1 Introduction

The present epidemic has asked for an urgent alternative to search for human antimicrobial resistance (AMR) and the cleaning of natural resources. Unfortunately, the AMR has emerged as a severe threat as the microbes show mutations, leading to the failure of existing antimicrobial agents, causing huge loss of human lives with economy [1, 2].

Nowadays, nanotechnology and nanoscience have arisen as the future technology for life. Researchers worldwide are working on the enrichment of the nanoworld. In that context, people are working on newer nanoparticle synthesis methods apart from existing methods. Biological methods, especially using plants and secondary metabolites for nanoparticle synthesis, have been the budding area for researchers worldwide owing to many benefits over existing methods [3,4,5,6,7].

Copper, a metal of the first transition series, is a key element for the kingdom Animalia. There we find ample studies on the phytofabrication of CuONPs [8,9,10,11,12,13,14,15]. White garland lily, also called ginger lily (Fig. 1), is a plant from the family Zingiberaceae and is a perennial ornamental species known for its beautiful white flowers used as garland flowers in Maharashtra. Hedychium coronarium Koenig is the botanical name of this species. It has some significant medicinal properties like antimicrobial, antioxidant, anti-hypertensive, and antimalarial potentials [16, 17].

Fig. 1
figure 1

White garland lily plant

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This article presents an eco-benevolent, simple phytofabrication of CuONPs, employing white garland lily leaves extract (WGLLE), its antibacterial and antifungal activities along with its photocatalytic efficacy. To date, this plant is being utilized only for AgNP synthesis, using rhizome extract [18]. So, this article devotes the phytosynthesis of CuONPs with WGLLE, for the first time.

2 Experimental

2.1 Materials

CuSO4.5H2O (AR grade), NaHCO3 (AR grade), and other chemicals were purchased from Molychem, Mumbai, India, and utilized as such.

2.2 Plant Recognition and WGLLE Preparation

The plant recognition was done by Mr. Amol Salve, based on its characteristics explained in Flora of Maharashtra [19]. The specimen was submitted to the Botany department. Freshly collected leaves (20 g) were carried from a household plot belonging to Mr. Satish Doshi, a retired headmaster located at Goregaon. Then, leaves were washed in the laboratory, first by tap water followed by double-distilled water to remove worthless material, and then sliced into very fine bits. These bits were transferred into a 250-mL beaker for boiling, containing 200 mL of double-distilled water for an hour using a hot plate. After an hour mixture was double filtered by ordinary and then by Whatman paper no.1 to get white garland lily leaves extract (WGLLE). The WGLLE was stored in a refrigerator until further use.

2.3 Synthesis of CuONPs

The freshly made 0.1 M CuSO4.5H2O solution with pH 4.6 was mixed to WGLLE in 1:4 ratios, obtained after optimization, which led to an instant alteration in color from green to dark green, which further turned black after stirring on a magnetic stirrer for the 50 min at 500 RPM [8]. The black-colored solid received was then centrifuged at 3500 RPM for around 45 min. After that, it was exposed for combustion in a muffle furnace at around 450 °C. Finally, it was gathered and preserved in a sample tube until further use at the final stage (Fig. 2).

Fig. 2
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Diagrammatic representation- Synthesis of CuONPs

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2.4 Characterization Techniques

The UV–Vis spectrum of CuONPs was recorded by Spectrophotometer (Model-JASCO V-770). Functional groups and chemical composition were analyzed by FT-IR (4600 TypeA D044761786) while PL spectra was recorded by spectrofluorometer (Model No. FP-8200, Sr.No.-C026661448). The XRD spectra were recorded by X-ray diffractometer (XRD, Bruker, D8-Advanced Diffractometer) using Cu-Kα radiation (λ = 0.154 nm) at 40 kV and 40 mA in the range 10–80. High-resolution transmission microscopy analysis was carried out with Model-JEM 200F, accelerating potential: 120 kV and 200 kV. The HRSEM-EDS (FEI Quanta, FEG-200) was used to record the exact size, shape, and elemental composition of CuONPs.

2.5 Phytochemical Screening

The active phytometabolites present in WGLLE were investigated following standard protocols [20].

2.6 Antibacterial Activities

The broth dilution method was used to evaluate the antibacterial efficacy of CuONPs [21, 22] with diluent as DMSO [23,24,25]. Two G + ve and two G –ve bacteria were tested in the experiment. The MIC was taken to the concentration which showed at least 99% inhibition. The results are displayed after triplicate analysis.

2.7 Antifungal Activities

The CuONPs were evaluated versus particular fungal strains using agar dilution protocol following Wiegand et al. [22]. The MIC was considered to be the concentration displaying minimum 99% inhibition with griseofulvin and nystatin as reference drugs. The results were tabulated after triplicate analysis.

2.8 Detoxification Study

This was carried out with MB dye. The 0.25 gm of CuO photocatalyst was dispersed in different concentrations of dye used viz., 1000, 750, 500, 250 ppm and stirred in dark for half an hour to achieve the adsorption–desorption equilibrium mechanism. Then, the solution was exposed to solar radiation and O.D. was recorded after every 10 min.

3 Results and Discussion

3.1 The Structural and Crystallographic Analysis

The phytofabricated CuONPs were shiny black in color. The structure and crystallinity of CuONPs fabricated from WGLLE had been examined by XRD patterns as shown in Fig. 3. A powder XRD was carried out using monochromatic CuKα1 28radiation (wavelength 1.5406 Å), in the angular range 2θ of 20°–80° operating at a voltage of 40 kV and a current 40 mA. XRD profile analysis revealed a series of prominent diffraction peaks at 32.48°, 35.54°, 38.72°, 48.8°, 53.48°, 58.32°, 61.58°, 68.6°, 72.38°, and 75.16° which corresponds to (110), (002), (111), (20–2), (020), (202), (11–3), (220), (311), and (004) sets of planes respectively. Also, some unidentifiable peaks can be seen attributed to some organic content or amorphous impurities. The observed sets of planes are indexed based on the monoclinic structure of CuO by comparing the data from JCPDS card No.48–1548. Due to the monoclinic structure of CuO, the XRD profile analysis thus clearly illustrated that the phytogenically synthesized CuONPs are good crystalline in nature with high purity. The particle size (average) of phytogenically synthesized CuONPs was 40 ± 0.5 nm, calculated using Debye–Scherrer’s formula [26,27,28,29,30,31,32].

Fig. 3
figure 3

XRD pattern of WGLLE mediated CuONPs

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3.2 Vibrational Properties

FT-IR spectrum of WGLLE mediated CuONPs is represented in Fig. 4. The broad peak at 3840 is credited to the stretching vibration of aromatic phenolic (− OH) compounds. The bands at 3242 cm−1 can be allied with asymmetric stretching of the C-H band of alkanes. The peak assigned at 1687 cm−1 is due to the carbon–carbon double bond stretching frequency of polyphenol confirming the aromatic compounds. The peaks at 619 cm−1 and 518 cm−1 prove the formation of metal oxide, i.e., Cu–O, resulted of Cu–O bond stretching [33]. The FT-IR results support the existence of biomolecules as detected by phytochemical screening.

Fig. 4
figure 4

FT-IR spectra of CuONPs

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3.3 FESEM-EDAX Study

The intention of this analysis was to decide the structure along with the morphology of synthesized material. The FESEM images in Fig. 5 supports the XRD analysis as particle size range from 30 to 95 nm with a quasi-spherical shape.

Fig. 5
figure 5

FESEM images of CuONPs

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The purity and chemical constituents of CuONPs were depicted by EDAX spectra shown in Fig. 6, which state that, the CuONPs are comprised of mainly Cu and O along with other elements S, K, C, Mg, Si, and P attributed to biomolecules associated with CuONPs stating crystallinity of the synthesized nanomaterial [34].

Fig. 6
figure 6

EDAX spectrum of CuONPs

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3.4 HRTEM Analysis

Figure 7 shows proof of the non-aggregated spherical, crystalline, and monoclinic nature of WGLLE-mediated CuONPs. The particle size ranges between 2–50 nm, well in agreement with XRD study.

Fig. 7
figure 7

HRTEM images and SAED pattern of CuONPs

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3.5 UV–Visible Study

The wavelength of 200–800 nm was the range to record the UV–visible spectra of CuONPs as depicted in Fig. 8. The absorbance around 300 nm is a clear indication of the establishment of CuONPs, attributed to the charge transition from valence band to conduction band (O2− to Cu2+ ion) [8].

Fig. 8
figure 8

UV–Visible spectra of CuONPs

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3.6 Photoluminescence Study

The PL spectrum was recorded in the 280–601 nm range. Figure 9 shows the luminescence character of WGLLE-mediated CuONPs as the emission bands appear at 295 and 590 nm, indicating green-yellow emission at an excitation wavelength of 290 nm. The first peak is attributed to band edge emission while the second one corresponds to the artifact. Furthermore, the Stokes pattern can be observed as the emission peak at 579 nm is twofold of excitation wavelength, i.e., 290 nm [8, 9].

Fig. 9
figure 9

PL spectra of synthesized CuONPs

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3.7 Phytochemical Screening of WGLLE

Table 1 represents the biomolecules existing in the WGLLE. These important phytochemicals are capable to act as natural reducing cum capping agents in the eco benign synthesis of CuONPs [35]. Furthermore, the existence of these biomolecules had been confirmed by FT-IR spectra. Figure 10 shows important molecules reported in WGLLE.

Table 1 Phytochemical testing of WGLLE
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Fig. 10
figure 10

Important biomolecules in WGLLE

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3.8 Possible Growth Mechanism of CuONPs

The molecules representing Fig. 10 are considered for working as natural stabilizing and reducing agents in the phytofabrication of CuONPs [8, 36].

Figure 11 represents the possible growth mechanism of CuONPs. Initially, active site of WGLLE gets bound with Cu2+ which later being reduced to Cu0. This Cu0 on oxidation leads to CuONPs.

Fig. 11
figure 11

Plausible mechanism of growth of CuONPs

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3.9 Antibacterial Activity

The antibacterial efficiency of the WGLLE-led CuONPs is tabulated in Table 2. The CuONPs showed outstanding antibacterial activities versus E. coli and S. pyogenus and reasonable bactericidal properties versus S. aureus and P. aeruginosa concerning reference drug ampicillin.

Table 2 MIC of CuONPs against bacteria
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3.10 Antifungal Activity

The antifungal efficacy of CuONPs phytofabricated from WGLLE is shown in Table 3. The fungal strains Aspergillus niger and Aspergillus clavatus showed reasonable antifungal activities while the Candida albicans showed lower activity versus CuONPs concerning griseofulvin and nystatin as reference drugs.

Table 3 MIC of CuONPs against fungi
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3.11 Photocatalytic Activity

The photocatalytic activities of CuONPs were tested towards photodegradation of MB under sunlight using 1.0 g/dm3 of CuONPs. Figures 12 and 13 show the decreasing concentration of MB versus time.

Fig. 12
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Images of photodegradation of MB with respect to time

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Fig. 13
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A plot of A/A0 with time for the photodegradation of MB

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The decomposition rate of dye concentration versus irradiation time is presented in Fig. 14. Initially, the blank experiment was conducted without adding a photocatalyst (photolysis). The degradation rate without catalyst was negligible; but on adding photocatalyst, the concentration of the MB gradually decreased under the sunlight and 100% degradation was achieved after 70 min.

Fig. 14
figure 14

Rate of decomposition of MB by using CuO NP

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The optimization of catalyst amount from 0.1 to 1.0 g/ dm3 helped to achieve 100% degradation in 70 min. But a further increase in the amount of photocatalyst above 1.0 g/dm3 decreased the efficiency, attributed to the aggregation of photocatalyst [37, 38].

Table 4 displays the comparison of photocatalytic potency of CuONPs with reported literature [39,40,41,42]. The data reveals the superiority of WGLLE-mediated CuONPs as a photocatalyst.

Table 4 Comparison of photocatalytic efficacy of phytofabricated CuONPs with recent literature
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4 Conclusion

The present article has been devoted to synthesizing CuONPs using WGLLE. The method reported for synthesis follows green chemistry ethics leading to an eco-balancing, sustainable and simple pathway. The synthesized CuONPs were characterized using basic and modern analytical tools like UV–visible spectra, XRD, FT-IR, FESEM-EDAX, HRTEM, and PL, and exhibited excellent antibacterial activities with reasonable antifungal potency against selected bacterial and fungal pathogens. This can lead to the development of antibacterial drugs while luminescent character can turn useful in optical materials, after a detailed investigation.

Moreover, 100% degradation of MB was achieved within 70 min using novel CuONPs under sunlight. This indicates that this material can be a very good photocatalyst for the detoxification of MB dye.