discharge or the pulsed laser ablation in liquids, as well as low-energy cluster beam deposition in the gas phase.
Nanowires with odd number of atoms present a distinct behavior than the ones with even numbers [56].
The high instability of bulk carbine, due to cross-linking between chains of carbon atoms, makes the availability of this material in bulk quantities and under ambient conditions very unlikely. The research concentrates therefore on isolated chains.
The nature of the contacts at the ends of the chains is of high importance.

There are essentially two ways to terminate a linear chain on a sp² graphitic fragment: [57] either the chain connects perpendicularly to the surface of the fragment (or the surface of a fullerenic cage), by means of an “interface” atom having the sp³ hybridization, like in the examples shown in Fig. 4.18e–f, or the chain can be attached to an edge, like in Fig. 4.18a–d. In the latter case the “interface” atom is also sp². Carbon linear chains, being highly reactive alone, can be substantially stabilized by this way.

Many methods can be applied for the synthesis of sp-carbon systems (Fig. 4.19): [58] arc discharge or laser ablation, and quenching can be accomplished by the use of inert gas molecules or liquids, supersonic cluster beam deposition (such as the pulsed microplasma cluster source), laser vaporization methods, and femtosecond laser ablation of graphite. Solid samples in the form of thin films on substrates are normally fabricated, containing sp–sp² moieties where sp wires are mixed in a mainly sp² amorphous carbon matrix (sp content up to 40% has been estimated in some cases). Chemical methods are also available, for instance, dehydropolycondensation of acetylene, polycondensation reactions of halides, and dehydrohalogenation of polymers, e.g., chemical carbonization of poly(vinylidene halides). Another approach targets molecules with a defined length and endgroup constitution, typically via the dimerization reaction of ethynyl groups. Polyynes are typically easier to produce than cumulenes probably due to higher stability, and nowadays polyynes up to 20 carbon atoms and more can be produced in solution even as size-selected samples.

As an example of CAW preparation, the synthesis of CAWs was carried out by nanosecond pulsed laser deposition exploiting the strong out-of-equilibrium conditions occurring when the ablation plasma is confined in a background gas [59]. It was revealed that CAWs are mixed with a mainly sp² amorphous carbon in a sp–sp² hybrid material, i.e., sp-carbon-atom wires embedded in a mainly sp² amorphous network. CAWs form in the gas phase where high-pressure and high-temperature gradients produce strong out-of-equilibrium conditions (i.e., at the plume shock front). Once formed, sp-carbon wires must be deposited on the substrate preventing fragmentation and reorganization. Under optimal conditions the as-produced material is a sp–sp² moiety in which CAWs appear to be embedded in an amorphous mainly sp² carbon network. CAWs are terminated by sp² carbon in many different ways, including both double bond and triple bond terminations which are able to induce both polyyne-like and cumulene-like wires.

The data on conductivity of CAWs are contradictory. Although it is noted in several reports that preliminary experiments do not confirm the predicted electrical conductivity, the electrical-transport measurements of monatomic carbon chains were reported [60] for the chains, obtained by unraveling carbon atoms from graphene ribbons, while an electrical current flowed through the ribbon and, successively, through the chain (Fig. 4.20). It was shown that atomic carbon chains exhibit electrical conductivity, albeit lower than predicted for ideal unstrained chains.

4.2 Elongated Carbon Nanostructures

Reproduced with permission of the American Chemical Society (Chem. Mater., 2003, 15(7), 1470–1473).

The following closely related nanostructures can be attributed to this type: nanolines, nanopencils, nanodumbbells, nanopins, nanoshuttles, nanopeapods, nanobricks, nanochains, nanowicks, nanobars, and nanopillars. Some of them have not yet been reported for carbon, such as, for instance, nanolines or nanoshuttles.

4.2.1 Nanopencils

Reports on carbon nanopencils are practically absent. Thus, a nanopencil of silicon oxide on a carbon nanotube (Fig. 4.21) was fabricated [61] by conformal deposition of silicon oxide on a carbon nanotube and subsequent “sharpening” to expose its tip. Its application as a wear-tolerant probe for ultrahigh-density data storage was proposed.

4.2.2 Nanobuds

Such carbon allotropes as carbon nanotubes (CNTs) and fullerenes (Fs) are known from the last decades of the twentieth century, but their combinations,^{Footnote 1} called “nanobuds” (NBs) and possessing unique properties superior to CNTs and Fs alone, were discovered relatively recently by Nasibulin and Kauppinen [62]. This structure seems like fusion of a cylinder with a sphere (Fig. 4.22); there is a covalent bond between outer sidewalls of the nanotube and the fullerene. In this material, fullerenes are covalently bonded to the outer sidewalls of the underlying nanotube [63]. Consequently, NBs exhibit properties of both carbon nanotubes and fullerenes. For example, their electrical conductivity and the mechanical properties are similar to those of CNTs. The attached fullerene molecules possess a higher reactivity, and so they can be functionalized by classic methods of fullerene chemistry [64]. In addition, fullerenes can prevent slipping of CNTs in hybrid materials; resulting mechanical and other properties of final composites could be thus changed.

We could still consider NBs as “less-common nanostructures” [65], despite that almost 10 years have passed after their discovery, due to a relatively low number of reports. In this section, we present main achievements on their synthesis, properties, and applications, with the objective to attract more attention to this unusual combination of carbon allotropes.

Synthesis of Carbon Nanobuds, Their Formation Mechanism, and In Situ Engineering

In the first reports on carbon NBs, the carbon monoxide–ferrocene system, in the presence of H₂O and CO₂ as etching agents, was used for fabrication of a hybrid material (Fig. 4.23) on the basis of single-walled carbon nanotubes (SWCNTs) in the reactor at 885–945 °C [66]. Both NBs precursors (CNTs and fullerenes) appeared as a result of a one-step continuous process of a disproportionation of CO on the surface of iron nanoparticles, formed from ferrocene vapor. For this process, the optimal concentrations of CO₂ and H₂O were found to be between 2000 and 6000 ppm for CO₂ and between 45 and 245 ppm for H₂O. Two main reactions take place: CO disproportionation (4.1)

$$ \mathrm{C}\mathrm{O}\left(\mathrm{g}\right)+\mathrm{CO}\left(\mathrm{g}\right)\leftrightarrow \mathrm{C}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right) $$

(4.1)

and CO hydrogenation (4.2)

$$ {\mathrm{H}}_2\left(\mathrm{g}\right)+\mathrm{CO}\left(\mathrm{g}\right)\leftrightarrow \mathrm{C}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) $$

(4.2)

Studying the mechanism of carbon nanobud formation [67], the authors assumed that the SWCNTs could appear in the reactor apart of fullerenes. The fullerenes are further deposited on the SWCNT surface. However, due to the detection of a F-SWCNT mixture in all samples, it was tentatively concluded that they are formed at the same time from graphitic carbon on the iron nanoparticle surface (Fig. 4.24). Certain carbon atoms can be attacked by etching molecules, for example, H₂O, releasing H₂ and CO, contributing to the formation of pentagons and hexagons.

As it will be shown below, carbon nanobuds can exist in various types of structures, all being stable. One NB geometry can be transformed to another kind, and this process can be monitored and visualized by transmission electron microscopy (TEM) [68]. The fullerenes can be converted into tubular branches via treatment of the electron-beam irradiation. SWCNT samples with NBs were fabricated by an aerosol-assisted CVD (carbon source, an aerosol of toluene with 5 wt.%; synthesis conditions, 800 °C, 15 min), collected on a substrate, placed at the end of the reactor, dispersed in acetone, sonicated, and transferred onto TEM grids. Resulting products (NBs, Fig. 4.25) contained fullerenes of various sizes on the SWCNTs. The electron beam provides enough energy to allow the fullerene to be transformed into a tube-like structure (Fig. 4.25f) before collapsing entirely (Fig. 4.25h).

DFT and MD Calculations for Carbon NBs

A relatively high number of reports are dedicated to DFT calculations of carbon NBs to investigate their stability, formation mode, and mechanical, electronic, structural, and other properties. Thus, for the fullerene C₆₀, attached on the surface of (10,0) and (6,6) SWCNTs, five types of configurations for the armchair (6,6) and zigzag (10,0) carbon NBs were considered (Fig. 4.26) [69]. All these NBs possess semiconductor properties nondependent on whether the original SWCNT base is semiconducting or metallic (semiconducting or metallic behavior depends on the nanotube size and the combination mode [70]). Young’s modulus of the carbon NBs was found to be decreased when attaching a fullerene C₆₀ molecule on the surface of zigzag and armchair SWCNTs. In addition, (a) the bandgap can be opened by C₆₀ attachment to single-walled CNTs, (b) impurity states can be introduced within the bandgap, and (c) changing the density of attached C₆₀, the bandgap can be modified [71]. Indeed, carbon NBs (i.e., the junction between C₆₀ and CNTs) are very stable at room temperature; their relative stabilities depend on the type of carbon–carbon bond dissociated in the cycloaddition reaction. The formation of a C₆₀ carbon nanobud on CNT caps is energetically more favorable than that on CNT sidewalls (Figs. 4.27 and 4.28) [72]. The dominant carbon NB formation mode for CNT caps in the conventional CNT sidewall case was found to be the [2 + 2] cycloaddition reaction.

In comparison with “classic” carbon nanobuds above, other different kinds of carbon NBs (in particular, shown in Fig. 4.29) can exist in case of being produced by C₆₀ bombardment on the CNTs, according to the molecular dynamic (MD) simulation data [73]. It was emphasized that thus formed fullerene–nanotube hybrid nanostructures generally decrease Young’s modulus and the maximum tensile strength of carbon nanotubes. Another intriguing type of carbon NBs is also known. Thus, MD simulations were applied to study the effects and mechanical properties of NBs and heat welded nanobud chains (C₆₀ chains embedded or attached on a SWCNT surface) [74]. It was noted that, despite both these hybrid structures lower the ultimate tensile strength of a defect-free SWCNT, heat welded nanobuds chains significantly enhance (by more than 20%) the mean post-peak strength of the CNT (after necking) due to the consolidation of the SWCNT bundles with vacancy defects. While C₆₀ chains are being attached, the maximum tensile strength of CNTs bundles with vacancy defects. Figure 4.30a–c illustrates the tensile process of a perfect SWCNT (10,10) containing two C₆₀ chains attached on the surface, and Fig. 4.30d–f gives information on the tensile process of a SWCNT (10,10) having a single vacancy defect and two heat welded C₆₀ chains connected with the CNT surface. So, the fullerenes definitively take part in the tensile deformation process of carbon nanotube.

In addition to mechanical peculiarities, other carbon NB properties, in particular their magnetism and optical properties, have been predicted by DFT, in particular the robust magnetic state of nanobuds (Fig. 4.31) [75]. Carbon radicals can be generated by substantial emergent amounts of unpaired spins; these radicals are mainly located on the CNT surface within the connecting region with C₆₀. Among other studies [76], optical properties of carbon NBs were studied using by means of optical spectroscopy, electron microscopy, and Raman spectroscopy for validation of results [77,78,79,80]. Quantitative information of the bond length, bond energy, mode cohesive energy, binding energy density, Debye temperature, and the compressibility of the C–C bond in carbon NBs and other carbon allotropes is also tabulated [81].

A few reports are devoted to the calculations of properties of carbon NBs, functionalized with inorganic adatoms or organic molecules. Electronic structure, transport, and other properties could be modified this way, so one of these attempts implied the attachment of tetrathiafulvalene molecules, as well as Li and F atoms [82]. Li (electron donor) and F (electron acceptor) adatoms were selected, knowing that they can be easily attached to the CNTs. According to the DFT simulations, these adatoms affect the electronic structure of the carbon NBs. However, the effect works mainly in the fullerene part of the NB and is not expanded to the related nanotube, so the CNT part of a NB is almost the same. In case of Li adsorption (Fig. 4.32) on a graphene–C₆₀ nanobud system [83], it was found to be enhanced in comparison with pure graphene and C₆₀, being in the range of 1.784–2.346 eV (adsorption of a single Li atom) and 1.905–2.229 eV (two Li atoms). It was supposed that Li atoms are preferably adsorbed (a) between C₆₀ and C₆₀, (b) between graphene and C₆₀, (c) on graphene, or (d) on C₆₀, rather than form Li clusters. An increase of number of metal atoms obviously leads to an enhancement of metallic character of the hybrid; in addition, a charge transfer from graphene to C₆₀ was detected.

A special case is a carbon nanobud containing small fullerenes (<60 carbon atoms). These carbon allotropes were intensively studied by Nobel laureate Harold Kroto et al. [84,85,86] and other researchers [87]. Among these fullerenes, C₂₀ (a dodecahedron with 12 pentagons, Fig. 4.33a) is considered to be the smallest. Thermal conduction of carbon NBs with C₂₀ was studied by MD simulations [88]. Figure 4.33b shows a schematic diagram of a C₂₀ fullerene-chained carbon NB, in which a linear row of closely located fullerenes is connected to a CNT and located close to one another. It was demonstrated that (a) nanobuds conduct thermal energy relatively well, within an order compared to CNTs, and (b) the main conduction path is along the CNTs. The C₆₀ nanobud was found to be more conductive than other forms of nanobuds with C₂₀, C₃₄, and C₄₂ because the long-wavelength, low-frequency acoustic modes are scattered to a greater degree at the interfaces.

Several reports are devoted to graphene nanobuds (e.g., composites [(C₆₀)₆+(5,5)] [89]), which are closely related analogues of CNT NBs. Their mechanical properties were studied by MD simulations using Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code [90], selecting seven configurations with distinct junction lengths and graphene sheet sizes (Fig. 4.34). Resulting failure stress changes were found to be calculated in the range of 100–200 GPa (decreasing with neck’s length and temperature increment) and Young’s modulus 440–760 GPa. All mechanical properties above increase with increment of the graphene sheet. We note that this hybrid could be better called as a triple carbon allotrope system “graphene-nanotube-nanobud,” since this is a real growth (Fig. 4.34a–d) of a SWCNT between fullerene molecule and graphene surface.

Related Noble Metal Nanobuds

Similar to carbon nanobuds above, gold nanobud-like structures are also known [91]. They were grown by CVD thermal decomposition of the two gas-phase precursors, [Au(HMDS)(NHC)] (HMDS = hexamethyldisilazide, NHC = 1,3-diisopropylimidazolidin-2-ylidene) and [Au(HMDS)(PMe₃)], at a variety of temperatures. At longer deposition times, more free sites for nanobudding became available; their formation was attributed by authors to a decline in surface concentration of surfactant. Distinct method (solid-state ionic method) [92] was applied for fabrication of a silver nanobud (AgNB) substrate with superior SERS activity. This product can be used for the analysis of trace biomacromolecules. Finally, a nanoscale neural probing device for in vitro sensing of neural activity, on the basis of single vertical platinum (Pt) nanowires-nanobuds, is known [93]. We note that these nanostructures cannot be strictly called as “nanobuds,” since the metallic “fullerene”-like particle on the surface of metal 1D prolonged nanostructure is not hollow, i.e., these hybrids are not similar to their carbon analogues.

Applications of Nanobuds

The carbon nanobuds, consisting of 1 nm diameter CNTs with attached buds, can substitute indium tin oxide (ITO) [94]. These nanobud thin films can bend, flex, and stretch without any adverse effects, instead of being brittle like ITO. The necessity of creation of such material appeared because of chemical neutrality of CNTs, which can be difficult to combine with other materials due to their low coupling and fractures upon compaction. On the contrary, C₆₀ is chemically active and creates conditions for good binding. For instance, carbon NBs are easily coupled with plastics, leading to the possibility to collocate sensor surface onto the material with any shape or curvature, enabling the flexible electronics. The stretchability (up to 120%) and bendability (as small as 1 mm) free the designer from flat-surface controllers. In addition, the NB is transparent (like ITO), but not fragile. Among other applications, carbon nanobud molecule with attached chromophore molecules is used to saturably absorb electromagnetic radiation [95, 96]. In addition, SWCNTs with and without defects and carbon NBs were tested for ethanol vapor sensing [97]. It was found that the pristine high-quality SWNTs do not exhibit any ethanol sensitivity, while the introduction of defects in the tubes results in the appearance of the ethanol sensitivity.

4.2.3 Nanopeapods

“Peapod”^{Footnote 2} is the descriptive term applied to a supramolecular hybrid assembly in which nanotubes are filled with a 1D chain of molecules [98]. The archetypal peapod is that in which C₆₀ molecules [99] are contained within carbon nanotubes (Fig. 4.35) [100]. Nanopeapods are mainly examined for carbon nanotubes and fullerenes (or their endohedral metal complexes), although several examples of other inorganic compounds have been reported. For CNTs and fullerenes incapsulated in them, a comprehensive investigations have been carried out, including, for example, synthesis [101], studies of charge transfer [102], binding fullerene–nanotube [103], atomic structure [104] and electronic properties [105], influence of electromechanical effects [106], fundamental mechanical principles and conventional applied mathematical modeling [107], structural evolutions [108], electrical transport [109], and density-functional study [110], among many others [111]. Thus, the dynamics of C₆₀ fullerene molecules inside single-walled carbon nanotubes was studied using inelastic neutron scattering [112]. C₆₀ vibrations and their sensitivity to temperature were identified. Additionally, a clear signature of rotational diffusion of the C₆₀ was evidenced, which persisted at lower temperature than in 3D bulk C₆₀.

A fascinating structural transformation occurring inside SWCNTs was found to be the fullerene coalescence, which is responsible for forming stable zeppelinlike carbon molecules [113]. Sequences of fullerene coalescence induced by electron irradiation on pristine nanotube peapods were revealed. It was indicated that the merging of fullerenes resulted in stable but corrugated tubules (5–7 Å in diameter) confined within SWCNTs. The process occurred via the polymerization of C₆₀ molecules followed by surface reconstruction, which can be triggered either by the formation of vacancies (created under electron irradiation) or by surface-energy minimization activated by thermal annealing. The rotation of fullerene chains in SWCNT peapods was studied using low-voltage high-resolution TEM [114]. Anisotropic fullerene chain structures (i.e., C₃₀₀) were formed in situ in carbon nanopeapods via electron-beam-induced coalescence of individual fullerenes (i.e., C₆₀). It was established that the large asymmetric C₃₀₀ fullerene structure exhibited translational motion inside the SWCNT and unique corkscrew like rotation motion. The axial stability of single-walled carbon nanopeapods was studied based on an elastic continuum shell model [115]. Dependence of thermal conductivity of carbon nanopeapods on filling ratios of fullerene molecules was recently investigated [116].

In case of metal endofullerenes, after heating nanopeapods of the SWCNTs encapsulating the La₂@C₈₀, the atomic wires of La atoms inside CNTs were obtained [117]. The La atoms formed dimers and linearly arranged inside the CNTs. The valence state of the La in atomic wires was the same as that in the pristine La₂@C₈₀ peapods. Also, a direct evidence of the dynamic behavior of the confined atoms in metallofullerenes was given [118] by observing individual atoms using the high-resolution TEM. Rapid movement of Gd atoms in Gd₂@C₉₂ peapod was identified. By comparison with simulation, the amplitude of the motion is roughly quantified as 0.2 nm at r.t. and was reduced to almost half at 100 K. In a related work [119], M@C₈₂ (M = Gd, Dy) and their composites with SWCNTs (Fig. 4.36) were studied. Cesium-doped C₆₀ nanopeapods were prepared from SWCNTs and characterized by electron energy loss spectroscopy [120]. The ordered Cs₂C₆₀ structure was observed inside the carbon nanotubes as well as cesium ions on the exterior of the carbon nanotubes. Single-atom migration of Tb, Gd, or Ce metal from cage to cage through an intentionally induced atomic path within a carbon nanopeapod was demonstrated [121]. Additionally, carbon nanotube peapods can be applied to a nano-electro-emitter when encapsulated endofullerenes are electro-emitted from the carbon nanotube under applied external electric fields.

Fullerenes can be encapsulated by not only CNTs but also in other nanotubes. Thus, ab initio simulations of the electronic properties of a chain of C₆₀ molecules encapsulated in a boron nitride nanotube [122] – so-called BN nanopeapod – were carried out [123, 124]. It was demonstrated that this structure can be effectively doped by depositing potassium atoms on the external wall of the BN nanotube. The resulting material became a true metallic 1D crystal. Other reported nanopeapods on carbon basis are AuCl₃@DWCNT [125].

4.2.4 Nanochains

Chain-like nanostructures on carbon basis are quite distinct: connected carbon nanocapsules, carbon nanotubes containing C₆₀, or other species inside like nanoonions.^{Footnote 3} Thus, aligned array of chain-like carbon nanocapsules was prepared by a simple CVD process [126]. It was revealed that the carbon nanochains were filled with Fe₃C particles other than Fe; also, the nanochain was formed by the converging of conjoint multi-nanocapsules. Also, the adsorption of C₆₀ on a bilayer film of pentacene on Ag(111) was studied with scanning tunneling microscopy and spectroscopy [127]. At low coverage, C₆₀ molecules form extended linear structures due to the templating effect of the pentacene bilayer. The C₆₀ molecules in the chains adsorbed at bridge sites between two neighboring pentacene molecules. In addition, carbon nanochains (CNCs), consisting of a 1D chain of interconnected carbon nanoonions (CNOs; see the section above), were produced by CVD method and can be used as supercapacitors (Fig. 4.37) [128]. The CNCs were further chemically activated using KOH (Fig. 4.38) to obtain micro-meso pore structures.

4.2.5 Nanobars and Nanobricks

In a difference with metals and their oxides, carbon nanobars are very rare.^{Footnote 4} Thus, the effect of magnetism and perpendicular external electric field strengths on the energy gap of length confined bilayer graphene nanoribbons (or nanobars) was studied [129] as a function of ribbon width and length using a first-principles density-functional electronic structure method and a semi-local exchange-correlation approximation. It was found that the gaps decreased with the applied electric fields due to large intrinsic gap of the nanobar. Magnetism between the layers played a major role in enhancing the gap values resulting from the geometrical confinement, hinting at an interplay of magnetism and geometrical confinement in finite size bilayer graphene. Brick-like objects^{Footnote 5} are relatively rare nanostructures in the nanoworld. These and other nanoforms useful in the nanolandscaping were examined in [130]. Carbon nanocubes and nanobricks were prepared by pyrolyzing rice powder at 600 °C under N₂ atmosphere [131]. Solid-state electronic spectrum showed several bands in the UV and visible region and excitation at 336 and 474 nm generated photoluminescence response in the UV and visible region.

4.2.6 Nanobelts

Carbon nanobelts (CNBs) are not widespread for carbon and are usually prepared [132] by pyrolysis/CVD techniques or reduction of carbonous materials (either organic or inorganic) with elemental metals, as well as applying several strategies below (Fig. 4.39). In one of the first reports on carbon nanobelts [134], the method of medial reduction at 500 °C was developed for their synthesis, using Mg as reductant and Na₂CO₃ and CCl₄ as carbon sources (reaction 4.3). It was shown that as-synthesized products were composed of a large number of carbon nanotubes with diameters of 60–200 nm and carbon nanobelts (Fig. 4.40) as coexistent material in the as-prepared products. CNBs were also synthesized on a large scale via pyrolysis of a 1,8-diaminonaphthalene (DAN)–NiCl₂⋅6H₂O mixture in Ar followed by acid leaching (Fig. 4.41) [135]. The product can be used as an effective fluorescent sensing platform for DNA with a detection limit of 5 nM.

$$ 6\mathrm{Mg}+2{\mathrm{Na}}_2{\mathrm{CO}}_3+{\mathrm{CCl}}_4=4\mathrm{NaCl}+6\mathrm{Mg}\mathrm{O}+3\mathrm{C} $$

(4.3)

CNBs (length, tens of micrometers; width, 470 nm; thickness, 5 nm, i.e., the aspect ratio of nanobelts is extremely high to be 1000:100:1 (length/width/thickness)), having long-term emission efficiency, were synthesized (Fig. 4.42) by APCVD at 550 °C using nanoporous anodic alumina as template and ethanol as precursor [136]. The crystallinity of formed nanobelts can be improved by thermal treatment. The formation mechanism of these nanobelts was offered as a radial deformation of large thin nanotubes. Another elevated-temperature approach, “stripping and cutting” strategy (Fig. 4.43) using biomass, was applied to produce N-doped 1D CNBs from tofu with irregular structures through a molten salt (ZnCl₂)-assisted technique [137]. ZnCl₂ performed several functional roles, including the intercalation of zinc ions into the lamination of tofu, acting as a hard template to generate mesopores during the carbonization process, and being a dehydration reagent to generate considerable micropores. These eco-friendly biomass-derived carbon materials can be applied for high-performance supercapacitor electrodes.

Composite and doped CNBs are rare. As an example, a MoO₃/C nanobelts (Fig. 4.44) anode material for lithium-ion batteries were obtained by a hydrothermal route from (NH₄)₆Mo₇O₂₄⋅4H₂O and activated carbon as starting materials [138]. The activated carbon possesses a polyporous structure, so molybdenum trioxide is formed in the pores and then grows along the preferential orientation to build nanobelts. These MoO₃/carbon nanobelts with the designed microstructure exhibited a high specific capacity (up to 1000 mAh⋅g⁻¹ after 50 cycles at a current density of 0.1 Ag⁻¹), superior rate capability (retaining a discharge capacity of 675 mAh⋅g⁻¹ at a current density of 5 A⋅g⁻¹), and long-term cycle stability (to 550 cycles). Also, metastable vanadium dioxide/carbon (VO₂(B)/C) nanobelts (Fig. 4.45, carbon content of 0.96 wt.%, average width of 120–200 nm, thickness of 40–60 nm, and length of 1–3 μm) were synthesized via a facile surfactant-free hydrothermal method using V₂O₅ and sucrose as reactants and showed preferable electrochemical performances [139]. In addition, nitrogen-doped and nitrogen- and oxygen-co-doped carbon nanobelts (CNBs) (denoted as N–CNBs and N–O–CNBs, respectively) were, respectively, obtained by pyrolyzing the self-aligned polypyrrole (PPy) NBs and Se@poly(2-methoxy-5-nitroaniline) core@shell nanowires [140]. Among other useful properties, the N–CNBs obtained at the pyrolysis temperature of 800 °C in symmetric electrochemical cells delivered a specific capacitance of 458 F⋅g⁻¹ and ultrahigh volumetric capacitance of 645 F⋅cm⁻³ in aqueous solution, which the authors consider among the best performance ever reported for carbon-based supercapacitive materials.

Similar to nanorings, the carbon nanobelts [141, 142], as the term, were also used for hydrocarbon aromatic molecules (Fig. 4.46), which are out of the scope of this book.

4.2.7 Nanobottles

A few examples of elemental nanobottles ,^{Footnote 6} having very useful possible applications, have been discovered. Thus, carbon nanobottle with guest molecules and C₆₀ was fabricated [144]. It was revealed that C₆₀ filled at the extremities of CNTs can act as caps to seal them. Releasing the incorporated molecules, CNT nanobottles could be applied in compound synthesis, in drug delivery, and even in material storage. In addition, a nanocapsule, which combines the advantages of a high-pressure vessel and adsorbents, was developed for storage of a large methane mass content and safekeeping [145]. It was a system of combined nanotubes forming bottle-like pores, the entrance to which was closed by a positively charged endohedral complex (K@C₆₀) with the help of an electric field. In r.t., the nanocapsule can retain the amount of methane adsorbed under charging conditions. These nanocapsules can retain ~17.5 wt.% of methane at an internal pressure of 10 MPa and a temperature of 300 K. In a related report [146], the mechanics for methane storage in a nanobottle was studied, comprising a metallofullerene located inside a carbon nanobottle (constructed from a half-fullerene as the base and two nanotubes joined by a nanocone). For methane storage, the metallofullerene serves the dual purposes of opening and closing the nanobottle, as well as an attractor for the methane gas. In addition, the concept of “gold-carbon nanobottles” (Fig. 4.47) was proposed [147] to develop CNTs as smart material for controlled release of cargo molecules. After encapsulating cis-diammineplatinum(II) dichloride (cisplatin) in CNTs, gold nanoparticles were covalently attached at the open-tips of CNTs via different cleavable linkages, namely, hydrazine, ester, and disulfide-containing linkages (Fig. 4.48), to be used as treating agent for human colon adenocarcinoma cells HCT116.

4.2.8 Nanocones^,

Nowadays, cone-like species on carbon basis are relatively not rare nanostructures, although 10 years ago they indeed belonged to less-common nanostructures. Some of their representative recent examples are discussed in this section. Carbon conical structures are made predominantly from carbon and which have at least one dimension of the order one micrometer or smaller and are promising practical phononic devices. Nanocones have height and base diameter of the same order of magnitude; this distinguishes them from tipped nanowires which are much longer than their diameter. Carbon nanocone (CNC) has a high asymmetric geometry and is characterized by the cone angle [148] {the largest cone angle observed experimentally and theoretically was 113° (Fig. 4.49)}. Also, the pentagonal carbon nanocones were found to be constructed from a graphene sheet by removing a 60° wedge, and joining the edges produces a cone with a single pentagonal defect at the apex [149]. In case of double-walled carbon nanocones, according to DFT calculations, the most favorable double-walled nanocone was found to be that of angles of 60°60°, with rotation angle of 36° and distance between apexes of 4.22 Å [150].

The growth of carbon nanocone arrays on metal catalyst particles by deposition from a low-temperature plasma was studied by multiscale Monte Carlo/surface diffusion numerical simulation [151]. It was revealed that the variation in the degree of ionization of the carbon flux provides an effective control of the growth kinetics of the carbon nanocones. The vibrational behavior of single-walled carbon nanocones was studied using molecular structural method and molecular dynamics simulations [152]. It was found that decreasing apex angle and the length of carbon nanocone results in an increase in the natural frequency and the effect of end condition on the natural frequency is more prominent for nanocones with smaller apex angles. Similar investigations were carried out with double-walled carbon nanocones [153].

A certain attention has been paid to the grade of sharpeness in nanocones and methods of its control. Thus, an approach to sharpen the CNC tip structure to make the material more appropriate for AFM applications was offered [154]. Such tapered nanocone tips can be obtained by heating oxidization in air under optimized conditions, without generation of defects or amorphous carbon impurities during the oxidation process. It was proposed that the oxidization initially occurs at the apex of CNCs and proceeds along the sidewall step by step and layer by layer (Fig. 4.50). In addition, a sharp carbon nanocone probe that possesses desirable thermal stability and mechanical toughness was fabricated using resist-free patterning of catalyst nanodots and electric field-guided CVD growth [155]. The catalyst particle on the nanocone tip can be completely eliminated, thus leading to an extremely sharp tip, which can be used for deep profile analysis and AFM imaging.

Large-scale production of conical carbon nanostructures is possible through pyrolysis of hydrocarbons in a plasma torch process [156]. The resulting carbon cones occurred in five distinctly different forms, and disk-shaped particles are produced as well. The carbon nanocones were found to exhibit several interesting structural features; instead of having a uniform cross section, the walls consist of a relatively thin inner graphite-like layer with a noncrystalline envelope, where the amount of the latter can be modified significantly by annealing. In addition to applications of carbon nanocone phononic devices, mentioned above, the carbon nanomaterial (BET surface area of 15–40 m²/g), containing 70 wt.% nanodisks and 30 wt.% nanocones, was used as a filter material for a gas mixture containing NO₂ and ozone which was permeable to NO₂ and impermeable to ozone [157]. Carbon nanocones can also be potentially applied for adsorption of ternary mixture of noble gases [158], gas storage (on the example of a hydrogen (see also additional data on hydrogen [159] and deuterium [160]) or methane molecule, or neon atom) [161], as nanosensors and nanoscale composites (due to more excellent mechanical properties than the equivalent CNTs) [162], electronic sensor for HCl gas [163] and ammonia [164].

4.2.9 Nanospikes

Carbon-based nanospikes^{Footnote 7} are very rare [165]. Thus, plasma-enhanced chemical vapor deposition (PECVD) was used to directly grow a thin layer of carbon nanospikes (CNS, Fig. 4.51) on cylindrical metal (Ta, Nb, Pd, Ni wires) substrates with no catalyst required [166]. The formation of these growing carbon nanospikes on metal wires was found to be a promising method to produce uniformly coated, carbon nanostructured cylindrical microelectrodes for sensitive dopamine detection. In addition, CNS-Ta microelectrodes exhibited promising selectivity to dopamine, uric acid, and ascorbic acid. Electrochemical sensing applications of several carbon nanostructures, including nanospikes, are reviewed [167]. Also, the catalyst, comprised of Cu nanoparticles on a highly textured, N-doped carbon nanospike film, was offered for the purpose of direct electrochemical conversion of CO₂ to ethanol [168].

In addition to the elongated carbon nanostructures above, the following related shapes are known.

Nanowicks

Nanowick can be defined as a strip full of dense arrays of nanotubes for liquid delivery [169]. In case of carbon nanotubes, a miniature wicking element is capable for liquid delivery and potential microfluidic chemical analysis devices. The delivery function of nanowicks enables novel fluid transport devices to run without any power input, moving parts or external pump. The intrinsically nanofibrous structure of nanowicks provides a sieving matrix for molecular separations and a high surface-to-volume ratio porous bed to carry catalysts or reactive agents.

Nanopillars

The study of tubulization process of amorphous carbon nanopillars, observed in situ by TEM, revealed that amorphous carbon nanopillars were transformed into graphitic tubules by annealing at 650–900 °C in the presence of iron nanoparticles [170].

4.3 Circle and Ball-Type Nanostructures

4.3.1 Nanorings

In a difference with nanosize rings of other compounds, the carbon nanorings are scarce. They can be classic (see image above) and of Möbius type (one-turn; see below). The nanorings are mainly studied by MD simulations and are rarely obtained in real experimental conditions. Thus, amorphous carbon micro- and nanorings (diameters between 2 and 10 μm and a rim thickness of ~50 nm, Fig. 4.52) were synthesized from carbon nanostructures derived from the carbonization of Pluronic P123 polymer inside mesoporous SBA-15 rods grown in a porous alumina membrane [171]. The presence of the alumina and the silica walls was found to efficiently restrict the diffusion of oxygen during calcination and to facilitate the carbonization process. The resulting carbonized nanostructures self-assembled around the water droplets in the presence of CCl₄ and formed ring structures (Fig. 4.53).

The structure of nanorings at equilibrium was computed by minimizing the total ring Brenner–Tersoff potential using a robust minimization method, resulting a beautiful family of untwisted nanorings with zigzag, armchair, and other chiralities (Fig. 4.54) [172]. Rings with large diameters have nearly circular cross-sectional shapes, whereas rings with small diameters have elliptical, wedding-band, and dog-bone cross-sectional shapes. The electronic structures of nanorings of C₁₀ to C₂₂, among other carbon nanostructures, were investigated based on time-of-flight (TOF) mass spectroscopy, laser spectroscopy, and first-principles ab initio calculations [173]. The ring structure with bond length alternation (Peierls’ dimerization) was found to be unstable at size up to C₂₂ ring.

The axial sliding of carbon-based normal nanorings (NCNs, Fig. 4.55a, b) and one-turn Möbius nanorings (MCNs, Fig. 4.55c) along inner coaxial carbon nanotubes with hydrogen-terminated edges was investigated [174] by classical MD simulations. Among other results, the NCN:CNT system exhibited an oscillatory movement with an initial frequency of about 10 gigahertz decaying slowly with time as the vibrational energy is transferred to radial and torsional modes of the nanoring. It was concluded that the sliding of carbon nanorings and Möbius carbon nanorings along a set of armchair nanotubes is strongly dependent on the nanoring topology. The response of a quasi-1D ballistic carbon ring to the field of an electromagnetic wave propagating along the normal to the ring plane was evaluated in the presence of a constant electric field collinear to the field of the wave [175]. In these conditions, the carbon nanoring may serve as a source of terahertz radiation. In addition, by varying the parameters of radiation incident on the ring, one can effectively control the dynamics of the electron in the ring. Also, thermal transport across a hybrid structure formed by two graphene nanoribbons and carbon nanorings (CNRs, Fig. 4.56) was investigated by MD simulations [176]. It was found that the thermal conductivity of overlapped graphene sheets increases significantly with two covalent-bonded CNRs and tops at 68.8 Wm⁻¹ K⁻¹, 28% of that of single-layer graphene sheet and 11 times higher than that of overlapped graphene sheets without CNRs. The diameter of CNR and density of CNR are found to be the two most important parameters which govern the thermal transport in the CNR–graphene hybrid structures.

In addition to pure carbon nanorings, we note well-studied hydrocarbon nanorings of sp² carbon made of syn-tetrabenzoheptafulvalene [177], related cycloparaphenylenes (Fig. 4.57) [179, 180], and their adducts with fullerenes [181,182,183].

4.3.2 Nanotori

The nanotori are practically the same structural form as nanorings (“two sides of the same medal”), are closely related to graphene, edges in graphene, nanocones, nanochains, and nanotubes, and can be constructed from nanotubes [184] (V-phenylenic nanotori are also known [185, 186]). Theoretically, such rings, stable under large tensile deformation, could be used to fabricate networks that are extremely flexible and offer a high strength-to-density ratio. Nanotori, just like graphene, have no boundary and no defects, i.e., no rings of any sizes other than six, so that such nanotori can be viewed as elemental benzenoids (in having no H atoms) or as graphene with cyclic boundary conditions (in two dimensions) [187]. It was found [188] that SWCNTs with a diameter ≈1.4 nm can be induced to coil and form tori (nanotube rings or “crop circles”; single continuous toroidal nanotubes with no beginning or end, effectively a SWCNT closed around onto itself so that the two open ends fuse together, stabilized by van der Waals forces alone, to form a perfect “nanotorus” (toroidal SWCNT) [189] with much larger overall diameters of 600–800 nm on treatment with acids plus hydrogen peroxide under sonication.

On the basis of ab initio DFT calculations combined with a continuum elasticity theory approach, CNT-formed nanotori were classified in accordance with their length, height, and rotational symmetry (Fig. 4.58) [190]. Thus, nanotori with changing side length L are shown in Fig. 4.59. The contribution to the excess energy from the elbow joints is negligible in the L → ∞ limit. The elastic energy is accounted for simply by the summation of the energy of the six constituent CNTs in this limit. Figure 4.60 shows the series of polygonal nanotori resembling a segment of height H of a DWCNT. The inner and outer tubes are connected at the top and the bottom by lip–lip interactions consisting of hexagonal and nonhexagonal rings. In the H → ∞ limit, the elastic energy contribution from the two ends is a constant. Figure 4.61 describes polygonal nanotori with changing rotational symmetry number n, being focused on two families of nanotori, where the relative positions of the nonhexagonal rings remain the same, while the rotational symmetry number n changes from n = 4 to 13. The dependence of the strain energy on n is very different for the two families of nanotori.

In addition, it is possible to construct a large number of toroidal caged carbon molecules, constructed from elbows (Figs. 4.62 and 4.63) formed from armchair and zigzag nanotubes connected through a pentagonal and heptagonal defect at each bend site [191]. For elbows constructed from two nanotubes, it was assumed that the atoms remain in their preferred position on the nanotube sections and join them in such a way that the bond lengths between adjacent atoms on the two sections are as close as possible to the carbon–carbon bond length in a least-squares sense. The geometric parameters of 20 possible nanotori were determined. These parameters are useful in incorporating such nanotori in nanomechanical systems (NEMS) .

The properties of nanotori, as an example of exotic carbon nanomatter [192], were substantially investigated mainly 10–15 years ago by DFT calculations and other methods [193]. In particular, studying their electronic structure (the roles of curvature, hybridization, and disorder) in terms of rotational symmetry [194], it was shown that the curvature-induced σ∗–π∗ hybridization effects play an important role in determining their electronic structure. The energy gap exhibits different oscillatory characteristics depending on their structure. With increasing torus size, the electronic structures evolve from one characteristic of the 0D system to that of the quasi-1D system, and a semiconductor–metal phase transition is observed. Among other relevant studies, the Zeeman effect on electronic structure of carbon nanotori in the presence of magnetic field perpendicular to the tori’s plane was investigated [195]. It was shown that the Zeeman effect has distinct influence on electronic structure of carbon nanotori, e.g., the Zeeman effect may lead to the destruction of periodical AB oscillation. When magnetic flux varies, the armchair tori could change from narrow-gap semiconductors into gapless metals, or vice versa, while the non-armchair (including types of zigzag and chiral) tori show the semiconducting behavior. Also, a series of calculations, using the Landauer–Büttiker formula, on the electric conductance of carbon nanotori contacted by SWCNTs, led to the conclusion that the conductance of the contacted carbon nanotorus is very sensitive to the transparency (chemistry) of the contacts [196].

Studies of magnetism in corrugated carbon nanotori revealed the existence of ferromagnetic nanocarbons and showed the importance of symmetry, defects, and negative curvature [197]. In particular, the carbon nanotori constructed by either coalescing C₆₀ molecules along the fivefold axis (incorporating pentagons and octagons) or by joining the ends of Haeckelite tubes (containing heptagons, hexagons, and pentagons) exhibit large magnetic moments when an external magnetic field is applied. It was found that the combination of negative and the positive Gaussian curvature (caused by the presence of pentagonal, heptagonal, or octagonal carbon rings) plays a crucial role in their magnetic behavior. Figure 4.64 shows three tori generated by coalescing C₆₀ molecules along the two-, three-, and fivefold symmetry axes, respectively. A paramagnetic response of corrugated nanotori containing hexagons, heptagons, pentagons, and octagons which could be obtained for perfect arrangements of nonmagnetic atoms such as carbon can be possible at low temperatures, if the structure does not contain defects. However, ferromagnetism and paramagnetism in carbon nanostructures are very sensitive to the introduction of defects and the rupture of symmetry. Carbon nanotori with unusually large (giant) paramagnetic moments were also theoretically discovered [198]. In them, the large paramagnetic moment is due to the interplay between the toroidal geometry and the ballistic motion of the π electrons in the metallic nanotube.

The structural stability of carbon nanotori (C₁₇₀ (Fig. 4.65), C₂₅₀, C₃₆₀, C₅₂₀, and C₇₅₀ tori) under heat treatment, investigated by performing molecular dynamics simulations [199], revealed their stability at high temperatures: C₁₇₀ nanotorus (almost circular appearance, deformed significantly at about 3700 K), C₂₅₀ (pentagon-like geometry, not distorted much up to deformation temperature at about 3000 K, deformed again at a knee region), C₃₆₀ (also pentagon-like geometry, but more rounded compared to C₂₅₀, the strongest: it persists up to 4500 K), C₅₂₀ (circular geometry, deformed at about 4200 K, nanotorus also deformed at a knee region), and C₇₅₀ (biggest in that work, pentagon-like inner geometry, deformed at about 4100 K at a knee region). The thermal stability of these nanotori was found to have a complex dependence on geometrical parameters; their deformation temperatures are comparable with carbon nanotubes and nanorods of similar cross-sectional radius.

4.3.3 Nanoballs

Nanoballs are closely related to nanospheres, but this first term is considerably lesser used in comparison with the last. Elemental nanoballs are represented by carbon (and metals too) [200]. Thus, a swirled fluidized bed chemical vapor deposition (SFCVD) reactor was manufactured and optimized to produce carbon nanostructures (in the absence of a catalyst at temperatures higher than 1000 °C) on a continuous basis using in situ formation of floating catalyst particles by thermal decomposition of ferrocene [201]. The fabrication of graphene-encapsulated nanoballs with copper nanoparticle cores (size range from 40 nm to 1 μm, Figs. 4.66 and 4.67) was reported using a solid carbon source of poly(methyl methacrylate) (PMMA) [202]. The PMMA was first converted to amorphous carbon layers through a pyrolysis process at 400 °C, which prevented the Cu nanoparticles from agglomeration, and they were converted to few-layer graphene at higher temperatures (800–900 °C). Graphene nanoballs were also produced [203] via flame synthesis method. Their studies revealed the crystalline nature and phase purity of the graphene. The samples annealed at higher temperature were shown to have more defects in comparison to unannealed samples. 3D graphene nanoballs were also prepared by flame combustion of edible sunflower oil using cotton wick coated with iron acetylacetonate [204]. Carbon nanoballs can also be synthesized from coal [205].

4.3.4 Nanospheres

The “nanosphere” term is closely related to nanoball, and it is not really rare; about 10,000 reports on nanotechnology using sphere-like nanoparticles are known, including organic, bioorganic, and polymeric nanospheres having a series of various applications, from drug delivery to hydrogen storage; here we will present only the most recent and representative examples for carbon. In case of carbon, its nanospheres were synthesized with 4% yield through the chemical reactions of calcium carbide and oxalic acid at 65–250 °C without using catalysts [206]. In a series of reports, the pyrolysis was shown to be the principal method. Thus, similar to nanoballs above, carbon nanospheres (diameter of 35–65 nm) with a high BET specific surface area (612.8 m²/g) were fabricated via the pyrolysis of polyacrylonitrile–poly(methyl methacrylate) (PAN–PMMA) core–shell nanoparticles [207]. These carbon nanospheres exhibited a large adsorption capacity of 190.0 mg/g for methylene blue, thus making them excellent adsorbents for the removal of organic pollutants from water. A general synthetic methodology, based on colloidal amphiphile-templated oxidative self-polymerization of dopamine (Fig. 4.68), was reported to grow ultrafine cobalt-based nanoparticles (2–7 nm in size, Fig. 4.69) within high-surface-area mesoporous carbon frameworks [208]. Polydopamine nanospheres containing Co²⁺ ions can be converted into hierarchical porous carbon frameworks containing ultrafine metallic Co nanoparticles using high-temperature pyrolysis. These porous Co-based hybrids were used as electrode materials for supercapacitors, which exhibit excellent supercapacitive performance with outstanding long-term cycling stability. Similarly, Ni/NiO encapsulated in carbon nanospheres was CVD-prepared using Ni(NO₂)₂·6H₂O and acetylene (C₂H₂) as the catalyst source and carbon source, respectively [209].

On the contrary, Pd nanoparticles (3 nm) supported and uniformly dispersed onto N-doped carbon nanospheres (Fig. 4.70) were prepared by the direct pyrolysis of the metal precursor impregnated on polybenzoxazine-based polymer nanospheres at 500 °C [210]. This hybrid composite was evaluated as catalyst for aerobic benzyl alcohol oxidation under mild conditions without using a base additive, showing good recyclability, and it can be easily regenerated by calcination at 200 °C. We note that N-doped hollow carbon nanospheres can be used as an anode material for sodium-ion batteries, since N-doping can form a disordered carbon structure and induce a large number of topological defects on carbon outer wall [211]. Silver-decorated carbon nanospheres (obtained by microwave deposition of Ag onto amorphous carbon templates) serve as effective visible light photocatalyst [212] suitable for the removal of methylene blue molecules from aqueous solutions. Core–shell carbon–TiO₂ composites (as well as hollow TiO₂ nanospheres) were prepared using carbon nanospheres as hard templates, coating them with TiO₂ using atomic layer deposition, and subsequent burning out of the carbon cores [213]. Both types of nanospheres can have great potential in the field of photocatalysis using solar energy. Other examples include graphene/carbon nanospheres/graphene sandwich supported Pt₃Ni nanoparticles possessing enhanced electrocatalytic activity in methanol oxidation [214].

Carbon nanospheres can be also prepared hydrothermally [215]. Their precursors are not only polymers but also various carbon-containing natural materials as hydrocarbon soot [216], deoil asphalt [217], and cooking palm oil [218], among others. In addition to applications above, we note other selected uses of carbon nanospheres. Thus, highly uniform flower-like hierarchical carbon nanospheres (FCNS, 200 nm, Figs. 4.71 and 4.72; see also the section on nanoflowers below) and their N-doped analogues (NFCNS) are suitable for sulfur accommodation for lithium/sulfur battery cathodes [219]. Medical applications include targeted delivery of chemotherapeutics in breast cancer therapy [220]. Antimicrobial quaternized carbon nanospheres (QCNSs, 110 nm), with superior antibacterial activity, were prepared via a one-pot hydrothermal treatment of chitosan and hexadecylbetaine [221]. These QCNSs could effectively kill (Fig. 4.73) Gram-positive bacteria with a minimum inhibitory concentration (MIC) of 2.0–5.0 μg mL⁻¹, at the same time being cytocompatible with normal human liver and lung cells and good hemocompatibility toward red blood cells. Carbon nanospheres (50–300 nm), synthesized by the pyrolysis of resorcinol formaldehyde copolymer, were applied for the development of inkjet-printed resistive layers and sensors [222].

We also note apart the possibility to carry out a scalable synthesis of sub-100 nm hollow carbon nanospheres for energy storage applications. Thus, hollow carbon nanospheres of unprecedentedly small sizes (~ 32.5–62.5 nm) and thickness of ~ 3.9 nm were produced on a large scale (Figs. 4.74 and 4.75) by a templating process [223].

4.3.5 Nanoonions

Carbon nanoonions (CNOs,^{Footnote 8} multilayer fullerenes, with the distance between the shells close to 0.34 nm) represent important carbon nanomaterials, which are not yet well-studied. They possess a unique 0D structure, small (<10 nm) diameter, high electrical conductivity, and relatively easy dispersion. The recent reviews [224, 225] describe its complete discovery history, starting from first pioneering experiments of S. Iijima in 1980, Ugarte in 1992, followed by L. Echegoyen [226,227,228,229,230,231,232,233] and Yu. Gogotsi [234,235,236] in this century and other developers. As it will be seen below, CNOs can be fabricated using electron-beam irradiation, vacuum annealing of nanodiamond (large-scale production in gram quantities, 1994), arc discharge between two graphite electrodes in water, laser ablation, plasma method, and chemical vapor deposition (CVD), among other techniques. The nanoonions contain concentric graphene shells, which are rarely ideal spherical; nanoonion structure could be different depending on the synthesis method, including appearance of hollow structures. As it will be seen below, nanoonions can be activated, decorated, and functionalized with a variety of organic molecules, in particular with biomolecules, so, having minimal toxicological effects, they represent a high potential interest for biomedicine. In this section, we will mainly discuss recent achievements in nanoonion area.

Synthesis of Carbon Nanoonions

Frequently used classic methods for obtaining carbon nanoonions are as follows, among others (Fig. 4.76):

Chemical vapor deposition (CVD) allows decomposing hydrocarbon gas and getting large quantities of the products. Particles of transition metals, as well as bimetallic alloys (Fe/Co, Fe/Ni, M/Cu, etc.), are used as catalysts.
Use of high-energy laser in the transformation of “hydrocarbon–carbon onion.”
Catalytic decomposition of CH₄ (850 °C, Ni/Fe catalyst).
Arc-discharge evaporation of carbon and metal, resulting encapsulated metal inside graphitic layers, and its further exposition to the electron beam in TEM, when the metal particle leaves its initial position and migrates away, yielding hollow carbon onions.

Apart we mention traditional (and most important) methods for massive synthesis of CNOs:

Arc discharge in water
Chemical vapor deposition (CVD)
ND annealing in a vacuum or in inert gases

Additional methods for fabricating CNOs in a large quantity:

Synthesis of CNOs using counterflow diffusion flames
Thermolysis route using a sodium azide (NaN₃)–divinyl acetylene (C₆Cl₆) mixture as a precursor for fabricating gram-scale CNOs (30–100 nm in diameter) [237]
The reaction between calcium carbide (CaC₂) and copper(II) chloride dehydrate (CuCl₂⋅2H₂O) at 600 °C
Combustion of naphthalene leading to 50 nm CNOs
Burning common carbon-rich sources such as camphor and polystyrene foam (5–20 nm CNOs)

Figure 4.77 shows HRTEM images of CNOs synthesized by these methods [238].

In the last decade, these and other methods have been developed and optimized. Thus, the carbon onion can be obtained by pyrolysis of propane (propane/oxygen flame) [239], yielding two different types of CNOs with diameters in the ranges of 18–25 and 9–12 nm. Some carbon onions were found to be almost spherical and have slight faceting profiles, and other CNOs have a polyhedral structure. This technique produces multi-shell fullerenes in large quantities and carbon tubular structures on the metal surface. The authors assumed that the substrate nature is a determinant factor in the carbon onion formation. In a related work [240], CNOs (diameters of 70–100 nm) were produced by CVD method at 800 °C starting from methane as carbon source and isolated from the substrate by HNO₃ refluxing, calcination in air at 500 °C, and magnetic separation for removal of catalyst particles and amorphous carbon.

As it was mentioned above, the CNOs (Fig. 4.78) were prepared in a stainless steel autoclave at 600 °C by a simple reaction between CuCl₂⋅2H₂O and CaC₂^{Footnote 9} according to the reactions 4.4–4.9 [241]. It was shown that the crystal water in CuCl₂⋅2H₂O plays an important role in the formation of CNOs. The product can be used as anode materials for lithium-ion batteries, which can deliver a reversible capacity of 391 mA⋅g⁻¹ up to 60 cycles. Also, the Fe–Ni alloy nanosheet serves as a catalyst for growing metal-encapsulated CNOs and as a support for anchoring these preformed nanoparticles, resulting in monodispersed catalyst nanoparticles (Figs. 4.79 and 4.80) [242]. As an application, the ferromagnetic Fe_0.64Ni_0.36@CNOs particles demonstrate their application in both water purification and magnetic storage.

$$ {\mathrm{CuCl}}_2+{\mathrm{CaC}}_2=\mathrm{Cu}+2\mathrm{C}+{\mathrm{CaC}\mathrm{l}}_2 $$

(4.4)

$$ {\mathrm{CuCl}}_2\cdot 2{\mathrm{H}}_2\mathrm{O}={\mathrm{CuCl}}_2+2{\mathrm{H}}_2\mathrm{O} $$

(4.5)

$$ {\mathrm{C}\mathrm{aC}}_2+2{\mathrm{H}}_2\mathrm{O}=\mathrm{Ca}{\left(\mathrm{OH}\right)}_2+{\mathrm{C}}_2{\mathrm{H}}_2 $$

(4.6)

$$ {\mathrm{C}\mathrm{uCl}}_2+{\mathrm{C}}_2{\mathrm{H}}_2=\mathrm{Cu}+2\mathrm{C}+2\mathrm{HCl} $$

(4.7)

$$ \mathrm{Ca}{\left(\mathrm{OH}\right)}_2+2\mathrm{HCl}={\mathrm{CaCl}}_2+2{\mathrm{H}}_2\mathrm{O} $$

(4.8)

$$ \mathrm{Overall}\ {\mathrm{reaction}\ \mathrm{CuCl}}_2\cdot 2{\mathrm{H}}_2\mathrm{O}+{\mathrm{CaC}}_2={\mathrm{CaC}\mathrm{l}}_2+\mathrm{Cu}+2\mathrm{C}+2{\mathrm{H}}_2\mathrm{O} $$

(4.9)

Arc-discharge fabrication (Fig. 4.81) of high-quality nanoparticles in the form of floating powder on the water surface including spherical CNOs and elongated fullerene-like nanoparticles similar to nanotubes in large quantities without the use of vacuum equipment was reported [243]. Their large specific surface area (984.3 m²/g, promising for gas storage) was attributed to the “surface roughness” induced by the defective nature of the carbon onion shells. A model of arc discharge in water with two quenching zones was proposed (Fig. 4.82). This arc discharge in water represents an alternative to conventional vacuum processes to produce carbon nanoonions in large quantities.

An unexpected formation of CNO-like honeycomb nanostructures (Figs. 4.83 and 4.84), among other products, was observed as a result of dispersion and unfolding of MWCNTs using a water-soluble cobalt octacarboxyphthalocyanine derivative “theraphthal” in ultrasonic treatment conditions [244]. Commercially fabricated theraphthal (TP) [245, 246] 4.3.5.1 is a water-soluble cobalt phthalocyanine salt and sonosensitizer, used in ultrasound therapy of cancers [247,248,249,250,251] due to insolubility of its calcium salt making a labile solid phase in a tumor [252], as well as a series of metal 2,3,9,10,16,17,23,24-octacarboxyphthalocyanines, their water-soluble sodium salts, and their functional derivatives can generate reactive oxygen species (ROS). Unfolding of MWCNTs in the conditions of TP addition was explained by the in situ formation of reactive oxygen species in TP solutions under ultrasonic treatment and their further attack on MWCNTs surface. It is well-known that cavitation triggers free radical processes, shock waves, cumulative streams, and a number of other phenomena in a system that are localized at collapsing cavitation bubbles. In these conditions, even at low-intensity ultrasound in cleaners (20–40 kHz), partial destruction of TP slowly takes place, and it is known to be accompanied by the formation of ROS. As a phthalocyanine derivative, TP can be coordinated to CNT surface via π–π-stacking through aromatic supramolecular ring or covalently through COO⁻ group(s) both those of the TP molecule and in the functionalized CNTs-COOH. Highly water-soluble TP , as ionic salt, transfers MWCNTs to solution and, due to action of appearing free radicals in ultrasound conditions, destroys and unfolds them forming graphene sheets. These sheets can then form co-grown single-walled carbon nanotubes (SWCNTs, diameter 1.7 nm). In some cases (in dilute dispersions), at lower TP concentrations, incomplete unfolding of MWCNTs takes place leading to the appearance of circular nanostructures (nanoonions), which are united to honeycomb nanostructures due to defects in MWCNTs caused by action of free radicals. Graphite is subject to similar transformations [253].

Main features of CNOs are as follows:

CNOs are composed of multilayered concentric graphitic shells.
Size of CNOs is in the range of 3–100 nm, depending on the synthesis method.
CNOs are of two types: hollow CNOs and core–shell-structured CNOs.
Hollow CNOs are spherical or polyhedral in shape.
The innermost layer of the spherical hollow CNO is a C₆₀ cage.
The inner space of the polyhedral CNO is usually much larger than a C₆₀ cage in volume.
Onion-like fullerenes (OLFs) are known; they can be generated by arc discharge in water between pure graphite electrodes [254]. It was revealed that the OLFs with diameter about 25 nm were of high degree graphitization. The structural stability of carbon nanoonion C₂₀@C₆₀@C₂₄₀ was investigated by performing molecular dynamics computer simulations [255].
A core–shell structured CNO (with transition metals and their oxides, alloy nanoparticles, or nanodiamonds) is usually quasispherical in shape.
Large specific surface area.
High electrical conductivity.
Typically, two broad Raman bands can be readily observed in the area between 1300 and 1600 cm⁻¹.
Analogous to carbon nanotubes, CNOs display poor solubility in both aqueous and organic solvents because of aggregation, promoted by strong intermolecular interactions such as van der Waals forces. Similar to CNTs, this solubility can be considerably improved by ozonolysis [256] or other types of functionalization.

Chemical Activation of CNOs

The CNOs, being a promising candidate for high-power supercapacitors due to the nonporous outer shell, easily accessible to electrolyte ions, suffer a difficulty, since the nonporous ion-accessible outer shells also limit the energy density of the CNOs, requiring large specific surface area. So, their electrochemical performance needs an improvement, which can be reached by chemical activation, for instance, using KOH, introducing porosity on the outer shells of CNOs [257]. This treatment (Fig. 4.85) dispersion of CNOs in KOH solutions under ultrasonication induced changes in structure, specific surface area (SSA), and pore size distribution of CNOs. In particular, the pristine CNOs (5–50 nm, concentric structures containing long-range ordered graphitic striations on each shell) changed to the CNOs with defects in the outer shell, creation of micropores and mesoporoses, and destruction of concentric structures. This porosity allowed improving the energy density and preserving the power density in CNO high-rate supercapacitor electrodes.

Decoration, Dopation, and Functionalization of CNOs

Decoration of CNOs with platinum nanoparticles was carried out using ascorbic acid as the reducing agent within a vortex fluidic device (VFD),^{Footnote 10} leading to PtNP@CNO nanocomposites (Fig. 4.86) [258]. Pristine- or plasma-modified CNOs were dispersed in Milli-Q water, mixed with H₂PtCl₆ solution, and placed in the VFD for subsequent reduction with ascorbic acid solution. Resulting agglomerations of Pt nanoparticles on CNOs are shown in Fig. 4.87, revealing promising electrocatalytic activity of the Pt@CNOs, which may be applicable to other forms of carbon for a wide range of applications.

Dopation of CNOs

CNOs doped with boron (B-CNOs; 0.76–3.21 at.% of boron substitution) were prepared by annealing commercial nanodiamond particles (NDs) at 1650 °C under an inert He atmosphere in the presence of boron [259]. It was revealed that the increased amount of boron doping resulted in decreased interlayer spacing and polygonization of the structures, leading to enhanced properties as electrodes for electrochemical capacitors. Authors noted that these active sites could also play a vital role in enhancing the catalytic activity of oxygen reduction. Nitrogen-doped nanoonions (NNOs) were prepared [260] from CNOs (in turn, obtained from NDs with size of 4–6 nm) by a modified Hummers’ method, using urea in the last step (Fig. 4.88). Nitrogen content and molar ratio of nitrogen-containing groups in the NNOs were varied by controlling the oxygen content of ONO (oxygen-doped nanoonions). Studying ORR activities of the NNOs using a rotating disk electrode, the NNOs showed a higher onset potential than that of CNOs, and the ORR activity of the NNO could be improved by increasing the number of active sites (N-containing groups) in the NNO.

Functionalization of CNOs

The reactions of CNOs (50–100 nm in diameter) with fluorine in the presence of H₂ in a Monel reactor at three different temperatures, 350, 410, and 480 °C, yield fluorinated nanoonions (F-CNOs , Fig. 4.89) of approximately C_10.1F, C_3.3F, and C_2.3F stoichiometry, respectively [261]. The purpose of using hydrogen in the process was in situ generation of HF, which is known to catalyze the fluorination of the other sp²-bonded carbon materials (e.g., graphite and CNTs). It was shown that even after breaking of the graphene layers in CNOs by F₂ action, the F-CNO products maintained the spherical morphology. The F-CNOs were found to be soluble in DMF and alcohols. Even after 1 year the suspension solutions of the most fluorinated F-NO-410 and F-NO-480 samples do not show any visible precipitation (Fig. 4.90). Due to this enhanced solubility, they could be useful for biomedical applications, paints, lubricating composites, etc. Further defluorination of F-CNOs using hydrazine resulted in remarkable “healing” of broken graphene layers which rejoin within the sphere to substantially restore the CNO microstructure. CNOs can also be functionalized with biomolecules. Thus, soluble small non-cytotoxic CNOs (with 6–8 shells) were prepared with high yield and functionalized with carboxylic groups and biomolecules biotin–avidin interactions on a gold surface by layer-by-layer assembly (Fig. 4.91) [262]. The film structure of formed self-assembled monolayers on the gold surface was found to be depended on the sequence of film component deposition. Biomolecules attached to the CNOs retained their biological activity.

Some Properties of CNOs

Diamagnetism of carbon onions was probed by NMR of adsorbed water. Thus, the ¹H chemical shift of water molecules adsorbed on defect sites of CNOs was compared with the shifts of bulk water and water adsorbed by chemically derived graphene (G), graphene oxide (GO), and nanodiamond (ND) [263, 264]. Authors revealed that the positions of ¹H resonances for insulator ND and GO are close to that of bulk water, while water molecules adsorbed by G and CNOs possessed a significant deviation in chemical shift from that of bulk water, attributing this to the diamagnetic screening effect of the conducting graphene layers. Highly fluorescent CNOs (2.5 nm height and size distribution from 10 to 65 nm, average 40 nm; 0.34 nm interlayer distance) were produced by thermal annealing at 400 °C of perylenetetracarboxylic anhydride in low molecular mass PEG (Fig. 4.92) [265]. These CNOs can be purified by silica gel chromatography to obtain fractions with a very homogeneous particle size of about 35 nm. These CNOs are highly biocompatible with Hep3B cells and can cross the cell membrane.

It is known that CNOs have a hydrophobic character, nonporous texture, moderate specific surface area (200–600 m²⋅g⁻¹), high electrical conductivity, short time charging, and high power density. Taking into account the purpose to be used in supercapacitors, CNOs were chosen as model material in order to understand the influence of the surface chemistry (nature and amount of oxygen groups) and structural defects (active surface area, ASA) on the capacitance [266]. The CNOs were prepared from high pure nanodiamonds at 1300 and 1700 °C and further modifications (Fig. 4.93). As a result, a predominant influence of the carbon defects on the capacitance in organic and aqueous electrolytes which counterbalance the functional group effect was highlighted.

Molecular Dynamics Simulations

CNOs provide exceptional friction and wear reduction through a rolling and sliding mechanism of the CNOs at the interface, so, the mechanisms of these processes were studied by performing atomistic MD simulations of their sliding between diamond-like carbon substrates (Fig. 4.94) [267]. It was revealed that the ability of the CNOs to roll is inhibited both by increased contact pressure and the presence of a diamond core within the nanoparticles that enhances the formation of interfacial bonds during friction. The transition from rolling to sliding behavior was accompanied by an order of magnitude increase in the coefficient of friction, from μ = 0.024 to 0.151, respectively.

The toxicological effects of pristine and CNOs, chemically modified with benzoicacid, pyridine, and pyridinium moieties (Fig. 4.95), on the development of the freshwater polyp Hydra vulgaris were studied in order to elucidate the ecotoxicological effects of CNOs [268]. Hydra specimens were exposed to the functionalized CNOs by prolonged incubation within their medium. On the basis of biodistribution of CNO nanoparticles in Hydra (Fig. 4.96), it was revealed the absence of adverse effects of CNOs (in the range 0.05–0.1 mg/L) in vivo at the whole animal level, testifying about their biosafety and suitability as materials for biomedical applications. There are indeed no much data on CNO toxicity; in case of closely related fullerenes, several toxic effects have been observed, depending on their properties (size, surface chemistry, solubility, aggregation/agglomeration, experimental setups such as exposure time, biological models, etc.). So, any data on toxicity of carbon allotropes are useful as a part of complex issue for prediction of potential harmful effects in the designing of new nanoparticle-based products.

Applications of CNOs

Current applications of carbon nanoonions are in/as:

Biosensors (for CNOs functionalized with biomolecules)
Environmental remediation, in particular for sorption of heavy metal ions
Lithium-ion batteries (anodes on the basis of highly graphitized and doped hollow CNOs with porous structure)
Electrode materials in supercapacitors
Fuel cells (CNOs as catalysts)
Catalysis (i.e., oxidative dehydrogenation of ethyl benzene to styrene)
Lubricants
Optical industry
Terahertz-based communication systems
Drug delivery, infection therapy, and neurodegenerative diseases

Potential applications of CNOs include also magnetic storage materials, single-electron devices, point source field emitters, biological marking, encapsulation of foreign materials, etc. These current and potential applications above of CNOs are related with the facts that/due to:

Their capacity to pass through cell membranes, carrying drugs, genes, biomolecules, and vaccines.
Biocompatibility.
Possibility to create collagen CNO materials as scaffolds in tissue generation and artificial implants, as well as smart drugs.
CNOs resist biodegradation.
CNOs are powerful engineering candidate over other existing materials used to repair defective organs.
CNOs are excellent implements for the therapeutic monitoring and the diagnosis of diseases.
CNOs are suitable for the analysis of drugs in different areas.
CNOs are applicable in a lot of electronic products, i.e., nanotransistors, nanocapacitors, supercapacitors, quantum computers, etc.
CNOs can be effectively used in the energy sector (energy-producing, energy-absorbing, and energy storage products), i.e., in batteries or fuel cells.
CNOs are frequently more durable, stronger, and lighter compared with non-nanotechnologically created materials.
Physical/chemical activation could increase the SSA of CNOs, improve the degree of graphitization, and introduce a porous structure, which would contribute to an enhanced electrochemical performance of the CNO anodes.

Limits for CNO uses are as follows, among others:

Relatively high cost compared with traditional technologies
Toxicity problems
Possible disappearance of certain markets and loss of jobs, if alternative energy sources on their bases will be developed

Among recent reports on CNO applications, we selected some representative and intriguing reports having good expectative and future progress. Thus, a fluorescent probe based on surface carboxyl-functionalized ND-derived CNOs (Fig. 4.97) for biological imaging was developed [269]. These water-soluble low-cytotoxic CNOs with high emission properties were prepared by a reaction involving the amide bond formation between fluoresceinamine and the carboxylic acids groups on their surface. Thus obtained CNOs were tested as probe for in vitro imaging of HeLa cells, showing their potential as multifunctional nanomaterial for theranostic applications. More details on CNOs as promising theranostic agents are shown in the recent article [270].

Also, a single carbon onion was welded (Fig. 4.98) onto the end of a tungsten tip through an intermediate carbide layer inside a HRTEM, representing a novel type of an electron field emitter [271]. Such individual C-onion emitters, similar to CNTs, can sustain large emission currents (>100 μA) and exhibited good long-term emission stability. Authors proposed that these CNO-based emitters can effectively be used as the point electron sources in, for example, high-resolution electron-beam-driven apparatuses in the future.

4.3.6 Nanorice

A few reports have been dedicated to a low-temperature hydrothermal synthesis of carbon nanorice. Thus, anisotropic fluorescent carbon nanorice (Fig. 4.99) was hydrothermally prepared, without using any template, from a commercially available beef extract bio-precursor (broth constituent) at a temperature of 150 °C [272]. Authors proposed that these nanorice structures are formed due to the coalescence of initially formed small spherical carbon nanocrystals during hydrothermal treatment. Potential future applications correspond to photonic devices. Carbon nanorice (a diameter in the range of 100 nm and a length of approximately 500 nm) was also prepared by the hydrothermal carbonization of heparin in a Nafion solution at a mild temperature of approximately 100 °C [273]. The mechanism of formation (Fig. 4.100) for this nanoscale rice-like structure was suggested to be a self-assembling process, in which the charring of the heparin caused desulfation followed by carbonization, ultimately forming 5-hydroxylmethyl furfural in the presence of a Nafion membrane. Carbon nanorice exhibited fluorescence and so can be useful for biomedical or optoelectronic applications.

4.4 Nanocage-Type Structures

4.4.1 Nanocages

Nanocage-type structures include closely related nanocages [274], nanocubes,^{Footnote 11} nanoboxes, and nanocapsules. Carbon cages/boxes have been intensively developed in last 15 years and have various applications (carbon nanocages consisting solely of benzene rings (“all-benzene carbon nanocages”) [275] do not fit to the theme of our book). They can be produced by a variety of methods from distinct precursors. Thus, a simple approach for spontaneous, catalyst-free formation of highly graphitic nitrogen-containing carbon nanocages (well-ordered graphitic shells with more compact graphite layer structure than that of conventional bulk graphite) was demonstrated by using commercial available graphite rods as the initial materials [276]. The incorporation of nitrogen into the graphitic backbone of carbon nanocages opens the potential for metal-free catalysis of oxygen reduction reaction in fuel cells. Template synthesis of ultrathin nitrogen-doped graphitic carbon nanocages (CNCs) derived from polyaniline (PANI) and their excellent capacitive properties involved one-pot hydrothermal synthesis of Mn₃O₄@PANI core–shell nanoparticles, carbonization at 800 °C to produce carbon-coated MnO nanoparticles, and then removal of the MnO cores by acidic treatment (Fig. 4.101) [277]. The product showed a great application potential in supercapacitors.

Several methods involve metal addition and/or elimination in reaction steps. Thus, hollow carbon spheres (nanocage sizes of 7.1, 14, and 20 nm in diameter) were prepared [278] using the core–shell (i.e., Cu@C) nanoparticles (obtained by carbonization of the Cu²⁺–cyclodextrin complexes) at 573 K for 2 h, etching them with HCl (Fig. 4.102). The presence of micropores with an opening of 0.45 nm allowed small molecules to diffuse in and out through the carbon shell, so these nanocages can be filled and used as nanoreactors for catalytic decomposition of methanol. Au nanoparticles were deposited on CNTs, and the nanocages were grown on these gold particles by electrical Joule heating of the CNTs, with further evaporation of metal, leaving the cages intact (Figs. 4.103 and 4.104) [279]. The CNTs were used as a carbon source, and the growth was templated by the gold particles, so this gold template technique could provide a general way for fabricating carbon nanostructures of predetermined shape.

Dodecahedral carbon nanocages (NCs, Fig. 4.105) modified with homogenously distributed Fe₃O₄ nanoparticles (Fe₃O₄/C NCs) and possessing a large surface area and inner cavity were obtained (Fig. 4.106) by utilizing a zeolitic imidazolate framework (ZIF-8) as the template and polydopamine (PDA) as the carbon source [280]. Their recommended use is as anode materials in lithium-ion batteries: they display stable capacity retention and cycling performance even at high rates of 3000 mA⋅g⁻¹ in comparison with C NCs.

In addition to Fe₃O₄-containing carbon nanocages above, other magnetic iron-containing carbon nanocages with significant surface area (177 m²⋅g⁻¹), microporosity, and mesoporosity (Fig. 4.107) were synthesized via a green one-step carbonization process in inert atmosphere using pine resin and iron nitrate salt as a carbon and iron source, respectively [281]. A homogeneous distribution of core–shell-type magnetic nanoparticles within the carbon matrix, formed by iron carbide (Fe₃C) and metallic iron (α-Fe), with sizes of 20–100 nm, surrounded by a few graphitic layers-walls, was observed. The material can be effectively used for As(III) removal from aqueous solutions. Other magnetic carbon nanocages with multiform pore structure (Fig. 4.108), synthesized [282] by a low-temperature carbonization process from biorenewable lignin, possessed a high degree of graphitization crystallinity and can be used as efficient and recycled adsorbents in the removal of dye staff from textile wastewater. Nanocages can be functionalized, as many other nanocarbons such as grapheme or CNTs. Thus, functionalization of ordered cage-type mesoporous carbons through oxidation using ammonium perchlorate led to carboxy carbon nanocage [283]. The degree of functionalization can be easily controlled by the adjustment of the oxidation parameters such as oxidation time, AP concentration, and oxidation temperature.

In addition to applications above, carbon nanocages are frequently used as electrocatalysts for oxygen reduction and evolution . Thus, double-shelled hybrid nanocages with outer shells of Co–N-doped graphitic carbon (Co-NGC) and inner shells of N-doped microporous carbon (NC) were elaborated (Fig. 4.109) by templating against core–shell metal–organic frameworks [284] exhibiting superior electrocatalytic properties to Pt and RuO₂ as a bifunctional electrocatalyst for ORR and OER. First-principles calculations revealed that the high catalytic activities of Co-NGC shells are due to the synergistic electron transfer and redistribution between the Co nanoparticles, the graphitic carbon, and the doped N species. The high ORR activity of the defective carbon nanocages (better than that of the B-doped carbon nanotubes and comparable to that of the N-doped carbon nanostructures) was attributed, using DFT calculations, to pentagon and zigzag edge defects (Fig. 4.110) [285]. The carbon nanocages prepared at 700 °C presented a quite good ORR performance with a high onset potential of ∼0.11 V versus the normal hydrogen electrode in a 0.1 mol/L KOH solution. Significant contribution of the intrinsic carbon defects to ORR activity was demonstrated.

Other uses are related with such properties of nanocages as adsorbents, sensors, and materials for supercapacitors. Thus, the hierarchical carbon nanocages (hCNC) were proposed as high-rate anodes for Li- and Na-ion batteries [286]. For the same purpose (Li-ion batteries), carbon nanocage-supported synthesis of V₂O₅ nanorods and V₂O₅/TiO₂ nanocomposites was carried out by a carbon nanocage (CNC)-assisted growth process, using vanadium triisopropoxide oxide and titanium isopropoxide precursors in air at 500 °C [287].

Large-pore cage-type mesoporous carbon nanocages, abbreviated by authors as CKT (carbon from KIT-5) using 3D large cage-type face-centered cubic Fm3m mesoporous silica materials (KIT-5) as inorganic templates prepared at different temperature [288], showed high adsorption capacity for amino acid (histidine), flavonoid (catechin), vitamin (vitamin E, α-tocopherol), endocrine disrupter (nonylphenol), and enzyme (lysozyme) and other biomolecules (Fig. 4.111). Carbon nanocage can also be useful for entrapment of harmful aromatic molecules [289]. Also, a thin-walled graphitic nanocage material with well-developed graphitic structure, large specific surface area, and pronounced mesoporosity was synthesized and used to construct a sensing interface for an amperometric glucose biosensor, showing a high and reproducible sensitivity [290].

4.4.2 Nanoboxes

Among several other carbon nanostructures, the nanoboxes were recently reviewed [291]. Main applications correspond to the catalytic and electrochemical areas too, as well as for other nanocage-like structures above. They are normally prepared from organic carbon-rich compounds and metal-containing frameworks, although a direct conversion of carbon dioxide can also lead to shape-controlled formation of nanocarbons [292]. As an example, N-doped porous and highly graphitic carbon nanobox-supported Fe-based nanoparticles (Fe–N-CNBs) were prepared from fructose, NH₃, and FeCl₃ by a self-propagating high-temperature synthesis process (Fig. 4.112) followed by a heat treatment process and used as ORR catalysts, showing to have a similar efficiency than expensive Pt/C catalyst in Zn–air batteries [293].

Multicomponent MoS₂/Co₉S₈/C hollow nanocubes, solvothermally produced (Fig. 4.113) and subjected to a subsequent calcination process [294], showed high capacity, rate capability as the anode of sodium-ion batteries, and further potential usage for energy storage devices. Hybrid core–shell nanoboxes CoSe@CNBs (CoSe-enriched inner shell is located within a carbon-enriched outer shell) were synthesized through manipulation of the template-engaged reaction between Co-based zeolitic imidazolate framework (ZIF-67) nanocubes and Se powder at 350 °C (Fig. 4.114) [295]. These nanoboxes showed excellent lithium-storage performance in terms of high specific capacity, excellent cycling stability, exceptional rate capability, and high initial Coulombic efficiency.

4.4.3 Nanocapsules

Capsule-like nanostructures^{Footnote 12} for carbon have become widespread during last decade. They can be hollow or metal-filled (main attention is paid nowadays to the last type), possessing simple or core–shell structures. Despite their similarity with nanocubes and nanoboxes, there are several differences in their synthesis, for example, more frequent use of arc-discharge methods. However, classic thermal methods as pyrolysis are also common. Thus, controlled synthesis of uniformly shaped carbon hollow structures was carried out by an ethanol-assisted thermolysis of zinc acetate [296]. It was revealed that the generated zinc oxide nanostructures acted as in situ templates to form (reactions 4.10–4.12) the carbon hollow structures {nanospheres, nanocapsules (Figs. 4.115, 4.116, and 4.117), nanorods, and microtubes}. These as-synthesized carbon hollow structures exhibited excellent thermal and structural stability to temperatures as high as 1200 °C. Another example of hollow capsules is monodisperse hollow core–shell carbon nanocapsules (<200 nm) with mesoporous shells, prepared by coating their outer shells with silica to prevent aggregation during their high-temperature annealing [297] (starting material, monodispersed silica nanoparticles; carbon source, octadecyltrimethoxysilane). The drug-loading and drug-release properties of these hollow carbon nanocapsules were also investigated.

$$ {\mathrm{CH}}_3{\mathrm{COOZnOOCCH}}_3\to {\mathrm{ZnCO}}_3+{\mathrm{CH}}_3{\mathrm{COCH}}_3 $$

(4.10)

$$ {\mathrm{ZnCO}}_3\to \mathrm{ZnO}+{\mathrm{CO}}_2 $$

(4.11)

$$ In\ presence\ of\ ZnO:m{\mathrm{CH}}_3{\mathrm{COCH}}_3+n{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{O}\mathrm{H}\to \mathrm{ZnO}@\mathrm{C}\ \mathrm{structures}+\left(2m+n\right){\mathrm{H}}_2+\left(m-n\right){\mathrm{H}}_2\mathrm{O} $$

(4.12)

Magnetic metals, their oxides, and carbides are the center of attention in developing core–shell carbon nanocapsules, due to many catalytic and electrochemical applications. Thus, decomposition of hydrocarbons (methane, ethane, and ethylene) on the nickel catalyst led to the formation of many disordered carbon structures and Ni nanocapsules coated with a graphite layer [298]. Electromagnetic wave absorption properties of FeNiMo/C nanocapsules with FeNiMo nanoparticles as cores and carbon as shells were studied [299]. These nanocapsules, synthesized by arc-discharging Fe₁₁Ni₇₉Mo₁₀ (at.%) alloy in ethanol, exhibited outstanding reflection loss (RL < −20 dB) in the range of 13–17.8 GHz with an absorber thickness of 1.7 mm, and an optimal RL of −64.0 dB was obtained at 13.2 GHz with an absorber thickness of 1.9 mm. The excellent electromagnetic properties were ascribed to the good match between high permeability from the core of FeNiMo nanoparticles and low permittivity from the special core–shell microstructure in the FeNiMo/C nanocapsules.

Fe-filled core–shell carbon nanocapsules (<40 nm; shells, deformed graphite layers; core, α-Fe and γ-Fe in the form of single crystals, Fe₃C) with a narrow size distribution and high magnetization were synthesized by a discharge in ethanol [300]. A MgO-filled rectangular carbon nanocapsules (40–60 nm) were fabricated by pyrolyzing acetonitrile with the assistance of MgO and a small quantity of Fe³⁺ [301]. A small quantity of Fe catalysts plays an important role in their growth. Carbon-encapsulated Fe₃O₄, γ-Fe₂O₃, and Fe nanostructures were prepared using FeOOH as a precursor and carbon nanocapsules as nanoreactors via controllable thermal transformation processes [302]. The magnetic property investigation revealed that all these nanostructures exhibited ferromagnetic behavior with quite high saturation magnetizations. Nanoparticles of iron carbides wrapped in multilayered graphitic sheets (carbon nanocapsules, 100–200 nm) were made by electric plasma discharge in an ultrasonic cavitation field in liquid ethanol, purified by selective oxidation and magnetic separation, and covered with PEG [303]. Also, Fe₃C-encapsulated carbon nanocapsules and carbon nanotubes were synthesized from C₆₀-saturated toluene solution and a solution of 2-propanol containing ferric nitrate nonahydrate (Fe(NO₃)₃·9H₂O) yielding iron-(Fe-)doped C₆₀ nanowhiskers, which were converted to the final product by heating at 1173 K [304]. In addition, core–shell-structured nanocapsules consisting of a nickel ferrite (NiFe₂O₄) nanoparticle core encapsulated in an onion-like carbon (C) shell were prepared by a modified arc-discharge method followed by an air annealing process and used in lithium-ion batteries retaining the NiFe₂O₄/onion-like C morphology after 500 cycles [305].

For the case of nonferrous metals, carbon-coated Cu nanocapsules were synthesized by an arc-discharge method, and the paraffin-Cu/C nanocapsule composite showed excellent electromagnetic absorption properties [306]. Starting with graphitic carbon nitride g-C₃N₄ and Co(CH₃COO)₂⋅4H₂O as precursors and as the only reactants (Fig. 4.118), Co nanoparticle-encapsulated N-doped carbon nanocapsules with a tetragonal microstructure (Fig. 4.119) were prepared without any template [307]. This stable catalyst showed excellent catalytic performance for both the ORR and OER. We also note that in situ oxidation of similar carbon-encapsulated cobalt nanocapsules (prepared from metallic cobalt and ethanol by modified arc-discharge technique) allowed to create highly active cobalt oxide catalysts (Fig. 4.120) for hydrocarbon combustion [308].

Possibility of solubilization and dispersion of nanocarbons, together with their toxicity [309], is an important aspect related with biomedical applications, among others. In case of nanocapsules, the solubility of nanospherical carbon nanocapsules was improved (Fig. 4.121) by using platelet-like clays (fluorinated mica, sodium montmorillonite, and synthetic smectite) [310]. We note that the second effective dispersing agent was also used for solubilization of CNTs [311]. This is a representative example on how 2D nanomaterials revealed powerful ability to redistribute or block the aggregated 0D or 1D nanomaterials improving their “solubility.” Water-dispersible carbon nanocapsules were also produced from a glycine solution by generating a pulsed arc discharge on the surface of the glycine solution under pressurized argon (Fig. 4.122) [312].

In addition to the applications above, carbon nanocapsules are used for chemotherapeutic delivery (cisplatin@US-tube carbon nanocapsules) [313], for imaging (radiometal-filled nanocapsules (⁶⁴Cu)) [314], for multifunctional superhydrophobic coatings (on the basis of mesoporous carbon nanocapsules with polyvinylidene fluoride) [315], and even for such nontraditional purposes (for the case of nanocarbons) as production of poly(D,L-lactic acid) nonwoven nanofiber mat [316].

4.5 “Nanovegetation” World

4.5.1 Nanotrees in General

Tree-like is a relatively frequent nano- and microstructural type, obtained for a series of inorganic compounds, mostly for silicon, silica, and carbon. Generally, nanotrees^{Footnote 13} are closely related to nanowires, which are modified with branches, sometimes they are produced from them [317], and can appear together with other nanostructures. Beautiful porous carbon tree-like nanostructures (Fig. 4.123) were obtained [319] (as well as SiC above) by electron-beam-induced deposition method using a TEM in poor vacuum conditions where hydrocarbons (being attracted to the substrates by the local electric fields) were present in the chamber. The authors found that the adequate ion dose to create well-defined sawtooth nano-patterns was between 8 and 10 nC/mm². A high concentration of sp² sites in nanostructures was revealed suggesting that they were made of graphite-like hydrogenated amorphous carbon. Y-junction hollow carbon nanotrees (with close-ended branches but open-ended roots, length ~5 μm, an average external trunk diameter of ~500 nm, branch diameters ranging from 70 to 100 nm, and wall thickness ranging from 24 to 30 nm) were obtained in a 90% yield by the reaction of ferrocene with 1,2-dichlorobenzene at 180 °C [320]. A simple and effective method based on Coulomb effect for separating SWCNTs from their bundles was developed [321]. The separated SWCNTs were radially distributed at the end of the original bundle and finally formed a nanotree (Fig. 4.124). The formation mechanism was proposed to be Coulomb explosion. As an important application of carbon nanotrees, the fuel cell, equipped with an anode and/or a cathode containing carbon–metal nanotree catalysts consisting of CNT trunks having a plurality of highly oriented carbon nanotube branches, where a metal is attached on inner and/or outer surfaces of the tubes [322], provided high-power generation efficiency by accelerating catalytic functions.

Y- (two-branched carbon nanofibers are connected to a short graphite nanorod supporting them) and comb-type (a second generation of carbon nanofibers nucleate on the inclined carbon nanorods to form a comb-like nanotree, where several parallel carbon nanofibers are lined up) crystallized carbon nanotrees (Fig. 4.125) with continuous connections of the branches were formed from branched carbon nanofibers grown by plasma-enhanced CVD [323]. It was revealed that the splitting of large catalyst particles is required for both kinds of nanotrees, whatever the involved growth mechanism. Stepwise formation of branched carbon nanotrees is shown in Fig. 4.126.

4.5.2 Nanopalms

Nanopalm-like carbon-containing trees are practically unknown. Silica nanowires (diameters in the range of 15–49 nm and lengths up to 500 nm), obtained by electron-beam irradiation on porous silicon films, were exposed to poor vacuum conditions in which carbon aggregation from the surrounding gas was promoted by the local electric fields enhanced at the tip of the silica wires, leading to heterostructures showing a nanopalm-like shape (see figure above) [324, 325].

4.5.3 Nanoleaves

Leaf-like nanostructures are known mainly for metal oxides, although some metals, intermetallic compounds, and metal salts have been also reported, as well as carbon. On the basis of the facts that “…nature always gives us inspiration… . It is well known that a ‘leaf’ can be simply considered as a hierarchical structure of leaf-blades and leaf-veins coupled with many branches. This exquisite structure ensures that moisture and nutrients are very quickly and adequately delivered to the whole blade through the veins” [326], L. Chen et al. asked the question of whether CNTs can be simulated into leaf-like structures with structural controllability through simple processing. As a result, carbon nanoleaf framework, possessing low density, large surface area, and good conductivity, was fabricated (Fig. 4.127) using MWCNTs as a single precursor useful for ORR catalysis. The carbon nanoleaves consisted of two building blocks (Fig. 4.128) in which 1D CNTs were bridged with 1D graphene nanoribbons (GNRs). Various applications, such as supercapacitors, batteries, and oxygen sensors, were offered for these nanostructures.

Highly integrated carbon nanofiber@nitrogen-doped graphene (CNF@NG) “vein-leaf” 3D complexes connected by carbon–carbon bonds were prepared [327] (Fig. 4.129) from biomass (urea and bacterial cellulose) by thermal condensation (calcination) and applied in the ORR exhibiting high activity, excellent tolerance to methanol, and superior stability in alkaline solutions. Carbon nanofibers played the role of the skeleton and nitrogen-doped graphene as the leaf (Fig. 4.130). The conductivity of the monolith of CNF@NG was a little bit higher than that of the bare CNF monolith, demonstrating the advantage of such a “leaf vein” structure for electron transfer by following the principle of water transfer inside real leaves (Fig. 4.130c). In addition, carbon 2D and 3D nanoflowers, prepared on silicon (111) substrates by plasma-enhanced CVD, using CH₄, H₂ and Ar as reactive gases in the presence of Fe catalyst, were formed by various nanoleaves (2D, related closely to the flux ratio of gas and the reaction pressure) or hundreds of nanofibers (3D, depended mainly on the growth temperature) [328].

4.5.4 Nanoforests

The nanoforests on the basis of carbon nanotubes belong indubitably to the most studied forest-like structures among other compounds, whose number is certainly limited, and have got useful applications. The CNTFs’ peculiarity, in comparison with other carbon and non-carbon species, is that the forests of carbon nanotubes are currently known as the darkest artificially produced materials [329], being able to adsorb the entire visible range of electromagnetic wave much more efficiently than any other black material. They exhibit near-perfect optical absorption (reflectance∼0.045%) due to low reflectance and nanoscale surface roughness. At the same time, carbon nanotubes are able to reflect light like a mirror when the CNTs in the forests are mechanically bent and flattened with proper control [330]. Under a controlled mechanical processing of the CNTs, the mirror-like reflection from the processed area with 10%–15% reflectivity was observed, having possible applications for fabrication of monolithically integrated reflector-absorber arrays.

Carbon nanotube forests may include “regular” [331], bamboo-like [332], helical [333], and branched structures, as well as a CNT forest-on-forest, where the number of layers in such a system can vary from 1 [334] to 2 [335], 4 [336], 8 [337], and even 40 [338], and second- and third-order CNT forest structures [339, 340]. Integrated simulation of active carbon nanotube forest growth, the diverse CNT forest morphologies, and mechanical compression is discussed in a recent report [341]. In particular, CNT forest morphologies may be generally aligned to the growth axis or highly tortuous, with persistently wavy CNTs intermixed with aligned and straight carbon nanotubes. This depends on the height of CNT forest, the CNT diameter, surface density, and growth conditions. The length of some CNTs may exceed the height of the carbon nanotube forest; different CNTs in the same nanotube forest can be different in tortuosity and length. Comprehensive information on CNT forests is present in a highly recommended excellent comprehensive recent review [342], citing 679 references. This shows an increasing interest to this type of nanostructure having a variety of applications, from catalysis to biosensors.

Synthesis

In general, CNT forests can be synthesized by catalytic pyrolysis on supported catalysts as described below, using various versions of the CVD method [343,344,345], by the template method with Al₂O₃ membranes, by graphite sputtering (this technique is used much more rarely), by electrophoresis or dielectrophoresis of CNTs from dispersions [346, 347], and by chemical grafting of CNTs onto substrates [348]. Particular aspects of methods for the synthesis of CNTFs are mentioned in several reviews [349, 350]. Among them, we note a wide use of mono- and polymetallic catalysts and supports for their preparation, mainly at high temperatures and using acetylene (reactions 4.13–4.17) as carbon source {although ethylene mixtures with H₂ [351] (the equipment is shown in Fig. 4.131) or C₂H₄/H₂/H₂O/Ar [352] were used}. Thus, the growth of dense CNT forests on some metallic layers (Mo, Ta, W, and Ir) by thermal decomposition of C₂H₂ diluted in NH₃ was studied [353]. The growth process and resulting structure of CNT forests were shown to depend on metal substrates, process duration, temperature, and thickness of the stabilizer (Al). In a related report [354], dense CNT forests (height of ∼300 nm and a mass density of 1.2 g⋅cm⁻³) were prepared on copper support at 450 °C, using Co/Al/Mo multilayer catalyst. The nanotubes exhibited very narrow inner spacing. Main characteristics of the formed material are high thermal effusivity and a thermal conductivity, suitable for possible uses in heat dissipation devices.

Another classic example consists of vertically aligned SWCNT forest, grown using FePt alloy particles on a MgO substrate [355]. Sometimes, metal-based catalyst should be additionally activated prior to use. Thus, an oxidative pretreatment of Fe, Co, or Ni growth catalyst on SiO₂ support can be used to switch the growth mode of CNTs from tip growth to root growth [356]. Dense vertically aligned nanotube forests can be grown this way. The oxidative treatment effect was explained by appeared strong interaction “catalyst-support (SiO₂),” limiting the surface diffusion, sinterization of catalyst NPs, and their binding to the surface of SiO₂ . In addition, vertically aligned small diameter (single- and few-walled) carbon nanotube forests were also grown by thermal CVD over the temperature range 560–800 °C and 10⁻⁵ to 14 mbar partial pressure range, using acetylene as the feedstock and Al₂O₃-supported Fe nanoparticles as the catalyst [357]. The following mechanism of their formation (Fig. 4.132) is described by reactions (4.13–4.17); alternative mechanism is shown in Fig. 4.133 [358]. Curiously (Fig. 4.133g), nanoforest zones consisting of sinuous (Fig. 4.133g, left section, up) and almost straight (Fig. 4.133g, right section, down) carbon nanotubes can be sometimes formed at the same bulk growth conditions.

$$ {\mathrm{C}}_2{\mathrm{H}}_{2\kern0.5em \mathrm{gas}}\leftrightarrow {\mathrm{C}}_2{\mathrm{H}}_{2\kern0.5em \mathrm{ads}} $$

(4.13)

$$ {\mathrm{C}}_2{\mathrm{H}}_{2\kern0.5em \mathrm{ads}}\leftrightarrow 2{\mathrm{C}\mathrm{H}}_{\mathrm{ads}} $$

(4.14)

$$ {\mathrm{C}\mathrm{H}}_{\mathrm{ads}}\leftrightarrow {\mathrm{C}}_{\mathrm{ads}}+{\mathrm{H}}_{\mathrm{ads}} $$

(4.15)

$$ 2{\mathrm{H}}_{\mathrm{ads}}\to {\mathrm{H}}_{2\mathrm{gas}} $$

(4.16)

$$ {\mathrm{C}}_{\mathrm{ads}}\to {\mathrm{C}}_{\mathrm{C}\mathrm{NT}} $$

(4.17)

In addition to metals above as supports, CVD-assisted formation of a dense CNTs (length 13–14 mm and diameter of 10–100 nm) forest is known using spin-coated iron oxide (Fe₂O₃) thin film on Si substrate starting from a mixture of acetylene, hydrogen, and nitrogen for 45 min at 700 °C [359]. Also, vertically aligned ohmic-conductive carbon nanotube forests were grown on TiSiN refractory conductive films and reached area densities of (5.1 ± 0.1) × 10 [12] tubes cm⁻² and mass densities of approximately 0.3 g⋅cm⁻³ [360]. The above support had a function as a diffusion barrier; the resulting nanoforest grew according to the root growth mechanism. An additional discontinuous AlO_x layer, inhibiting catalyst nanoparticle sintering, allowed maximizing the CNT area density. Highly porous and conductive ZnO/C core–shell hexagonal nanosheets (HNS) nanoforests (Fig. 4.134) were fabricated through the direct decomposition of zinc acetate dihydrate in a sealed thermolysis stainless steel vessel at 400 °C without using a catalyst, solvent, or template [361] according to the reactions 4.18–4.21 at heating conditions. The final ZnO/C core–shell structure was then formed by the deposition of carbon onto the ZnO surfaces. The formed nanomaterial could possess practical utility of the materials in dye-sensitized solar cells, nanocrystal photovoltaic devices, white light emitters, and white light photocatalyst applications.

$$ \mathrm{Zn}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_2\cdot 2{\mathrm{H}}_2\mathrm{O}\to \mathrm{Zn}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_2+2{\mathrm{H}}_2\mathrm{O} $$

(4.18)

$$ 4\kern0.5em \mathrm{Zn}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_2+2{\mathrm{H}}_2\mathrm{O}\to {\mathrm{Zn}}_4\mathrm{O}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_6+2{\mathrm{CH}}_3\mathrm{COO}\mathrm{H} $$

(4.19)

$$ {\mathrm{Zn}}_4\mathrm{O}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_6+3{\mathrm{H}}_2\mathrm{O}\to 4\mathrm{ZnO}+6{\mathrm{CH}}_3\mathrm{COO}\mathrm{H} $$

(4.20)

$$ {\mathrm{Zn}}_4\mathrm{O}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_6\to 4\mathrm{ZnO}+3{\mathrm{CH}}_3{\mathrm{OCH}}_3+3{\mathrm{CO}}_2 $$

(4.21)

To optimize high-temperature growth of CNTFs, several studies have been carried out, since an important obstacle of CNT fabrication in industrial mass production is the growth efficiency. Thus, for the case of C₂H₂ as precursor in water-assisted CVD, it was established [362] that, for 10 min. optimum growth conditions, SWCNT forests with ~350 μm/min initial growth rates, ~2500 μm height, and extended catalyst lifetimes could be reached by increasing the dwell time to ~5 s. It demonstrated the generality of dwell time control to highly reactive gases. In another research, in order to tune the CVD growth of CNT forests (DWCNTs or SWCNTs) on wafers, introduction of CO₂ is a simple and controlled way [363]. When its concentration grows, the CNT forests are transformed as follows: CNT forests → radial blocks → bowl-shaped forests. It is possible to control the diameter distribution and wall number of the CNTs this way. At 36.8 mol% of CO₂, the content of SWCNTs in the forest was found to be 70%. Also, under increased CO₂ concentration, a smaller diameter and decreased wall number for CNTs were revealed. It was suggested that CO₂ could be as a weak oxidant and generates water. Among other synthesis methods [364] for CNTFs, we note high-voltage electrophoretic deposition (HVEPD), used to obtain forests of aligned MWCNTs on long strips of conductive substrates [365].

Special Studies of CNTF Internal Structure and Other Properties

XPS analysis of a CVD-grown forest of MWCNTs using monochromatic Al Kα radiation showed essentially only carbon presence (1 s peak at 284.5 eV) [366]. In order to evaluate properties of the “internal content” of CNTFs, the precise and continuous control method for the average diameter of SWCNTs in a forest ranging from 1.3 to 3.0 nm with 1 Å resolution was offered [367]. This control was reached through tuning of the catalyst state (composition, size, and density) applying arc plasma deposition of nanoparticles. These results showed a direct relationship between the achievable height and the diameter of SWCNTs. On their basis, the fundamental difficulty in fabrication of tall and small diameter SWCNT forests was suggested. In addition, the internal nanostructure of the CNT forest, consisting of mostly empty space between the nanotubes, allows to capture photons effectively yet allows electrons to escape easily (Fig. 4.135) [368]. This makes possible to use CNT forests in ranging from photocathodes to solar cells.

Vertically aligned CNTs possess a peculiarity of waviness, regardless of the control of their fabrication process. Study of this phenomena showed [369] that the inherent waviness is the main mechanism by which the effective modulus of CNTs is reduced by several orders of magnitude. The high compliance of forests of carbon nanotubes was found to be because of the inherent waviness of individual CNTs and not necessarily due to bending and buckling of CNTs. The mechanical compression effect on the thermal conductivity of the closely aligned parallel SWCNT forest was investigated by molecular dynamics simulations [370]. Among other findings, the thermal conductivity was shown to be linearly enhanced by increasing compression before the buckling of SWCNT forests. At the same time, the thermal conductivity decreases quickly with further increasing compression after the forest is buckled. The intertube van der Waals interaction is strengthened by the compression, and the smoothness of the intertube interface is maintained during compression. In addition, buckling-driven delamination of CNT forests from their growth substrates when subjected to compression was revealed [371]. It was postulated that the post-buckling tensile stresses, being developed at the base of the CNT forests, serve as the driving force for delamination. Also, the fundamental dependence electrical conductance and thermal diffusivity on the diameter and defect level for aligned SWCNT forests (fabrication scheme see Fig. 4.136) was evaluated [372]. It was definitively concluded that high thermal diffusivity and electrical conductance would be extremely difficult to simultaneously reach by a single SWCNT forest structure using CVD technique.

Liquid flow slippage over superhydrophobic surfaces made of CNT forests, incorporated in microchannels, was also studied [373]. We need to note that CNTF composites with highly hydrophobic properties can be created by special methods. Thus, a stable superhydrophobic surface was created using the nanoscale roughness inherent in a vertically aligned CNT forest [374]. This became possible due to the use of a thin conformal hydrophobic polytetrafluoroethylene (PTFE), which coated the surface of the CNTs. In this material, essentially spherical, micrometer-sized water droplets can be suspended on top of the CNT forest. This effect could be explained on the basis that that the appearing difluorocarbene radicals may attach covalently to the nanotube surface and subsequently polymerize from these sites. The product could get several applications, in particular as fillers for nanocomposites and single-strand conductors in molecular electronics. Among other important studies, we mention the linearized Gouy–Chapman–Stern theory of an electric double layer, generalized for morphologically complex and disordered electrodes [375]; in particular its significance was illustrated for a forest of nanopillars. The theory allows analyzing the effect of compact layer thickness, concentration, shapes, and their fluctuations, developing a general understanding of capacitance in complex interfacial systems.

Applications of CNTFs and their composites belong to a variety of areas, from academic to technical and medicinal. Thus, CNT nanoforests, each with a thin conformal coating of dielectric, can provide an economic fabrication of sensitive and uniform SERS templates [376]. CNTFs are also considered as particularly promising templates for the formation of porous metal oxides (Al₂O₃, TiO₂, V₂O₅, and ZnO) [377]. A bilayer Au–carbon nanotube composite (a vertically aligned MWCNT forest, sputtered with an Au layer) was fabricated as a potential low-force electrical contact surface for possible applications in MEM switching devices [378]. The penetration of Au atoms into the forest directly influences the electrical characteristics of the composite, depending on loading conditions (the effective resistivities are in the range from 303 nΩ m down to 54 nΩ m).

Sensing uses are also common. Thus, a unique combination process of a sharp Si microneedle array and MWCNT forest was developed and applied as a reference electrode for a nonenzymatic glucose sensing [379]. The registered sensitivity was found to be 17.73 ± 3 μA/mM-cm². This electrode can be used for painless diabetes testing applications. Also, carbon nanofiber forests (CNFFs) grown on glass microballoons are able to detect directly Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) antigen as low as 0.025 ng/mL concentration in phosphate-buffered saline [380]. This effect can be applied for early diagnosis of malaria and other infectious diseases. Among technical applications, CNT forests have been revealed to reduce the access of abrasive particles to compressible sealing elements of joints [381]. In addition, a spray-based coating technique was applied for deposition of nanoscale coatings of polystyrene and poly-3-hexylthiophene onto carbon nanotube forests, being as a bonding medium that produces thermal resistance by expanding the area available for heat transfer at CNT contacts [382].

Diamond-based nanoforests are known, in addition to CNTFs and CNFFs above. Thus, an electrode with 3D structure on the basis of boron-doped diamond nanorod forest (BDDNF) was fabricated by hot-filament CVD method (HFCVD) method (Fig. 4.137) [383]. In its preparation, the electroless metal deposition (EMD) method and HFCVD technique were combined for growing the BDDNF on Si nanowires; as a result, a 2D B-doped diamond electrode was transformed to 3D analogue. This electrode was found to exhibit a better selectivity and sensitivity for biomolecule detection (e.g., for glucose oxidation in basic conditions) in comparison with conventional planar B-doped diamond electrodes.

4.5.5 Nanobushes

Nanobush^{Footnote 14} structures are still rare for carbon. The CNTs were grown with bush-like nanostructures covered around the micron-fibers or web-like nanostructures crossing between the fibers at different synthetic conditions [384, 385]. The developed CNT-metal-filter had higher filtration efficiency without significant difference in pressure drop compared with the conventional metal filter, which is because the CNTs function as the trap of pollutant nanoparticles.

4.5.6 Nanomushrooms

Mushroom-like nanostructures are known for a series of elemental substances, their oxides, nitrides, salts, polymers, as well as their combinations. Carbon, traditionally obtained in a grand variety of nanostructures, can sometimes exist also as nanomushrooms.^{Footnote 15} Thus, two types of nanocarbons with a mushroom shape (of a conical tip, made from helically stacked graphitic cones, and pyramidal tip, made from graphitic cups stacking to each other), having ~2 μm length and 0.5 ~μm diameter, were found in common glassy carbon powder [386]. It was established that their diamagnetic behavior strongly depends on both the temperature and the magnetic field. A facile thermal CVD method for fabricating dense and vertically well-aligned bamboo-like CNT arrays on a Cu substrate from acetone was developed [387] resulting mushroom-like carbon nanostructures, formed at 800 °C, and well-aligned CNTs, produced at 850 °C.

4.5.7 Nanoflowers

Nanoflowers^{Footnote 16} (flower-like nanoparticles) [388, 389] are not currently reported so frequently, as, for example, nanowires [390] or one of the hottest nanotechnology area – well-known carbon nanotubes. However, last decade the number of related literature is being increased. Last years, a series of various nanoflower and nanoflower-like structures have been obtained, frequently together or in equilibrium with other nanoforms, depending on reaction conditions. Nanoflower structure may consist of such simpler nanostructures, as nanorods, nanowalls, or nanowires. Current and possible applications of nanoflowers as optoelectronics devices or sensors, in catalysis, and solar cells caused a definite interest to them. Nanoflowers obviously are at the initial stage of their research, and it is expected further intensive development of this area.

In respect of carbon itself, in addition to thousands of patents, books, and experimental and review articles, dedicated to intensively studied carbon nanotubes and fullerenes, this element was obtained also in the nanoflower form. Thus, carbon nanoflowers with graphitic feature were prepared at 650 °C with high yields using a reduction–pyrolysis–catalysis route using glycerin as carbon source and magnesium and ferrocene as reductants and catalysts [391]. The obtained nanoflowers with a hollow core had diameters ranging from 200 to 600 nm. In another report [392], iron was used as a catalyst for CNTs flowers formation from a gas mixture of Ar and C₂H₂ at a temperature range of 700–900 K for 300 s (5 min). Iron wire was sparked for 1, 2, 10, and 100 times to form iron dots/islands on the glass slides, where CNTs, composed of carbon with hexagonal structure, were further grown. Also, carbon nanoflowers, among other nanostructures (fullerene, carbon nanopowders, nanofibers, and nanotubes), were produced by carrying out a gas membrane microarc discharge on a cathode in an aqueous solution (basic electrolyte, 0.01–2 mol/L solutions of mineral acids, bases, or chlorides) [393].

Flower-like carbon dots/manganese dioxide (CQDs/MnO₂) nanocomposites with specific surface area of 168.8 m² g⁻¹ were investigated as electrode materials for supercapacitors [394]. CQDs were found to be uniformly distributed on the transparent petal of δ-MnO₂. In addition, nitrogen-doped mesoporous hollow 3D carbon nanoflowers (N-HCNF, Fig. 4.138) with high specific surface area (507.5 m² g⁻¹) were prepared (Fig. 4.139) by a facile hard-template route via a hydrothermal process, subsequent carbonization, and etching [395] and recommended to be used as a potential anode material for lithium-ion batteries. Their outstanding electrochemical performances were attributed to the N-doped carbon shell, large BET surface area, and unique hollow flower-like nanostructure. For similar uses, Na-ion battery anodes and flower-like MoS₂/C nanospheres were fabricated [396].

4.5.8 Nanobouquets

The term “nanobouquets”^{Footnote 17} is a blurred (diffuse) one: corresponding nanostructures may be called quite differently. Nanobouquets, which may be formed together with other nanostructures in varying synthesis conditions, can consist usually not only of nanoflowers but also of nanowires, nanorods, nanotrees, and nanoplates. Carbon-based nanobouquets are little known up to date. Thus, the nitrogen-doped carbon nanotube bouquets (Fig. 4.140) were synthesized by the pyrolysis of nitrogen-containing ion-exchange resin [397]. The material shows excellent ORR performance after being supported by the Pt nanoparticles, confirming the hypothesis that carbon supports doped with nitrogen improve catalyst support interactions by improving dispersion, electrical conductivity, durability, and catalytic activity of the overlying Pt nanoparticles.

4.5.9 Broccoli-Like Architectures

A few reports have been dedicated to clearly expressed broccoli-like nano- and microparticles on carbon basis. Thus, superhydrophobic polyvinylidene fluoride (PVDF/DMF/candle soot particle and PVDF/DMF/camphor soot particle composite) porous materials were fabricated by combustion of precursors (Fig. 4.141) [398], yielding, in particular, broccoli-like particles (Fig. 4.142c, d). Such hierarchical architecture combined with micro- and nano-scaled roughness of both formation of nanocauliflower and nanobroccoli structure is schematically illustrated in Fig. 4.143. As-measured wettability property of the obtained PVDF-based composite coatings revealed superhydrophobicity with water contact angle nearly touches 170°; thus it was considered by authors as water-repellent materials.

4.5.10 Nanograsses

Nanograss^{Footnote 18} (as well as nanofur) is an example of dynamically tunable nanostructured surfaces, whose behavior can be reversibly switched between superhydrophobic and hydrophilic states either actively, by the application of electric voltage, or passively, in response to the change in environmental conditions such as humidity [399]. Such “superlyophobic” surfaces that repel virtually any liquid even if the surface material by itself is highly wettable have potential applications in an exceptionally broad range, including areas as diverse as self-cleaning coatings, controllable permeability membranes for portable power generation, substrates for directed biological cell migration and differentiation, and hydrodynamic drag reduction surfaces.

Carbon nanoforms in nanograss forms are little known. Thus, boron-doped diamond (BDD) nanograss array was prepared [400] simply on a heavily doped BDD film by reactive ion etching for use as an electrochemical sensor, which improved the reactive site, promoted the electrocatalytic activity, accelerated the electron transfer, and enhanced the selectivity. In particular, detection of catechol was performed on the as-grown BDD electrodes and the nanograss array BDD [401]. The nanograss array BDD showed higher electrocatalytic activity toward the catechol detection than did the as-grown BDD. Good linearity was observed for a concentration range from 5 to 100 μM with a sensitivity of 719.71 mAM⁻¹ cm⁻² and a detection limit of 1.3 μM on the nanograss array BDD. Various morphologies of CNTs such as individuals, random networks parallel to the surface of the substrate (“grasses”), and vertically aligned forests of single- and multiwalled carbon nanotubes were CVD-grown by varying the nominal thickness of cobalt catalyst under the same reaction condition [402]. Longer growth time increased the CNT length, which caused further change in CNT morphologies from individuals to grasses and grasses to forests. Additionally, CNT nanograss is applied as gamma detector [403].

4.6 “Nanoanimal” World

4.6.1 Nanoworms

Several carbon nanostructures are known in worm-like^{Footnote 19} forms, which are frequently formed together with various other structures at the same time depending on reaction conditions. Thus, high-purity (99.21 wt.%) helical carbon nanotubes (HCNTs) were prepared in large quantity over Fe nanoparticles (fabricated using a coprecipitation/H₂ reduction method) by acetylene decomposition at 450 °C, together with worm-like carbon nanotubes (CNTs) as well as carbon nanocoils (CNCs, produced in large quantities), if H₂ was present throughout acetylene decomposition [404]. Since the HCNTs and worm-like CNTs were attached to Fe nanoparticles, the nanomaterials were found to be high in magnetization. Pyrolysis of ruthenocene carried out in an atmosphere of argon or hydrogen was found to give rise to spherical carbon nanostructures, in particular worm-like carbon structures (Fig. 4.144) [405]. Worm-like expanded structures (graphite flakes) (Fig. 4.145) are commonly observed in expanded graphite intercalated compounds. Also, properties of graphene wormholes in which a short nanotube acts as a bridge between two graphene sheets, where the honeycomb carbon lattice is curved from the presence of 12 heptagonal defects, were studied [407].

An interesting worm-like nanostructure was reported for cubic Pd crystals inside giant carbon clusters, forming worm-like carbon nanoworms [408]. The head of the worm, typically 20–50 nm, consisted of Pd encapsulated in carbon, and the body of the worm, several hundred nanometers in length, consisted of many sections of carbon tubes with cone-shaped voids. Graphite was found to be a superior support for Pd (worm-like small Pd nanostructures) catalyst for the direct synthesis of H₂O₂ from H₂ and O₂ [409]. Worm-like nanostructures have been used in other catalytic processes; in particular, the catalytic carbon “nanoworm” model (Fig. 4.146) was used to understand the role of the phases prevailing in the catalyst particles and the causes of the synergistic effects observed in gasification rates of activated carbon by CO₂, NO, and N₂O [410, 411].

4.6.2 Nano-urchins

Nano-urchins which belong to a similar structural type as nanoflowers (indeed, nano-urchins are frequently confused with flower-like nanostructures) are known for a variety of inorganic compounds and a few organics and have a lot of applications, first of all in catalysis due to high surface area of this nanostructures. In case of carbon, sea urchin-shaped nanostructured hollow carbon microspheres (e.g., hollow carbon microspheres containing carbon nanotubes extending outward from the central microsphere) were fabricated by formation of the carbon microsphere followed by incorporation of iron nanospheres (as growth catalysts) and then CVD of carbon (as nanotubes) from ethylene as the carbon source (Fig. 4.147) [412]. After incorporation of platinum on such carbon support, the formed nanocomposite could be used for methanol electrochemical oxidation in fuel cells. Hollow, urchin-like ferromagnetic carbon spheres with electromagnetic function and high conductivity at room temperature could be used as a reversible dye adsorbent. These nanostructures were prepared from template-free-synthesized, urchin-like, hollow spheres of polyaniline (PANI) containing FeCl₃ as the precursors by a carbonization process at 1200 °C under an argon atmosphere [413]. The high conductivity at room temperature resulted from the graphite-like structure, whereas α-Fe or γ-Fe₂O₃ nanoparticles produced by FeCl₃ during the carbonization were attributed to the ferromagnetic properties.

An urchin-structured multiwalled carbon nanotubes-hard carbon spherule (MWNTs/HCS) composite, where HCS was thoroughly coated by intercrossed MWNTs, was synthesized through acetylene pyrolysis [414] and showed an outstanding lithium uptake/release property: reversible charge capacity of 445 mAh⋅g⁻¹ can be delivered by this composite after 40 cycles. The hybrid sphere/CNT nanostructures were grown in the aerosol phase by an on-the-fly process by spray pyrolysis, followed by CNT catalytic growth (Fig. 4.148) at the surface of the spherical nanoparticles yielding urchin-like nanostructures consisting of numerous CNTs attached to an alumina/iron oxide sphere [415]. These hybrid nanoparticles were dispersed to poly-alpha-olefin with sonication and a small amount of surfactants to form stable nanofluids, whose effective thermal conductivity of the fluids was increased by about 21% at room temperature for particle volume fractions of 0.2%. The role of sulfur in the synthesis of novel carbon morphologies was studied [416]. For the materials, obtained by sulfur-assisted CVD, it was demonstrated that S not only acted on the catalyst, but also can be detected in the carbon lattice of the nanostructures. Sulfur is responsible for inducing curvature and therefore influencing the final carbon nanostructure morphology, in particular sea urchin-like nanostructures. Carbon nano-urchins are reviewed, among other nanostructures, as nanostructured materials for batteries [417].

Among most recent reports, we note that hydro-/solvothermal techniques are predominant for preparation of nano-urchin hybrid composites. Thus, hybrid urchin-like nanostructures composed of a spherical onion-like carbon (OLC) core and MoS₂ nanoleaves were synthesized by a solvothermal method followed by thermal annealing treatment [418] and offered to be used for lithium-ion batteries. A pre-lithiation method (Fig. 4.149) based on placing the nano-urchins in direct contact with the lithium foil was then employed to increase the initial CE to 97.6%. Similarly, a hybrid nano-urchin structure consisting of spherical onion-like carbon and MnO₂ nanosheets (Fig. 4.150) was synthesized by hydrothermal method [419]. Using the formed material for rechargeable lithium batteries, the improved performance arose from the unique nanostructure which facilitated fast ion and electron transport and stabilized the MnO₂ nanoparticles during charge storage.

4.7 “Home”-Like Nanostructures

4.7.1 Nanobowls

Nanobowl-like structures^{Footnote 20} are rare for carbon. Thus, vertically aligned CNT film was grown on a metal-coated polystyrene (PS) submicron sphere array and then transferred onto a polycarbonate (PC) substrate by microwave heating leading a new architecture of 2D metallic nanobowl array on a thermoplastic substrate [420]. In case of CNT nanobowls theirselves, the introduction of CO₂ was found to be a facile way to tune the growth of vertically aligned double- or single-walled carbon nanotube forests on wafers in the CVD fabrication of CNTs from ethylene as a precursor [421]. In the absence of CO₂, a double-walled CNT convexity was obtained; meanwhile with increasing concentration of CO₂, the morphologies of the forests transformed first into radial blocks and finally into bowl-shaped forests (Fig. 4.151). The addition of CO₂ was speculated to generate water and serve as a weak oxidant for high-quality CNT growth.

4.7.2 Nanocups

Nanocups are closely related to nanobowls and nanocaps. In case of carbon, the electrochemical activity of stacked N-doped carbon nanotube cups (NCNCs, Fig. 4.152) was explored in comparison to commercial Pt-decorated carbon nanotubes [422], demonstrating for the nanocup catalyst comparable performance to that of Pt catalyst in oxygen reduction reaction. The NCNC electrodes were used for H₂O₂ oxidation and consequently for glucose detection. Also, highly engineered hollow CNT nanocup arrays were fabricated (Fig. 4.153) using precisely controlled short nanopores inside anodic aluminum oxide templates [423]. The nanocups were effectively used to hold and contain metal nanoparticles, leading to the formation of multicomponent hybrid nanostructures with unusual morphologies. Also, cup-shaped nanocarbons generated by the electron-transfer reduction of cup-stacked carbon nanotubes were functionalized with porphyrins (H₂P) as light-capturing chromophores [424]. In addition, high-power electric double-layer capacitors (EDLCs) were fabricated (Fig. 4.154) using carbon-based 3D hybrid nanostructured electrodes, consisting of vertically aligned CNTs on highly porous carbon nanocups (CNCs), by a combination of anodization and CVD techniques [425, 426]. A 3D electrode-based supercapacitor showed enhanced areal capacitance by accommodating more charges in a given footprint area than that of a conventional CNC-based device. The increase in this capacitance was attributed to the larger surface area of the hybrid 3D CNT–CNC structure .

4.7.3 Nanoplates

The plate-like^{Footnote 21} nanostructures are relatively widespread and represented practically by inorganic compounds, mainly by noble metals (gold, silver, palladium, rhodium, sometimes as composites with polymers), metal oxides, and oxygen-containing metal salts. In case of carbon, we have observed only a few examples of carbon nanoplates (despite the fact that graphene nanoplates are the thinnest material discovered in the universe [427]), in particular those fabricated starting from natural precursors. Thus, carbon-based microporous nanoplates containing numerous heteroatoms (H-CMNs) were fabricated (Fig. 4.155) from regenerated silk fibroin by the carbonization and activation of KOH,^{Footnote 22} exhibiting superior electrochemical performance suitable for usage as supercapacitors [428]. Similar conditions (pyrolysis and KOH activation) were also used for obtaining carbon nanoplated from cellulose [429]. Dispersible mesoporous N-doped hollow carbon nanoplates were synthesized by pyrolysis using gibbsite nanoplates as templates and dopamine as carbon precursor (Fig. 4.156) [430]. The product possessed uniform hexagonal morphology with specific surface area of 460 m²·g⁻¹ and fairly accessible small mesopores (∼3.8 nm); excellent colloidal stability in water was applied as electrode materials for symmetric supercapacitors. Some data on the toxicity of graphite nanoplates are also available [431].

4.7.4 Nanobrooms and Nanotepees

Several reports on relatively rare broomlike nanostructures belonging to distinct types of mainly inorganic compounds are known. Carbon nanotubes were also obtained in the said form. Thus, a dual-porosity CNT material of seamlessly connected highly porous aligned nanotubes and lowly porous closely packed nanotubes was created [432] by using capillary action of liquids. Millimeter-tall SWCNT forests synthesized by water-assisted chemical vapor deposition were used as model system. As a result, diverse structures using toothpicks, broomlike objects (Fig. 4.157b, c), tepees (Fig. 4.157f), as well as liquid thin films, bubbles, vapors, and superink jet printing were obtained.

4.7.5 Nanobrushes

This nanostructural type, as well as some others reported above and below, are mainly represented by zinc oxide, prepared by distinct routes. Carbon-based nanobrushes are generally formed by CNT arrays . Thus, a multifunctional nanobrush^{Footnote 23} (attributed to nanodevices) using carbon nanotubes was described [433]. In a related report, superlong (7 mm) aligned, mainly double-walled, high-density CNTs (Fig. 4.158) were synthesized from ethylene, used as the source gas of carbon, with high reproducibility using CVD technique (typical CVD growth was carried out at 750 °C for 30 min as the standard growth time) [434]. Thin layers of Fe were used as the catalyst, and an Al₂O₃ buffer layer was used between the Si/SiO₂ substrate and the Fe catalyst. The relative levels of ethylene and water, as well as ethylene and H₂ during the CVD, were found to be the most important factor for the growth of such superlong aligned CNTs. Also, amorphous carbon nanotube brushes (Fig. 4.159) were prepared using glucose as the carbon precursor [435]. The functional surfaces of these nanotubes were covered with gallium ions and then calcined to get gallium oxide nanotube brushes, which were further converted to crystalline GaN nanotube brushes by treatment of ammonia at 800 °C.

CNT arrays, as nanobrush formers, being used in switches and other devices, can undergo to damage, exfoliation, and deformations at high strains [436]. These damages (Fig. 4.160) can be nearly recovered by capillary evaporation of solvents from the freestanding aligned nanotube brushes.

Nanobrushes on carbon basis have found a few applications. Thus, the composites of carbon nanobrushes embedded in a biocompatible poloxamer gel have relevance for tissue and cellular engineering and tissue regeneration in clinical medicine [437, 438]. Another example is a bioactive microelectrode for glucose biosensing , suitable especially for potential use in implantable devices, which was designed on the basis of CNT fiber directly spun from an aerogel, showing a unique, well-aligned nanostructure (nano-pore and nanobrush, Fig. 4.161) [439].

4.7.6 Nanocarpets

Relatively rare carpet-like nanostructures,^{Footnote 24} related to nanobrushes, are formed mainly by nanotubes, nanowires, or nanorods , belong to different type of compounds, and possess especial properties (in particular, superhigh hydrophobicity) in comparison with major part of other less-common nanostructures. For slender nanostructures, the nanostructure may change after coming into contact with liquid (this phenomenon is known as the “nanocarpet effect” [440,441,442]). The newly formed nanostructures may have a great impact on the hydrophobicity of a surface. The nanocarpet effect is a simple and effective way to apply to a variety of nanowire, nanotube, or nanorod structures to generate a hierarchical structure with both microscale domains and nanoscale feature (nanorod tips) for superhydrophobicity and other surface property studies.

Carbon nanotube carpet-like nanostructures have been obtained mainly by CVD. Thus, massive carpets of well-packed, vertically aligned, and very long MWCNTs were synthesized by this classic technique [443]. Ferrocene was frequently used as a precursor in such syntheses, for instance, in a CVD-assisted growth of MWCNTs (Fig. 4.162) in 60:40 toluene/1,2-diazine at 760 °C in argon [444] or in the pyrolysis of aerosols obtained from C₆H₆/NiCp₂/FeCp₂ mixtures generating aligned Invar (Fe–Ni alloy, Fe₆₅Ni₃₅)-filled carbon nanotube carpet-like samples of high purity [445]. Radio-frequency hot-filament CVD (RFHFCVD), where the reactant gases (methane and hydrogen gas used as the carbon source and diluted gas, respectively) were first dissociated by the MW field before entering the chamber, thus, ensuring that there was a dense growth of CNTs from a large Ni catalyst particle, was proposed for CNT films and carpet-like nanostructure (Fig. 4.163) fabrication [446]. The growth mechanisms were found to be either “tip growth” or “base growth” depending on the size of the catalyst metal particles involved. It was concluded that the oxide iron group alloys like Ni/NiO_x, CuNi/CuNiO_x, and AgNi/AgNiO_x were essential to yield successful growth of CNTs.

In similar reports, CVD method was used for anchoring densely packed, vertically aligned arrays of CNTs (Fig. 4.164) into silicone layers using spin-coating, CNT insertion, curing, and growth substrate removal [447]. CNT arrays of 51 and 120 μm in height were anchored into silicone layers of thickness 26 and 36 μm, respectively. Alternatively to CVD techniques, the pulse electrodeposition technique was utilized to deposit nanosized (≤10 nm) Ni catalysts on carbon fabric (CF) [448] allowing the growth of carbon nanofibers (CNFs) on CF. The preparation of CNF-coated CF (carpet-like CF) was carried out in a thermal CVD system with an optimum loading of Ni catalysts deposited in the PED pulse range from 20 to 320 cycles. CNFs that grew at 813 K had a hydrophobic surface, like lotus leaves. Among other potential applications for carbon-based nanocarpets, an effective technique for large-scale integration of oriented CNTs inside functional devices, based on capillary assembly and buried dielectrophoresis electrodes allowing aligning and assembling with high accuracy dense CNT carpets, was offered [449].

4.7.7 Nanospindles

Spindle-like nanostructures have been found for a series of elements and inorganic compounds; we note that a certain number of reports are devoted to oxides and salts of rare-earth elements. Frequently, this nanostructural type was formed together with a variety of other structures, such as, for example, nanorods or nanoflowers. For carbon, nanospindles are almost unknown. Thus, the pyrolysis strategy was applied for obtaining robust yolk–shell nanospindles with very sufficient internal void space for high-rate and long-term lithium-ion batteries, in which an Fe₃O₄@Fe₃C core@shell nanoparticle is well confined in the compartment of a hollow carbon nanospindle (Fig. 4.165) [450]. These nanospindles were fabricated in situ thermally annealing the as-made Fe₂O₃@RF core@shell nanospindles at 550 °C. In this structure, a heterogeneous Fe₃O₄@Fe₃C core@shell nanoparticle (15–25 nm) was found to be sandwiched in the compartment of a hollow carbon nanospindle (30 nm in width and 100 nm in length).

4.7.8 Nanowebs

Nanowebs [451] ^{Footnote 25} are of great technological interest since they contain nanowire densities on the order of 10⁹/cm². Nanowebs are beautiful objects, reported for some nonrelative to each other compounds. First of all, we note that a series of porous polymers [452], frequently obtained by electrospinning technique, have been reported in web-like nanoform; here we note only some of them. Nanoweb porous structures are currently applied in filters [453,454,455], fibers [456], and composites [457, 458], in particular those containing carbon nanotubes, for example, MWCNT/poly(ethylene terephthalate) (PET) nanowebs, obtained by electrospinning [459]. It was established that tensile strength, tensile modulus, thermal stability, and the degree of crystallinity increased with increasing MWCNT concentration. Another example of CNTs–polymer composite nanowebs is polyurethane (PU) and PU/MWCNT nanocomposite nanofibers and nanowebs, both with diameters of 350 nm, which were prepared by an electrospinning process from PU DMF solutions [460]. Multifunctional nanowebs were prepared using cyclodextrin-based inclusion complex (CD-IC) to disperse MWCNTs within electrospun polyvinylidene fluoride nanofibrous membranes (PVdF-NFM) [461]. Subsequently, MWCNT(CD-IC)/PVdF-NFM was loaded with gold particles. The Au/MWCNT(CD-IC)/PVdF-NFM was found to be electroactive and showed excellent electrocatalytic activity toward oxidation of ascorbic acid. As an example of non-CNT-containing web-like polymers, we note the octaphenyl-POSS (polyhedral oligomeric silsesquioxane OPPOSS), which was blended with PMMA to prepare inorganic–organic hybrid nanofibers/nanowebs using electrospinning method [462].

Web-like carbon nanotubes (Fig. 4.166) were formed by laser ablation (Nd:YAG laser with 532 nm wavelength, 10.54 W power, 30 min) using a graphite target containing Ni and Co catalysts, each with weight percentage of 10% [463]. It was shown that the diameter of the carbon nanotubes formed using Ni and Co catalysts was between 50 and 150 nm in size. Carbon nanostructures may be precursors of other nanoweb structures. Thus, when carbon nanofilms were deposited on the Si(100) wafers at substrate temperatures from r.t. to 700 °C by ultrahigh-vacuum ion-beam sputtering [464], a nanoweb-like morphology of the crystalline SiC formation was also observed on the surface of film. The much enhanced hardness and Young’s modulus at 700 °C were attributed to the SiC formation as well as nanoweb-like morphology. Additionally, web-like SWCNT structures on the surface of zeolite template (Fig. 4.167) were reported. Carbon-based nanowebs are also readily prepared from natural precursors. Thus, cellulose nanowhisker (CNW), prepared by acid hydrolysis of microcrystalline cellulose, was carbonized at different temperatures in the range of at 800–1200 °C, yielding carbon nanoweb [466]. The better carbon structure was observed when the carbonization temperature was higher.

A considerable part of carbon nanoweb applications is related with their uses in supercapacitors and lithium batteries. Thus, air-electrode architecture based on 3D open macroporous carbon nanowebs was found to be particularly advantageous for Li-O₂ batteries utilizing the redox mediators in the electrolyte by facilitating the efficient transport [467]. Oxygen- and nitrogen-doped carbon nanowebs were applied as an efficient, metal-free ORR catalyst for hybrid Li-air batteries [468]. The oxygen- and nitrogen-doping led to highly active pyridone species on the carbon nanoweb surface for ORR. Also, uniform Li₄Ti₅O₁₂/carbon composite nanowebs with high surface area and porosity consisting of ultrasmall crystals in carbon core–shell architecture were prepared by thermal pyrolysis and oxidation of a composite of electrospun lithium–titanium/polyacrylonitrile nanowebs in argon atmosphere [469]. This composite was found to be a promising anode candidate for lithium-ion batteries. In addition, high-performance wearable supercapacitor (area capacitance of 2.5 mA cm⁻²) fabrics based on flexible metallic fabrics (Ni–cotton), on which nanofiber webs containing MWCNTs are directly electrospun without the need for any post-treatment, was fabricated (Fig. 4.168) [470]. Such supercapacitor fabrics can be integrated into commercial textiles with any desirable forms.

Catalytic applications are also common. Thus, studying Co₃O₄/CNW bifunctional catalysts (Fig. 4.169), individual functionality of Co₃O₄ and the N-doped carbon nanoweb (CNW) in ORR and OER was investigated [471] by rotating disk electrode measurements. It was found that Co₃O₄ alone exhibited poor ORR catalytic activity, but, in the presence of CNW, it assisted the selective four-electron oxygen reduction over the two-electron pathway. CNW underwent serious degradation at the high potential of the OER, but its stability improved greatly upon the deposition of Co₃O₄.

4.7.9 Nanosponges

Carbon-based nanosponges are normally prepared by CVD, although they can be also obtained by laser ablation (see below) or by a pulsed microplasma cluster source [472] in the presence of a metal–organic catalyst (Fig. 4.170), and are of the permanent interest for the purposes of oil adsorption. Thus, carbon nanostructures (nanotubes, nanofibers, and nanosponges, identified as a mixture of sp² and sp³ hybridizations) were synthesized onto Si (001) substrates using a microwave-assisted plasma-enhanced CVD (PECVD) from C₂H₂–Ar mixtures at low substrate temperatures (120 °C) [473]. For the higher C₂H₂ partial pressures, dense sponge-like (nanosponge) structures, consisting of a large number of bundles, were formed, in a difference with less C₂H₂ partial pressures, when other nanostructures were observed. Boron-infused carbon nanosponge can be applied for oil absorption,^{Footnote 26} reaching nearly 100% of the oil [474]. It was revealed that sponges with higher amounts of boron infused into them are able to achieve the special properties of boron that helped increased the surface area and the extremely oleophilic nature of the sponge.

Similar ultra-lightweight 3D architectures consisting of boron-doped MWCNTs (CB_XMWNTs , macroscale (cm³ in size), entirely made up of randomly orientated and entangled CNTs with little to no amorphous carbon, Fig. 4.171), were grown directly onto the walls of a quartz tube furnace via an aerosol-assisted catalytic CVD method using triethylborane as the boron source [475]. Boron was found to be responsible for the creation of “elbow-like” junctions and covalent nanojunctions. CB_XMWNTs can be used as sorbent materials (in particular, for oil), hydrogen storage, and flexible conductive scaffolds as porous 3D electrodes. Also, CVD synthesis of carbon nanotubes and nanofibers on the surface of expanded vermiculite was used to produce a highly hydrophobic floatable absorbent to remove oil spilled on water [476]. It was shown that the carbon nanotubes and nanofibers grew on FeMo catalyst impregnated on the vermiculite surface to form a “sponge structure.” As a result of these carbonaceous nanosponges, the absorption of different oils remarkably increased ca. 600% with a concomitant strong decrease of the undesirable water absorption.

SWCNT bundles dispersed in a highly polar fluid were found to agglomerate into a porous structure (Fig. 4.172) being exposed to low levels of laser radiation (514.5 nm) in DMF [477]. An interesting effect was observed: under laser illumination, the bundles agglomerate, leading to a substantial decrease in the measured sound velocity (significantly lower than that of pure DMF, though the SWCNT bundles have a much higher sound speed than the DMF) with increasing SWCNT concentration.

4.7.10 Nanofoams

Currently, nanofoams^{Footnote 27} are known for a series of elements and compounds, mainly for carbon [478], and are applied, in particular, as materials for supercapacitors [479,480,481] and cathode catalysts for Li–O₂ batteries [482, 483]. Fundamental properties of high-quality uniform carbon nanofoams , comprised of predominantly sp²-type carbon, were recently studied, hydrothermally producing them with different densities by changing the process temperature in the autoclave reactor [484]. The low-density foams were found to consist of micropearls with ≈2–3 μm average diameter, and higher-density foams contained larger-sized micropearls (≈6–9 μm diameter), frequently coalesced to form nonspherical μm-sized units. With higher autoclave temperature, the carbonization process became more effective, leading to an increase in sphere size and a thickening of the internal wall structure. Among other conclusions, the nanofoam materials exhibit physical properties originating from a mixture of carbon atoms with sp² and sp³ hybridization. This was also confirmed by DFT calculations [485]. The foam may accommodate the same type of defects as graphene (Fig. 4.173). In addition, a fundamental theoretical finding of the re-emergence of superconductivity in heavily compressed CaC₆ and formation of carbon nanofoam in these conditions was reported [486].

Laser ablation is one of techniques leading to carbonization and foam formation [487]. The corresponding equipment is shown in Fig. 4.174 [488]. Thus, high-repetition-rate laser ablation and deposition of carbon vapors resulted in the formation of quite different carbonaceous structures depending on the pressure of the ambient Ar gas in the chamber [489]. Diamond-like carbon films formed at a pressure below ~ 0.1 Torr, whereas a diamond-like carbon nanofoam (Fig. 4.175) was created above 0.1 Torr. The bulk density of various foam samples was found to be in the range (2–10) × 10⁻³ g/cm³, and the specific surface area was 300–400 m²/g. Carbon nanofoams (CNFs) were also prepared [490] by air cooling the pyrolysate of high purified acetylene gas. Each particle of the nanofoam was constructed by 2 to 4 mutually nested carbon balls with ~300 nm in diameter. Undoubted room-temperature ferromagnetism with saturation magnetization of 0.11 emu/g at 300 K in CNFs can be attributed to the carbon balls themselves instead of impurities. Additionally, within foam-like carbon, onion concentric fullerene-like structures (see details below) can be formed [491]. It was shown that an optimal annealing temperature of 4000 K is required to form well-ordered onions concentric fullerene-like spheres. The onions formed from the outer layer first, and a model was offered in which the background pressure must be sufficient to allow atoms to cluster, yet low enough to allow annealing into well-ordered onions.

4.7.11 Nanoladders

A series of reports are devoted to carbon nanotube ladder-like structures. Thus, various single-walled CNTs (SWCNTs) and double-walled CNTs (DWCNTs) having different diameters were used as containers for cubic octameric H₈Si₈O₁₂ molecules (Fig. 4.176) [492]. Depending on the diameter of the CNTs, two types of structures were formed inside the CNTs: in the case of those CNTs having inner diameters ranging from 1.2 to 1.4 nm, an ordered self-assembled structure composed of H₈Si_4nO_8n-4 molecules was formed through the transformation of H₈Si₈O₁₂; in the case of CNTs having inner diameters larger than 1.7 nm, a disordered structure was formed, indicating strong interactions between the CNTs and the encapsulated H₈Si_4nO_8n−4 molecules. Also, multiwalled carbon nanotubes (MWCNTs) were uniformly grown directly on metal-catalyzed carbon fibers by catalytic decomposition of acetylene at ~700 °C using thermal CVD process, accompanying by formation of various carbon nanostructures such as nanofilaments, nanofibers, nanoladders (Fig. 4.177), nanospirals, nanojunctions, nanocones, nanoonions, etc. accompanying nanotubes [493]. The authors noted that precise control of the process parameters was extremely important to grow a desired morphology; otherwise it could result in a wide variety of undesired carbon nanospecies too.

4.8 “Nanotechnical” Structures and Devices

4.8.1 Nanosprings/Nanocoils/Nanospirals

Helix-shaped nanostructures are described in available literature as nanosprings, nanocoils,^{Footnote 28} and nanospirals. These structures are generally reviewed among other related nanoforms (such as nanowires, nanorods, or nanoneedles) [494, 495]. Computational quantum chemistry design of nanospirals was also reported [496]. As well as majority of other related nanostructures, helix nanostructures are represented mainly by inorganic compounds, in particular carbon nanotubes [497, 498] and other carbon nanoforms. Thus, a constant-force nanospring might be formed from a configuration of concentric carbon nanotubes (Fig. 4.178), where the van der Waals force provided the extension-independent restoring force [499]. A telescoped nanotube with only one active (sliding) surface pair was expected to act as a constant-force spring. A fully telescoped MWCNT (Fig. 4.179) originally had nine walls, with an outer diameter of 8 nm and an inner diameter of 1.3 nm.

Carbon microcoils can be prepared by catalytic CVD of acetylene, using Ni as the catalyst and thiophene as the promoter [500]. A catalyst (ball-milled nickel sulfide) was developed on purpose to avoid the introduction of noxious and unpleasant thiophene during the reaction process. Additionally, coil-in-coil [501] carbon nanocoils (CNCs, Fig. 4.180) were similarly synthesized by means of acetylene decomposition using nickel nanoparticles as catalysts. It was revealed that there were often several CNCs self-assembled in one nanospring. The yield of coil-in-coil CNCs was high up to 11 g in each run at the decomposition temperature of 450 °C. Among metal–carbon composite helices, tungsten-containing carbon (WC) nanosprings fabricated by focused-ion-beam CVD (FIB-CVD) using a source gas mixture of phenanthrene and W(CO)₆ showed unique characteristics they could expand and contract as flexibly as macroscale springs [502]. It was found that the spring constants of the springs rose as the tungsten content increased.

Diamond-like carbon (DLC) nanowires were used to compose nanosprings fabricated by focused-ion-beam CVD (FIB-CVD) [503]. The DLC nanowires of the as-grown nanosprings had elastic double structures, in which a 50-nm-diameter core containing 3-at.% gallium in addition to carbon was enclosed in an outer 25-nm-wide DLC shell. It was revealed that the carbon densities of the core and the shell were similar, indicating that the density of the core was higher than that of the shell owing to the incorporation of Ga into the core. However, the core density was approximately halved by 800 °C annealing. This was attributed to the vaporization of Ga and the movement of C from the core to the shell.

An individual carbon nanocoil was clamped between two AFM cantilevers and loaded in tension to a maximum relative elongation of ~42% [504]. The nanocoil behad like an elastic spring with a spring constant K of 0.12 N/m in the low strain region. No plastic deformation was detected. In several reports, nanocoil-like structures have been investigated by MD simulations, for instance, their elastic behavior [505]. Also, the instability of a freestanding one-sided hydrogenated/fluorinated graphene nanoribbon, i.e., graphone/fluorographene, was studied using ab initio, semiempirical, and large-scale MD simulations (Fig. 4.181) [506]. Freestanding semi-infinite armchair-like hydrogenated/fluorinated graphene (AC-GH/AC-GF) and boatlike hydrogenated/fluorinated graphene (B-GH/B-GF) (nanoribbons which are periodic along the zigzag direction) are unstable and spontaneously transform into spiral structures. The spiral structures exhibited strong mechanical rigidity that prevents them from unrolling. Possible applications of carbon nanosprings and related structures can be related with adjustment of the viscoelasticity and reduction of the resulting hysteresis loss of elastomeric polymer materials [507].

4.8.2 Nanothermometers

Several reviews on nanothermometers have been published [508, 509], in particular those describing nanothermometers using liquid metals and nanotubes of oxides (e.g., In₂O₃, MgO, SiO₂) [510,511,512]. But the first and the most important example of these nanodevices consisted on carbon nanotubes. Thus, a nanothermometer on the basis of carbon nanotubes was synthesized in a vertical radio-frequency furnace (which differs from a one-step arc-discharge method) [513]. In a related work [514], an interesting concept was proposed for an electromechanical nanothermometer. The temperature measurements were performed by measuring the conductivity of the nanosystem on the CNT basis (shuttle nanothermometer with a movable outer wall and the telescopic nanothermometer with a movable inner wall, Fig. 4.182), which depends substantially on the temperature due to the relative thermal vibrations of nanoobjects forming the nanosystem. It was shown that this nanothermometer can be used for measuring the temperature in localized regions with sizes of the order of several hundred nanometers. Also, the systems of the shuttle nanothermometer with a movable inner wall and the telescopic nanothermometer with a movable outer wall are also possible. In addition, the mechanics of CNTs constituting two well-known configurations for nanothermometer, namely, shuttle configuration and telescope configuration, were fully investigated [515]. It was found that these geometrical parameters have a considerable effect on the potential energy.

A homogeneous mixture of Ga₂O₃ and pure, amorphous, active carbon (weight ratio, 7.8:1) was reacted in an open carbon crucible under a flow of pure N₂ gas: at 1360 °C, the reaction 4.22 occurred. However, on the inner surface of a pure graphite outlet pipe at the top of the furnace, the temperature was lower (around 800 °C), causing the reaction 4.23 to occur, during which the “nanothermometers” (Fig. 4.183) were created. As an improvement of this technique, the following oxidation-assisted approach was proposed [516]. When a Ga-filled carbon nanotube was heated in air for an appropriate length of time, an oxide marker was formed on the inner wall of the carbon nanotube due to partial oxidation of the gallium. Thus, the temperature to which the nanotube was exposed can be retrieved by progressively heating the carbon nanotube until the liquid gallium reached the oxide marker. Additionally, it was found that Ga-filled carbon nanotubes possess a unique combination of two types of conductivity: low-resistive Ga-filled nanotube segments and relatively high-resistive empty nanotube regions [517]. It was possible to produce gaps in the Ga filling of any required length by AFM indentation, thus affecting the nanotube electrical properties.

$$ {\mathrm{Ga}}_2{\mathrm{O}}_3\left(\mathrm{solid}\right)+2\mathrm{C}\left(\mathrm{solid}\right)\to {\mathrm{Ga}}_2\mathrm{O}\left(\mathrm{vapor}\right)+2\mathrm{C}\mathrm{O}\left(\mathrm{vapor}\right) $$

(4.22)

$$ {\mathrm{Ga}}_2\mathrm{O}\left(\mathrm{vapor}\right)+3\mathrm{CO}\left(\mathrm{vapor}\right)\to 2\mathrm{Ga}\left(\mathrm{liquid}\right)+\mathrm{C}\left(\mathrm{solid}\right)+2{\mathrm{CO}}_2\left(\mathrm{vapor}\right) $$

(4.23)

In addition to gallium-filled CNTs, described above, indium-filled carbon nanotubes (diameters of 100–200 nm and length of ~10 μm) were synthesized via a CVD technique [518]. It was shown that the melting and expansion behavior of indium were different from that in a macroscopic state allowing to clarify the problems of indium filling usage in carbon nanotube-based nanothermometer. Fabrication of non-filled CNTs nanothermometers is also possible; thus, an interesting concept was proposed for an electromechanical nanothermometer [519, 520]. In this device, the temperature measurements were performed by measuring the condition of the nanosystem (CNTs), which depends substantially on the temperature due to the relative thermal vibrations of nanoobjects forming the nanosystem. It was shown that this nanothermometer can be used for measuring the temperature in localized regions with sizes of the order of several hundred nanometers.

Nanothermometers, on the basis of CNTs or other inorganics, have been applied also for biological systems . Thus, filled carbon nanotubes (Fig. 4.184) have potential to act as sensors that might provide noninvasive temperature control in biological systems on a cellular level; in this case the temperature can be detected by measuring NMR parameters on the filling materials [521]. The most temperature-sensitive parameter was found to be the [126] spinlattice relaxation rate in CuI-CNT which can provide the temperature detection with an accuracy of 2 K. The beneficial feature of a carbon nanotube was to provide protection of both (i) a human body against toxic adverse effects from the filling material and (ii) a filling material against chemical and biochemical exposure.

Another approach, without use of CNTs, was applied for creation of another type of nanothermometers on carbon nanodots basis. Thus, temperature measurements in biology and medical diagnostics are of great importance; however, it still faces significant challenges. To develop this area, a “turn-on” carbon-dot-based fluorescent nanothermometry device for spatially resolved temperature measurements in living cells was presented [522]. p-Phenylenediamine was carbonized by microwave irradiation in an ethanol/H₂O solution to form CNDs (Fig. 4.185). Red-emitting CNDs can be utilized for “turn-on” fluorescent nanothermometry through the fluorescence quenching and recovery processes, respectively (Fig. 4.186). In a related report [523], the nanothermometer was based on biocompatible fluorescent carbon nanodots (CDs) obtained via one-step microwave-assisted synthesis too and two kinds of polymers, including thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and non-thermosensitive polyethylene glycol (PEG) (Fig. 4.187). When heating up above the lower critical solution temperature (LCST) of PNIPAM, hydrophobic phase transition occurred to PNIPAM, and the nanothermometer evolved into the core–shell–corona structure, with a freshly formed and collapsed PNIPAM shell. The fluorescence response to temperature of the MSCD can be followed through gradual heating up from 20 to 50 °C (Fig. 4.188). In addition to microwave-assisted synthesis, carbon nanodots, to be used as nanothermometers, can be prepared solvothermally [524] or by simple heating of C₃N₄ and ethanediamine at 80 °C for 12 h yielding N-doped carbon dots [525].

4.8.3 Nanotweezers

CNT nanotweezers are well-known objects in the nanoworld [526, 527]. Thus, both bent-type and straight-type nanotweezers based on two carbon nanowires by means of localized CVD using a focused ion beam (FIB-CVD) were demonstrated [528]. The location, dimension, and gap between the two nanowires were precisely controlled such that the tweezing motion and the operation voltage can be easily adjusted. Potential applications of these nanotweezers include manipulation of nanoparticles and nanoscale objects. Also, a method to make a nanotweezer composed of two CNT arms was offered [529]. The CNT arm was fabricated by attaching a multiwalled carbon nanotube on a tungsten tip via manual assembly. Since each CNT arm has a macro-actuator, namely, a separated tweezer arm, it was possible to close and open the nanotweezer repeatedly. Electrochemical etching was used to cut the carbon nanotube in the CNT arm, and the cutting resolution was ~ a few hundred nanometers.

In addition to CNTs-based nanotweezers, carbon nanotubes themselves can be objects for manipulations by organic/organometallic spacers on porphyrin and pyrene basis acting as nanotweezers. Thus, host–guest chemistry for separation of CNTs according to diameter, metallicity, and even handedness was developed using host molecules named “nanotweezers” consisting of a rigid core and two receptors and suitable for CNT separation (Figs. 4.189 and 4.190) [530]. These nanotweezers are much deeper and wider cavities to accept CNTs and much more interactions of π–π and C–H–π to make CNT complexes much more stable.

4.8.4 Nanocars and Nanotrucks

Nanocars , being developed by research group of James M. Tour [531,532,533,534,535,536,537], are “molecular machines consisting of molecular-scale chassis, axles and wheels that can directionally roll across solid surfaces.” Two complementary approaches can be considered in fabrication of miniaturized devices: [538] (a) the top-down approach, which reduces the size of macroscopic objects to reach an equivalent microscopic entity using photolithography and related techniques and (b) the bottom-up approach, which builds functional microscopic or nanoscopic entities from molecular building blocks. These nanocars are mainly based on carborane and fullerene wheels; additionally, a class of molecular wheels was developed based on a trans-alkynyl(dppe)₂ruthenium complex [539, 540]. The low rotation barrier around the alkyne bond in this complex allows a free rotation of the wheel, while the bulky phosphine ligands offer good interactions with metallic surfaces.

A motorized nanocar (Fig. 4.191) was synthesized which bears a light-activated unidirectional molecular motor and an oligo(phenylene ethynylene) chassis and axle system with four carboranes to serve as the wheels [541]. His proposed propulsion scheme is shown in Fig. 4.192.

Design, syntheses (Fig. 4.193) by in situ ethynylation of fullerenes, and testing of fullerene-wheeled single molecular nanomachines (Fig. 4.194), namely, nanocars and nanotrucks, composed of three basic components that include spherical fullerene wheels, freely rotating alkynyl axles, and a molecular chassis, were also presented [542, 543]. The use of spherical wheels based on C₆₀ and freely rotating axles based on alkynes permitted directed nanoscale rolling of the molecular structure on gold surfaces. The obtained nanocars were stable and stationary on the gold surface at room temperature for a wide range of tunneling parameters. The authors attributed their stability to a relatively strong adhesion force between the fullerene wheels and the underlying gold.

4.8.5 Nanobalances

The nanobalance for applying a voltage across the nanotube and its count electrode was constructed on the basis of carbon nanotubes (have diameters of 5–50 nm and lengths of 1–20 μm), produced by an arc-discharge technique and agglomerated into a fiber-like rod [544]. The specimen holder required the translation of the nanotube via either mechanical movement by a micrometer or axial directional piezo. The carbon nanotube can be charged by an externally applied voltage. The induced charge is distributed mostly at the tip of the carbon nanotube and the electrostatic force results in the deflection of the nanotube (Fig. 4.195). The nanotube is a very flexible structure, and it can be bent to 90° and still recovers its original shape. Additionally, the mass of a particle attached at the end of the spring (Fig. 4.196) can be determined if the vibration frequency is measured, provided the spring constant is calibrated. This “nanobalance” (the most sensitive and smallest balance in the world) was shown to be able to measure the mass of a particle as small as 22 ± 6 fg (1 f = 10⁻¹⁵). Other nanobalances have been described in [545,546,547].

4.8.6 Nanomesh

Several carbon-based mesh^{Footnote 29}-like nanostructures are known, in particular those of C₆₀ and graphene [548]. A variety of precursors and physical, chemical, and biological methods to create channels have been used. Thus, a new graphene nanostructure, called by authors [549] as a graphene nanomesh, can open up a bandgap in a large sheet of graphene to create a semiconducting thin film. These nanomeshes were prepared using block copolymer lithography and can have variable periodicities and neck widths as low as 5 nm. Graphene nanomesh field-effect transistors can support currents nearly 100 times greater than individual graphene nanoribbon devices, and the on–off ratio, which is comparable with the values achieved in individual nanoribbon devices, can be tuned by varying the neck width. Among other related publications, hexagonal graphene nanomeshes with sub-10 nm ribbon width were fabricated [550].

Local photodegradation of graphene oxide sheets at the tip of ZnO nanorods was used to achieve semiconducting graphene nanomeshes (Fig. 4.197) [551]. These graphene nanomeshes contained smaller O-containing carbonaceous bonds and higher defects as compared to the as-prepared graphene oxide sheets. An extended 2D C₆₀ nanomesh was fabricated by controlling the binary molecular phases of C₆₀ and pentacene on Ag(111) [552]. The skeleton of the C₆₀ nanomesh was found to be stabilized by the strong molecule–metal interfacial interactions [C₆₀-Ag(111) and pentacene-Ag(111)] and was further modified by the pentacene-C₆₀ donor–acceptor intermolecular interactions. This C₆₀ nanomesh can serve as an effective template to selectively accommodate guest C₆₀ molecules at the nanocavities.

CVD method was applied to prepare carbon nanomesh (CNM, Figs. 4.198 and 4.199) with MgAl-layered double oxides (LDO) as sacrificial template and ferrocene as carbon precursor [553]. This hexagonal thin-sheet CNM featured a hierarchical pore system consisting of micropores and small mesopores with a size range of 1–6 nm and a great number of random large mesopores with a pore size of 10–50 nm and was found to be suitable as supercapacitor electrode. The in-plane large mesopores serve as fast ion channels across the carbon thin sheets, which helps to greatly accelerate the ion kinetic in the interior of the electrode, resulting in an improved capacitive performance. A graphene nanomesh was also prepared through UV-mediated oxidation of a graphene oxide film in air (Fig. 4.200) [554]. It was observed that a nanoporous network structure was progressively produced in the basal plane, which can be attributed to the fact that highly ROS (UV-generated O₃) preferentially attack sp³ carbon-rich regions of the GO. The field-effect transistors were fabricated using graphene nanomesh as the active channel. Finally, in order to produce nanostructured channels of SWCNTs for localized active devices such as local bottom-gated field-effect transistors (FETs), a biologically templated approach in combination of microfabrication processes was offered, assembling in solution a large-scale nanostructured network, nanomesh, of SWCNTs using an M13 phage [555].

In addition to classic chemicals, carbon-rich natural wastes have been also used as carbon nanomesh precursors, for instance, biowaste-poplar catkins [556]. Their in situ calcination (at 600 °C) etching with Ni(NO₃)₂⋅6H₂O and KOH in N₂ flow combined with an acid dissolution technique led to the formation of hollow activated carbon nanomesh (PCACM) with a hierarchical porous structure (Fig. 4.201, reactions 4.24–4.31). PCACM kept the natural tubular morphology of poplar catkins with a fascinating nanomesh structure on the walls, large specific surface area (S_BET = 1893.0 m² g⁻¹), and high pore volume (V_p = 1.495 cm³ g⁻¹). The formed nanomesh has potential uses as electrode materials for supercapacitors. Together with applications as transistors [557], this use of nanomesh is typical for various nanocarbons.

$$ 2\mathrm{Ni}{\left({\mathrm{NO}}_3\right)}_2=2\mathrm{Ni}\mathrm{O}+2{\mathrm{NO}}_2 $$

(4.24)

$$ \mathrm{C}+6\mathrm{KOH}=2{\mathrm{K}}_2{\mathrm{CO}}_3+2\mathrm{K}+3{\mathrm{H}}_2 $$

(4.25)

$$ {\mathrm{K}}_2{\mathrm{CO}}_3={\mathrm{K}}_2\mathrm{O}+{\mathrm{CO}}_2 $$

(4.26)

$$ {\mathrm{K}}_2{\mathrm{CO}}_3+2\mathrm{C}=2\mathrm{K}+3\mathrm{CO} $$

(4.27)

$$ {\mathrm{K}}_2\mathrm{O}+\mathrm{C}=2\mathrm{K}+3\mathrm{CO} $$

(4.28)

$$ 2\mathrm{K}+2{\mathrm{H}}_2\mathrm{O}=2\mathrm{K}\mathrm{OH}+{\mathrm{H}}_2 $$

(4.29)

$$ \mathrm{KOH}+\mathrm{HCl}=\mathrm{KCl}+{\mathrm{H}}_2\mathrm{O} $$

(4.30)

$$ \mathrm{NiO}+2\mathrm{HCl}={\mathrm{NiCl}}_2+{\mathrm{H}}_2\mathrm{O} $$

(4.31)

4.8.7 Nanojunctions

Nanojunctions are known mainly for metals, although some oxides and other compounds have also been reported. For carbon allotropes, the available data are highly limited [558]. Thus, Fe₃W₃C/WC/graphitic carbon (GC) ternary nanojunction hybrids were synthesized through a solid-state pyrolysis process to be used for dye-sensitized solar cells (DSSCs) [559]. Using hybrid counter electrodes on their basis, a photoelectrical conversion efficiency of 7.1% was achieved (for comparison: pure GC – 5.02%, WC/GC hybrids – 6.11%). DFT calculations were used to study electronic properties and doping and structural defects in carbon nanojunctions, for instance, to investigate charge transport in pentacene–graphene nanojunctions employing DFT calculations and the Landauer transport formalism [560]. It was revealed that the unique electronic properties of graphene strongly influence the transport in the nanojunctions. The charge transport was found to be strongly influenced by the edge structure of the graphene electrodes. The behavior of B-doped defects in nanodevice carbon heterojunctions was investigated by DFT for 36 different heterojunction CNTs [561]. Among other discoveries, the highest surface reactivity was found for the B-doped zigzag–armchair heterojunctions, followed by B-doped armchair–armchair heterojunctions, and the smallest surface reactivity is for B-doped zigzag–zigzag heterojunction CNTs. Similarly, quantum conductance of silicon-doped carbon wire nanojunctions was evaluated [562].

4.8.8 Nanopaper

Nanopapers^{Footnote 30} are known, in particular, for various carbon-containing [563] compounds and are being intensively developed during the last decade. An excellent comprehensive review [564] describes nanopapers on the basis of cellulose; carbon (highly recommended state-of-the-art section on carbon nanopapers); inorganic compounds; electrospun nanopaper; water-repellent nanopaper; fire-retardant nanopapers; electrically and thermally conductive nanopapers; magnetic, photocatalytic, and bioactive nanopapers; and their multiple applications. Carbon nanopapers (“on-woven fibrous entangled assemblies of carbon nanomaterials with a 2D paper-like morphology, held together by van der Waals forces between carbon nanomaterial junctions, similar to ordinary paper made from wood pulp fiber”) are made of carbon-based nanomaterials (e.g., carbon nanofibers, graphene, and CNTs) [565] and nonionic surfactants (e.g., Triton X-100 and sodium lauryl sulfate), which aid their dispersion into aqueous or organic solvents (Fig. 4.202). Another route to the carbon nanopaper is mechanical pressing/rolling. A representative example of a composite nanopaper (binder-free), made of graphite oxide and Si nanoparticles as an anode material for Li-ion batteries, is shown in Fig. 4.203.

Among various types of carbon nanopapers (e.g., those with flame-retardant efficiency [568]), considerable efforts have been recently made, mainly by the research group of H. Lu, in the development of the area of shape-memory materials on their basis, including their manufacturing, characterization, improvement, and development [569]. Thus, the electrical and shape-memory behavior of self-assembled carbon nanofiber (CNF) nanopaper incorporated with shape-memory polymer (SMP) was studied [570, 571]. The CNF nanopaper could have highly conductive properties. Being aligned into the nanopaper upon a magnetic field, CNTs made significantly lower the electrical resistivity of SMP nanocomposites [572]. CNFs were self-assembled to form multilayered nanopaper (Fig. 4.204) to enhance the bonding and shape recovery behavior of SMP, respectively [573]. It was revealed that both glass transition temperature (T_g) and electrical properties of the SMP nanocomposites can be improved by incorporating multilayers of self-assembled nanopapers. In addition, the synergistic effect of self-assembled CNF and boron nitride (BN) nanopaper (Fig. 4.205) on the electrical and thermal properties, and electro-activated shape-memory effect (SME) of polymeric shape-memory nanocomposites , was studied [574]. BN was introduced to improve the thermal conductivity and large dissimilarity of the nanocomposite for enhanced heat transfer and electric-activated shape recovery.

Multifunctional nanocomposites were fabricated using carbon nanopaper sheets [575]. Vapor-grown carbon nanofibers were preformed as carbon nanopaper sheet, resulting in a porous structure with highly entangled carbon nanofibers , which was integrated into the laminates through vacuum-assisted resin transfer molding process. It was revealed that carbon nanopaper sheet was fully integrated to the laminates. Metal-coated carbon nanopapers have been reported too. For instance, after synthesizing a nanopaper (10–20-μm-thick, freestanding sheets of self-assembled SWCNTs), it was decorated with Pt nanoparticles by electroless deposition [576]. Also, the carbon nanopaper sheet, consisting of randomly oriented single-walled nanotubes and vapor-grown carbon nanofibers, was coated with nickel by laser pulse deposition [577].

4.8.9 Nanobatteries

Nanobatteries are fabricated batteries employing nanoscale technology, which can be nano in size or may use nanotechnology in a macroscale battery. In the first case, for example, carbon nanotubes, encapsulating metallic lithium, can potentially act as a miniaturized nanobattery [578]. Such a battery would be potentially useful in the next generation of communication and remote sensing devices, where a pulse of current is required for their operation. Both anode and cathode in nanobatteries can be nanostructured. Talking about carbon materials in Li- and Na-ion batteries, the electrodes can be made or coated with mainly carbon nanotubes, as well as graphite, graphene, and various carbon-based composites to improve their rate capability. High number of reports is observed during the last decade in the field of nanocarbons to be used in batteries [579,580,581,582], so here we present only selected representative recent examples on CNTs composites.

An effective method was offered for the modification of separators in lithium–sulfur batteries [583]. Grafted long-chain molecules and tube-like CNTs were shown to enable the formation of micropores in CNTs, which could accommodate polysulfides. The hydrophilic groups (Fig. 4.206) help trapping polysulfides to suppress shuttle effect. Also, the conductive nature of CNTs also contributes to a decrease in internal resistance. In case of CNTs filled with iron sulfide nanoparticles, prepared [584] by inserting sulfur and ferrocene into the hollow core of CNTs followed by heat treatment, it was found that FeS nanoparticles (15 nm in size) are encapsulated in the tubular cavity of the CNTs (Fe-S@CNTs, Fig. 4.207). The CNTs not only play an essential role in accommodating the volume expansion of the Fe–S nanoparticles but also provide a fast transport path for Li ions. Being used as the anode material of lithium-ion batteries, this material exhibited excellent electrochemical lithium-storage performance in terms of high reversible capacity, good cyclic stability, and desirable rate capability. Also, electrodes on the basis of mesoporous Si-coated CNT composite powders, prepared by combining a sol–gel method and the magnesiothermic reduction process, exhibited excellent cycle and rate performances as anodes in Li-ion batteries, which can be attributed to the efficient accommodation of volume change from mesoporous Si structure and the enhanced electrical conductivity from CNT core [585].

Among other nanocarbons, 3D macroporous CNT foam (see also the section above on nanofoams) was tested as a sulfur cathode for lithium sulfur batteries, revealing stable electrochemical performance with high initial capacity and decent cycleability [586]. A seamless graphene–carbon nanotube (GCNT , Fig. 4.208) electrode contributed to reversibly store Li metal with complete dendrite formation suppression [587]. A full battery based on GCNT-Li/sulfurized carbon (SC) showed high-energy density (752 Wh kg⁻¹ total electrodes, where total electrodes = GCNT-Li + SC + binder), high areal capacity (2 mAh cm⁻²), and cyclability (80% retention at >500 cycles), at the same time being free of Li polysulfides and dendrites that would cause severe capacity fade.

4.8.10 E-Nose and E-Tongue

Electronic instruments mimicking the mammalian olfactory system are often referred to as “electronic noses” (E-noses, Fig. 4.209) [589, 590]. The human nose is widely used as an analytical sensing tool to assess the quality of drinks, foodstuffs, perfumes, and many other household products in our daytime activities and of many products in the food, cosmetic, and chemical industries [591]. However, practical use of the human nose is severely limited by the fact that the human senses of smell is subjective, often affected by physical and mental conditions, and tires easily. Consequently, there is considerable need for a device that could mimic the human sense of smell and could provide an objective, quantitative estimation of smell or odor. Thanks to recent nanotechnology breakthroughs the fabrication of mesoscopic and even nanoscopic E-noses is now feasible in the size domain where miniaturization of the microanalytical systems encounters principal limitations. Electronic noses have provided a plethora of benefits to a variety of commercial industries, including the agricultural, biomedical, cosmetics, environmental, food, manufacturing, military, pharmaceutical, regulatory, and various scientific research fields [592]. Advances have improved product attributes, uniformity, and consistency as a result of increases in quality control capabilities afforded by electronic-nose monitoring of all phases of industrial manufacturing processes.

Among a series of reported E-noses and E-tongues on carbon basis, a portable E-nose based on hybrid carbon nanotube-SnO₂ gas sensors were fabricated using electron-beam (E-beam) evaporation by powder mixing [593]. Doping of carbon nanotube (CNT) improved the sensitivity of hybrid gas sensors, while quantity of CNT had a direct effect on the selectivity to volatile organic compounds, i.e., MeOH and EtOH. Based on the proposed methods, this instrument can monitor and classify 1 vol.% of MeOH contamination in whiskeys. Similar SnO₂–glycine-functionalized carbon nanotube-based electronic nose was used for detection of explosive materials [594]. Wearable electronic nose (CNTs/polymer sensor array) can respond to a variety of complex odors [595]. Detection of cotton damaged by Nezara viridula is useful in agriculture [596]. Other uses of E-noses and E-tongues include determination of the quality of foods and beverages, consisting of several hundred components in different ranges of concentrations (the working principle is shown in Fig. 4.210) [597].

Another rapidly developing area, which could be attributed to this “nanotechnical” section, corresponds to nanoelectromechanical systems (NEMs). We here only note this field of nanotechnology mentioning three new types of nanoelectromechanical systems based on carbon nanotubes, reported in [598]: an electromechanical nanothermometer (see also section above), a nanorelay, and a nanomotor . The nanorelay was a prototype of a memory cell, and the nanoactuator can be used for transformation of the forward force into the relative rotation of the walls. Relative motion of the walls in these nanosystems was defined by the shape of the interwall interaction energy surface. In addition, such rare “technical” carbon nanostructures are nanoturbins (Fig. 4.211) [599], nanogrids [600], and those based on hybrids of fullerenes and carbon nanotubes A⁺@C_n@tubeC_m, called nano-autoclaves [601]. This autoclave was used to dimerize C₂₀. It was shown that (C₂₀)₂ dimer can be really synthesized this way. The advantage of such nano-autoclave is garantized absence of any impurities inside the capsule tube@C_n, so the final dimerization product (C₂₀)₂ does not contain atoms of other chemical elements.

4.9 Nanostructures Classified as Polyhedral

Despite a variety of polyhedron-like nanostructures for other compounds (elemental metals, their oxides or salts), similar data for nanocarbons are relatively rare. In this respect, for geometrical structures with high coordination numbers, important observations on icosahedron and related structures were generalized in a review [602]. The authors emphasized that classical theory of nanoparticle stability predicts that for sizes <1.5–2 nm the icosahedral structure should be the most stable and then between around 2–5 nm, the decahedral shape should be the most stable. Beyond that, face-centered-cubic (FCC) structures will be the predominant phase. However, in the experimental side, icosahedral (I_h) and decahedral (D_h) particles can be observed (Fig. 4.212) much beyond the 5 nm limit. In fact, it is possible to find I_h and D_h particles even in the mesoscopic range. Conversely, it is possible to find FCC particles with a size <1.5 nm. Mechanisms to stabilize fivefold nanoparticles are as follows, among others: internal strain, introduction of planar defects (twins, stacking faults), the introduction of steps, and kinks on the surface, external modification of shape by facet truncation, displacement of the five-fold axis which reduces the elastic energy, and splitting of the fivefold axis.

4.9.1 Nanotriangles

Nanotriangles are very common for gold, but very scarce for nanocarbons [603]. Graphene, nanofiber, nanoonion triangles have been obtained, as well as some their composites. Thus, the electronic shell structure of triangular, hexagonal, and round graphene quantum dots (flakes) near the Fermi level was studied using a tight-binding method [604]. Armchair triangles can be used as building blocks for other types of flakes. The interaction between calf-thymus dsDNA and water-soluble carbon nanoonion (wsCNO) in water followed denaturation of ds (double-stranded) DNA to ss (single-stranded) DNA [605]. The ssDNA concomitantly wrapped the spiky surface of wsCNO to create triangular aggregate (Fig. 4.213) as the building block as observed by time-dependent SEM images. These triangles further aggregate leading to six-petal flower arrangement (Fig. 4.214) via hexagon and finally reach a dead-end network.

Vertically aligned carbon nanofibers were grown by catalytically controlled glow discharge CVD [606] from C₂H₂/NH₃ gas mixture using Ni catalyst, yielding flattened carbon nanostructures (carbon nanotriangles, Fig. 4.215). The morphology and chemical composition of isolated product were found to have a strong dependence upon the growth conditions. In addition, an unusual sp³ hybridization-assembled metallic 3D conductive carbon allotrope, named Tri-carbon (Fig. 4.216), constructed by helical triangle chains and mechanically and dynamically stable at ambient pressure, was computationally reported [607]. High ring strain in the carbon triangle blocks forces the C–C bond in Tri-carbon to be a “bent bond” rather than the common single bond in diamond or the π bond in graphite. The electron density difference for Tri-carbon in comparison with graphite and diamond to gain more insight into the chemical bonding is shown in Fig. 4.217. Tri-carbon is expected to be synthesized by chemical methods, such as the synthesis of cyclopropane derivatives (e.g., triangulane and tetrahedrane).

4.9.2 Nanotetrahedra

Collapse of a carbon nanotube can result in the formation of a nanoribbon, and a switching of the collapse direction yields a nanotetrahedron in the middle of a nanoribbon (Fig. 4.218) [608, 609]. These nanotetrahedron/nanoribbon structures were found to be thermally stable and did not transform into a tubular form up to a temperature at which they were broken off. Studying these processes in detail, it was revealed that chains of carbon nanotetrahedra/nanoribbons (Fig. 4.219) can be formed via sequential switching of the flattening direction of MWCNTs, in which neighboring two nanotetrahedra are connected by a short nanoribbon [610]. It was proposed that the formation of nanotetrahedra chains is caused by a quasiperiodic instability of catalyst iron nanoparticles during the CVD growth. In addition, two adjoining carbon nanotetrahedra were found (Fig. 4.220). The splitting-and-joining process involving only one metal catalyst nanoparticle and a self-folding mechanism (called by authors as the origami mechanism) was offered to explain the process and the formation of these nanoribbons and nanotetrahedra (Fig. 4.221) [611].

4.9.3 Nanocubes

Nanocubes^{Footnote 31} on carbon basis are not so frequently reported as nanocages (see one of sections above). They are mainly prepared by pyrolysis (in particular, pyrolysis of such natural products as rice [612]) and generally have electrochemical (batteries) and electrocatalytic applications [613] (in particular, due to certain advantages being compared with carbon black electrodes,^{Footnote 32} Fig. 4.222) (although other uses, as, e.g., bioimaging [614], have been reported). Thus, high-surface nitrogen-doped porous CNCs with a high surface area, prepared by carbonization from Prussian blue (PB) nanocubes coated with poly(furfuryl alcohol), were used as a support for Pt nanoparticles to be applied as an electrocatalyst for the oxidation of methanol [615]. Similarly, nanocomposites of Pt nanoparticles (3–5 nm) anchored on carbon nanocubes (PtNPs/CNCs, Fig. 4.223) efficiently catalyzed the electrochemical oxidation of glucose [616]. The proposed biosensor displayed relatively wider linear range and lower detection limit for glucose detection; the current response of the electrode retained 93.7% of the initial signal after 20 days storage, demonstrating acceptable long-term stability of the system.

Other carbon nanostructures can also take part as supports for nanocubes of the same PB, like in the case of graphene oxide sheets (GOs)–PB nanocomposites, which were fabricated via a spontaneous redox reaction in a aqueous solution containing FeCl₃, K₃[Fe(CN)₆], and graphene oxide sheets [617]. The products represented PB nanocubes formed on the surface of GOs retaining their excellent electrochemical activity; moreover, the obtained nanocomposites even showed a higher sensitivity toward the electrocatalytical reduction of H₂O₂ than that of MWCNT/PB nanocomposites. Main applications for these nanocomposites could be electrochemical sensor and biofuel cell. Also, (Fe,Co)@nitrogen-doped graphitic carbon (NGC) nanocubes (NCs), obtained via the pyrolysis of polydopamine-encapsulated Fe₃[Co(CN)₆]₂ NCs at 700 °C (Fig. 4.224), showed comparable catalytic activity for oxygen reduction reaction (ORR) to the Pt/C catalyst [618]. It was recommended as a component of highly efficient nonprecious electrocatalysts in order to replace precious metal catalysts for energy conversion application.

Other nanocubes can serve as templates for CNCs. Thus, graphitic carbon nanocubes (GCNCs), prepared by pyrolysis of ZIF-8 nanocubes (Fig. 4.225) [619], resembled the structure of N-doped graphite and exhibited a high photothermal conversion efficiency of 40.4%. They are highly biocompatible and induced an effective photothermal therapy effect under 808 nm irradiation. As the first work on the simultaneous generation of FeN_x and CoN_x active species from crystalline precursors, hollow FeCo-N-doped porous carbon (Fig. 4.226) was obtained by pyrolysis at 900 °C of metalloporphyrinic MOFs, PCN-224-FeCo, with adjustable molar ratio of Fe^II/Co^II alternatively residing inside the porphyrin center and was shown to be suitable for efficient electrocatalysis for ORR reactions [620].

An example of carbon nanocube use as containers is homogenous poly(3,4-ethylenedioxythio-phene) (PEDOT)-coated multi-chambered micro-/mesoporous carbon nanocube encapsulated sulfur (P@CNC-S) composites (Fig. 4.227), which can serve as polysulfide reservoirs for lithium–sulfur batteries (Fig. 4.228) [621].

4.9.4 Nanoprisms

Nanocarbons in nanoprism form are rare. Thus, large-area vertically aligned uniform-shape carbon hexagonal nanoprism (30 nm in diameter, 30° internal angles, Fig. 4.229) arrays were grown (Figs. 4.230 and 4.231) on molybdenum substrates by the catalyst-assisted pulsed laser deposition techniques [622]. The sample of these nanoprism arrays showed better field emission behavior than that with aligned carbon nanorod arrays.

Notes

1.
Reproduced with permission of Nature (Nature Chemistry, 2012, 4, 195–200).
2.
Reproduced with permission of the Royal Society of Chemistry (J. Mater. Chem., 2012, 22, 24230–24253).
3.
Reproduced with permission of the American Chemical Society (J. Phys. Chem. C, 2010, 114, 12062–12068).
4.
Reproduced with permission of Nature (upper image: Nature Mater., 2016, 15, 634–640).
5.
Reproduced with permission of the American Chemical Society (image below: ACS Nano, 2013, 7(11), 10075–10082).
6.
The name carbyne has been adopted to indicate an infinite sp-carbon wire as a model system; meanwhile carbynoid structures have been used to indicate finite systems or moieties comprising sp-carbon in amorphous systems.
7.
Reproduced with permission of Wiley (Phys. Status Solidi, 2010, 247(8), 2017–2021).
8.
The nanopencil image above in the subtitle is reproduced with permission of the John Wiley and Sons (Adv. Funct. Mater., 2006, 16, 410–416).
9.
Other combinations between carbon allotropes are known, for instance, carbon nanodots immobilized on single-walled carbon nanotubes (Chem. Sci., 2015, 6, 6878–6885).
10.
The nanopeapod image above in the subtitle is reproduced with permission of the Elsevier Science (Carbon, 2015, 95, 302–308.).
11.
See sections above on carbynes and carbon-atom wires, which are also carbon chains of lesser size.
12.
The nanobar image above in the subtitle is reproduced with permission of the American Chemical Society (Nano Lett., 2007, 7(4), 1032–1036).
13.
The nanobrick image above in the subtitle is reproduced with permission of the American Chemical Society (Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, United States, March 22–26, 2009, POLY-333.). Nanobricks are closely related to nanoblocks (Chinese Journal of Catalysis, 2016, 37(8), 1275–1282).
14.
The images of nanobelts are reproduced with permission of the Elsevier Science (Carbon, 2008, 46, 741–746).
15.
The nanobottle image above in the subtitle is reproduced with permission of the American Chemical Society (J. Am. Chem. Soc., 2006, 128, 2520–2521).
16.
Sometimes referred as nanohorns.
17.
The nanocone images above in the subtitle are reproduced with permission of the Elsevier Science (Vacuum, 2016, 134, 40–47.) (right) and from the Web site https://www.forskningsradet.no (left).
18.
The nanospike image above in the subtitle is reproduced with permission of the Wiley (ChemistrySelect, 2016, 1, 6055–6061).
19.
The nanoring image is reproduced with permission of the Elsevier Science (left: Computational Materials Science, 2008, 43, 943–950; right: Chemical Physics Letters, 2007, 433, 327–330).
20.
The nanotorus image is reproduced with permission of the American Chemical Society (left: J. Phys. Chem. C, 2009, 113, 19123–19133) and APS Physics (right: Phys. Rev. B, 2015, 91, 165433.).
21.
Image above is reproduced with permission of the American Chemical Society (ACS Nano, 2010, 4(8), 4396–4402).
22.
More detailed information on the carbide-derived carbons see in the chapter below.
23.
The VFD is a microfluidic device that has been used for disassembling self-organized systems, exfoliation of graphite and hexagonal boron nitride, wrapping multilayer graphene sheets around algal cells, and controlling the particle size and distribution of decorated metal nanoparticles on various carbon nanomaterials.
24.
The nanocage image is reproduced with permission of Nature (Sci. Rep., 2014, 4, 4437).
25.
Nanocubes will be discussed in the section below, dedicated to polyhedral-like carbon nanostructures.
26.
The nanocapsule images above are reproduced with permission of Elsevier Science (left, Materials Chemistry and Physics, 2010, 122, 164–168) and Hindawi (right, Journal of Nanotechnology, Volume 2012, Article ID 613746, 6 pp.).
27.
The nanotree image above is reproduced with permission of the American Chemical Society (Nano Lett., 2009, 9(1), 239–244).
28.
The nanobush image above was reproduced with permission of the American Institute of Physics (Appl. Phys. Lett., 2006, 89, 223102).
29.
The nanomushroom image above was reproduced with permission of the Royal Society of Chemistry (Chem. Commun., 2009, (24), 3615–3617.).
30.
The nanoflower image above was reproduced with permission of the American Chemical Society (J. Phys. Chem. B, 2005, 109, 10779–10785).
31.
The nanobouquet image above was reproduced with permission of the http://radio-weblogs.com/0105910/2004/06/22.html
32.
The nanograss image above was reproduced with permission of the American Chemical Society (J. Phys. Chem.C, 2010, 114(7), 2936–2940.).
33.
The nanoworm image above was reproduced with permission of the American Chemical Society (J. Phys. Chem. C, 2008, 112(1), 106–111).
34.
Image reproduced with permission of the Royal Society of Chemistry (J. Mater. Chem., 2006, 16(29), 2984–2989).
35.
The nanobowl image is reproduced with permission of the American Chemical Society (Langmuir, 2009, 25(3), 1822–1827).
36.
The nanoplate image is reproduced with permission of the American Chemical Society (ACS Appl. Mater. Interfaces, 2016, 8(43), 29628–29636).
37.
We note that KOH activation was also used for other nanocarbons (see previous sections).
38.
The nanobrush image above is reproduced with permission of Springer (J. Mater. Sci. Mater. Med. 2015, 26(1), 5356).
39.
The nanocarpet image above is reproduced with permission of the American Chemical Society (Nano Lett., 2005, 5(12), 2394–2398).
40.
The nanoweb image above is reproduced with permission of the Elsevier Science (Energy, 2013, 55, 925–932).
41.
The nanosponge images above are reproduced with permission of Nature (Sci. Rep., 2012, 2, Article number: 363).
42.
Applications of nanomaterials for oil remediation were recently reviewed. (a) Journal of Petroleum Science and Engineering, 2014, 122, 705–718; (b) Nanomaterial-based methods for cleaning contaminated water in oil spill sites. In: Nanotechnology for Energy Sustainability. B. Raj, M. Van de Voorde, Y. Mahajan (Eds.), Wiley-VCH, 2016, 1139–1160.).
43.
The nanofoam image above is reproduced with permission of the Springer (Nanoscale Res. Lett., 2013, 8, 233).
44.
The nanocoil images above are reproduced with permission of AIP Publishing Co. (up, AIP Adv., 2015, 5, 117114.) and Elsevier Science (down, Comput. Mater. Sci., 2012, 55, 344–349).
45.
The nanotweezer image is reproduced with permission of the American Chemical Society (J. Am. Chem. Soc., 2012, 134, 9183–9192).
46.
The nanomesh images above are reproduced with permission of the Royal Society of Chemistry (J. Mater. Chem. A, 2017, 5, 9709–9716).
47.
The nanojunction image above is reproduced with permission of the American Chemical Society (J. Phys. Chem. Lett., 2013, 4(5), 809–814).
48.
The nanopaper image above is reproduced with permission of the Elsevier Science (Composites: Part B, 2012, 43, 3293–3305).
49.
The nanobattery image above is reproduced with permission of Wiley (Adv. Sci., 2016, 3, 1600113).
50.
The E-nose image above is reproduced with permission from Springer (Anal. Bioanal. Chem., 2014, 406(16), 3985–3994).
51.
The nanocube image above is reproduced with permission of Elsevier Science (Nano Energy, 2015, 16, 268–280).
52.
“For the CB electrode, the nanopores are formed between CB nanoparticles. During the discharge process, the nanopores are easily to be blocked by the discharge products in the initial discharge process. The MCC electrode consists of carbon nanocubes. Each carbon nanocube contains numerous mesopores, which can facilitate the electrolyte impregnation and oxygen diffusion. Furthermore, large amount of macropores is also formed between carbon nanocubes.” (adapted from Adv. Funct. Mater. 2015, 25, 4436–4444).
53.
The nanoprism image above is reproduced with permission of Elsevier Science (Appl. Surf. Sci., 2009, 255, 5939–5942).

References

B.I. Kharisov, O.V. Kharissova, U. Ortiz Mendez, Handbook on Less-Common Nanostructures (CRC Press, Boca Raton, 2012)
Google Scholar
G.G. Parigger, J.O. Hornkohl, A.M. Keszler, L. Nemes, Measurement and analysis of atomic and diatomic carbon spectra from laser ablation of graphite. Appl. Opt. 42(30), 6192–6198 (2003)
Article CAS Google Scholar
C.G. Parigger, A.C. Woods, D.M. Surmick, et al., Computation of diatomic molecular spectra for selected transitions of aluminum monoxide, cyanide, diatomic carbon, and titanium monoxide. Spectrochim. Acta B At. Spectrosc. 107, 132–138 (2015)
Article CAS Google Scholar
R. Hoffmann, Marginalia: C₂ in all its guises. Am. Sci. 83(4), 309–311 (1995)
Google Scholar
P.B. Shevlin, Formation of atomic carbon in the decomposition of 5-tetrazolyldiazonium chloride. J. Am. Chem. Soc. 94(4), 1379–1380 (2002)
Article Google Scholar
S.A. Krasnokutski, F.A. Huisken, A simple and clean source of low-energy atomic carbon. Appl. Phys. Lett. 105(11), 113506 (2014)
Article CAS Google Scholar
S. Shaik, D. Danovich, W. Wu, P. Su, H.S. Rzepa, P.C. Hiberty, Quadruple bonding in C₂ and analogous eight-valence electron species. Nat. Chem. 4, 195–200 (2012)
Article CAS Google Scholar
J.M. Matxain, F. Ruipérez, I. Infante, X. Lopez, J.M. Ugalde, G. Merino, M. Piris, Chemical bonding in carbon dimer isovalent series from the natural orbital functional theory perspective. J. Chem. Phys. 138, 151102 (2013)
Article CAS Google Scholar
P.S. Skell, J.H. Plonka, Chemistry of the singlet and triplet C₂ molecules. Mechanism of acetylene formation from reaction with acetone and acetaldehyde. J. Am. Chem. Soc. 92(19), 5620–5624 (1970)
Article CAS Google Scholar
B. Garg, T. Bisht, Carbon nanodots as peroxidase nanozymes for biosensing. Molecules 21, 1653, 16 pp (2016)
Article CAS Google Scholar
J. Wang, H. Soo Choi, Y.-X.J. Wáng, Exponential growth of publications on carbon nanodots by Chinese authors. J. Thorac Dis. 7(7), E201–E205 (2015)
Google Scholar
A.M. Ibarra-Ruiz, D.C. Rodríguez Burbano, J.A. Capobianco, Photoluminescent nanoplatforms in biomedical applications. Adv. Phys. 1(2), 194–225 (2016)
Google Scholar
Q. Li, T.Y. Ohulchanskyy, R.L. Liu, K. Koynov, D.Q. Wu, A. Best, R. Kumar, A. Bonoiu, P.N. Prasad, Photoluminescent carbon dots as biocompatible nanoprobes for targeting cancer cells in vitro. J. Phys. Chem. C 114, 12062–12068 (2010)
Article CAS Google Scholar
J. Zuo, T. Jiang, X. Zhao, X. Xiong, S. Xiao, Z. Zhu, Preparation and application of fluorescent carbon dots. J. Nanomater. 2015, 787862, 13 pp (2015)
Article CAS Google Scholar
P. Roy, P.-C. Chen, A.P. Periasamy, Y.-N. Chen, H.-T. Chang, Photoluminescent carbon nanodots: synthesis, physicochemical properties and analytical applications. Mater. Today 18(8), 447–458 (2015)
Article CAS Google Scholar
Y. Song, S. Zhu, B. Yang, Bioimaging based on fluorescent carbon dots. RSC Adv. 4, 27184–27200 (2014)
Article CAS Google Scholar
S.H. Song, M.-H. Jang, J. Chung, S.H. Jin, B.H. Kim, et al., Highly efficient light-emitting diode of graphene quantum dots fabricated from graphite intercalation compounds. Adv. Opt. Mater. 2(11), 1016–1023 (2014)
Article CAS Google Scholar
X. Han, S. Zhong, W. Pan, W. Shen, A simple strategy for synthesizing highly luminescent carbon nanodots and application as effective down-shifting layers. Nanotechnology 26, 065402, 11 pp (2015)
Article CAS Google Scholar
J. Zhang, F. Zhang, Y. Yang, et al., Composites of graphene quantum dots and reduced graphene oxide as catalysts for nitroarene reduction. ACS Omega 2, 7293–7298 (2017)
Article CAS Google Scholar
Y. Cheng, B. Li, B. Li, B. Li, L. Wang, D. Wei, Y. Feng, D. Jia, Fluorescent zinc doped carbon nanodots derived from chitosan/metal ions complex for cell imaging. Nanomedicine 12(2), 506–507 (2016)
Article Google Scholar
W. Lu, X. Qin, A.M. Asiri, A.O. Al-Youbi, X. Sun, Green synthesis of carbon nanodots as an effective fluorescent probe for sensitive and selective detection of mercury(II) ions. J. Nanopart. Res. 15, 1344 (2013)
Article CAS Google Scholar
X. Qin, W. Lu, A.M. Asiri, A.O. Al-Youbi, X. Sun, Microwave-assisted rapid green synthesis of photoluminescent carbon nanodots from flour and their applications for sensitive and selective detection of mercury(II) ions. Sensors Actuators B 184, 156–162 (2013)
Article CAS Google Scholar
A. Loukanov, R. Sekiya, M. Yoshikawa, N. Kobayashi, Y. Moriyasu, S. Nakabayashi, Photosensitizer-conjugated ultrasmall carbon nanodots as multifunctional fluorescent probes for bioimaging. J. Phys. Chem. C 120(29), 15867–15874 (2016)
Article CAS Google Scholar
V. Strauss, J.T. Margraf, C. Dolle, et al., Carbon nanodots: toward a comprehensive understanding of their photoluminescence. J. Am. Chem. Soc. 136(49), 17308–17316 (2014)
Article CAS Google Scholar
H. Li, Z. Kang, Y. Liu, S.-T. Lee, Carbon nanodots: synthesis, properties and applications. J. Mater. Chem. 22, 24230–24253 (2012)
Article CAS Google Scholar
B.-P. Qi, L. Bao, Z.-L. Zhang, D.-W. Pang, Electrochemical methods to study photoluminescent carbon nanodots: preparation, photoluminescence mechanism and sensing. ACS Appl. Mater. Interfaces 8(42), 28372–28382 (2016)
Article CAS Google Scholar
D. Reyes, M. Camacho, M. Camacho, et al., Laser ablated carbon nanodots for light emission. Nanoscale Res. Lett. 11, 424, 11 pp (2016)
Article CAS Google Scholar
A. Jose Amali, H. Hoshino, C. Wu, M. Ando, Q. Xu, From metal–organic framework to intrinsically fluorescent carbon nanodots. Chem. 20(27), 8279–8282 (2014)
Article CAS Google Scholar
S. Kim, J.K. Seo, J.H. Park, Y. Song, Y.S. Meng, M.J. Heller, White-light emission of blue-luminescent graphene quantum dots by europium (III) complex incorporation. Carbon 124, 479–485 (2017)
Article CAS Google Scholar
J. Zhang, S.-H. Yu, Carbon dots: large-scale synthesis, sensing and bioimaging. Mater. Today 19(7), 382–393 (2016)
Article CAS Google Scholar
J. Xu, T. Lai, Z. Feng, X. Weng, C. Huang, Formation of fluorescent carbon nanodots from kitchen wastes and their application for detection of Fe³⁺. Luminescence 30(4), 420–424 (2015)
Article CAS Google Scholar
S.A. Chechetka, E. Miyako, Optical regulation of carbon nanodots by chemical functionalization. Chem. Lett. 45(8), 854–856 (2016)
Article CAS Google Scholar
A.B. Bourlinos, A. Bakandritsos, A. Kouloumpis, D. Gournis, M. Krysmann, E.P. Giannelis, K. Polakova, K. Safarova, K. Hola, et al., Gd(III)-doped carbon dots as a dual fluorescent-MRI probe. J. Mater. Chem. 22, 23327–23330 (2012)
Article CAS Google Scholar
J. Zhang, L. Tang, G. Hu, et al., Carbon nanodots-based nanocomposites with enhanced photocatalytic Performance and photothermal effects. Appl. Phys. Lett. 111, 013904 (2017)
Article CAS Google Scholar
M. Li Liu, B. Bin Chen, T. Yang, et al., One-pot carbonization synthesis of europium-doped carbon quantum dots for highly selective detection of tetracycline. Methods Appl. Fluoresc. 5(1), 015003 (2017)
Article CAS Google Scholar
J.-S. Li, Y.-J. Tang, S.-L. Li, et al., Carbon nanodots functional MOFs composites by a stepwise synthetic approach: enhanced H2 storage and fluorescent sensing. CrystEngComm 17, 1080–1085 (2015)
Article CAS Google Scholar
C.-L. Shen, L.-X. Su, J.-H. Zang, et al., Carbon nanodots as dual-mode nanosensors for selective detection of hydrogen peroxide. Nanoscale Res. Lett. 12, 447, 10 pp (2017)
Article CAS Google Scholar
J. Shen, Y. Zhu, X. Yang, C. Li, Graphene quantum dots: emergent nanolights for bioimaging, sensors, catalysis and photovoltaic devices. J. Chem. Soc. Chem. Commun. 48, 3686–3699 (2012)
Article CAS Google Scholar
W. Dai, Y. Lei, M. Xu, et al., Rare-earth free self-activated graphene quantum dots and copper-cysteamine phosphors for enhanced white light-emitting-diodes under single excitation. Sci. Rep. 7, 12872 (2017)
Article CAS Google Scholar
A. Kocsis, S.W. Cranford, Carbyne: a one dimensional carbon allotrope, in Carbon Nanomaterials Sourcebook. Nanoparticles, Nanocapsules, Nanofibers, Nanoporous Structures, and Nanocomposites, ed. by K. D. Sattler (Ed), vol. II, (CRC Press, Boca Raton, FL, USA, 2016), pp. 3–25
Chapter Google Scholar
J.M. Alred, N. Gupta, M. Liu, Z. Zhang, B.I. Yakobson, Mechanics of materials creation: nanotubes, graphene, carbyne, borophenes. 2016 IUTAM Symposium on Nanoscale Physical Mechanics. Procedia IUTAM 21, 17–24 (2017)
Article Google Scholar
C.R. Ma, J. Xiao, G.W. Yang, Giant nonlinear optical responses of carbyne. J. Mater. Chem. C 4, 4692–4698 (2016)
Article CAS Google Scholar
L. Shi, P. Rohringer, K. Suenaga, et al., Confined linear carbon chains as a route to bulk carbyne. Nat. Mater. 15, 634–640 (2016)
Article CAS Google Scholar
B. Pan, J. Xiao, J. Li, P. Liu, C. Wang, G. Yang, Carbyne with finite length: the one-dimensional sp carbon. Sci. Adv. 1(9), e1500857 (2015)
Article Google Scholar
E.A. Belenkov, V.V. Mavrinsky, Crystal structure of a perfect carbyne. Crystallogr. Rep. 53(1), 83–87 (2008)
Article CAS Google Scholar
G.M. Demyashev, A.L. Taube, E. Siores, Surface modification of titanium carbide with carbyne-containing nanocoatings. J. Nanosci. Nanotechnol. 2(2), 133–137 (2002)
Article CAS Google Scholar
Q. Sun, L. Cai, S. Wang, Bottom-up synthesis of metalated carbyne. J. Am. Chem. Soc. 138(4), 1106–1109 (2016)
Article CAS Google Scholar
A.K. Nair, S.W. Cranford, M.J. Buehler, The minimal nanowire: mechanical properties of carbyne. EPL 95, 16002, 5 pp (2011)
Article CAS Google Scholar
M. Wang, S. Lin, Ballistic thermal transport in carbyne and cumulene with micron-scale spectral acoustic phonon mean free path. Sci. Rep. 5, 18122 (2015)
Article CAS Google Scholar
S. Kotrechko, I. Mikhailovskij, T. Mazilova, E. Sadanov, A. Timoshevskii, N. Stetsenko, Y. Matviychuk, Mechanical properties of carbyne: experiment and simulations. Nanoscale Res. Lett. 10, 24 (2015)
Article CAS Google Scholar
Y. NuLi, Q. Chen, W. Wang, et al., Carbyne polysulfide as a novel cathode material for rechargeable magnesium batteries. Sci. World J. 2014, 107918, 7 pp (2014)
Article CAS Google Scholar
F. Cataldo, Y. Keheyan, Generation of higher fullerenes from laser ablation of carbyne and C₆₀ photopolymer astrochemical implications. Fullerenes, Nanotubes, Carbon Nanostruct. 10, 99–106 (2002)
Article CAS Google Scholar
S. Kotrechko, A. Timoshevskii, E. Kolyvoshko, Y. Matviychuk, N. Stetsenko, Thermomechanical stability of carbyne-based nanodevices. Nanoscale Res. Lett. 12, 327 (2017)
Article CAS Google Scholar
F. Banhart, Chains of carbon atoms: a vision or a new nanomaterial? Beilstein J. Nanotechnol. 6, 559–569 (2015)
Article CAS Google Scholar
L. Shen, M. Zeng, S.-W. Yang, C. Zhang, X. Wang, Y. Feng, Electron transport properties of atomic carbon nanowires between graphene electrodes. J. Am. Chem. Soc. 132(33), 11481–11486 (2010)
Article CAS Google Scholar
R.Y. Oeiras, E.Z. da Silva, Bond length and electric current oscillation of long linear carbon chains: density functional theory, MpB model, and quantum spin transport studies. J. Chem. Phys. 140, 134703 (2014)
Article CAS Google Scholar
G. Onida, N. Manini, L. Ravagnan, E. Cinquanta, D. Sangalli, P. Milani, Vibrational properties of sp carbon atomic wires in cluster-assembled carbon films. Phys. Status Solidi 247(8), 2017–2021 (2010)
Article CAS Google Scholar
C.S. Casari, M. Tommasini, R.R. Tykwinski, A. Milani, Carbon-atom wires: 1-D systems with tunable properties. Nanoscale 8, 4414–4435 (2016)
Article CAS Google Scholar
C.S. Casari, C.S. Giannuzzi, V. Russo, Carbon-atom wires produced by nanosecond pulsed laser deposition in a background gas. Carbon 104, 190–195 (2016)
Article CAS Google Scholar
O. Cretu, A.R. Botello-Mendez, I. Janowska, et al., Electrical transport measured in atomic carbon chains. Nano Lett. 13, 3487–3493 (2013)
Article CAS Google Scholar
N. Tayebi, Y. Narui, R.J. Chen, C.P. Collier, K.P. Giapis, Y. Zhang, Nanopencil as a wear-tolerant probe for ultrahigh density data storage. Appl. Phys. Lett. 93(10), 103112/1–103112/3 (2008)
Article CAS Google Scholar
A.G. Nasibulin, P.V. Pikhitsa, H. Jiang, D.P. Brown, A.V. Krasheninnikov, A.S. Anisimov, P. Queipo, A. Moisala, D. Gonzalez, G. Lientschnig, A. Hassanien, S.D. Shandakov, G. Lolli, D.E. Resasco, M. Choi, D. Tománek, E.I. Kauppinen, A novel hybrid carbon material. Nat. Nanotechnol. 2, 156–161 (2007)
Article CAS Google Scholar
Y. Tian, D. Chassaing, A.G. Nasibulin, P. Ayala, H. Jiang, A.S. Anisimov, A. Hassanien, E.I. Kauppinen, The local study of a nanoBud structure. Phys. Status Solidi B 245(10), 2047–2050 (2008)
Article CAS Google Scholar
http://www.nanodic.com/carbon/Carbon_nanobud.htm. Accessed on May 5, 2016
B.I. Kharisov, O.V. Kharissova, U. Ortiz-Mendez, Handbook of Less-Common Nanostructures (CRC Press, 2012), 862 pp
Google Scholar
A.G. Nasibulin, A.S. Anisimov, P.V. Pikhitsa, H. Jiang, D.P. Brown, M. Choi, E.I. Kauppinen, Investigations of NanoBud formation. Chem. Phys. Lett. 446, 109–114 (2007)
Article CAS Google Scholar
A. Anisimov, Aerosol synthesis of carbon nanotubes and nanobuds. Ph.D. thesis, Aalto University, Finland, 2010
Google Scholar
R.J. Nicholls, J. Britton, S. Shayan Meysami, A.A. Koos, N. Grobert, In situ engineering of NanoBud geometries. Chem. Commun. 49, 10956–10958 (2013)
Article CAS Google Scholar
M. Ghorbanzadeh Ahangari, M.D. Ganji, F. Montazar, Mechanical and electronic properties of carbon nanobuds: first-principles study. Solid State Commun. 203, 58–62 (2015)
Article CAS Google Scholar
H.Y. He, B.C. Pan, Electronic structures and Raman features of a carbon Nanobud. J. Phys. Chem. C 113, 20822–20826 (2009)
Article CAS Google Scholar
X. Wu, X. Cheng Zeng, First-principles study of a carbon Nanobud. ACS Nano 287, 1459–1465 (2008)
Article CAS Google Scholar
J. Il Choi, H. Seok Kim, H. Seul Kim, G. In Lee, J.K. Kang, Y.-H. Kim, Carbon nanobuds based on carbon nanotube caps: a first-principles study. Nanoscale 8, 2343–2349 (2016)
Article CAS Google Scholar
X. Yang, L. Wang, Y. Huang, Z. Han, A.C. To, Carbon nanotube–fullerene hybrid nanostructures by C₆₀ bombardment: formation and mechanical behavior. Phys. Chem. Chem. Phys. 16(39), 21615–21619 (2014)
Article CAS Google Scholar
X. Yang, L. Wang, Y. Huang, A.C. To, B. Cao, Effects of nanobuds and heat welded nanobuds chains on mechanical behavior of carbon nanotubes. Comput. Mater. Sci. 109, 49–55 (2015)
Article CAS Google Scholar
X. Zhu, H. Su, Magnetism in hybrid carbon nanostructures: Nanobuds. Phys. Rev. B 79, 165401 (2009)
Article CAS Google Scholar
J. Yazdani, A. Bahrami, Topological index of carbon Nanobud. Aust. J. Basic Appl. Sci. 4(8), 3575–3577 (2010)
CAS Google Scholar
Z. Haseeb, A. Kumari, Study of the optical properties of SWCNT and nanobuds. IJECT 6(4), 45–48 (2015)
Google Scholar
S. Gorantla, F. Börrnert, A. Bachmatiuk, M. Dimitrakopoulou, R. Schönfelder, F. Schäffel, J. Thomas, T. Gemming, E. Borowiak-Palen, J.H. Warner, B.I. Yakobson, J. Eckert, B. Büchnera, M.H. Rümmeli, In situ observation of fullerene fusion and ejection in carbon nanotubes. Nanoscale 2, 2077–2079 (2010)
Article CAS Google Scholar
Y. Tian. Optical Properties of Single-walled Carbon Nanotubes and Nanobuds. Ph.D. Thesis, Aalto University, 2012
Google Scholar
Y. Tian, Combined Raman spectroscopy and transmission electron microscopy studies of a NanoBud structure. J. Am. Chem. Soc. 130, 7188–7189 (2008)
Article CAS Google Scholar
X.X. Yang, Z.F. Zhou, Y. Wang, J.W. Li, N.G. Guo, W.T. Zheng, J.Z. Peng, C.Q. Sun, Raman spectroscopic determination of the length, energy, Debye temperature, and compressibility of the C–C bond in carbon allotropes. Chem. Phys. Lett. 575, 86–90 (2013)
Article CAS Google Scholar
P. Havu, A. Sillanpaa, N. Runeberg, J. Tarus, E.T. Seppala, R.M. Nieminen, Effects of chemical functionalization on electronic transport in carbon nanobuds. Phys. Rev. B 85, 115446 (2012)
Article CAS Google Scholar
W. Koh, J. Hye Lee, S. Geol Lee, J. Il Choic, S. Soon Jang, Li adsorption on a graphene–fullerene nanobud system: density functional theory approach. RSC Adv. 5, 32819–32825 (2015)
Article CAS Google Scholar
H.W. Kroto, The stability of the fullerenes C_n, with n = 24, 28, 32, 36, 50, 60 and 70. Nature 329, 529–531 (1987)
Article CAS Google Scholar
H.W. Kroto, C₆₀^B buckminsterfullerene, other fullerenes and the icospiral shell. Comp. Math. Appl. 17(1–3), 417–423 (1989)
Article Google Scholar
P.W. Dunk, N.K. Kaiser, M. Mulet-Gas, A. Rodríguez-Fortea, J.M. Poblet, H. Shinohara, C.L. Hendrickson, A.G. Marshall, H.W. Kroto, The smallest stable Fullerene, M@C₂₈ (M = Ti, Zr, U): stabilization and growth from carbon vapor. J. Am. Chem. Soc. 134(22), 9380–9389 (2012)
Article CAS Google Scholar
X. Lu, Z. Chen, Curved Pi-conjugation, aromaticity, and the related chemistry of small fullerenes (<C₆₀) and single-walled carbon nanotubes. Chem. Rev. 105, 3643–3696 (2005)
Article CAS Google Scholar
G.C. Loha, D. Baillargeat, Thermal transport in C₂₀ fullerene-chained carbon nanobuds. J. Appl. Phys. 113, 123504 (2013)
Article CAS Google Scholar
E.F. Sheka, L.Kh. Shaymardanova, C₆₀-based composites in view of topochemical reactions. III. C₆₀ + graphene nanobuds. arXiv:1106.0644 [cond-mat.mtrl-sci], Cornell University Library, 2011
Google Scholar
A. Fereidoon, M. Khorasani, M. Darvish Ganji, F. Memarian, Atomistic simulation study of mechanical properties of periodic graphene nanobuds. Comput. Mater. Sci. 107, 163–169 (2015)
Article CAS Google Scholar
M.B.E. Griffiths, S.E. Koponen, D.J. Mandia, J.F. McLeod, J.P. Coyle, J.J. Sims, J.B. Giorgi, E.R. Sirianni, G.P.A. Yap, S.T. Barry, Surfactant directed growth of gold metal nanoplates by chemical vapor deposition. Chem. Mater. 27, 6116–6124 (2015)
Article CAS Google Scholar
C. Deng, W. Ma, J.-L. Sun, Fabrication of highly rough Ag nanobud substrates and surface-enhanced raman scattering of λ-DNA molecules. J. Nanomater 2012, 820739, 5 pp (2012)
Google Scholar
D.S. Choi, A.O. Fung, H. Moon, G. Villareal, Y. Chen, D. Ho, N. Presser, G. Stupian, M. Leung, Detection of neural signals with vertically grown single platinum nanowire-nanobud. J. Nanosci. Nanotechnol. 9(11), 6483–6486(4) (2009)
Article CAS Google Scholar
R. Colin Johnson, Carbon nanobuds flex, replace indium tin oxide. Unique nanobuds stretch, bend, flex. http://www.eetimes.com/document.asp?doc_id=1324698. Accessed May 5, 2016
D.P. Brown, B.J. Aitchison, Uses of a carbon nanobud molecule and devices comprising the same. EP 2308112 A1, 2011; WO 2009156596 A1, 2009
Google Scholar
D.P. Brown, B.J. Aitchison, Uses of a carbon nanobud molecule and devices comprising the same. Patent US 20110127488, 2011
Google Scholar
I.V. Anoshkin, A.G. Nasibulin, P.R. Mudimela, M. He, V. Ermolov, E.I. Kauppinen, Single-walled carbon nanotube networks for ethanol vapor sensing applications. Nano Res. 6(2), 77–86 (2013)
Article CAS Google Scholar
D. E. Luzzi. Synthesis, structure, and properties of fullerene and nonfullerene nanopeapods, in Abstracts of Papers, 225th ACS National Meeting, New Orleans, 23–27 March 2003, COLL-370
Google Scholar
T. Okazaki, H. Shinohara, Nano-peapods encapsulating fullerenes, in Applied Physics of Carbon Nanotubes, ed. by S. V. Rotkin, S. Subramoney (Eds), (Springer, New York, 2005), pp. 133–150
Google Scholar
T. Okazaki, S. Okubo, T. Nakanishi, S.-K. Joung, T. Saito, M. Otani, S. Okada, S. Bandow, S. Iijima, Optical band gap modification of single-walled carbon nanotubes by encapsulated fullerenes. J. Am. Chem. Soc. 130, 4122–4128 (2008)
Article CAS Google Scholar
Q. Wang, R. Kitaura, Y. Yamamoto, S. Arai, H. Shinohara, Synthesis and TEM structural characterization of C₆₀-flattened carbon nanotube nanopeapods. Nano Res. 7(12), 1843–1848 (2014)
Article CAS Google Scholar
Y. Cho, S. Han, G. Kim, H. Lee, J. Ihm, Orbital hybridization and charge transfer in carbon nanopeapods. Phys. Rev. Lett. 90(10), 106402/1–106402/4 (2003)
Article CAS Google Scholar
T. Yumura, M. Kertesz, S. Iijima, Local modifications of single-wall carbon nanotubes induced by bond formation with encapsulated fullerenes. J. Phys. Chem. B 111(5), 1099–1109 (2007)
Article CAS Google Scholar
R. Kitaura, H. Shinohara, Carbon-nanotube-based hybrid materials. Nanopeapods. Chem. Asian J. 1(5), 646–655 (2006)
Article CAS Google Scholar
A.N. Enyashin, A.L. Ivanovskii, Atomic structure and electronic properties of nanopeapods: isomers of endohedral dititanofullerenes Ti₂@C₈₀ in carbon nanotubes. Zh. Neorg. Khim. 51(9), 1576–1585 (2006)
CAS Google Scholar
I.V. Krive, R. Ferone, R.I. Shekhter, M. Jonson, P. Utko, J. Nygaard, The influence of electro-mechanical effects on resonant electron tunneling through small carbon nano-peapods. New J. Phys. 10(Apr.), 043043 (2008)
Article CAS Google Scholar
D. Baowan, N. Thamwattana, J.M. Hill, Encapsulation of C₆₀ fullerenes into single-walled carbon nanotubes: Fundamental mechanical principles and conventional applied mathematical modeling. Phys. Rev. B: Condens. Matter Mater. Phys. 76(15), 155411/1–155411/8 (2007)
Article CAS Google Scholar
A. Gloter, K. Suenaga, H. Kataura, R. Fujii, T. Kodama, H. Nishikawa, I. Ikemoto, K. Kikuchi, S. Suzuki, Y. Achiba, S. Iijima, Structural evolutions of carbon nano-peapods under electron microscopic observation. Chem. Phys. Lett. 390(4–6), 462–466 (2004)
Article CAS Google Scholar
R. Pati, L. Senapati, P.M. Ajayan, S.K. Nayak, Theoretical study of electrical transport in a fullerene-doped semiconducting carbon nanotubes. J. Appl. Phys. 95(2), 694–697 (2004)
Article CAS Google Scholar
Y. Liu, R.O. Jones, X. Zhao, Y. Ando, Carbon species confined inside carbon nanotubes: A density functional study. Phys. Rev. B: Condens. Matter Mater. Phys. 68(12), 125413/1–125413/7 (2003)
CAS Google Scholar
H. Terrones, Beyond Carbon Nanopeapods. ChemPhysChem 13(9), 2273–2276 (2012)
Article CAS Google Scholar
S. Rols, J. Cambedouzou, M. Chorro, H. Schober, V. Agafonov, P. Launois, V. Davydov, A.V. Rakhmanina, H. Kataura, J.-L. Sauvajol, How confinement affects the dynamics of C₆₀ in carbon nanopeapods. Phys. Rev. Lett. 101(6), 065507/1–065507/4 (2008)
Article CAS Google Scholar
E. Hernandez, V. Meunier, B.W. Smith, R. Rurali, H. Terrones, M. Buongiorno Nardelli, M. Terrones, D.E. Luzzi, J.-C. Charlier, Fullerene coalescence in nanopeapods: a path to novel tubular carbon. Nano Lett. 3(8), 1037–1042 (2003)
Article CAS Google Scholar
J.H. Warner, Y. Ito, M. Zaka, L. Ge, T. Akachi, H. Okimoto, K. Porfyrakis, A.A.R. Watt, H. Shinohara, G.A.D. Briggs, Rotating fullerene chains in carbon nanopeapods. Nano Lett. 8(8), 2328–2335 (2008)
Article CAS Google Scholar
A.N. Sohi, R. Naghdabadi, Stability of single-walled carbon nanopeapods under combined axial compressive load and external pressure. Physica E Low Dimens. Syst. Nanostruct. 41(3), 513–517 (2009)
Article CAS Google Scholar
L. Cui, Y. Feng, X. Zhang, Dependence of thermal conductivity of carbon nanopeapods on filling ratios of fullerene molecules. J. Phys. Chem. A 119(45), 11226–11232 (2015)
Article CAS Google Scholar
L. Guan, K. Suenaga, S. Okubo, T. Okazaki, S. Iijima, Metallic wires of lanthanum atoms inside carbon nanotubes. J. Am. Chem. Soc. 130(7), 2162–2163 (2008)
Article CAS Google Scholar
K. Suenaga, R. Taniguchi, T. Shimada, T. Okazaki, H. Shinohara, S. Iijima, Evidence for the intramolecular motion of Gd atoms in a Gd₂@C₉₂ nanopeapod. Nano Lett. 3(10), 1395–1398 (2003)
Article CAS Google Scholar
R. Kitaura, H. Okimoto, H. Shinohara, Magnetism of the endohedral metallofullerenes M@C₈₂ (M=Gd, Dy) and the corresponding nanoscale peapods: Synchrotron soft x-ray magnetic circular dichroism and density-functional theory calculations. Phys. Rev. B 76, 172409 (2007)
Article CAS Google Scholar
Y. Sato, K. Suenaga, S. Bandow, S. Iijima, Site-dependent migration behavior of individual cesium ions inside and outside C₆₀ fullerene nanopeapods. Small 4(8), 1080–1083 (2008)
Article CAS Google Scholar
K. Urita, Y. Sato, K. Suenaga, A. Gloter, A. Hashimoto, M. Ishida, T. Shimada, H. Shinohara, S. Iijima, Defect-induced atomic migration in carbon nanopeapod: tracking the single-atom dynamic behavior. Nano Lett. 4(12), 2451–2454 (2004)
Article CAS Google Scholar
A. Trave, F.J. Ribeiro, S.G. Louie, M.L. Cohen, Energetics and structural characterization of C₆₀ polymerization in BN and carbon nanopeapods. Phys. Rev. 70, 205418 (2004)
Article CAS Google Scholar
V. Timoshevskii, M. Cote, Doping of C₆₀-induced electronic states in BN nanopeapods: Ab initio simulations. Phys. Rev. B: Condens. Matter Mater. Phys. 80(23), 235418/1–235418/5 (2009)
Article CAS Google Scholar
X. Li, W. Yang, B. Liu, Fullerene coalescence into metallic heterostructures in boron nitride nanotubes: a molecular dynamics study. Nano Lett. 7(12), 3709–3715 (2007)
Article CAS Google Scholar
S. Tsuruoka, H. Matsumoto, V. Castranov, et al., Differentiation of chemical reaction activity of various carbon nanotubes using redox potential: classification by physical and chemical structures. Carbon 95, 302–308 (2015)
Article CAS Google Scholar
J. Su, Y. Gao, R. Che, Synthesis and microstructure of Fe₃C encapsulated inside chain-like carbon nanocapsules. Mater. Lett. 64(6), 680–683 (2010)
Article CAS Google Scholar
D.B. Dougherty, W. Jin, W.G. Cullen, G. Dutton, J.E. Reutt-Robey, S.W. Robey, Local transport gap in C₆₀ nanochains on a pentacene template. Phys. Rev. B: Condens. Matter Mater. Phys. 77(7), 073414/1–073414/4 (2008)
Article CAS Google Scholar
M. Zhang, C. He, E. Liu, et al., Activated carbon nanochains with tailored micro-meso pore structures and their application for supercapacitors. J. Phys. Chem. C 119(38), 21810–22181 (2015)
Article CAS Google Scholar
B. Sahu, H. Min, S.K. Banerjee, Effects of magnetism and electric field on the energy gap of bilayer graphene nanobars. arXiv.org, e-Print Archive, Condensed Matter, 2009, 1–6, arXiv:0910.2719v1 [cond-mat.mtrl-sci]. Publisher: Cornell University Library
Google Scholar
T. Krupenkin, Nanograss, nanobricks, nanonails, and other things useful in your nanolandscaping, in Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, 22–26 Mar 2009, POLY-333
Google Scholar
S.K. Sonkar, M. Saxena, M. Saha, S. Sarkar, Carbon nanocubes and nanobricks from pyrolysis of rice. J. Nanosci. Nanotechnol. 10(6), 4064–4067 (2010)
Article CAS Google Scholar
X. Wang, C.-m. Zhao, T. Deng, et al., From amorphous carbon to carbon nanobelts and vertically oriented graphene nanosheets synthesized by plasma-enhanced chemical vapor deposition. Chem. Res. Chin. Univ. 29(4), 755–758 (2013)
Article CAS Google Scholar
X. Lu, J. Wu, After 60 years of efforts: the chemical synthesis of a carbon nanobelt. Chem 2(5), 619–620 (2017)
Article CAS Google Scholar
J. Liu, M. Shao, Q. Tang, S. Zhang, Y. Qian, Synthesis of carbon nanotubes and nanobelts through a medial-reduction method. J. Phys. Chem. B 107, 6329–6332 (2003)
Article CAS Google Scholar
X. Sun, Z. Xing, R. Ning, A.M. Asiri, A.Y. Obaid, Carbon nanobelts as a novel sensing platform for fluorescence-enhanced DNA detection. Analyst 139, 2318–2321 (2014)
Article CAS Google Scholar
C.-T. Lin, T.-H. Chen, T.-S. Chin, C.-Y. Lee, H.-T. Chiu, et al., Quasi two-dimensional carbon nanobelts synthesized using a template method. Carbon 46, 741–746 (2008)
Article CAS Google Scholar
T. Ouyang, K. Cheng, F. Yang, et al., From biomass with irregular structures to 1D carbon nanobelts: a stripping and cutting strategy to fabricate high performance supercapacitor materials. J. Mater. Chem. A 5, 14551–14561 (2017)
Article CAS Google Scholar
Q. Xia, H. Zhao, Z. Du, et al., Facile synthesis of MoO₃/carbon nanobelts as high-performance anode material for lithium ion batteries. Electrochim. Acta 180, 947–956 (2015)
Article CAS Google Scholar
Q. Zhao, L. Jiao, W. Peng, et al., Facile synthesis of VO₂(B)/carbon nanobelts with high capacity and good cyclability. J. Power Sources 199, 350–354 (2012)
Article CAS Google Scholar
C. Su, C. Pei, B. Wu, J. Qian, Y. Tan, Highly doped carbon nanobelts with ultrahigh nitrogen content as high-performance supercapacitor materials. Small 13, 1700834, 12 pp (2017)
Article CAS Google Scholar
G. Povie, Y. Segawa, T. Nishihara, Y. Miyauchi, K. Itami, Synthesis of a carbon nanobelt. Science 356, 172–175 (2017)
Article CAS Google Scholar
K. Matsui, M. Fushimi, Y. Segawa, K. Itami, Synthesis, structure, and reactivity of a cylinder-shaped cyclo[12]orthophenylene[6]ethynylene: toward the synthesis of zigzag carbon nanobelts. Org. Lett. 18, 5352–5355 (2016)
Article CAS Google Scholar
Y. Segawa, A. Yagi, H. Ito, K. Itami, A theoretical study on the strain energy of carbon nanobelts. Org. Lett. 18, 1430–1433 (2016)
Article CAS Google Scholar
Y. Ren, G. Pastorin, Incorporation of hexamethylmelamine inside capped carbon nanotubes. Adv. Mater. 20(11), 2031–2036 (2008)
Article CAS Google Scholar
A.V. Vakhrushev, M.V. Suyetin, Methane storage in bottle-like nanocapsules. Nanotechnology 20, 125602 (2009)
Article CAS Google Scholar
R.K. Lee, J.M. Hill, Design parameters for carbon nanobottles to absorb and store methane. J. Nanosci. Nanotechnol. 11(8), 6893–6903 (2011)
Article CAS Google Scholar
J. Li, S.L. Yoong, W.J. Goh, et al., In vitro controlled release of cisplatin from gold-carbon nanobottles via cleavable linkages. Int. J. Nanomedicine 10, 7425–7441 (2015)
CAS Google Scholar
N. Yang, G. Zhang, B. Li, Carbon nanocone: A promising thermal rectifier. Appl. Phys. Lett. 93, 243111 (2008)
Article CAS Google Scholar
M.H. Khalifeh, H. Yousefi-Azari, A.R. Ashrafi, A method for computing the Wiener index of one-pentagonal carbon nanocones. Curr. Nanosci. 6(2), 155–157 (2010)
Article CAS Google Scholar
E. Brito, A. Freitas, T. Silva, T. Guerra, S. Azevedo, Double-walled carbon nanocones: stability and electronic structure. Eur. Phys. J. B. 88, 153 (2015)
Article CAS Google Scholar
I. Levchenko, K. Ostrikov, J. Khachan, S.V. Vladimirov, Growth of carbon nanocone arrays on a metal catalyst: the effect of carbon flux ionization. Phys. Plasmas 15, 103501 (2008)
Article CAS Google Scholar
R. Ansari, A. Momen, S. Rouhi, S. Ajori, On the vibration of single-walled carbon nanocones: molecular mechanics approach versus molecular dynamics simulations. Shock. Vib. 2014, 410783, 8 pp (2014)
Google Scholar
S. Rouhi, R. Ansariy, S. Nickabadiz, Modal analysis of double-walled carbon nanocones using the nite element method. Int. J. Mod. Phys. B 31, 1750262, 18 pp (2017)
Article CAS Google Scholar
W. Huang, J. Xu, X. Lu, Tapered carbon nanocone tips obtained by dynamic oxidation in air. RSC Adv. 6, 25541–25548 (2016)
Article CAS Google Scholar
I.-C. Chen, L.-H. Chen, X.-R. Ye, C. Daraio, S. Jin, Extremely sharp carbon nanocone probes for atomic force microscopy imaging. Appl. Phys. Lett. 88, 153102 (2006)
Article CAS Google Scholar
S.N. Naess, A. Elgsaeter, G. Helgesen, K.D. Knudsen, Carbon nanocones: wall structure and morphology. Sci. Technol. Adv. Mater. 10(6), 065002 (2009)
Article CAS Google Scholar
A. Pauly, M. Dubois, K. Guerin, A. Hamwi, J. Brunet, C. Varenne, B. Lauron, Use of carbon nanomaterials as a filtration material impermeable to ozone. WO 2010000956, 2010, 20 pp
Google Scholar
R. Majidi, Adsorption of ternary mixture of noble gases on carbon nanocone: molecular dynamics simulation. Nanosci. Nanotechnol. Lett. 5(7), 750–753 (2013)
Article CAS Google Scholar
S.A. Aal, A.S. Shalabi, K.A. Soliman, High capacity hydrogen storage in Ni decorated carbon nanocone: a first-principles study. J. Quan. Inf. Sci 5, 134–149 (2015)
Google Scholar
S. Moradi, Deuterium adsorption on Multi Carbon Nano-cone (MNC_x, X=2-7) including BN Nano-cone: a model for D₂ storage. Orient. J. Chem. 31(3), 1355–1364 (2015)
Article CAS Google Scholar
O.O. Adisa, B.J. Cox, J.M. Hill, Open carbon nanocones as candidates for gas storage. J. Phys. Chem. C 115, 24528–24533 (2011)
Article CAS Google Scholar
M.-L. Li, F. Lin, Y. Chen, Study on the mechanical properties of carbon nanocones using molecular dynamics simulation. Acta Phys. Sin. 62(1), 016102 (2013)
Google Scholar
E. Vessally, F. Behmagham, B. Massoumi, A. Hosseinian, L. Edjlali, Carbon nanocone as an electronic sensor for HCl gas: quantum chemical analysis. Vacuum 134, 40–47 (2016)
Article CAS Google Scholar
M.T. Baei, A. Ahmadi Peyghan, Z. Bagheri, Carbon nanocone as an ammonia sensor: DFT studies. Struct. Chem. 24, 1099–1103 (2013)
Article CAS Google Scholar
L.B. Sheridana, D.K. Hensley, N.V. Lavrik, et al., Growth and electrochemical characterization of carbon nanospike thin film electrodes. J. Electrochem. Soc. 161(9), H558–H563 (2014)
Article CAS Google Scholar
A.G. Zestos, C. Yang, C.B. Jacobs, D. Hensley, B.J. Venton, Carbon nanospikes grown on metal wires as microelectrode sensors for dopamine. Analyst 140, 7283–7292 (2015)
Article CAS Google Scholar
A.S. Shanta, K.A. Al Mamun, S.K. Islam, N. McFarlane, Carbon nanotubes, nanofibers and nanospikes for electrochemical sensing: a review. Int. J. High Speed Electron. Syst. 26(3), 1740008, 12 pp (2017)
Article CAS Google Scholar
Y. Song, R. Peng, D.K. Hensley, et al., High-selectivity electrochemical conversion of CO₂ to ethanol using a copper nanoparticle/N-doped graphene electrode. ChemistrySelect 1, 6055–6061 (2016)
Article CAS Google Scholar
J. Zhou, Nanowicking: multi-scale flow interaction with nanofabric structures, Ph.D. Thesis, California Institute of Technology, 2005, 129 pp
Google Scholar
T. Ichihashi, J.-i. Fujita, M. Ishida, Y. Ochiai, In situ observation of carbon-nanopillar tubulization caused by liquidlike iron particles. Phys. Rev. Lett. 92(21), 215702, 4 pp (2004)
Article CAS Google Scholar
K. Sai Krishna, M. Eswaramoorthy, Novel synthesis of carbon nanorings and their characterization. Chem. Phys. Lett. 433, 327–330 (2007)
Article CAS Google Scholar
C. Pozrikidis, Structure of carbon nanorings. Comput. Mater. Sci. 43, 943–950 (2008)
Article CAS Google Scholar
H. Ding, J.P. Maier, Electronic structures of one-dimension carbon nano wires and rings. J. Phys. Conf. Ser. 61, 252–256 (2007)
Article CAS Google Scholar
S.G. dos Santos, J. Mendes Filho, V.N. Freire, E.W.S. Caetano, E.L. Albuquerque, Carbon-based nanorings sliding along inner coaxial nanotubes: Mobius topology effects in damping gigahertz oscillations. J. Appl. Phys. 116, 124311, 5 pp (2014)
Article CAS Google Scholar
E.G. Fedorov, N.N. Yanyushkina, M.B. Belonenko, Terahertz radiation from carbon nanorings in external collinear constant and varying electric fields. Tech. Phys. 58(4), 584–588 (2013)
Article CAS Google Scholar
G. Shi, J. Zhang, Y. He, S. Ju, D. Jiang, Thermal conductivity of carbon nanoring linked graphene sheets: a molecular dynamics investigation. Chin. Phys. B 26(10), 106502, 6 pp (2017)
Article CAS Google Scholar
K. Yin Cheung, S. Yang, Q. Miao, From tetrabenzoheptafulvalene to sp² carbon nano-rings. Org. Chem. Front. 4, 699–703 (2017)
Article CAS Google Scholar
B.M. Wong, Optoelectronic properties of carbon nanorings: excitonic effects from time-dependent density functional theory. J. Phys. Chem. C 113, 21921–21927 (2009)
Article CAS Google Scholar
H. Omachi, Y. Segawa, K. Itami, Synthesis of cycloparaphenylenes and related carbon nanorings: a step toward the controlled synthesis of carbon nanotubes. Acc. Chem. Res. 45(8), 1378–1389 (2012)
Article CAS Google Scholar
R. Franklin-Mergarejo, D. Ondarse Alvarez, S. Tretiak, S. Fernandez-Alberti, Carbon nanorings with inserted acenes: breaking symmetry in excited state dynamics. Sci. Rep. 6, 31253, 11 pp (2016)
Article CAS Google Scholar
T. Kawase, M. Oda, Complexation of carbon nanorings with fullerenes. Pure Appl. Chem. 78(4), 831–839 (2006)
Article CAS Google Scholar
K. Miki, T. Matsushita, Y. Inoue, et al., Electron-rich carbon nanorings as macrocyclic hosts for fullerenes. Chem. Commun. 49, 9092–9094 (2013)
Article CAS Google Scholar
T. Kawase, K. Tanaka, Y. Seirai, N. Shiono, M. Oda, Complexation of carbon nanorings with fullerenes: supramolecular dynamics and structural tuning for a fullerene sensor. Angew. Chem. Int. Ed. 42, 5597–5600 (2003)
Article CAS Google Scholar
N. Chen, M.T. Lusk, A.C.T. van Duin, W.A. Goddard III, Mechanical properties of connected carbon nanorings via molecular dynamics simulation. Phys. Rev. B 72, 085416 (2005)
Article CAS Google Scholar
V. Alamian, A. Bahrami, B. Edalatzade, PI polynomial of V-phenylenic nanotubes and nanotori. Int. J. Mol. Sci. 9, 229–234 (2008)
Article CAS Google Scholar
Y. Chel Kwun, M. Munir, W. Nazeer, S. Rafique, S. Min Kang, M-polynomials and topological indices of V-phenylenic nanotubes and nanotori. Sci. Rep. 7, 8756, 9 pp (2016)
Article CAS Google Scholar
A.T. Balaban, D.J. Klein, Claromatic carbon nanostructures. J. Phys. Chem. C 113, 19123–19133 (2009)
Article CAS Google Scholar
J. Liu, H. Dai, J.H. Hafner, D.T. Colbert, R.E. Smalley, S.J. Tans, C. Dekker, Fullerene ‘crop circles’. Nature 385, 780–781 (1997)
Article CAS Google Scholar
T.A. Hilder, J.M. Hill, Orbiting atoms and C₆₀ fullerenes inside carbon nanotori. J. Appl. Phys. 101, 064319 (2007)
Article CAS Google Scholar
P.C. Chuang, J. Guan, D. Witalka, et al., Relative stability and local curvature analysis in carbon nanotori. Phys. Rev. B 91, 165433 (2015)
Article CAS Google Scholar
B.J. Cox, J.M. Hill, New carbon molecules in the form of elbow-connected nanotori. J. Phys. Chem. C 111, 10855–10860 (2007)
Article CAS Google Scholar
F. Koorepazan-Moftakhar, A. RezaAshrafi, O. Ori, M.V. Putz, Geometry and topology of nanotubes and nanotori, in Exotic Properties of Carbon Nanomatter, Carbon Materials: Chemistry and Physics, ed. by M. V. Putz, O. Ori (Eds), (Springer, Dordrecht, 2015), pp. 131–152
Google Scholar
S. Madani, A.R. Ashrafi, The energies of (3,6)-fullerenes and nanotori. Appl. Math. Lett. 25(12), 2365–2368 (2012)
Article Google Scholar
C.P. Liu, J.W. Ding, Electronic structure of carbon nanotori: the roles of curvature, hybridization, and disorder. J. Phys. Condens. Matter 18, 4077–4084 (2006)
Article CAS Google Scholar
C.P. Liu, Zeeman effect on the electronic structure of carbon nanotori in a strong magnetic field. Int. J. Mod. Phys. B 22(27), 4845–4852 (2008)
Article CAS Google Scholar
Y.Y. Chou, G.-Y. Guo, Electrical conductance of carbon nanotori in contact with single-wall carbon nanotubes. J. Appl. Phys. 96(4), 2249–2253 (2004)
Article CAS Google Scholar
J.A. Rodriguez-Manzo, F. Lopez-Urias, M. Terrones, H. Terrones, Magnetism in corrugated carbon nanotori: the importance of symmetry, defects, and negative curvature. Nano Lett. 4(11), 2179–2183 (2004)
Article CAS Google Scholar
L. Liu, G.Y. Guo, C.S. Jayanthi, S.Y. Wu, Colossal paramagnetic moments in metallic carbon nanotori. Phys. Rev. Lett. 88(12), 217206, 4 pp (2002)
Article CAS Google Scholar
E. Taşci, E. Yazgan, O.B. Malcıoğlu, Ş. Erkoç, Stability of carbon nanotori under heat treatment: molecular-dynamics simulations. Fullerenes, Nanotubes, Carbon Nanostruct. 13, 147–154 (2005)
Article CAS Google Scholar
M. Tonigold, J. Hitzbleck, S. Bahnmueller, G. Langstein, D. Volkmer, Copper (II) Nanoballs as monomers for polyurethane coatings: synthesis, urethane derivatization and kinetic stability. Dalton Trans. (8), 1363–1371 (2009)
Google Scholar
S.E. Iyuke, T.A. Mamvura, K. Liu, V. Sibanda, M. Meyyappan, V.K. Varadan, Process synthesis and optimization for the production of carbon nanostructures. Nanotechnology 20(37), 375602/1–375602/10 (2009)
Article CAS Google Scholar
S. Lee, J. Hong, J.H. Koo, et al., Synthesis of few-layered graphene nanoballs with copper cores using solid carbon source. ACS Appl. Mater. Interfaces 5(7), 2432–2437 (2013)
Article CAS Google Scholar
K.S. Chetna, A. Kapoor. Effect of annealing on structural and optical properties of graphene nanoballs. in: Recent Trends in Materials and Devices, ed by V. Jain, S. Rattan, A. Verma. Springer Proceedings in Physics (Springer, New York, 2017), vol. 178
Google Scholar
N. Kumar, A. Shukla, J. Singh, M.K. Patra, P. Ghosal, S.R. Vadera, Simple route for synthesis of multilayer graphene nanoballs by flame combustion of edible oil. Graphene 1(1), 63–67 (2013)
Article Google Scholar
T. Das, B.K. Saikia, B.P. Baruah, Formation of carbon nano-balls and carbon nano-tubes from northeast Indian Tertiary coal: Value added products from low grade coal. Gondwana Res. 31, 295–304 (2016)
Article CAS Google Scholar
Y. Xie, Q. Huang, B. Huang, X. Xie, Low temperature synthesis of high quality carbon nanospheres through the chemical reactions between calcium carbide and oxalic acid. Mater. Chem. Phys. 124(1), 482–487 (2010)
Article CAS Google Scholar
D. Wei, Y. Zhang, J. Fu, Fabrication of carbon nanospheres by the pyrolysis of polyacrylonitrile–poly(methyl methacrylate) core–shell composite nanoparticles. Beilstein J. Nanotechnol. 8, 1897–1908 (2017)
Article CAS Google Scholar
B. Liu, L. Jin, H. Zheng, H. Yao, Y. Wu, A. Lopes, J. He, Ultrafine co-based nanoparticle@mesoporous carbon nanospheres toward high-performance supercapacitors. ACS Appl. Mater. Interfaces 9(2), 1746–1758 (2017)
Article CAS Google Scholar
F. Ghaemi, L. Chuah Abdullah, P. Tahir, Core/shell structure of Ni/NiO encapsulated in carbon nanosphere coated with few- and multi-layered graphene: synthesis, mechanism and application. Polymers 8, 381 (2016)
Article CAS Google Scholar
Y. Hao, S. Wang, Q. Sun, L. Shi, A.-H. Lu, Uniformly dispersed Pd nanoparticles on nitrogen-doped carbon nanospheres for aerobic benzyl alcohol oxidation. Chin. J. Catal. 36, 612–619 (2015)
Article CAS Google Scholar
Y. Yang, M. Qiu, L. Liu, D. Su, Y. Pi, G. Yan, Nitrogen-doped hollow carbon nanospheres derived from dopamine as high-performance anode materials for sodium-ion batteries. NANO: Brief Rep. Rev. 11(11), 1650124, 9 pp (2016)
Article CAS Google Scholar
W. Armstrong, B. Sapkota, S.R. Mishra, Silver decorated carbon nanospheres as effective visible light photocatalyst, in MRS Proceedings, 2013, Volume 1509, mrsf12-1509-cc09-38
Google Scholar
L.P. Bakos, N. Justh, K. Hernádi, et al., Core-shell carbon nanosphere-TiO₂ composite and hollow TiO₂ nanospheres prepared by atomic layer deposition. J. Phys. Conf. Ser. 764, 012005 (2016)
Article CAS Google Scholar
W. Niu, L. Li, X. Liu, et al., One-pot synthesis of graphene/carbon nanospheres/graphene sandwich supported Pt₃Ni nanoparticles with enhanced electrocatalytic activity in methanol oxidation. Int. J. Hydrog. Energy 40, 5106–5114 (2015)
Article CAS Google Scholar
P. Karna, M. Ghimire, S. Mishra, S. Karna, Synthesis and characterization of carbon nanospheres. Open Access Library Journal 4, e3619 (2017)
Google Scholar
A.N. Mohan, B. Manoj, Synthesis and characterization of carbon nanospheres from hydrocarbon soot. Int. J. Electrochem. Sci. 7, 9537–9549 (2012)
CAS Google Scholar
M. Ibrahim Mohammed, R. Ismaeel Ibrahim, L. Hussein Mahmoud, M. Abdulahad Zablouk, N. Manweel, A. Mahmoud, Characteristics of carbon nanospheres prepared from locally deoiled asphalt. Adv. Mater. Sci. Eng. 2013, 356769, 5 pp (2013)
Article CAS Google Scholar
H. Kristianto, C.D. Putra, A.A. Arie, M. Halim, J.K. Lee, Synthesis and characterization of carbon nanospheres using cooking palm oil as natural precursors onto activated carbon support. Procedia Chem. 16, 328–333 (2015)
Article CAS Google Scholar
D. Guo, X. Chen, H. Wei, et al., Controllable synthesis of highly uniform flower-like hierarchical carbon nanospheres and their application in high performance lithium–sulfur batteries. J. Mater. Chem. A 5, 6245–6256 (2017)
Article CAS Google Scholar
L. Zhang, P. Wang, W. Zheng, X. Jiang, Hollow carbon nanospheres for targeted delivery of chemotherapeutics in breast cancer therapy. J. Mater. Chem. B 5, 6601–6607 (2017)
Article CAS Google Scholar
Y.-W. Jiang, G. Gao, X. Zhang, H.-R. Jia, F.-G. Wu, Antimicrobial carbon nanospheres. Nanoscale 9, 15786–15795 (2017)
Article CAS Google Scholar
R. Vié, E. Drahi, O. Baudino, S. Blayac, S. Berthon-Fabry, Synthesis of carbon nanospheres for the development of inkjetprinted resistive layers and sensors. Flex. Print. Electron 1, 015003 (2016)
Article CAS Google Scholar
H. Zhao, F. Zhang, S. Zhang, et al., Scalable synthesis of Sub-100 nm hollow carbon nanospheres for energy storage applications. Nano Res. 11(4), 1822–1833 (2018)
Article CAS Google Scholar
J. Saini, M. Kumar, K. Anshu, S. Singh, S. Singh Kamal, G. Kaur, S.L. Harikumar, Future prospectives of nano onions: a review. Int. J. Curr. Med. Pharma. Res. 2(3), 222–234 (2016)
Google Scholar
J. Bartelmess, S. Giordani, Carbon nano-onions (multi-layer fullerenes): chemistry and applications. Beilstein J. Nanotechnol. 5, 1980–1998 (2014)
Article CAS Google Scholar
A.N. Papathanassiou, M.E. Plonska-Brzezinska, O. Mykhailiv, L. Echegoyen, I. Sakellis, Combined high permittivity and high electrical conductivity of carbon nano-onion/polyaniline composites. Synth. Met. 209, 583–587 (2015)
Article CAS Google Scholar
D.M. Bobrowska, K. Brzezinski, L. Echegoyen, M.E. Plonska-Brzezinska, A new perspective on carbon nano-onion/nickel hydroxide/oxide composites: Physicochemical properties and application in hybrid electrochemical systems. Fullerenes, Nanotubes, Carbon Nanostruct. 25(3), 193–203 (2017)
Article CAS Google Scholar
J. Bartelmess, M. Frasconi, P.B. Balakrishnan, A. Signorellia, L. Echegoyen, T. Pellegrino, S. Giordani, Non-covalent functionalization of carbon nano-onions with pyrene-BODIPY dyads for biological imaging. RSC Adv. 5, 50253–50258 (2015)
Article CAS Google Scholar
D.M. Bobrowska, J. Czyrko, K. Brzezinski, L. Echegoyen, M.E. Plonska-Brzezinska, Carbon nano-onion composites: physicochemical characteristics and biological activity. Fullerenes, Nanotubes, Carbon Nanostruct. 25(3), 185–192 (2017)
Article CAS Google Scholar
M.E. Plonska-Brzezinska, A. Molina-Ontori, L. Echegoyen, Post-modification by low-temperature annealing of carbon nano-onions in the presence of carbohydrates. Carbon 67, 304–317 (2014)
Article CAS Google Scholar
L. Zhou, C. Gao, D. Zhu, et al., Facile functionalization of multilayer fullerenes (carbon nano-onions) by nitrene chemistry and “grafting from” strategy. Chem. Eur. J. 15, 1389–1396 (2009)
Article CAS Google Scholar
S. Giordani, J. Bartelmess, M. Frasconi, I. Biondi, S. Cheung, M. Grossi, D. Wu, L. Echegoyen, D.F. O'Shea, NIR fluorescence labelled carbon nano-onions: synthesis, analysis and cellular imaging. J. Mater. Chem. B 2, 7459–7463 (2014)
Article CAS Google Scholar
C.T. Cioffi, A. Palkar, F. Melin, et al., Carbon nano-onion–ferrocene donor–acceptor system:synthesis, characterization and properties. Chem. Eur. J. 15, 4419–4427 (2009)
Article CAS Google Scholar
D. Pech, M. Brunet, H. Durou, P. Huang, V. Mochalin, Y. Gogotsi, P.-L. Taberna, P. Simon, Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon. Nat. Nanotechnol. 5, 651–654 (2010)
Article CAS Google Scholar
J.K. McDonough, A.I. Frolov, V. Presser, J. Niu, C.H. Miller, T. Ubieto, M.V. Federov, Y. Gogotsi, Influence of the structure of carbon onions on their electrochemical performance in supercapacitor electrodes. Carbon 50(9), 3298–3309 (2012)
Article CAS Google Scholar
J.K. McDonough, Y. Gogotsi, Carbon onions: synthesis and electrochemical applications. Electrochem. Soc. Interface 22(3), 61–66 (2013)
Article CAS Google Scholar
P. Bystrzejewski, M.H. Rummeli, T. Gemming, H. Lange, A. Huczco, Catalyst-free synthesis of onion-like carbon nanoparticles. New Carbon Mater. 25(1), 1–8 (2010)
Article CAS Google Scholar
Y. Zheng, P. Zhu, Carbon nano-onions: large-scale preparation, functionalization and their application as anode material for rechargeable lithium ion batteries. RSC Adv. 6, 92285–92298 (2016)
Article CAS Google Scholar
T. Garcia-Martin, P. Rincon-Arevalo, G. Campos-Martin, Method to obtain carbon nano-onions by pyrolisys of propane. Cent. Eur. J. Phys. 11(11), 1548–1558 (2013)
CAS Google Scholar
W.-k. Zhang, J.-j. Fu, J. Chang, M. Zhang, Y.-q. Yang, L.-z. Gao, Fabrication and purification of carbon nano onions. New Carbon Mater. 29(5), 398–403 (2014)
Google Scholar
F.-D. Han, B. Yao, Y.-J. Bai, Preparation of carbon nano-onions and their application as anode materials for rechargeable lithium-ion batteries. J. Phys. Chem. C 115, 8923–8927 (2011)
Article CAS Google Scholar
C. Zhang, J. Li, C. Shi, C. He, E. Liu, N. Zhao, Self-anchored catalysts for substrate-free synthesis of metal-encapsulated carbon nano-onions and study of their magnetic properties. Nano Res. 9(4), 1159–1172 (2016)
Article CAS Google Scholar
N. Sano, H. Wang, I. Alexandrou, M. Chhowalla, K.B.K. Teo, G.A.J. Amaratunga, Properties of carbon onions produced by an arc discharge in water. J. Appl. Phys. 92(5), 2783–2788 (2002)
Article CAS Google Scholar
O.V. Kharissova, H.V.R. Dias, B.I. Kharisov, J. Jiang, Preparation of carbon nano-onions by the low-temperature unfolding of MWCNTs via interaction with theraphthal. RSC Adv. 5, 57764–57770 (2015)
Article CAS Google Scholar
O.L. Kaliya, E.A. Luk’yanets, On the article about the component composition of Theraphthal preparation. Pharm. Chem. J. 43(10), 587–587 (2009)
Article CAS Google Scholar
M.S. Goizman, E.V. Degterev, K.F. Turchin, A.P. Arzamastsev, Quality control of theraphthal production. 1. Chemical composition. Pharm. Chem. J. 41(12), 670–675 (2007)
Article CAS Google Scholar
Patent of Russian Federation 2106146 (1995)
Google Scholar
M.E. Volpin, Agent for suppressing tumor growth, U.S. Patent 6,004,953, 1999
Google Scholar
Patent of Japan 3672928, 2005
Google Scholar
Canada application for a patent 2200220, 1996
Google Scholar
Antitumor composition comprising ascorbic acid and metal complexes of (na)phthalocyanines. EP 0786253 (1997)
Google Scholar
A.L. Nikolaev, A.V. Gopin, V.E. Bozhevolnov, S.E. Mazina, A.V. Severin, V.N. Rudin, N.V. Andronova, E.M. Treschalina, O.L. Kaliya, L.I. Solovyeva, E.A. Lukyanets, Sonodynamic therapy of cancer. A comprehensive experimental study. Russ. Chem. Bull. 63(5), 1 (2014)
Article CAS Google Scholar
O.V. Kharissova, J. Rodríguez, B.I. Kharisov, Non-standard ROS-generating combination “theraphthal–ascorbic acid” in low-temperature transformations of carbon allotropes. Chem. Pap. (2018). https://doi.org/10.1007/s11696-018-0571-y
Y. Yao, X. Wang, J. Guo, X. Yang, B. Xu, Tribological property of onion-like fullerenes as lubricant additive. Mater. Lett. 62(16), 2524–2527 (2008)
Article CAS Google Scholar
S. Erkoc, Stability of carbon nanoonion C₂₀@C₆₀@C₂₄₀: molecular dynamics simulations. Nano Lett. 2(3), 215–217 (2002)
Article CAS Google Scholar
M.E. Plonska-Brzezinska, A. Lapinski, A.Z. Wilczewska, et al., The synthesis and characterization of carbon nano-onions produced by solution ozonolysis. Carbon 49(15), 5079–5089 (2011)
Article CAS Google Scholar
Y. Gao, Y. Shen Zhou, M. Qian, et al., Chemical activation of carbon nano-onions for high-rate supercapacitor electrodes. Carbon 51, 52–58 (2013)
Article CAS Google Scholar
Y.A. Goh, X. Chen, F. Md Yasin, et al., Shear flow assisted decoration of carbon nano-onions with platinum nanoparticles. Chem. Commun. 49, 5171–5173 (2013)
Article CAS Google Scholar
O. Mykhailiv, K. Brzezinski, B. Sulikowski, et al., Boron-doped polygonal carbon nano-onions: synthesis and applications in electrochemical energy storage. Chem. Eur. J. 23, 7132–7141 (2017)
Article CAS Google Scholar
E.Y. Choi, C.K. Kim, Fabrication of nitrogendoped nano-onions and their electrocatalytic activity toward the oxygen reduction reaction. Sci. Rep. 7, 4178 (2017)
Article CAS Google Scholar
Y. Liu, R.L.V. Wal, V.N. Khabashesku, Functionalization of carbon nano-onions by direct fluorination. Chem. Mater. 19, 778–786 (2007)
Article CAS Google Scholar
J. Luszczyn, M.E. Plonska-Brzezinska, A. Palkar, A.T. Dubis, A. Simionescu, D.T. Simionescu, B. Kalska-Szostko, K. Winkler, L. Echegoyen, “Small” noncytotoxic carbon nano-onions: first covalent functionalization with biomolecules. Chem. Eur. J. 16, 4870–4880 (2010)
Article CAS Google Scholar
A.M. Panich, V.Y. Osipov, K. Takai, Diamagnetism of carbon onions probed by NMR of adsorbed water. Carbon 82, 608–610 (2015)
Article Google Scholar
A.M. Panich, V.Y. Osipov, K. Takai, Diamagnetism of carbon onions probed by NMR of adsorbed water. New Carbon Mater. 29(5), 392–397 (2014)
Article Google Scholar
H.G. Baldoví, J.R. Herance, V.M. Víctor, M. Alvaro, H. Garcia, Perylenetetracarboxylic anhydride as a precursor of fluorescent carbon nanoonion rings. Nanoscale 7, 12484–12491 (2015)
Article CAS Google Scholar
G. Moussa, C. Matei Ghimbeu, P.-L. Taberna, P. Simon, C. Vix-Guterl, Relationship between the carbon nano-onions (CNOs) surface chemistry/defects and their capacitance in aqueous and organic electrolytes. Carbon 105, 628–637 (2016)
Article CAS Google Scholar
E.W. Bucholz, S.R. Phillpot, S.B. Sinnott, Molecular dynamics investigation of the lubrication mechanism of carbon nano-onions. Comput. Mater. Sci. 54, 91–96 (2012)
Article CAS Google Scholar
V. Marchesano, A. Ambrosone, J. Bartelmess, F. Strisciante, A. Tino, L. Echegoyen, C. Tortiglione, S. Giordani, Impact of carbon nano-onions on hydra vulgaris as a model organism for nanoecotoxicology. Nano 5, 1331–1350 (2015)
CAS Google Scholar
M. Frasconi, V. Maffeis, J. Bartelmess, L. Echegoyen, S. Giordani, Highly surface functionalized carbon nano-onions for bright light bioimaging. Methods Appl. Fluoresc. 3, 044005 (2015)
Article CAS Google Scholar
A. Camisasca, S. Giordani, Carbon nano-onions in biomedical applications: promising theranostic agents. Inorg. Chim. Acta 468, 67 (2017)
Article CAS Google Scholar
M.-S. Wang, D. Golberg, Y. Bando, Carbon “onions” as point electron sources. ACS Nano 4(8), 4396–4402 (2010)
Article CAS Google Scholar
A. Pramanik, S. Biswas, A.K. Kole, C.S. Tiwary, R.N. Krishnarajd, P. Kumbhakar, Template-free hydrothermal synthesis of amphibious fluorescent carbon nanorice towards anti-counterfeiting applications and unleashing its nonlinear optical properties. RSC Adv. 6, 99060–99071 (2016)
Article CAS Google Scholar
P.S. Parasuraman, H.-C. Tsai, T. Imae, In-situ hydrothermal synthesis of carbon nanorice using Nafion as a template. Carbon 77, 660–666 (2014)
Article CAS Google Scholar
Q. Wu, L. Yang, X. Wang, Z. Hu, From carbon-based nanotubes to nanocages for advanced energy conversion and storage. Acc. Chem. Res. 50(2), 435–444 (2017)
Article CAS Google Scholar
K. Matsui, Y. Segawa, K. Itami, All-benzene carbon nanocages: size-selective synthesis, photophysical properties, and crystal structure. J. Am. Chem. Soc. 136(46), 16452–16458 (2014)
Article CAS Google Scholar
Y. Li, C. Zhou, X. Xie, G. Shi, L. Qu, Spontaneous, catalyst-free formation of nitrogen-doped graphitic carbon nanocages. Carbon 48(14), 4190–4196 (2010)
Article CAS Google Scholar
Y. Tan, C. Xu, G. Chen, et al., Synthesis of ultrathin nitrogen-doped graphitic carbon nanocages as advanced electrode materials for supercapacitor. ACS Appl. Mater. Interfaces 5(6), 2241–2248 (2013)
Article CAS Google Scholar
C.-K. Tsai, H.Y. Kang, C.-I. Hong, et al., Preparation of hollow spherical carbon nanocages. J. Nanopart. Res. 14, 1315 (2012)
Article CAS Google Scholar
R. Zhang, M. Hummelgard, H. Olin, Carbon nanocages grown by gold templating. Carbon 48, 424–430 (2010)
Article CAS Google Scholar
S. Xiang, Y. Shi, K. Zhang, et al., Design and synthesis of dodecahedral carbon nanocages incorporated with Fe₃O₄. RSC Adv. 7, 13257–13262 (2017)
Article CAS Google Scholar
E. Petala, Y. Georgiou, V. Kostas, et al., Magnetic carbon nanocages: an advanced architecture with surface- and morphology-enhanced removal capacity for arsenites. ACS Sustain. Chem. Eng. 5(7), 5782–5792 (2017)
Article CAS Google Scholar
H. Qin, Y. Huang, S. Liu, et al., Synthesis and properties of magnetic carbon nanocages particles for dye removal. J. Nanomater. 2015, 604201, 8 pp (2015)
Google Scholar
J.T. Li, A mild method prepared carboxy carbon nanocage. Adv. Mater. Res. 560–561, 742–746 (2012)
Google Scholar
S. Liu, Z. Wang, S. Zhou, et al., Metal–organic-framework-derived hybrid carbon nanocages as a bifunctional electrocatalyst for oxygen reduction and evolution. Adv. Mater. 29(31), 1700874 (2017)
Article CAS Google Scholar
Y. Jiang, L. Yang, T. Sun, et al., Significant contribution of intrinsic carbon defects to oxygen reduction activity. ACS Catal. 5, 6707–6712 (2015)
Article CAS Google Scholar
Z. Lyu, L. Yang, D. Xu, et al., Hierarchical carbon nanocages as high-rate anodes for Li-and Na-ion batteries. Nano Res 8(11), 3535–3543 (2015)
Article CAS Google Scholar
M.J. Armstrong, D.M. Burke, et al., Carbon nanocage supported synthesis of V₂O₅ nanorods and V₂O₅/TiO₂ nanocomposites for Li-ion batteries. J. Mater. Chem. A 1, 12568–12578 (2013)
Article CAS Google Scholar
A. Vinu, M. Miyahara, T. Mori, K. Ariga, Carbon nanocage: a large-pore cage-type mesoporous carbon material as an adsorbent for biomolecules. J. Porous. Mater. 13(3–4), 379–383 (2006)
Article CAS Google Scholar
K.K.R. Datta, A. Vinu, S. Mandal, et al., Carbon nanocage: super-adsorber of intercalators for DNA protection. J. Nanosci. Nanotechnol. 11(4), 3084–3090 (2011)
Article CAS Google Scholar
C.X. Guo, Z.M. Sheng, Y.Q. Shen, Z.L. Dong, C.M. Li, Thin-walled graphitic nanocages as a unique platform for amperometric glucose biosensor. ACS Appl. Mater. Interfaces 2(9), 2481–2484 (2010)
Article CAS Google Scholar
M. Hui Yap, K. Loon Fow, G. Zheng Chen, Synthesis and applications of MOF-derived porous nanostructures. Green Energy Environ 2, 218–245 (2017)
Article Google Scholar
H. Zhang, X. Zhang, X. Sun, Y. Ma, Shape-controlled synthesis of nanocarbons through direct conversion of carbon dioxide. Sci. Rep. 3, 3534 (2013)
Article Google Scholar
L. Cao, Z.-h. Li, Y. Gu, Rational design of N-doped carbon nanobox-supported Fe/Fe₂N/Fe₃C nanoparticles as efficient oxygen reduction catalysts for Zn–air batteries. J. Mater. Chem. A 5, 11340–11347 (2017)
Article CAS Google Scholar
J. Xiang, T. Song, One-pot synthesis of multicomponent (Mo, Co) metal sulfide/carbon nanoboxes as anode materials for improving Na-ion storage. Chem. Commun. 53, 10820–10823 (2017)
Article CAS Google Scholar
H. Hu, J. Zhang, B. Guan, X.W. (David) Lou, Unusual formation of CoSe@carbon nanoboxes, which have an inhomogeneous shell, for efficient lithium storage. Angew. Chem. 55(33), 9514–9518 (2016)
Article CAS Google Scholar
M. Zheng, Y. Liu, S. Zhao, W. He, Y. Xiao, D. Yuan, Simple shape-controlled synthesis of carbon hollow structures. Inorg. Chem. 49(19), 8674–8683 (2010)
Article CAS Google Scholar
B. Quan, G.-E. Nam, H. Jae Choi, Y. Piao, Synthesis of monodisperse hollow carbon nanocapsules by using protective silica shells. Chem. Asian J. 8(4), 765–770 (2013)
Article CAS Google Scholar
U. Narkiewicz, M. Podsiadly, R. Jedrzejewski, I. Pelech, Catalytic decomposition of hydrocarbons on cobalt, nickel and iron catalysts to obtain carbon nanomaterials. Appl. Catal. A Gen. 384(1–2), 27–35 (2010)
Article CAS Google Scholar
X.G. Liu, Z.Q. Ou, D.Y. Geng, Z. Han, H. Wang, B. Li, E. Brueck, Z.D. Zhang, Enhanced absorption bandwidth in carbon-coated supermalloy FeNiMo nanocapsules for a thin absorb thickness. J. Alloys Compd. 506(2), 826–830 (2010)
Article CAS Google Scholar
H. Kuratani, Y. Fujiwara, K. Maeda, T. Kobayashi, M. Jimbo, Synthesis of carbon nanocapsules containing Fe produced by discharge in ethanol. J. Magn. Soc. Jpn. 37(3–2), 206–209 (2013)
Article CAS Google Scholar
Y. Liu, J. Su, Synthesis and characterization of MgO-filled rectangular carbon nanocapsules. Adv. Mater. Res. 785-786, 444–448 (2013)
Article CAS Google Scholar
P. Wu, N. Du, H. Zhang, J. Yu, D. Yang, Carbon nanocapsules as nanoreactors for controllable synthesis of encapsulated iron and iron oxides: magnetic properties and reversible lithium storage. J. Phys. Chem. C 115, 3612–3620 (2011)
Article CAS Google Scholar
S. Kim, R. Sergiienko, E. Shibata, T. Nakamura, Iron-included carbon nanocapsules coated with biocompatible poly(ethylene glycol) shells. Mater. Chem. Phys. 122, 164–168 (2010)
Article CAS Google Scholar
T. Kizuka, K. Miyazawa, D. Matsuura, Synthesis of carbon nanocapsules and nanotubes using Fe-doped fullerene nanowhiskers. J. Nanotechnol. 613746, 6 (2012)
Google Scholar
D. Han, G. Song, B. Liu, H. Yan, Core–shell-structured nickel ferrite/onion-like carbon nanocapsules: an anode material with enhanced electrochemical performance for lithium-ion batteries. RSC Adv. 5, 42875–42880 (2015)
Article CAS Google Scholar
Y. Suna, C. Feng, X. Liu, S. Wing Orc, C. Jin, Synthesis, characterization and microwave absorption of carbon-coated Cu nanocapsules. Mater. Res. 17(2), 477–482 (2014)
Article CAS Google Scholar
E. Hu, J. Ning, B. He, et al., Unusual formation of tetragonal microstructures from nitrogen-doped carbon nanocapsules with cobalt nanocores as a bi-functional oxygen electrocatalyst. J. Mater. Chem. A 5, 2271–2279 (2017)
Article CAS Google Scholar
H. Wang, C. Chen, Y. Zhang, et al., In situ oxidation of carbon-encapsulated cobalt nanocapsules creates highly active cobalt oxide catalysts for hydrocarbon combustion. Nat. Commun. 6, 7181 (2015)
Article CAS Google Scholar
A.C.L. Tang, G.-L. Hwang, S.-J. Tsai, et al., Biosafety of non-surface modified carbon nanocapsules as a potential alternative to carbon nanotubes for drug delivery purposes. PLoS One 7(3), e32893 (2012)
Article CAS Google Scholar
Y.-F. Lan, S.-C. Cheng, Dispersion of carbon nanocapsules by using highly aspect-ratio clays. Appl. Phys. Lett. 100, 153109 (2012)
Article CAS Google Scholar
O.V. Kharissova, B.I. Kharisov, Solubilization and Dispersion of Carbon Nanotubes (Springer-Nature, New York, 2017), 250 pp
Book Google Scholar
Y. Hayashi, N. Takada, W. Diono, H. Kanda, M. Goto, One-step synthesis of water–dispersible carbon nanocapsules by pulsed arc discharge over aqueous solution under pressurized argon. Res. Chem. Intermed. 43, 4201–4211 (2017)
Article CAS Google Scholar
A. Guven, I.A. Rusakova, M.T. Lewis, L.J. Wilson, Cisplatin@US-tube carbon nanocapsules for enhanced chemotherapeutic delivery. Biomaterials 33(5), 1455–1461 (2012)
Article CAS Google Scholar
H. Ge, P.J. Riss, V. Mirabello, et al., Behavior of supramolecular assemblies of radiometal-filled and fluorescent carbon nanocapsules in vitro and in vivo. Chem 3, 437–460 (2017)
Article CAS Google Scholar
N. Mittal, R. Kumar, G. Mishra, D. Deva, A. Sharma, Mesoporous carbon nanocapsules based coatings with multifunctionalities. Adv. Mater. Interfaces 3(10), 1500708 (2016)
Article CAS Google Scholar
H.-S. Chien, C. Wang, Effects of temperature and carbon nanocapsules (CNCs) on the production of Poly(D,L-lactic acid) (PLA) nonwoven nanofibre mat. Fibres Text. East. Eur 97(1), 72–77 (2013)
Google Scholar
P. Gentile, T. David, F. Dhalluin, D. Buttard, N. Pauc, M. Den Hertog, P. Ferret, T. Baron, The growth of small diameter silicon nanowires to nanotrees. Nanotechnology 19(12), 125608/1–125608/5 (2008)
Article CAS Google Scholar
http://www.ifn.upr.edu/people/17-luis-fonseca
F. Sola, O. Resto, A. Biaggi-Labiosa, L.F. Fonseca, Growth and characterization of branched carbon nanostructures arrays in nano-patterned surfaces from porous silicon substrates. Micron 40, 80–84 (2009)
Article CAS Google Scholar
Z. Yao, X. Zhu, X. Li, Y. Xie, Synthesis of novel Y-junction hollow carbon nanotrees. Carbon 45(7), 1566–1570 (2007)
Article CAS Google Scholar
G. Liu, Y. Zhao, K. Zheng, Z. Liu, W. Ma, Y. Ren, S. Xie, L. Sun, Coulomb explosion: a novel approach to separate single-walled carbon nanotubes from their bundle. Nano Lett. 9(1), 239–244 (2009)
Article CAS Google Scholar
M. Haba, Fuel cell using carbon-metal nanotree electrocatalyst. 2006, JP 2006294493 (11 pp)
Google Scholar
Z. He, J.-L. Maurice, C. Seok Lee, C.S. Cojocaru, D. Pribat, Growth mechanisms of carbon nanostructures with branched carbon nanofibers synthesized by plasma-enhanced chemical vapour deposition. CrystEngComm 16, 2990–2995 (2014)
Article CAS Google Scholar
F. Sola, O. Resto, A.M. Biaggi-Labiosa, L.F. Fonseca, Electron-beam induced growth of silica nanowires and silica/carbon heterostructures. Mater. Res. Soc. Symp. Proc. (2007), 1017E (Low-Dimensional Materials--Synthesis, Assembly, Property Scaling, and Modeling), Paper #: 1017-DD12-31
Google Scholar
F. Sola, O. Resto, A. Biaggi-Labiosa, L.F. Fonseca, Electron-beam induced growth of silica nanorods and heterostructures in porous silicon. Nanotechnology 18, 405308 (2007)
Article CAS Google Scholar
L. Chen, C. Xu, R. Du, et al., Rational design of three-dimensional nitrogendoped carbon nanoleaf networks for highperformance oxygen reduction. J. Mater. Chem. A 3, 5617–5627 (2015)
Article CAS Google Scholar
T.-N. Ye, L.-B. Lv, X.-H. Li, M. Xu, J.-S. Chen, Strongly veined carbon nanoleaves as a highly efficient metal-free electrocatalyst. Angew. Chem. 126, 7025–7029 (2014)
Article Google Scholar
X. Ma, B. Yuan, Fabrication of carbon nanoflowers by plasma-enhanced chemical vapor deposition. Appl. Surf. Sci. 255(18), 7846–7850 (2009)
Article CAS Google Scholar
H. Butt, R. Rajesekharan, Q. Dai, S. Sarfraz, R.V. Kumar, G.A.J. Amaratunga, T.D. Wilkinson, Cylindrical Fresnel lenses based on carbon nanotube forests. Appl. Phys. Lett. 101(24), 243116 (2012)
Article CAS Google Scholar
T. Saleh, M. Vahdani Moghaddam, M. Sultan Mohamed Ali, M. Dahmardeh, C. Alden Foell, A. Nojeh, K. Takahata, Transforming carbon nanotube forest from darkest absorber to reflective mirror. Appl. Phys. Lett. 101, 061913 (2012)
Article CAS Google Scholar
H. Chen, A. Roy, J.-B. Baek, L. Zhu, J. Qu, L. Dai, Controlled growth and modification of vertically-aligned carbon nanotubes for multifunctional applications. Mater. Sci. Eng. R. Rep. 70, 63–91 (2010)
Article CAS Google Scholar
N. Hayashi, S.-I. Honda, K. Tsui, K.-Y. Lee, T. Ikuno, K. Fujimoto, S. Ohkura, M. Katayama, K. Oura, T. Hirao, Highly aligned carbon nanotube arrays fabricated by bias sputtering. Appl. Surf. Sci. 212–213, 393–396 (2003)
Article CAS Google Scholar
C. Daraio, V.F. Nesterenko, S. Jin, Impact response by a foamlike forest of coiled carbon nanotubes. J. Appl. Phys. 100, 064309, 4 pp (2006)
Article CAS Google Scholar
Y. Taki, M. Kikuchi, K. Shinohara, A. Tanaka, Selective growth of vertically aligned single-, double-, and triple-walled carbon nanotubes by radiation-heated chemical vapor deposition. Jpn. J. Appl. Phys. 47, 721–724 (2008)
Article CAS Google Scholar
A.M. Cassell, M. Meyyappan, J. Han, Multilayer film assembly of carbon nanotubes. J. Nanopart. Res. 2(4), 387–389 (2000)
Article CAS Google Scholar
Q. Zhang, W. Zhou, W. Qian, R. Xiang, J. Huang, D. Wang, F. Wei, Synchronous growth of vertically aligned carbon nanotubes with pristine stress in the heterogeneous catalysis process. J. Phys. Chem. C 111, 14638–14643 (2007)
Article CAS Google Scholar
X. Li, A. Cao, Y.J. Jung, R. Vajtai, P.M. Ajayan, Bottom-up growth of carbon nanotube multilayers: unprecedented growth. Nano Lett. 5, 1997–2000 (2005)
Article CAS Google Scholar
S. Huang, L. Dai, A.W.H. Mau, Nanotube “crop circles”. J. Mater. Chem. 9, 1221–1222 (1999)
Article CAS Google Scholar
C.K. Tan, K.P. Loh, T.T.L. John, Direct amperometric detection of glucose on a multiple-branching carbon nanotube forest. Analyst 133, 448–451 (2008)
Article CAS Google Scholar
S. Li, H. Li, X. Wang, Y. Song, Y. Liu, L. Jiang, D. Zhu, Super-hydrophobicity of large-area honeycomb-like aligned carbon nanotubes. J. Phys. Chem. B 106(36), 9274–9276 (2002)
Article CAS Google Scholar
M.R. Maschmann, Integrated simulation of active carbon nanotube forest growth and mechanical compression. Carbon 86, 26–37 (2015)
Article CAS Google Scholar
E.G. Rakov, Materials made of carbon nanotubes. The carbon nanotube forest. Russ. Chem. Rev. 82(6), 538–566 (2013)
Article CAS Google Scholar
M. Pinault, V. Pichot, H. Khodja, P. Launois, C. Reynaud, M. Mayne-L'Hermite, Evidence of sequential lift in growth of aligned multiwalled carbon nanotube multilayers. Nano Lett. 5(12), 2394–2398 (2005)
Article CAS Google Scholar
R. Xiang, G. Luo, Z. Yang, Q. Zhang, W. Qian, F. Wei, Temperature effect on the substrate selectivity of carbon nanotube growth in floating chemical vapor deposition. Nanotechnology 18(41), 415703 (2007)
Article CAS Google Scholar
Z. Yang, H. Nie, X. Zhou, Z. Yao, S. Huang, X. Chen, Synthesizing a well-aligned carbon nanotube forest with high quality via the nebulized spray pyrolysis method by optimizing ultrasonic frequency. Nano 6, 343–348 (2011)
Article CAS Google Scholar
C. Du, N. Pan, High power density supercapacitor electrodes of carbon nanotube films by electrophoretic deposition. Nanotechnology 17(21), 5314–5318 (2006)
Article CAS Google Scholar
S. Shekhar, P. Stokes, S. Khondaker, Ultrahigh density alignment of carbon nanotube arrays by dielectrophoresis. ACS Nano 5(3), 1739–1746 (2011)
Article CAS Google Scholar
P. Diao, Z. Li, Vertically aligned single-walled carbon nanotubes by chemical assembly – methodology, properties, and applications. Adv. Mater. 22, 1430–1449 (2010)
Article CAS Google Scholar
C. Soldano, S. Talapatra, S. Kar, Carbon nanotubes and graphene nanoribbons: potentials for nanoscale electrical interconnects. Electronics 2, 280–314 (2013)
Article CAS Google Scholar
J. Prasek, J. Drbohlavova, J. Chomoucka, J. Hubalek, O. Jasek, V. Adam, R. Kizek, Methods for carbon nanotubes synthesis—review. J. Mater. Chem. 21, 15872–15884 (2011)
Article CAS Google Scholar
E.R. Meshot, D.L. Plata, S. Tawfick, Y. Zhang, E.A. Verploegen, A.J. Hart, Engineering vertically aligned carbon nanotube growth by decoupled thermal treatment of precursor and catalyst. ACS Nano 3(9), 2477–2486 (2009)
Article CAS Google Scholar
K. Hasegawa, S. Noda, H. Sugime, K. Kakehi, S. Maruyama, Y. Yamaguchi, Growth window and possible mechanism of millimeter-thick single-walled carbon nanotube forests. J. Nanosci. Nanotechnol. 8(11), 6123–6128 (2008)
Article CAS Google Scholar
J. Olivares, T. Mirea, B. Díaz-Durán, M. Clement, M. De Miguel-Ramos, J. Sangrador, J. De Frutos, E. Iborra, Growth of carbon nanotube forests on metallic thin films. Carbon 90, 9–15 (2015)
Article CAS Google Scholar
H. Sugime, S. Esconjauregui, L. D'Arsié, J. Yang, A.W. Robertson, R.A. Oliver, S. Bhardwaj, C. Cepek, J. Robertson, Low-temperature growth of carbon nanotube forests consisting of tubes with narrow inner spacing using Co/Al/Mo catalyst on conductive supports. ACS Appl. Mater. Interfaces 7(30), 16819–16827 (2015)
Article CAS Google Scholar
T. Ohashi, T. Shima, Synthesis of vertically aligned single-walled carbon nanotubes with metallic chirality through facet control of catalysts. Carbon 87(1), 453–461 (2016)
Google Scholar
S. Esconjauregui, M. Fouquet, B.C. Bayer, S. Eslava, S. Khachadorian, S. Hofmann, J. Robertson, Manipulation of the catalyst-support interactions for inducing nanotube forest growth. J. Appl. Phys. 109, 044303 (2011)
Article CAS Google Scholar
C.T. Wirth, C. Zhang, G. Zhong, S. Hofmann, J. Robertson, Diffusion- and reaction-limited growth of carbon nanotube forests. ACS Nano 3(11), 3560–3566 (2009)
Article CAS Google Scholar
M. Bedewy, E.R. Meshot, H. Guo, E.A. Verploegen, W. Lu, A.J. Hart, Collective mechanism for the evolution and self-termination of vertically aligned carbon nanotube growth. J. Phys. Chem. C 113(48), 20576–20582 (2009)
Article CAS Google Scholar
R. Siddheswaran, D. Manikandan, R.E. Avila, C.E. Jeyanthi, R.V. Mangalaraja, Formation of carbon nanotube forest over spin-coated Fe2O 3 reduced thin-film by chemical vapor deposition. Fullerenes Nanotubes Carbon Nanostruct. 23(5), 392–398 (2015)
Article CAS Google Scholar
J. Yang, S. Esconjauregui, A.W. Robertson, Y. Guo, T. Hallam, H. Sugime, G. Zhong, G.S. Duesberg, J. Robertson, Growth of high-density carbon nanotube forests on conductive TiSiN supports. Appl. Phys. Lett. 106(8), 083108 (2015)
Article CAS Google Scholar
M. Mohsin Hossain, H. Shima, B.-C. Ku, J. Ryang Hahn, Nanoforests composed of ZnO/C core–shell hexagonal nanosheets: fabrication and growth in a sealed thermolysis reactor and optical properties. J. Mater. Sci. 50, 93–103 (2015)
Article CAS Google Scholar
N. Matsumoto, A. Oshima, S. Sakurai, T. Yamada, M. Yumura, K. Hata, D.N. Futaba, The application of gas dwell time control for rapid single wall carbon nanotube forest synthesis to acetylene feedstock. Nano 5, 1200–1210 (2015)
CAS Google Scholar
J. Huang, Q. Zhang, M. Zhao, F. Wei, Process intensification by CO₂ for high quality carbon nanotube forest growth: double-walled carbon nanotube convexity or single-walled carbon nanotube bowls? Nano Res. 2, 872–881 (2009)
Article CAS Google Scholar
M. Zhang, O. O. I. Okoli, H. Hoang Van, Graphene nanoribbons and methods. US Patent 2015/0013896 A1, 2015
Google Scholar
S. Santhanagopalan, A. Balram, E. Lucas, F. Marcano, D. Desheng Meng, High voltage electrophoretic deposition of aligned nanoforests for scalable nanomanufacturing of electrochemical energy storage devices. Key Eng. Mater. 507, 67–72 (2012)
Article CAS Google Scholar
D.S. Jensen, S.S. Kanyal, N. Madaan, M.A. Vail, A.E. Dadson, M.H. Engelhard, M.R. Linford, Multiwalled carbon nanotube forest grown via chemical vapor deposition from iron catalyst nanoparticles, by XPS. Surf. Sci. Spectra 20, 62–67 (2013)
Article CAS Google Scholar
G. Chen, Y. Seki, H. Kimura, S. Sakurai, M. Yumura, K. Hata, D.N. Futaba, Diameter control of single-walled carbon nanotube forests from 1.3–3.0 nm by arc plasma deposition. Sci. Rep. 4, 3804 (2014)
Article CAS Google Scholar
M. Vahdani Moghaddam, P. Yaghoobi, G.A. Sawatzky, A. Nojeh, Photon-impenetrable, electron-permeable: the carbon nanotube forest as a medium for multiphoton thermal-photoemission. ACS Nano 9(4), 4064–4069 (2015)
Article CAS Google Scholar
N.J. Ginga, W. Chen, S.K. Sitaraman, Waviness reduces effective modulus of carbon nanotube forests by several orders of magnitude. Carbon 66, 57–66 (2014)
Article CAS Google Scholar
J.-W. Jiang, Strain engineering for thermal conductivity of single-walled carbon nanotube forests, Cornell University Library, arXiv:1406.4559
Google Scholar
P. Pour Shahid Saeed Abadi, S.B. Hutchens, J.R. Greer, B.A. Cola, S. Graham, Buckling-driven delamination of carbon nanotube forests. Appl. Phys. Lett. 102, 223103 (2013)
Article CAS Google Scholar
G. Chen, D.N. Futaba, H. Kimura, S. Sakurai, M. Yumura, K. Hata, Absence of an ideal single-walled carbon nanotube forest structure for thermal and electrical conductivities. ACS Nano 7(11), 10218–10224 (2013)
Article CAS Google Scholar
P. Joseph, C. Cottin-Bizonne, J.-M. Benoıt, C. Ybert, C. Journet, P. Tabeling, L. Bocquet, Slippage of water past superhydrophobic carbon nanotube forests in microchannels. Phys. Rev. Lett. 97, 156104 (2006)
Article CAS Google Scholar
K.K.S. Lau, J. Bico, K.B.K. Teo, M. Chhowalla, G.A.J. Amaratunga, W.I. Milne, G.H. McKinley, K.K. Gleason, Superhydrophobic carbon nanotube forests. Nano Lett. 3(12), 1701–1705 (2003)
Article CAS Google Scholar
R. Kant, M. Birla Singh, Generalization of the Gouy-Chapman-Stern model of an electric double layer for a morphologically complex electrode: deterministic and stochastic morphologies. Phys. Rev. E 88, 052303 (2013)
Article CAS Google Scholar
A. Ozhan Altun, S. Ki Youn, N. Yazdani, T. Bond, H.G. Park, Metal-dielectric-CNT nanowires for femtomolar chemical detection by surface enhanced Raman spectroscopy. Adv. Mater. 25(32), 4377–4377 (2013)
Article CAS Google Scholar
S. Deng, M. Kurttepeli, D.J. Cott, S. Bals, C. Detavernier, Porous nanostructured metal oxides synthesized through atomic layer deposition on a carbonaceous template followed by calcination. J. Mater. Chem. A 3(6), 2642–2649 (2015)
Article CAS Google Scholar
M.P. Down, A.P. Lewis, L. Jiang, J.W. McBride, A nano-indentation study of the contact resistance and resistivity of a bi-layered Au/multi-walled carbon nanotube composite. Appl. Phys. Lett. 106(10), 101911 (2015)
Article CAS Google Scholar
Y. Yoon, G.S. Lee, K. Yoo, J.-B. Lee, Fabrication of a microneedle/CNT hierarchical micro/nano surface electrochemical sensor and its in-vitro glucose sensing characterization. Sensors 13, 16672–16681 (2013)
Article CAS Google Scholar
E. Gikunoo, A. Abera, E. Woldesenbet, A novel carbon nanofibers grown on glass microballoons immunosensor: a tool for early diagnosis of malaria. Sensors 14, 14686–14699 (2014)
Article CAS Google Scholar
P. Sui, D. Duckworth, G. Weaver, Joints comprising carbon nanoforests. US Patent 2015/0204444 A1, 2015
Google Scholar
J.H. Taphouse, T.L. Bougher, V. Singh, P.P.S.S. Abadi, S. Graham, B.A. Cola, G.W. Woodruff, Carbon nanotube thermal interfaces enhanced with sprayed on nanoscale polymer coatings. Nanotechnology 24(10), 105401 (2013)
Article CAS Google Scholar
D. Luo, L. Wu, J. Zhi, Fabrication of boron-doped diamond nanorod forest electrodes and their application in nonenzymatic amperometric glucose biosensing. ACS Nano 3(8), 2121–2128 (2009)
Article CAS Google Scholar
D.G. Lee, S.J. Park, Y.O. Park, E.I. Ryu, Synthesis of nanostructures by direct growth of carbon nanotubes on micron-sized metal fiber filter and its filtration performance. Hwahak Konghak 45(3), 264–268 (2007)
CAS Google Scholar
S.J. Park, D.G. Lee, Performance improvement of micron-sized fibrous metal filters by direct growth of carbon nanotubes. Carbon 44(10), 1930–1935 (2006)
Article CAS Google Scholar
T. Ohtani, T. Nishikawa, K. Harada, K. Ikeda, N. Takayama, Novel nanocarbons with a mushroom shape found in glassy carbon powder. J. Alloys Compd. 483(1–2), 491–494 (2009)
Article CAS Google Scholar
X. Peng, K. Koczkur, A. Chen, Synthesis of well-aligned bamboo-like carbon nanotube arrays from ethanol and acetone. J. Phys. D. Appl. Phys. 41(9), 095409/1–095409/6 (2008)
Article CAS Google Scholar
B.I. Kharisov, A review for synthesis of nanoflowers. Recent Pat. Nanotechnol. 2(3), 190–200 (2008)
Article CAS Google Scholar
H. Heli, A. Rahi, Synthesis and applications of nanoflowers. Recent Pat. Nanotechnol. 10(2), 86–115 (2016)
Article CAS Google Scholar
C.N.R. Rao, F.L. Deepak, G. Gundiah, A. Govindaraj, Inorganic nanowires. Prog. Solid State Chem. 31(1), 5–147 (2003)
Article CAS Google Scholar
J. Du, Z. Liu, Z. Li, B. Han, et al., Carbon nanoflowers synthesized by a reduction–pyrolysis–catalysis route. Mater. Lett. 59(4), 456–458 (2005)
Article CAS Google Scholar
S. Thongtem, P. Singjai, T.P.S. Thongtem, Growth of carbon nanoflowers on glass slides using sparked iron as a catalyst. Mater. Sci. Eng. A 423(1), 209–213 (2006)
Article CAS Google Scholar
Y. He, H. Zhao, X. Kong, CN 1962431 A 20070516, 2007
Google Scholar
J. Xua, K. Houa, Z. Jua, et al., Synthesis and electrochemical properties of carbon dots/manganese dioxide (CQDs/MnO₂) nanoflowers for supercapacitor applications. J. Electrochem. Soc. 164(2), A430–A437 (2017)
Article CAS Google Scholar
C. Qian, P. Guo, X. Zhang, et al., Nitrogen-doped mesoporous hollow carbon nanoflowers as high performance anode materials of lithium ion batteries. RSC Adv. 6, 93519–93524 (2016)
Article CAS Google Scholar
J. Wang, C. Luo, T. Gao, A. Langrock, A.C. Mignerey, C. Wang, An advanced MoS₂/carbon anode for high-performance sodium-ion batteries. Small 11(4), 473–481 (2015)
Article CAS Google Scholar
C.H. Pei, K. Shen, Synthesis of the nitrogen-doped carbon nanotube (NCNT) bouquets and their electrochemical properties. Electrochem. Commun. 35, 80–83 (2013)
Article CAS Google Scholar
B. Nanda Sahoo, K. Balasubramanian, Facile synthesis of nano cauliflower and nano broccoli like hierarchical superhydrophobic composite coating using PVDF/carbon soot particles via gelation technique. J. Colloid Interface Sci. 436, 111–121 (2014)
Article CAS Google Scholar
T. Krupenkin, Nanograss, nanobricks, nanonails, and other things useful in your nanolandscaping, in Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, United States, 22–26 Mar 2009, POLY-333
Google Scholar
M. Wei, C. Terashima, M. Lv, A. Fujishima, Z.-Z. Gu, Boron-doped diamond nanograss array for electrochemical sensors. Chem. Commun. (24), 3624–3626 (2009)
Google Scholar
M. Lv, M. Wei, F. Rong, C. Terashima, A. Fujishima, Z.-Z. Gu, Electrochemical detection of catechol based on as-grown and nanograss array boron-doped diamond electrodes. Electroanalysis 22(2), 199–203 (2010)
Article CAS Google Scholar
K. Kakehi, S. Noda, S. Maruyama, Y. Yamaguchi, Individuals, grasses, and forests of single- and multi-walled carbon nanotubes grown by supported Co catalysts of different nominal thicknesses. Appl. Surf. Sci. 254(21), 6710–6714 (2008)
Article CAS Google Scholar
M. Luling, G. Matthieu, A. Veneruso, Nanograss gamma detector. Eur. Pat. Appl. EP 2007-103888, 2008(13 pp)
Google Scholar
X. Qi, W. Zhong, Y. Deng, C. Au, Y. Du, Synthesis of helical carbon nanotubes, worm-like carbon nanotubes and nanocoils at 450°C and their magnetic properties. Carbon. Volume Date 2010 48(2), 365–376 (2009)
Article CAS Google Scholar
L.S. Panchakarla, A. Govindaraj, Carbon nanostructures and graphite-coated metal nanostructures obtained by pyrolysis of ruthenocene and ruthenocene–ferrocene mixtures. Bull. Mater. Sci. 30(1), 23–29 (2007)
Article CAS Google Scholar
S.-C. Wong, E.M. Sutherland, F.M. Uhl, Materials processes of graphite nanostructured composites using ball milling. Mater. Manuf. Process. 21, 159–166 (2006)
Article CAS Google Scholar
J. Gonzalez, J. Herrero, Graphene wormholes: a condensed matter illustration of Dirac fermions in curved space. Nucl. Phys. B B825(3), 426–443 (2009)., Volume Date 2010
Article CAS Google Scholar
Y. Wang, Encapsulation of palladium crystallites in carbon and the formation of wormlike nanostructures. J. Am. Chem. Soc. 116(1), 397–398 (1994)
Article CAS Google Scholar
B. Hu, Q. Zhang, Y. Wang, Pd/graphite as a superior catalyst for the direct synthesis of hydrogen peroxide from H₂ and O₂. Chem. Lett. 38(3), 256–257 (2009)
Article CAS Google Scholar
L. Sousa Lobo, Intrinsic kinetics in carbon gasification: understanding linearity, “nanoworms” and alloy catalysts. Appl. Catal. B Environ. 148–149, 136–143 (2014)
Article CAS Google Scholar
S.A.C. Carabineiro, L. Sousa Lobo, Understanding the reactions of CO₂, NO, and N₂O with activated carbon catalyzed by binary mixtures. Energy Fuel 30(9), 6881–6891 (2016)
Article CAS Google Scholar
Y. Piao, K. An, J. Kim, T. Yu, T. Hyeon, Sea urchin shaped carbon nanostructured materials: carbon nanotubes immobilized on hollow carbon spheres. J. Mater. Chem. 16(29), 2984–2989 (2006)
Article CAS Google Scholar
Y. Zhu, J. Li, M. Wan, L. Jiang, Electromagnetic functional urchin-like hollow carbon spheres carbonized by polyaniline micro/nanostructures containing FeCl₃ as a precursor. Eur. J. Inorg. Chem. 2009(19), 2860–2864 (2009), https://onlinelibrary.wiley.com/doi/abs/10.1002/ejic.200900040
Article CAS Google Scholar
J. Shu, Urchin-structured MWNTs/HCS composite as anode material for high-capacity and high-power lithium-ion batteries. Electrochem. Solid-State Lett. 11(12), A219–A222 (2008)
Article CAS Google Scholar
Z.H. Han, B. Yang, S.H. Kim, M.R. Zachariah, Application of hybrid sphere/carbon nanotube particles in nanofluids. Nanotechnology 18, 105701, 4 pp (2007)
Article CAS Google Scholar
J.M. Romo-Herrera, D.A. Cullen, E. Cruz-Silva, D. Ramirez, B.G. Sumpter, V. Meunier, H. Terrones, D.J. Smith, M. Terrones, The role of sulfur in the synthesis of novel carbon morphologies: from covalent Y-junctions to sea-urchin-like structures. Adv. Funct. Mater. 19(8), 1193–1199 (2009)
Article CAS Google Scholar
J. Chen, F. Cheng, Combination of lightweight elements and nanostructured materials for batteries. Acc. Chem. Res. 42(6), 713–723 (2009)
Article CAS Google Scholar
Y. Wang, G. Xing, Z. Jun Han, Pre-lithiation of onion-like carbon/MoS₂ nano-urchin anodes for high-performance rechargeable lithium ion batteries. Nanoscale 6, 8884–8890 (2014)
Article CAS Google Scholar
Y. Wang, Z. Jun Han, S. Fung Yu, et al., Core-leaf onion-like carbon/MnO₂ hybrid nano-urchins for rechargeable lithium-ion batteries. Carbon 64, 230–236 (2013)
Article CAS Google Scholar
T.-H. Chen, T.-Y. Tsai, K.-C. Hsieh, S.-C. Chang, N.-H. Tai, H.-L. Chen, Two-dimensional metallic nanobowl array transferred onto thermoplastic substrates by microwave heating of carbon nanotubes. Nanotechnology 19(46), 465303/1–465303/6 (2008)
CAS Google Scholar
J. Huang, Q. Zhang, M. Zhao, F. Wei, Process intensification by CO₂ for high quality carbon nanotube forest growth: double-walled carbon nanotube convexity or single-walled carbon nanotube bowls? Nano Res. 2(11), 872–881 (2009)
Article CAS Google Scholar
Y. Tang, B.L. Allen, D.R. Kauffman, A. Star, Electrocatalytic activity of nitrogen-doped carbon nanotube cups. J. Am. Chem. Soc. 131(37), 13200–13201 (2009)
Article CAS Google Scholar
H. Chun, M.G. Hahm, Y. Homma, R. Meritz, K. Kuramochi, L. Menon, L. Ci, P.M. Ajayan, Y.J. Jung, Engineering low-aspect ratio carbon nanostructures: nanocups, nanorings, and nanocontainers. ACS Nano 3(5), 1274–1278 (2009)
Article CAS Google Scholar
M. Ohtani, K. Saito, S. Fukuzumi, Synthesis, characterization, redox properties, and photodynamics of donor-acceptor nanohybrids composed of size-controlled cup-shaped nanocarbons and porphyrins. Chem Eur J 15(36), 9160–9168 (2009)., S9160/1-S9160/3
Article CAS Google Scholar
M. Gwan Hahm, A. Leela Mohana Reddy, D.P. Cole, et al., Carbon nanotube–nanocup hybrid structures for high power supercapacitor applications. Nano Lett. 12(11), 5616–5621 (2012)
Article CAS Google Scholar
B. Kumar Gupta, G. Kedawat, P. Kumar, Field emission properties of highly ordered low-aspect ratio carbon nanocup arrays. RSC Adv. 6, 9932–9939 (2016)
Article CAS Google Scholar
A.A. Moosa, F. Kubba, M. Raad, S.A. A. Ramazani, Mechanical and thermal properties of graphene nanoplates and functionalized carbon-nanotubes hybrid epoxy nanocomposites. Am. J. Mater. Sci. 6(5), 125–134 (2016)
Google Scholar
Y. Soo Yun, S. Youn Cho, J. Shim, et al., Microporous carbon nanoplates from regenerated silk proteins for supercapacitors. Adv. Mater. 25(14), 1993–1998 (2013)
Article CAS Google Scholar
S. Lee, M. Eui Lee, M. Yeong Song, et al., Morphologies and surface properties of cellulose-based activated carbon nanoplates. Carbon Lett. 20, 32–38 (2016)
Article Google Scholar
J. Cao, C.J. Jafta, J. Gong, et al., Synthesis of dispersible mesoporous nitrogen-doped hollow carbon nanoplates with uniform hexagonal morphologies for supercapacitors. ACS Appl. Mater. Interfaces 8(43), 29628–29636 (2016)
Article CAS Google Scholar
J.R. Roberts, R.R. Mercer, A.B. Stefaniak, et al., Evaluation of pulmonary and systemic toxicity following lung exposure to graphite nanoplates: a member of the graphenebased nanomaterial family. Part. Fibre Toxicol. 13(34), 22 (2016)
Google Scholar
D.N. Futaba, K. Miyake, K. Murata, Y. Hayamizu, T. Yamada, S. Sasaki, M. Yumura, K. Hata, Dual porosity single-walled carbon nanotube material. Nano Lett. 9(9), 3302–3307 (2009)
Article CAS Google Scholar
M.N. Ghasemi-Nejhad, A. Cao. Editor(s): M. Laudon; B. Romanowicz. Development of nanodevices, nanostructures, nanocomposites, and hierarchical nanocomposites at Hawaii Nanotechnology Laboratory. in NSTI Nanotech 2007, Nanotechnology Conference and Trade Show, Santa Clara, 20–24 May 2007, 4, 538–542
Google Scholar
S. Chakrabarti, T. Nagasaka, Y. Yoshikawa, L. Pan, Y. Nakayama, Growth of super long aligned brush-like carbon nanotubes. Jpn. J. Appl. Phys. 45(28), L720–L722 (2006)
Article CAS Google Scholar
J. Dinesh, M. Eswaramoorthy, C.N.R. Rao, Use of amorphous carbon nanotube brushes as templates to fabricate GaN nanotube brushes and related materials. J. Phys. Chem. C 111(2), 510–513 (2007)
Article CAS Google Scholar
V. Pushparaj, L. Mahadevan, S. Sreekala, L. Ci, R. Nalamasu, P.M. Ajayan, Deformation and capillary self-repair of carbon nanotube brushes. Carbon 50, 5618–5630 (2012)
Article CAS Google Scholar
W. Marks, S. Yang, G. Dombi, S. Bhatia, Hydrogel composites containing carbon nanobrushes as tissue scaffolds. MRS Proc. 1498, 53–58 (2013)
Article CAS Google Scholar
W. Marks, S. Yang, G. Dombi, S. Bhatia, Carbon nanobrush-containing poloxamer hydrogel. Composites for tissue regeneration. J. Long Term Eff. Med. Implants. 22(3), 229–236 (2012)
Article CAS Google Scholar
Z. Zhu, L. Garcia-Gancedo, A.J. Flewitt, F. Moussy, Y. Li, W.I. Milne, Design of carbon nanotube fiber microelectrode for glucose biosensing. Chem. Techn. Biotechnol. 87(2), 256–262 (2012)
Article CAS Google Scholar
J.-G. Fan, J.-X. Fu, A. Collins, Y.-P. Zhao, The effect of the shape of nanorod arrays on the nanocarpet effect. Nanotechnology 19(4), 045713/1–045713/8 (2008)
Article CAS Google Scholar
Y.-P. Zhao, J.-G. Fan, Clusters of bundled nanorods in nanocarpet effect. Appl. Phys. Lett. 88(10), 103123/1–103123/3 (2006)
Article CAS Google Scholar
J.-G. Fan, D. Dyer, G. Zhang, Y.-P. Zhao, Nanocarpet effect: pattern formation during the wetting of vertically aligned nanorod arrays. Nano Lett. 4(11), 2133–2138 (2004)
Article CAS Google Scholar
M. Castellino, M. Tortello, S. Bianco, S. Musso, M. Giorcelli, M. Pavese, R.S. Gonnelli, A. Tagliaferro, Thermal and electronic properties of macroscopic multi-walled carbon nanotubes blocks. J. Nanosci. Nanotechnol. 10(6), 3828–3833 (2010)
Article CAS Google Scholar
K. Krzysztof, M. Shaffer, A. Windle, Three-dimensional internal order in multiwall carbon nanotubes grown by chemical vapor deposition. Adv. Mater. 17(6), 760–763 (2005)
Article CAS Google Scholar
N. Grobert, M. Mayne, M. Terrones, J. Sloan, R. E. Dunin-Borkowskif, R. Kamalakaran, T. Seeger, H. Terrones, M. Riihle, D.R.M. Walton, H. W. Kroto, H. L. Hutchisonf. Metal and alloy nanowires: iron and invar inside carbon nanotubes. in: CP591, Electronic Properties of Molecular Nanostructures, ed by H. Kuzmany, et al. (Ed), (American Institute of Physics, College Park, Mariland, USA, 2001), pp. 287–290
Google Scholar
S.Y. Chen, H.Y. Miao, J.T. Lue, M.S. Ouyang, Fabrication and field emission property studies of multiwall carbon nanotubes. J. Phys. D. Appl. Phys. 37, 273–279 (2004)
Article CAS Google Scholar
E.B. Sansom, D. Rinderknecht, M. Gharib, Controlled partial embedding of carbon nanotubes within flexible transparent layers. Nanotechnology 19, 035302, 6 pp (2008)
Article CAS Google Scholar
H. Kai-Hsuan, T. Shinn-Shyong, K. Wen-Shyong, W. Bingqing, K. Tse-Hao, Growth of carbon nanofibers on carbon fabric with Ni nanocatalyst prepared using pulse electrodeposition. Nanotechnology 19, 295602 (2008)
Article CAS Google Scholar
F. Seichepine, S. Salomon, M. Collet, et al., A combination of capillary and dielectrophoresis-driven assembly methods for wafer scale integration of carbon-nanotube-based nanocarpets. Nanotechnology 23(9), 1–7 (2012)
Article CAS Google Scholar
J. Zhang, K. Wang, Q. Xu, et al., Beyond yolk–shell nanoparticles: Fe₃O₄@Fe₃C core@shell nanoparticles as yolks and carbon nanospindles as shells for efficient lithium ion storage. ACS Nano 9(3), 3369–3376 (2015)
Article CAS Google Scholar
R. Liping, Z. Hangyu, L. Hanlin, L. Jingping, T. Fushan, S. Ying-Kang, Z. Xiaojun, Designed amphiphilic peptide forms stable nanoweb, slowly releases encapsulated hydrophobic drug, and accelerates animal hemostasis. PNAS 106(13), 5105–5110 (2009) http://www.pnas.org/content/106/13/5105.full.pdf+html
S. Borhani, S.A.H. Ravandi, S.G. Etemad, Evaluation of surface roughness of polyacrylonitrile nanowebs. Iran. J. Polym Sci. Technol. (Persian Edition) 21(1), 61–69 (2008)
CAS Google Scholar
G. Chen, H.J.C. Gommeren, L.M. Knorr, Liquid filtration media. U.S. Pat. Appl. US 2009026137, Publ. 2009, 8 pp. Cont.-in-part of U.S. Ser. No. 74,164. A1 20090129 US 2008-284027
Google Scholar
C.-H. Chi, H.S. Lim, Pleated nanoweb structures for filters. Appl. Publ. 2009, 8 pp. US 2009064648 A1 20090312 US 2007-899803
Google Scholar
D. C. Jones, W. H. Stone Fuel filter. U.S. Pat. Appl. Publ. 2008, 5 pp. US 2008105626 A1 20080508 US 2006-591733
Google Scholar
S. Torres-Peiro, A. Diez, J.L. Cruz, M.V. Andres, C.M.B. Cordeiro, C.J. de Matos Fabrication and postprocessing of Ge-doped nanoweb fibers. in SAIP Conference Proceedings, 2008, 1055 (1st Workshop on Specialty Optical Fibers and Their Applications, 2008), 50–53
Google Scholar
K.W. Hutchenson, M.A. Page, A. Raghavanpillai, S. Reinartz, C.M. Stancik, J.J. Van Gorp, Method for production of nanoweb composite material containing short perfluorinated alkyl chains. US Patent Appl. Publ. 2009, 11 pp. US 2009047498 A1 20090219 US 2007-837647
Google Scholar
K.A. Darling, C.L. Reynolds Jr., D.N. Leonard, G. Duscher, R.O. Scattergood, C.C. Koch, Self-assembled three-dimensional Cu-Ge nanoweb composite. Nanotechnology 19(13), 135603/1–135603/6 (2008)
Article CAS Google Scholar
B.W. Ahn, Y.S. Chi, T.J. Kang, Preparation and characterization of multi-walled carbon nanotube/poly(ethylene terephthalate) nanoweb. J. Appl. Polym. Sci. 110(6), 4055–4063 (2008)
Article CAS Google Scholar
D. Kimmer, P. Slobodian, D. Petras, M. Zatloukal, R. Olejnik, P. Saha, Polyurethane/multiwalled carbon nanotube nanowebs prepared by an electrospinning process. J. Appl. Polym. Sci. 111(6), 2711–2714 (2009)
Article CAS Google Scholar
T.-G. Kim, D. Ragupathy, A.I. Gopalan, K.-P. Lee, Electrospun carbon nanotubes-gold nanoparticles embedded nanowebs: prosperous multi-functional nanomaterials. Nanotechnology 21(13), 134021 (2010)
Article CAS Google Scholar
S.-G. Kang, Y.-H. Bae, S.-L. Quan, I.-J. Chin, Electrospun PMMA/polyhedral oligomeric silsesquioxane (POSS) nanohybrid nanofibers. PMSE Prepr. 101, 1293–1294 (2009)
CAS Google Scholar
N. Yahya, B.H. Guan, L.K. Pah, Catalytic effect of formation of a web-like carbon nanostructures. Solid State Sci. Technol. 15(1), 22–29 (2007)
Google Scholar
C.K. Chung, S.T. Hung, C.W. Lai, Effect of microstructure on the mechanical properties of carbon nanofilms deposited on the Si(100) at high temperature under ultra high vacuum. Surf. Coat. Technol. 204(6–7), 1066–1070 (2009)
Article CAS Google Scholar
M. Endo, T. Hayashi, Y.A. Kim, M. Terrones, M.S. Dresselhaus, Applications of carbon nanotubes in the twenty-first century. Phil. Trans. R. Soc. Lond. A 362, 2223–2238 (2004)
Article CAS Google Scholar
H.E. Cho, S.J. Seo, M.-S. Khil, H. Kim, Preparation of carbon nanoweb from cellulose nanowhisker. Fibers Polym. 168(2), 271–275 (2015)
Article CAS Google Scholar
H.-D. Lim, Y. SooYun, Y. Ko, et al., Three-dimensionally branched carbon nanowebs as air-cathode for redox-mediated Li-O₂ batteries. Carbon 118, 114–119 (2017)
Article CAS Google Scholar
L. Li, A. Manthiram, O- and N-doped carbon nanowebs as metal-free catalysts for hybrid Li-air batteries. Adv. Energy Mater. 4(10), 1301795 (2014)
Article CAS Google Scholar
Z. Yang, Q. Meng, Z. Guo, et al., Highly reversible lithium storage in uniform Li₄Ti₅O₁₂/carbon hybrid nanowebs as anode material for lithium-ion batteries. Energy 55, 925–932 (2013)
Article CAS Google Scholar
Q. Huang, L. Liu, D. Wang, et al., One-step electrospinning of carbon nanowebs on metallic textiles for high-capacitance supercapacitor fabrics. J. Mater. Chem. A 4, 6802–6808 (2016)
Article CAS Google Scholar
S. Liu, L. Li, H.S. Ahn, A. Manthiram, Delineating the roles of Co₃O₄ and N-doped carbon nanoweb (CNW) in bifunctional Co₃O₄/CNW catalysts for oxygen reduction and oxygen evolution reactions. J. Mater. Chem. A 3, 11615–11623 (2015)
Article CAS Google Scholar
G. Benedek, H. Vahedi-Tafreshi, E. Barborini, P. Piseri, P. Milani, C. Ducati, J. Robertson, The structure of negatively curved spongy carbon. Diam. Relat. Mater. 12(3–7), 768–773 (2003)
Article CAS Google Scholar
F.H. Oliveira Carvalho, A. Rodrigues Vaz, S. Moshkalev, R. Valentim Gelamo, Synthesis of carbon nanostructures near room temperature using microwave PECVD. Mater. Res. 18(4), 860–866 (2015)
Article CAS Google Scholar
N.Q. Le, Increasing carbon nanosponge oil absorbency through infusion of boron. AAAS 2015 Annual Meeting, 2015., https://aaas.confex.com/aaas/2015/webprogram/Paper15430.html
D.P. Hashim, N.T. Narayanan, J.M. Romo-Herrera, et al., Covalently bonded three-dimensional carbon nanotube solids via boron induced nanojunctions. Sci. Rep. 2, 363 (2012)
Article CAS Google Scholar
F.C.C. Moura, R.M. Lago, Catalytic growth of carbon nanotubes and nanofibers on vermiculite to produce floatable hydrophobic “nanosponges” for oil spill remediation. Appl. Catal. B Environ. 90(3–4), 436–440 (2009)
Article CAS Google Scholar
W. Zhou, R.P. Tiwari, R. Annamalai, R. Sooryakumar, V. Subramaniam, D. Stroud, Sound propagation in light-modulated carbon nanosponge suspensions. Phys. Rev. B 79, 104204 (2009)
Article CAS Google Scholar
A.V. Rode, E.G. Gamaly, A.G. Christy, J.G. Fitz Gerald, S.T. Hyde, R.G. Elliman, B. Luther-Davies, A.I. Veinger, J. Androulakis, J. Giapintzakis, Unconventional magnetism in all-carbon nanofoam. Phys. Rev. B 70, 054407, 9 pp (2004)
Article CAS Google Scholar
N.K. Sidhu, A.C. Rastogi, Bifacial carbon nanofoam-fibrous PEDOT composite supercapacitor in the 3-electrode configuration for electrical energy storage. Synth. Met. 219, 1–10 (2016)
Article CAS Google Scholar
K. Lee, H. Song, K. Hoon Lee, et al., Nickel nanofoam/different phases of ordered mesoporous carbon composite electrodes for superior capacitive energy storage. ACS Appl. Mater. Interfaces 8(34), 22516–22525 (2016)
Article CAS Google Scholar
R. Della Noce, S. Eugénio, M. Boudard, et al., One-step process to form a nickel-based/carbon nanofoam composite supercapacitor electrode using Na₂SO₄ as an eco-friendly electrolyte. RSC Adv. 6, 15920–15928 (2016)
Article CAS Google Scholar
P. Ramakrishnan, S. Shanmugam, J. Hyun Kim, Dual heteroatom-doped carbon nanofoam-wrapped iron monosulfide nanoparticles: an efficient cathode catalyst for Li–O₂ batteries. ChemSusChem 10(7), 1554–1562 (2017)
Article CAS Google Scholar
C.N. Chervin, M.J. Wattendorf, J.W. Long, N.W. Kucko, D.R. Rolison, Carbon nanofoam-based cathodes for Li–O₂ batteries: correlation of pore–solid architecture and electrochemical performance. J. Electrochem. Soc. 160(9), A1510–A1516 (2013)
Article CAS Google Scholar
N. Frese, S. Taylor Mitchell, C. Neumann, A. Bowers, A. Gölzhäuser, K. Sattler, Fundamental properties of high-quality carbon nanofoam: from low to high density. Beilstein J. Nanotechnol. 7, 2065–2073 (2016)
Article CAS Google Scholar
Z. Zhu, D. Tomanek, Formation and stability of cellular carbon foam structures: an ab initio study. Phys. Rev. Lett. 109, 135501 (2012)
Article CAS Google Scholar
Y.-L. Li, W. Luo, X.-J. Chen, Z. Zeng, H.-Q. Lin, R. Ahuja, Formation of Nanofoam carbon and re-emergence of Superconductivity in compressed CaC₆. Sci. Rep. 3, 3331 (2013)
Article Google Scholar
E.G. Gamaly, A.V. Rode, Nanostructures created by lasers, in Encyclopedia of Nanoscience and Nanotechnology, ed. by H. S. Nalwa (Ed), vol. 7, (American Scientific Publishers, Valencia, California, 2004), pp. 783–809
Google Scholar
A. Seral-Ascaso, R. Garriga, M.L. Sanjuán, et al., ‘Laser chemistry’ synthesis, physicochemical properties, and chemical processing of nanostructured carbon foams. Nanoscale Res. Lett. 8, 233 (2013)
Article CAS Google Scholar
A.V. Rode, E.G. Gamaly, B. Luther-Davies, Formation of cluster-assembled carbon nano-foam by high-repetition-rate laser ablation. Appl. Phys. A Mater. Sci. Process. 70, 135–144 (2000)
Article CAS Google Scholar
S. Li, J. Guangbin, L. Liya, Magnetic carbon nanofoams. J. Nanosci. Nanotechnol. 9, 1133–1136 (2009)
Article CAS Google Scholar
D.W.M. Lau, D.G. McCulloch, N.A. Marks, N.R. Madsen, A.V. Rode, High-temperature formation of concentric fullerene-like structures within foam-like carbon: experiment and molecular dynamics simulation. Phys. Rev. B 75, 233408 (2007)
Article CAS Google Scholar
Z. Liu, S.-K. Joung, T. Okazaki, K. Suenaga, Y. Hagiwara, T. Ohsuna, K. Kuroda, S. Iijima, Self-assembled double ladder structure formed inside carbon nanotubes by encapsulation of H₈Si₈O₁₂. ACS Nano 3(5), 1160–1166 (2009)
Article CAS Google Scholar
S.P. Sharma, S.C. Lakkad, Morphology study of carbon nanospecies grown on carbon fibers by thermal CVD technique. Surf. Coat. Technol. 203(10–11), 1329–1335 (2009)
Article CAS Google Scholar
C. Ronning, D. Schwen, One dimensional material from semiconductors. Nanowires, nanosaws, nanospirals. Physik in Unserer Zeit 37(1), 34–40 (2006)
Article CAS Google Scholar
V.Y. Prinz, Three-dimensional self-shaping nanostructures based on free stressed heterofilms. Russ. Phys. J. (Translation of Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika) 46(6), 568–576 (2003)
CAS Google Scholar
P.G. Mezey, Computational quantum chemistry design of nanospirals and nanoneedles. Lecture Series on Computer and Computational Sciences 6(Trends and Perspectives in Modern Computational Science), 222–230 (2006)
CAS Google Scholar
S. Vaudreuil, M. Bousmina, Stretchable carbon nanosprings production by a catalytic growth process. J. Nanosci. Nanotechnol. 9(8), 4880–4885 (2009)
Article CAS Google Scholar
L. Liu, J. Zhao, Toroidal and coiled carbon nanotubes, in Syntheses and Applications of Carbon Nanotubes and Their Composites, (InTech, London, UK, 2013), pp. 257–281
Google Scholar
A. Zettl, C. John, Sharpened nanotubes, nanobearings, and nanosprings, in CP544, Electronic Properties of Novel Materials—Molecular Nanostructures, ed. by H. Kuzmany et al. (Eds), (American Institute of Physics, College Park, Maryland, USA, 2000)
Google Scholar
K. Mukhopadhyay, D. Porwal, K.U.B. Rao, Carbon micro/nano spring structures in the absence of sulphurous promoter by CCVD method. J. Nanosci. Nanotechnol. 7(6), 1851–1854 (2007)
Article CAS Google Scholar
N. Tang, W. Kuo, C. Jeng, L. Wang, K. Lin, Y. Du, Coil-in-coil carbon nanocoils: 11 gram-scale synthesis, single nanocoil electrical properties, and electrical contact improvement. ACS Nano 4(2), 781–788 (2010)
Article CAS Google Scholar
K. Nakamatsu, J. Igaki, M. Nagase, T. Ichihashi, S. Matsui, Mechanical characteristics of tungsten-containing carbon nanosprings grown by FIB-CVD. Microelectron. Eng. 83(4–9), 808–810 (2006)
Article CAS Google Scholar
K. Nakamatsu, T. Ichihashi, K. Kanda, Y. Haruyama, T. Kaito, S. Matsui, Nanostructure analysis of nanosprings fabricated by focused-ion-beam chemical vapor deposition. Jpn. J. Appl. Phys. 48(10), 105001/1–105001/4 (2009)
Article CAS Google Scholar
X. Chen, S. Zhang, D.A. Dikin, W. Ding, R.S. Ruoff, Mechanics of a carbon nanocoil. Nano Lett. 3(9), 1299–1304 (2003)
Article CAS Google Scholar
M. Mahdi Zaeria, S. Ziaei-Rad, Elastic behavior of carbon nanocoils: a molecular dynamics study. AIP Adv. 5, 117114 (2015)
Article CAS Google Scholar
M. Neek-Amal, J. Beheshtian, F. Shayeganfar, S.K. Singh, J.H. Los, F.M. Peeters, Spiral graphone and one-sided fluorographene nanoribbons. Phys. Rev. B 87, 075448 (2013)
Article CAS Google Scholar
J. Liu, Y.-L. Lu, M. Tian, F. Li, J. Shen, Y. Gao, L. Zhang, The interesting influence of nanosprings on the viscoelasticity of elastomeric polymer materials: simulation and experiment. Adv. Funct. Mater. 23(9), 1156–1163 (2013)
Article CAS Google Scholar
J. Zhan. Editor(s): Voler, Nicolas H., Carbon nanotubes as use of nanothermometer. Bando, Yoshio. Materials Integration 17(6), 34–40 (2004)
Google Scholar
Y. Bando, World smallest nanothermometer using carbon nanotube. Kagaku 59(6), 20–24 (2004)
CAS Google Scholar
Y. Bando, Oxide-nanotubes as use of nanothermometer. Seramikkusu 41(4), 262–266 (2006)
CAS Google Scholar
Y. Bando, Nanothermometer using oxide nanotubes. Materials Integration 18(1), 42–47 (2004). Volume Date 2005
Google Scholar
Y. Bando, Study of nanomaterials by using state-of-the-art microscopy. Kagaku to Kogyo 57(6), 595–600 (2004)
CAS Google Scholar
G. Yihua, B. Yoshio, Carbon nanothermometer containing gallium. Nature 415(7), 599–600 (2002)
Google Scholar
A.M. Popova, Y.E. Lozovik, E. Bichoutskaia, G.S. Ivanchenko, N.G. Lebedev, E.K. Krivorotov, An electromechanical nanothermometer based on thermal vibrations of carbon nanotube walls. Phys. Solid State 51(6), 1306–1314 (2009)
Article CAS Google Scholar
R. Ansari, M. Daliri, M. Hosseinzadeh, On the van der Waals interaction of carbon nanotubes as electromechanical nanothermometers. Acta Mech. Sinica 29(4), 622–632 (2013)
Article CAS Google Scholar
Z. Liu, Y. Bando, J. Hu, K. Ratinac, S.P. Ringer, A novel method for practical temperature measurement with carbon nanotube nanothermometers. Nanotechnology 17(15), 3681–3684 (2006)
Article CAS Google Scholar
J. Zhan, Y. Bando, J. Hu, D. Golberg, Nanothermometers: bulk synthesis and calibration, in Abstracts of Papers, 232nd ACS National Meeting, San Francisco, 10–14 Sept 2006, INOR-488
Google Scholar
Y. Gao, Y. Bando, D. Golberg, Melting and expansion behavior of indium in carbon nanotubes. Appl. Phys. Lett. 81(22), 4133–4135 (2002)
Article CAS Google Scholar
A.M. Popov, Y.E. Lozovik, E. Bichoutskaia, G.S. Ivanchenko, N.G. Lebedev, E.K. Krivorotov, An electromechanical nanothermometer based on thermal vibrations of carbon nanotube walls. Phys. Solid State 51(6), 1306–1314 (2009)
Article CAS Google Scholar
A.M. Popov, Y.E. Lozovik, E. Bichoutskaia, G.S. Ivanchenko, N.G. Lebedev, E.K. Krivorotov, Electromechanical nanothermometer based on carbon nanotubes. Fullerenes, Nanotubes, Carbon Nanostruct. 16(5–6), 352–356 (2008)
Article CAS Google Scholar
A. Vyalikh, R. Klingeler, S. Hampel, D. Haase, M. Ritschel, A. Leonhardt, E. Borowiak-Palen, M. Rümmeli, A. Bachmatiuk, R.J. Kalenczuk, H.-J. Grafe, B. Büchner, A nanoscaled contactless thermometer for biological systems. Phys. Status Solidi B 244(11), 4092–4096 (2007)
Article CAS Google Scholar
C. Wang, K. Jiang, Q. Wu, J. Wu, C. Zhang, Green synthesis of red-emitting carbon nanodots as a novel “turn-on” nanothermometer in living cells. Chem. Eur. J. 22(41), 14475–14479 (2016)
Article CAS Google Scholar
X. Liu, X. Tang, Y. Hou, Q. Wu, G. Zhang, Fluorescent nanothermometers based on mixed shell carbon nanodots. RSC Adv. 5, 81713–81722 (2015)
Article CAS Google Scholar
K. Jiang, J. Wu, Q. Wu, X. Wang, C. Wang, Y. Li, Stable fluorescence of green-emitting carbon nanodots as a potential nanothermometer in biological media. Part. Part. Syst. Charact. 4(2), 1600197 (2017)
Article CAS Google Scholar
Y. Yang, W. Kong, H. Li, et al., Fluorescent N-doped carbon dots as in vitro and in vivo nanothermometer. ACS Appl. Mater. Interfaces 7(49), 27324–27330 (2015)
Article CAS Google Scholar
Y. Nakayama, Nanomachine “nanotweezers”. Kagaku to Kogyo 56(6), 663–666 (2003)
CAS Google Scholar
C. M. Lieber, J. H. Hafner, C. Cheung Li, P. Kim, Direct growth of carbon nanotubes, and their use in nanotweezers, 2002, 46 pp. WO 2002026624
Google Scholar
J. Chang, B.-K. Min, J. Kim, S.-J. Lee, L. Lin, Electrostatically actuated carbon nanowire nanotweezers. Smart Mater. Struct. 18(6) (2009). 065017/1-065017/7
Article CAS Google Scholar
J. Lee, S. Kim, Manufacture of a nanotweezer using a length controlled CNT arm. Sensors Actuators A Phys. A120(1), 193–198 (2005)
Article CAS Google Scholar
G. Liu, Y. Miyake, N. Komatsu, Nanocalipers as novel molecular scaffolds for carbon nanotubes. Org. Chem. Front. 4, 911–919 (2017)
Article CAS Google Scholar
J. M. Tour, NanoCars, in Abstracts, 65th Southwest Regional Meeting of the American Chemical Society, El Paso, 4–7 Nov 2009, SWRM-130
Google Scholar
T. Sasaki, A.J. Osgood, L.B. Alemany, K.F. Kelly, J.M. Tour, Synthesis of a nanocar with an angled chassis. Toward circling movement. Org. Lett. 10(2), 229–232 (2008)
Article CAS Google Scholar
T. Sasaki, J.M. Tour, Synthesis of a dipolar nanocar. Tetrahedron Lett. 48(33), 5821–5824 (2007)
Article CAS Google Scholar
A.V. Akimov, A.V. Nemukhin, A.A. Moskovsky, A.B. Kolomeisky, J.M. Tour, Molecular dynamics of surface-moving thermally driven nanocars. J. Chem. Theory Comput. 4(4), 652–656 (2008)
Article CAS Google Scholar
T. Sasaki, J.M. Guerrero, J.M. Tour, The assembly line: self-assembling nanocars. Tetrahedron 64(36), 8522–8529 (2008)
Article CAS Google Scholar
S. Khatua, J.M. Guerrero, K. Claytor, G. Vives, A.B. Kolomeisky, J.M. Tour, S. Link, Micrometer-scale translation and monitoring of individual nanocars on glass. ACS Nano 3(2), 351–356 (2009)
Article CAS Google Scholar
G.J. Simpson, V. García-López, P. Petermeier, L. Grill, J.M. Tour, How to build and race a fast nanocar. Nat. Nanotechnol. 12, 604–606 (2017)
Article CAS Google Scholar
G. Vives, J.M. Tour, Synthesis of single-molecule nanocars. Acc. Chem. Res. 42(3), 473–487 (2009)
Article CAS Google Scholar
G. Vives, J. M. Tour, Synthesis of a nanocar with organometallic wheels, in Abstracts of Papers, 238th ACS National Meeting, Washington, DC, 16–20 Aug 2009, INOR-346
Google Scholar
G. Vives, J.M. Tour, Synthesis of a nanocar with organometallic wheels. Tetrahedron Lett. 50(13), 1427–1430 (2009)
Article CAS Google Scholar
J.-F. Morin, Y. Shirai, J.M. Tour, En route to a motorized nanocar. Org. Lett. 8(8), 1713–1716 (2006)
Article CAS Google Scholar
Y. Shirai, A.J. Osgood, Y. Zhao, Y. Yao, L. Saudan, H. Yang, Y.-H. Chiu, L.B. Alemany, T. Sasaki, J.-F. Morin, J.M. Guerrero, K.F. Kelly, J.M. Tour, Surface-rolling molecules. J. Am. Chem. Soc. 128(14), 4854–4864 (2006)
Article CAS Google Scholar
Y. Shirai, A.J. Osgood, Y. Zhao, K.F. Kelly, J.M. Tour, Directional control in thermally driven single-molecule nanocars. Nano Lett. 5(11), 2330–2334 (2005)
Article CAS Google Scholar
Z.L. Wang, P. Poncharal, W.A. de Heer, Measuring physical and mechanical properties of individual carbon nanotubes by in situ TEM. J. Phys. Chem. Solids 61, 1025–1030 (2000)
Article CAS Google Scholar
A. Mirmohseni, M. Shojaei, M.A.H. Feizi, F.F. Azhar, M. Rastgouye-Houjaghan, Application of quartz crystal nanobalance and principal component analysis for detection and determination of nickel in solution. J. Environ. Sci. Health, Part A: Tox. Hazard. Subst. Environ. Eng. 45(9), 1119–1125 (2010)
Article CAS Google Scholar
O.A. Williams, V. Mortet, M. Daenen, K. Haenen, The diamond nano-balance. J. Nanosci. Nanotechnol. 9(6), 3483–3486 (2009)
Article CAS Google Scholar
Y. Huang, X. Bai, Y. Zhang, In situ mechanical properties of individual ZnO nanowires and the mass measurement of nanoparticles. J. Phys. Condens. Matter 18(15), L179–L184 (2006)
Article CAS Google Scholar
J. Bai, X. Zhong, S. Jiang, Y. Huang, X. Duan, Graphene nanomesh. Nat. Nanotechnol. 5(3), 190–194 (2010)
Article CAS Google Scholar
B. Jingwei, Z. Xing, J. Shan, H. Yu, D. Xiangfeng, Graphene nanomesh. Nat. Nanotechnol. 5(3), 190–194 (2010)
Article CAS Google Scholar
X. Liang, Y.-S. Jung, S. Wu, A. Ismach, D.L. Olynick, S. Cabrini, J. Bokor, Formation of bandgap and subbands in graphene nanomeshes with sub-10 nm ribbon width fabricated via nanoimprint lithography. Nano Lett. 10(7), 2454–2460 (2010)
Article CAS Google Scholar
O. Akhavan, Graphene nanomesh by ZnO nanorod photocatalysts. ACS Nano 4(7), 4174–4180 (2010)
Article CAS Google Scholar
H.L. Zhang, W. Chen, H. Huang, L. Chen, A.T.S. Wee, Preferential trapping of C₆₀ in nanomesh voids. J. Am. Chem. Soc. 130, 2720–2721 (2008)
Article CAS Google Scholar
H. Wang, L. Zhi, K. Liu, et al., Thin-sheet carbon nanomesh with an excellent electrocapacitive performance. Adv. Funct. Mater. 25(34), 5420–5427 (2015)
Article CAS Google Scholar
D.-P. Yang, X. Wang, X. Guo, et al., UV/O₃ generated graphene nanomesh: formation mechanism, properties, and FET studies. J. Phys. Chem. C 118(1), 725–731 (2014)
Article CAS Google Scholar
H.-H. Byeon, W. Chul Lee, W. Kim, et al., Bio-fabrication of nanomesh channels of single-walled carbon nanotubes for locally gated field-effect transistors. Nanotechnology 28, 025304 (2017)
Article CAS Google Scholar
X.-L. Su, M.-Y. Cheng, L. Fu, et al., Superior supercapacitive performance of hollow activated carbon nanomesh with hierarchical structure derived from poplar catkins. J. Power Sources 362, 27–38 (2017)
Article CAS Google Scholar
S.-J. Choi, P. Bennett, D. Lee, J. Bokor, Highly uniform carbon nanotube nanomesh network transistor. Nano Res. (8), 1320 (2015)
Article CAS Google Scholar
X.F. Yang, H.L. Wang, Y.S. Chen, et al., Giant spin thermoelectric effects in all-carbon nanojunctions. Phys. Chem. Chem. Phys. 17, 22815–22822 (2015)
Article CAS Google Scholar
Y. Liao, Y. Xie, K. Pan, et al., Fe₃W₃C/WC/graphitic carbon ternary nanojunction hybrids for dye-sensitized solar cells. ChemSusChem 8(4), 726–733 (2015)
Article CAS Google Scholar
I.A. Pshenichnyuk, P.B. Coto, S. Leitherer, M. Thoss, Charge transport in pentacene-graphene nanojunctions. J. Phys. Chem. Lett. 4(5), 809–814 (2013)
Article CAS Google Scholar
M.M. Hassan, A.A. El-Barbary, M.A. Kamel, K.M. Eid, H.O. Taha, Mono-vacancy and B-doped defects in carbon heterojunction nanodevices. Graphene 4, 84–90 (2015)
Article CAS Google Scholar
D. Szczesniak, A. Khater, Z. Bak, R. Szczesniak, M. Abou Ghantous, Quantum conductance of silicon-doped carbon wire nanojunctions. Nanoscale Res. Lett. 7, 616 (2012)
Article CAS Google Scholar
A.G. Krivenko, N.S. Komarova, Electrochemistry of nanostructured carbon. Russ. Chem. Rev. 77(11), 927–943 (2008)
Article CAS Google Scholar
A. Barhoum, P. Samyn, T. Öhlundd, A. Dufresnee, Review of recent research on flexible multifunctional nanopapers. Nanoscale 9, 15181–15205 (2017)
Article CAS Google Scholar
Y. Zhao, E.D. Cabrera, M.C. Jose, L.J. Lee, Chapter 4 - Carbon nanopaper: a platform to high-performance multifunctional composites, in Nanopapers From Nanochemistry and Nanomanufacturing to Advanced Applications, Micro and Nano Technologies, (Elsevier Science, New York, 2018), pp. 87–120
Chapter Google Scholar
L. Hu, N. Liu, M. Eskilsson, G. Zheng, J. McDonough, L. Wågberg, Y. Cui, Silicon-conductive nanopaper for Li-ion batteries. Nano Energy 2, 138–145 (2013)
Article CAS Google Scholar
D.P. Wong, R. Suriyaprabha, R. Yuvakumar, V. Rajendran, Y.-T. Chen, B.-J. Hwang, L.-C. Chen, K.-H. Chen, Binder-free rice husk-based silicon–graphene composite as energy efficient Li-ion battery anodes. J. Mater. Chem. A 2, 13437–13441 (2014)
Article CAS Google Scholar
J. Zhuge, J. Gou, R.-H. Chen, et al., Fire retardant evaluation of carbon nanofiber/graphite nanoplatelets nanopaper-based coating under different heat fluxes. Compos. Part B 43, 3293–3305 (2012)
Article CAS Google Scholar
H. Lu, Y. Liu, J. Leng, Carbon nanopaper enabled shape memory polymer composites for electrical actuation and multifunctionalization. Marcomol. Mater. Eng. 297(12), 1138–1147 (2012)
CAS Google Scholar
H. Lu, Y. Liu, J. Gou, J. Leng, S. Du, Electrical properties and shape-memory behavior of self-assembled carbon nanofiber nanopaper incorporated with shape-memory polymer. Smart Mater. Struct. 19(7), 075021/1–075021/7 (2010)
Article CAS Google Scholar
H. Lu, Y. Liu, J. Gou, J. Leng, S. Du, Synergistic effect of carbon nanofiber and carbon nanopaper on shape memory polymer composite. Appl. Phys. Lett. 96(8), 084102/1–084102/3 (2010)
Article CAS Google Scholar
H. Lu, P. Bai, W. Yin, F. Liang, J. Gou, Magnetically aligned carbon nanotubes in nanopaper for electro-activated shape-memory nanocomposites. Nanosci. Nanotechnol. Lett. 5(7), 732–736 (2013)
Article Google Scholar
H. Lu, F. Liang, Y. Yao, J. Gou, D. Hui, Self-assembled multi-layered carbon nanofiber nanopaper for significantly improving electrical actuation of shape memory polymer nanocomposite. Compos. Part B 59, 191–195 (2014)
Article CAS Google Scholar
H. Lu, W.M. Huang, J. Leng, Functionally graded and self-assembled carbon nanofiber and boron nitride in nanopaper for electrical actuation of shape memory nanocomposites. Compos. Part B 62, 1–4 (2014)
Article CAS Google Scholar
X. Zhao, J. Gou, G.G. Song, J. Ou, Strain monitoring in glass fiber reinforced composites embedded with carbon nanopaper sheet using Fiber Bragg Grating (FBG) sensors. Compos. Part B Eng. 40B(2), 134–140 (2009)
Article CAS Google Scholar
M.R. Bromberg, A. Patlolla, R. Segal, Y. Feldman, Q. Wang, Z. Iqbal, A.I. Frenkel, Synthesis and characterization of platinum nanoparticles on single-walled carbon nanotube “nanopaper” support. J. Phys. Conf. Ser. 190, 012155 (2009)
Article CAS Google Scholar
J. Gou, R. Blanco, Z. Zhao, A. Khan, A. Appalla, Synthesis of nickel-coated carbon nanopaper sheets by pulse laser deposition. Materials Research Society Symposium Proceedings, 2007, 1006E (Transport Behavior in Heterogeneous Polymeric Materials and Composites), No pp. given, Paper #: 1006-R01-09
Google Scholar
M. Das, C. Bittencourt, J.-J. Pireaux, S.A. Shivashankar, Metallic Li in carbonaceous nanotubes grown by metalorganic chemical vapor deposition from a metalorganic precursor. Appl. Organomet. Chem. 22(11), 647–658 (2008)
Article CAS Google Scholar
D.A. Lowy, A. Patrut, Nanobatteries: decreasing size power sources for growing technologies. Recent Pat. Nanotechnol. 2(3), 208–219 (2008)
Article CAS Google Scholar
Fast-charging nano batteries. Am. Ceram. Soc. Bull. 85(10), 21–22 (2006) https://bulletin-archive.ceramics.org/uctv2f/
J.W. Long, B. Dunn, D.R. Rolison, H.S. White, Three-dimensional battery architectures. Chem. Rev. 104, 4463–4492 (2004)
Article CAS Google Scholar
P. Sehrawat, C. Julien, S.S. Islam, Carbon nanotubes in Li-ion batteries: a review. Mater. Sci. Eng. B 213, 12–40 (2016)
Article CAS Google Scholar
B. Liu, X. Wu, S. Wang, et al., Flexible carbon nanotube modified separator for high-performance lithium-sulfur batteries. Nano 7, 196 (2017)
Google Scholar
W.-J. Yu, C. Liu, L. Zhang, et al., Synthesis and electrochemical lithium storage behavior of carbon nanotubes filled with iron sulfide nanoparticles. Adv. Sci. 3, 1600113 (2016)
Article CAS Google Scholar
W.-S. Kim, J. Choi, S.-H. Hong, Meso-porous silicon-coated carbon nanotube as an anode for lithium-ion battery. Nano Res. 9(7), 2174–2181 (2016)
Article CAS Google Scholar
C. Shen, J. Xie, M. Zhang, et al., Carbon nanotube (CNT) foams as sulfur hosts for high performance lithium sulfur battery. ECS Trans. 77(11), 457–465 (2017)
Article CAS Google Scholar
A.-R.O. Raji, R. Villegas Salvatierra, N. Dong Kim, et al., Lithium batteries with nearly maximum metal storage. ACS Nano 11(6), 6362–6369 (2017)
Article CAS Google Scholar
http://www.nanowerk.com/spotlight/spotid=3331.php
A.C. Romain, J. Nicolas, Long term stability of metal oxide-based gas sensors for e-nose environmental applications: an overview. Sensors Actuators B Chem. B146(2), 502–506 (2010)
Article CAS Google Scholar
F. Korel, M.O. Balaban, Electronic nose technology in food analysis, in Handbook of Food Analysis Instruments, ed. by S. Otles (Ed), (CRC Press, Boca Raton, FL, USA, 2009), pp. 365–378
Google Scholar
H. Nanto, Electronic nose (e-NOSE) system. Materials Integration 21(5, 6), 99–104 (2008)
CAS Google Scholar
A.D. Wilson, M. Baietto, Applications and advances in electronic-nose technologies. Sensors 9(7), 5099–5148 (2009)
Article CAS Google Scholar
C. Wongchoosuk, A. Wisitsoraat, A. Tuantranont, T. Kerdcharoen, Portable electronic nose based on carbon nanotube-SnO₂ gas sensors and its application for detection of methanol contamination in whiskeys. Sensors Actuators B Chem. B147(2), 392–399 (2010)
Article CAS Google Scholar
S. Kaur, A. Kumar, J.K. Rajput, P. Arora, H. Singh, SnO₂—glycine functionalized carbon nanotubes based electronic nose for detection of explosive materials. Sens. Lett. 14(7), 733–739 (2016)
Article Google Scholar
P. Lorwongtragool, E. Sowade, N. Watthanawisuth, R.R. Baumann, T. Kerdcharoen, A novel wearable electronic nose for healthcare based on flexible printed chemical sensor array. Sensors 14, 19700–19712 (2014)
Article Google Scholar
B.D. Lampson, A. Khalilian, J.K. Greene, Y.J. Han, D.C. Degenhardt, Development of a portable electronic nose for detection of cotton damaged by Nezara viridula (Hemiptera: Pentatomidae). J. Insects 2014, 297219, 8 pp (2014)
Article Google Scholar
M.L. Rodríguez-Méndez, J.A. De Saja, R. González-Antón, et al., Electronic noses and tongues in wine industry. Front. Bioeng. Biotechnol. 4, 81 (2016)
Article Google Scholar
A.M. Popov, E. Bichoutskaia, Y.E. Lozovik, A.S. Kulish, Nanoelectromechanical systems based on multi-walled nanotubes: nanothermometer, nanorelay, and nanoactuator. Phys. Status Solidi A 204(6), 1911–1917 (2007)
Article CAS Google Scholar
J. Li, X. Wang, L. Zhao, X. Gao, Y. Zhao, R. Zhouc, Rotation motion of designed nano-turbine. Sci. Rep. 4, 5846 (2014)
Article CAS Google Scholar
J. Basu, C. Roy Chaudhuri, Graphene nanogrids FET immunosensor: signal to noise ratio enhancement. Sensors 16, 1481 (2016)
Article CAS Google Scholar
O.E. Glukhova, I.N. Salii, V.P. Meshchanov, Nano-autoclave on the basis of carbon nanopeapod. Nano- i Mikrosistemnaya Tekhnika 10, 47–52 (2007)
Google Scholar
A. Mayoral, H. Barron, R. Estrada-Salas, A. Vazquez-Duran, M. Jose-Yacaman, Nanoparticle stability from the nano to the meso interval. Nanoscale 2, 335–342 (2010)
Article CAS Google Scholar
W. Wang, T. Christensen, A.-P. Jauho, K.S. Thygesen, M. Wubs, N.A. Mortensen, Plasmonic eigenmodes in individual and bow-tie graphene nanotriangles. Sci. Rep. (2015). https://doi.org/10.1038/srep09535
H.P. Heiskanen, M. Manninen, J. Akola, Electronic structure of triangular, hexagonal and round graphene flakes near the Fermi level. 2008, arXiv:0809.4162v1. https://arxiv.org/pdf/0809.4162
Article CAS Google Scholar
D. Gorakh Babar, B. Pakhira, S. Sarkar, DNA–carbon nano onion aggregate: triangle, hexagon, six-petal flower to dead-end network. Appl. Nanosci. 7(6), 291–297 (2017)
Article CAS Google Scholar
V.I. Merkulov, A.V. Melechko, M.A. Guillorn, D.H. Lowndes, M.L. Simpson, Effects of spatial separation on the growth of vertically aligned carbon nanofibers produced by plasma-enhanced chemical vapor deposition. Appl. Phys. Lett. 80(3), 476–478 (2002)
Article CAS Google Scholar
M. Hu, X. Dong, Y. Pan, et al., A metallic carbon consisting of helical carbon triangle chains. J. Phys. Condens. Matter 26, 235402, 6 pp (2014)
Article CAS Google Scholar
Y. Masuda, H. Yoshida, S. Takeda, H. Kohno, In situ transmission electron microscopy of individual carbon nanotetrahedron/nanoribbon structures in Joule heating. Appl. Phys. Lett. 105, 083107 (2015)
Article CAS Google Scholar
H. Kohno, Y. Masuda, In situ transmission electron microscopy of individual carbon nanotetrahedron/ribbon structures in bending. Appl. Phys. Lett. 106, 193103 (2015)
Article CAS Google Scholar
H. Kohno, T. Hasegawa, Chains of carbon nanotetrahedra/nanoribbons. Sci. Rep. 5, 8430 (2015)
Article CAS Google Scholar
T. Hasegawa, H. Kohno, Splitting and joining in carbon nanotube/nanoribbon/nanotetrahedron growth. Phys. Chem. Chem. Phys. 17, 3009–3013 (2015)
Article CAS Google Scholar
S. Kumar Sonkar, M. Saxena, M. Saha, S. Sarkar, Carbon nanocubes and nanobricks from pyrolysis of rice. J. Nanosci. Nanotechnol. 10, 4064–4067 (2010)
Article CAS Google Scholar
B. Sun, S. Chen, H. Liu, G. Wang, Mesoporous carbon nanocube architecture for high-performance lithium–oxygen batteries. Adv. Funct. Mater. 25, 4436–4444 (2015)
Article CAS Google Scholar
G. Oza, M. Ravichandran, V.-I. Merupo, et al., Camphor-mediated synthesis of carbon nanoparticles, graphitic shell encapsulated carbon nanocubes and carbon dots for bioimaging. Sci. Rep. 6, 21286 (2016)
Article CAS Google Scholar
Y. Liang, J. Wei, X. Zhang, et al., Synthesis of nitrogen-doped porous carbon nanocubes as a catalyst support for methanol oxidation. ChemCatChem 8(11), 1901–1904 (2016)
Article CAS Google Scholar
F. Gao, F. Zhou, Y. Yao, et al., Ordered assembly of platinum nanoparticles on carbon nanocubes and their application in the non-enzymatic sensing of glucose. J. Electroanal. Chem. 803, 165–172 (2017)
Article CAS Google Scholar
X.-W. Liu, Z.-J. Yao, Y.-F. Wang, X.-W. Wei, Graphene oxide sheet-prussian blue nanocomposites: green synthesis and their extraordinary electrochemical properties. Colloids Surf. B. Biointerfaces 81(2), 508–512 (2010)
Article CAS Google Scholar
J. Xi, Y. Xia, Y. Xu, J. Xiao, S. Wang, (Fe,Co)@nitrogen-doped graphitic carbon nanocubes derived from polydopamine-encapsulated metal–organic frameworks as a highly stable and selective non-precious oxygen reduction electrocatalyst. Chem. Commun. 51, 10479–10482 (2015)
Article CAS Google Scholar
W. Chen, X. Zhang, F. Ai, Graphitic carbon nanocubes derived from ZIF-8 for photothermal therapy. Inorg. Chem. 55(12), 5750–5752 (2016)
Article CAS Google Scholar
X. Fang, L. Jiao, S.-H. Yu, H.-L. Jiang, Metal–organic framework-derived FeCo-N-doped hollow porous carbon nanocubes for electrocatalysis in acidic and alkaline media. ChemSusChem 10, 3019–3024 (2017)
Article CAS Google Scholar
S. Chen, B. Sun, X. Xie, et al., Multi-chambered micro/mesoporous carbon nanocubes as new polysulfides reservoirs for lithium–sulfur batteries with long cycle life. Nano Energy 16, 268–280 (2015)
Article CAS Google Scholar
H.X. Zhang, P.X. Feng, Synthesis of the vertically aligned carbon hexagonal nanoprism arrays and their application for field emission. Appl. Surf. Sci. 255, 5939–5942 (2009)
Article CAS Google Scholar

Download references

Author information

Authors and Affiliations

Universidad Autónoma de Nuevo León, Monterrey, Mexico
Boris Ildusovich Kharisov & Oxana Vasilievna Kharissova

Authors

Boris Ildusovich Kharisov
View author publications
You can also search for this author in PubMed Google Scholar
Oxana Vasilievna Kharissova
View author publications
You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

Copyright information

About this chapter

Cite this chapter

Kharisov, B.I., Kharissova, O.V. (2019). Less-Common Carbon Nanostructures. In: Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications. Springer, Cham. https://doi.org/10.1007/978-3-030-03505-1_4

Download citation

DOI: https://doi.org/10.1007/978-3-030-03505-1_4
Published: 03 January 2019
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-03504-4
Online ISBN: 978-3-030-03505-1
eBook Packages: Chemistry and Materials ScienceChemistry and Material Science (R0)

Publish with us

Policies and ethics

Less-Common Carbon Nanostructures

Abstract

Keywords

4.1 Atomic, Dotted, and Chain Molecular Carbon Forms

4.1.1 Atomic and Diatomic Carbon

4.1.2 Carbon Nanodots, and Graphene Quantum Dots

Synthesis

Functionalization, Grafting, and Doping

Applications

4.1.3 Carbyne, ,

4.1.4 Carbon-Atom Wires

4.2 Elongated Carbon Nanostructures

4.2.1 Nanopencils

4.2.2 Nanobuds

Synthesis of Carbon Nanobuds, Their Formation Mechanism, and In Situ Engineering

DFT and MD Calculations for Carbon NBs

Related Noble Metal Nanobuds

Applications of Nanobuds

4.2.3 Nanopeapods

4.2.4 Nanochains

4.2.5 Nanobars and Nanobricks

4.2.6 Nanobelts

4.2.7 Nanobottles

4.2.8 Nanocones,

4.2.9 Nanospikes

Nanowicks

Nanopillars

4.3 Circle and Ball-Type Nanostructures

4.3.1 Nanorings

4.3.2 Nanotori

4.3.3 Nanoballs

4.3.4 Nanospheres

4.3.5 Nanoonions

Synthesis of Carbon Nanoonions

Chemical Activation of CNOs

Decoration, Dopation, and Functionalization of CNOs

Dopation of CNOs

Functionalization of CNOs

Some Properties of CNOs

Molecular Dynamics Simulations

Applications of CNOs

4.3.6 Nanorice

4.4 Nanocage-Type Structures

4.4.1 Nanocages

4.4.2 Nanoboxes

4.4.3 Nanocapsules

4.5 “Nanovegetation” World

4.5.1 Nanotrees in General

4.5.2 Nanopalms

4.5.3 Nanoleaves

4.5.4 Nanoforests

Synthesis

Special Studies of CNTF Internal Structure and Other Properties

4.5.5 Nanobushes

4.5.6 Nanomushrooms

4.5.7 Nanoflowers

4.5.8 Nanobouquets

4.5.9 Broccoli-Like Architectures

4.5.10 Nanograsses

4.6 “Nanoanimal” World

4.6.1 Nanoworms

4.6.2 Nano-urchins

4.7 “Home”-Like Nanostructures

4.7.1 Nanobowls

4.7.2 Nanocups

4.7.3 Nanoplates

4.7.4 Nanobrooms and Nanotepees

4.7.5 Nanobrushes

4.7.6 Nanocarpets

4.7.7 Nanospindles

4.7.8 Nanowebs

4.7.9 Nanosponges

4.7.10 Nanofoams

4.7.11 Nanoladders

4.8 “Nanotechnical” Structures and Devices

4.8.1 Nanosprings/Nanocoils/Nanospirals

4.8.2 Nanothermometers

4.8.3 Nanotweezers

4.8.4 Nanocars and Nanotrucks

4.8.5 Nanobalances

4.1.2 Carbon Nanodots^, and Graphene Quantum Dots

4.1.3 Carbyne^, ^,

4.2.8 Nanocones^,