Introduction

There are a large number of methods (physical, chemical, and biological) to synthesize various types of nanomaterials [1]. The exploitation of ecofriendly materials such as plant for fabrication of nanoparticles provides considerable benefits of compatibility and eco-friendliness for biomedical applications [1]. Using microorganisms or plant extract could be an alternative to chemical and physical procedures for the production of metal or metal oxide nanoparticles in an ecofriendly manner. Taking a biological synthesis of nano-products into account, plant different organs, including leaf, root, fruit, and seed may be utilized. Phytochemical compounds are proteins, vitamins, terpenoids, sugar, and the phenolic substances which act as capping, reducing, and stabilizing agents [2]. Nanomaterials are known as materials with a particle size of 100 nm or less with the particular characteristics [3], determining their interactions with biomolecules [4, 5]. With the novel size and unique features, nanomaterials have been extensively investigated over a decade [6, 7]. These properties hold promises for remarkable performance in several crucial fields of application such as catalytic, magnetic, mechanical, and biological applications [8]. These materials have also high potential to affect cell differentiation in vitro cultures for diverse biological aims [9].

Iron (Fe) is a vital micronutrient for plants, which is mostly in the form of Fe3+ in aerobic soils and high pH. Thus, these soils are mainly deficient in Fe2+, an available form of iron, leading to iron deficiency in plants [10]. Iron is a crucial element for a photosynthetic process, plant growth, activating various enzymes that are implicated in the reduction, nitrogen fixation, and lignin synthesis [10]. Many researchers have stated that nanomaterials should be utilized as a fertilizer to achieve sustainable agriculture [3,4,5, 11].

Several lines of reports indicated that Fe2O3 nanoparticles at an optimized dose can promote growth rate and resistance against stress in various plant species, such as Triticum aestivum [12], Brassica juncea [13], and Arachis hypogaea [10]. In recent years, metal oxide nanoparticles have attracted considerable interest because of their unique physical and chemical properties [5, 14, 15]. Iron oxide nanoparticles are widely studied material, which is extensively used as photocatalysts, sensors, fine ceramics, medical applications, data storage materials, pigments, and photo electrochemical cells [16].

Cornus mas L. has extensively grown in some part of Europe and Asia including Iran. Cornelian cherry fruit provides a highly valuable supply of the highest ascorbic acid, anthocyanin, phenolic and antioxidant activity among many other fruits [17]. This plant, therefore, is suitable for the synthesis of nanoparticles due to outstanding phytochemistry of its fruits having anthocyanins, flavonoids, plenty of oxalic acids butylated hydroxyanisole, and butylated hydroxytoluene [18]. These non-toxic antioxidants can reduce the metal ion and protect them from aggregation. Various plant-derived iron nanoparticles have been synthesized by several researchers [2, 19, 20].

As highlighted above, the utilization of iron chemical fertilizers to optimize crop productivity is inevitable. It is important to note that the application of conventional chemical fertilizers can cause water and soil contamination. Considering green nanotechnology as a multidisciplinary field, diverse attempts have been made to introduce safe and ecofriendly nano-based fertilizer to reduce consumption of chemical fertilizers. However, there are knowledge gaps on the potential phytotoxicity of nano-compounds and possible variations in plant responses to bulk or nano-type of materials, especially Fe2O3 nanoparticles. Taking green nanotechnology, sustainable agriculture, and environmental pollution into account, this study deals with the fabrication of iron oxide nanoparticles using the fruit extract of C. mas. Moreover, there are few scientific reports to compare the effects of nano- and bulk forms of Fe2O3 on plant growth and biomass. Hence, the possible changes in barley (Hordeum vulgare) growth was also addressed in response to the application of the produced nano- or bulk forms of Fe2O3 nanoparticles.

Experimental

Biosynthesis of α-Fe2O3 nanoparticle

Fresh fruits of C. mas were prepared from the local greengrocery of Tehran, Iran. Fe (NO3)3. 9H2O (99. 9%; Merck) was used to prepare the sample. Iron oxide nanoparticles were first synthesized by green synthesis method according to Ahmmad et al. [8] with a minor modification. Air-dried fruits were well grinded. Afterwards, 1.5 L of water was added to 20 g of fruit powder. After 48 h, the extract was prepared by maceration method. Then, 5 mL HCL solution was injected into the mixture drop wise and stirred. The extract solution was stocked at 10 °C. 5 g of Fe (NO3)3. 9H2O was dissolved in 30 mL of the fruit extract and then adjusted to 50 mL by distilled water. The solution was heated at temperature (190 °C) for 14 h under ambient pressure in autoclave. The solution was cooled to room temperature. The obtained nanoparticles were washed with water and then dried in 80 °C for 30 min.

Physicochemical traits of the nanoparticles

Characterization of the obtained nanoparticles was determined using a FTIR spectrophotometer (Nexus 780, Thermo Nicolet, USA), XRD (3003 PTS, Seifert, Germany), transmission electron microscopy (TEM), scanning electron microscope (SEM), (TESCAN, VEGA 3, USA), and energy-dispersive X-ray fluorescence spectrometry (EDXRF).

Complementary experiment

In a complementary experiment, the effects of the synthesized nanoparticle were evaluated on the growth of barley seedlings. The seeds were sterilized with 1% sodium hypochlorite, containing one drop liquid detergent for 10 min, and washed three times with sterile distilled water. The seeds were planted in pot containing vermiculite and perlite. Plants were watered with Hoagland solution containing different doses of Fe bulk or nano-forms, including 0, 10, 20, and 100 mg L−1 for five times with a week interval. The treatment groups were called as follows:

C: control; BFe10: bulk Fe2O3 of 10 mg L−1; BFe20: bulk Fe2O3 of 20 mg L−1; BFe100: bulk Fe2O3 of 100 mg L−1; NFe10: nano-Fe2O3 of 10 mg L−1; NFe20: nano-Fe2O3 of 20 mg L−1; NFe100: nano-Fe2O3 of 100 mg L−1.

Root and shoot fresh biomass were measured for all the treatment groups.

Statistical analysis

The results were statistically evaluated SPSS software. Data were represented in mean and standard error (SE) of three replications. Means were statistically separated using the Duncan test at p ≤ 0.05.

Results and discussion

Physicochemical characteristics of the synthesized nanoparticles

The FTIR spectroscopy was utilized to detect the presence of the functional groups, which can act both as metal-reducing and capping agents, there by resulting in color change. The FTIR spectra of the fruit extract is presented in Fig. 1a. The absorption peaks at 3363 and 1638 cm−1 reflect the O–H and N–H stretching vibration in the phenolic compound and protein in the fruit extract. The bands at 2079 cm−1 is assigned to C–H stretching in carbohydrates. The bands at 1071 cm−1 is caused by the (C=O) NH2 stretching. FTIR spectra of synthesized iron oxide nanoparticles using extract of C. mas is shown in Fig. 1b. Band at 442–501 cm−1 as characteristic peaks of α-Fe2O3 is observed [21]. Comparing Fig. 1a and b, The hydroxyl and amid groups at 3363 and 1638 cm−1 in the fruit extract shift to 3408 and 1623 cm−1 in the IR spectra of the synthesized iron oxide nanoparticle sample. From these IR spectra, it is observed that hydroxyl and amino groups of protein and carbohydrate have the ability to perform dual functions of reduction and stabilization of iron oxide nanoparticles.

Fig. 1
figure 1

FTIR spectra of aCornus mas L. fruit extract and b synthesized iron oxide nanoparticles

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The crystal structure of Fe2O3 nanoparticle was examined by XRD. The ranges of angles were 20°–60°. Figure 2a shows the XRD pattern of the synthesized Fe2O3 nanoparticle. The pattern has been compared with reference to the standard XRD pattern of hematite (in accordance with the standard card JCPDS No. 33-0664). All reflection peaks relate to the pure and single α-Fe2O3 phase. The average particle size (D) of the α-Fe2O3 nanoparticles was estimated using Debye–Scherer equation (Eq. (1)) [22]:

$$D = \frac{k\lambda }{{\beta \cos \theta }},$$
(1)
Fig. 2
figure 2

XRD powder pattern of α-Fe2O3 nanoparticle (a), SEM image (b), TEM (c) images of the synthesized Fe2O3 nanoparticles, as well as EDXRF spectrum of α-Fe2O3 nanoparticles

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where, λ is the X-ray wavelength, K is a dimensionless shape factor, with a value close to unity. The shape factor has a typical value of about 0.9, but varies with the actual shape of the crystallite. β is the line broadening at half the maximum intensity (FWHM), after subtracting the instrumental line broadening, in radians. This quantity is also sometimes denoted as Δ (2θ), and θ is the diffraction angle. XRD analysis of the synthesized nano-product showed the average particle size of 20 nm.

The size and morphology of the Fe2O3 nanoparticle were examined by TEM and SEM analyses. The SEM image of synthesized Fe2O3 nanoparticle demonstrates the morphology of nanoparticles is spherical and spongy (Fig. 2b). It is clear that Fe2O3 nanoparticles are mainly present as granules with small and big spherical-shaped particles and are well crystallize in nature. TEM images of the synthesized nanoparticles are shown in Fig. 2c. This image shows very fine spherical Fe2O3 nanoparticles (20–40 nm) which are very close to XRD calculations. In the EDXRF spectra (Fig. 2d), the peaks around 0.8, 6.2, and 6.9 keV are related to the binding energies of Fe. The EDXRF spectra shows only iron and oxygen elements, which implies that the sample is highly pure Fe2O3 nanoparticle. The remarkable potential of plant extracts (especially fruits) for application in the green synthesis of nano-products is due to the presence of various phytochemicals, such as flavones, polyphenols, and amides which can act as reducing and stabilizing agents [23].

The nano-product-mediated changes in plant early growth

With increase in concentration of nano- or bulk forms of Fe2O3, shoot fresh mass increased in all treated plants over the control. The highest fresh mass was observed at NFe100 group (Fig. 3a). The application of bulk form of Fe2O3 increased shoot biomass by an average of 32.6%, whereas the synthesized nano-type enhanced this parameter by a mean of 68%, implying the higher efficiency of nano-Fe2O3 than the bulk to improve plant growth.

Fig. 3
figure 3

Changes in shoot (a) and root (b) fresh mass in response to the applications of bulk or nano-Fe supplements. C control, BFe10 bulk Fe2O3 of 10 mg L−1, BFe20 bulk Fe2O3 of 20 mg L−1, BFe100 bulk Fe2O3 of 100 mg L−1, NFe10 nano-Fe2O3 of 10 mg L−1, NFe20 nano-Fe2O3 of 20 mg L−1, NFe100 nano-Fe2O3 of 100 mg L−1

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The Fe2O3 nanoparticle and its bulk form at the concentrations of 10, 20, and 100 mg L−1 showed statistically significant stimulation in root fresh mass of the treated plants (Fig. 3b). It was clearly observed that Fe2O3 nanoparticle was more effective than the bulk to stimulate plant early growth. The nano-form stimulated root biomass by an average of 42%, while the bulk type increased this trait by a mean of 18%. The result of this research showed that biologically synthesized Fe2O3 nanoparticles improved plant growth and biomass accumulation much higher than the corresponding doses of bulk type. Nanomaterials have specific features, including a more particular surface area and increased density of reactive areas, thereby easily penetrating the plant cell and affecting cellular biochemistry. In line with our results, several lines of evidence confirmed the differences between the bulk and nanomaterials [5, 6]. Iron oxide nanoparticles could be utilized as a reliable non-toxic substitution for other iron sources [2, 19]. The application of Fe2O3 nanoparticles may associate with particular signaling, especially due to the changes in concentrations of reactive oxygen species leading to stimulation of plant growth. Rui et al., [10] have demonstrated that lower doses of Fe2O3 nanoparticle improved the translocation of iron from the root to the shoot. Rui et al., [10] also found that the adsorption of Fe2O3 nanoparticles to the soil particles can decrease nutrient loss and enhance their cost effectiveness as a fertilizer.

Conclusion

A simple, facile and ecofriendly method has been carried out for biosynthesizing Fe2O3 nanoparticle using the fruit extract of C. mas. The characteristics of the biosynthesized Fe2O3 nanoparticles were examined by FTIR, XRD, TEM and SEM techniques confirming the production of nanoparticles with high quality and purity. This study would help to develop a new method for biosynthesis of nanoparticles with excellent properties. Moreover, comparative data were presented on the changes in biomass accumulations in root and shoot in response to the applications of the synthesized nano-compound or bulk material. The findings displayed a high efficiency of the biologically synthesized Fe2O3 nanoparticle to improve growth of barley seedlings relative to the corresponding levels of bulk counterpart.