Eco-friendly synthesis of crystalline and amorphous copper-based nanomaterials using Moringa oleifera leaf, seed, and stem bark: a sustainable approach for biological and environmental applications

Green synthesis of nanomaterials using plant extracts has gained significant interest. This method replaces toxic reducing and capping agents with natural sources such as plant extracts, microorganisms, algae, fungi, or biomolecules. In this study, copper-based nanomaterials were synthesized using aqueous extracts from various parts of Moringa oleifera, including leaves, seeds, and stem bark. The synthesized copper oxide materials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The prepared materials were then tested for their antimicrobial, antioxidant, and Eriochrome Black-T (EBT) degradation activities. Structural characterization via XRD revealed the successful formation of a mixed phase of crystalline cuprous oxide and copper (Cu2O/Cu) along with amorphous copper oxide materials. FT-IR analysis confirms that compounds such as polyphenols, alkaloids, flavonoids, terpenoids, and reducing sugars significantly contribute to the synthesis of these copper oxide nanomaterials, supporting their formation. SEM and TEM analysis confirmed the formation of nanomaterials. Additionally, the study measured the concentrations of total phenols, flavonoids, and tannins in various parts of Moringa oleifera to better understand their influence on copper oxide synthesis. Notably, an amorphous copper oxide material derived from Moringa oleifera leaf extract exhibited higher antimicrobial and antioxidant activities and achieved 40% EBT degradation, while the crystalline material showed lower activity. The study discusses these results in detail, correlating the activity with the characterization studies.

Green chemistry, also known as sustainable chemistry, focuses on designing chemical products and processes that minimize or eliminate the use and generation of hazardous substances (Anastas and Warner, 2000; Iravani, 2011). Its core principles promote safety, efficiency, environmental compatibility, waste prevention, and sustainability. In general, green nanotechnology involves the development of nanomaterials by synthesizing them in an environmentally friendly manner using biological systems and renewable resources (Ahmed et al., 2016; Mahmoud et al., 2017). Biomolecules often play dual roles in this synthesis process, they act as reducing agents to convert metal ions into stable nanoparticles and as stabilising or capping agents to enhance biocompatibility and reduce particle aggregation. Furthermore, the green chemistry approach to nanomaterial synthesis replaces toxic reducing and capping agents with plant extracts, microorganisms, algae, fungi or biomolecules.

Nanomaterials have emerged as versatile constituents due to their distinctive physicochemical properties and significant biological activities. Notably, copper-based nanomaterials exhibit broad-spectrum antimicrobial effects, capable of inactivating over 99% of bacterial cells within a few hours of contact. In addition to their biocidal properties, the catalytic and conductive characteristics of copper-based materials make them appealing for various applications, including coatings, water treatment, and medical uses. Moreover, they are often regarded as a more cost-effective alternative to silver nanoparticles for antimicrobial applications, underscoring the remarkable antimicrobial activity of copper ions. This is further supported by historical observations of the self-sterilizing properties of copper surfaces (Ren et al., 2009; Santo et al., 2010).

Plant extracts are rich sources of phytochemicals, including flavonoids, phenolic acids, tannins, alkaloids, terpenoids, and proteins, which collectively contribute to nanomaterial synthesis. These biomolecules perform two major functions in green synthesis. First, they reduce metal ions by donating electrons. Second, they cap and stabilize nascent nanoparticles by adsorbing onto particle surfaces, thereby preventing aggregation. Similarly, tannins and saponins from seeds or bark participate in capping through their multiple functional groups. The rich phytochemical composition of plant extracts underpins the green synthesis of nanomaterials (Iravani, 2011; Cowan, 1999).

Moringa oleifera, or the drumstick tree, is known for its rich phytochemical profile, which benefits traditional medicine, nutrition, and water purification. All parts of the plant contain bioactive compounds with varying compositions. Therefore, Moringa can be considered a phytochemical factory, with its leaves acting as strong antioxidants due to their high phenol content (Abimbola et al., 2025; Anwar et al., 2006; Natalina et al., 2025; Mounir et al., 2025). Changes in extract or phytochemical composition may affect the production of biomaterials. Plant extracts rich in low-molecular-weight phytochemicals might yield smaller, more uniform nanoparticles, whereas those with lower reducing power yield larger particles. Strong capping agents, such as proteins and polysaccharides, enhance stability in colloidal solutions (Aisha et al., 2023; Great et al., 2025; Makarov et al., 2014).

Several studies have investigated the synthesis of copper-based nanomaterials using various plant extracts (Khan et al., 2015; Amaliyah et al., 2020; Luque-Jacobo et al., 2023; Emilia et al., 2021; Sastry et al., 2013). However, to the best of our knowledge, no studies have examined the synthesis of nanomaterials from the same plant using different parts at room temperature under identical conditions. The present study aims to investigate the role of plant parts in the synthesis of nanomaterials and their application towards environmental and biological studies. Therefore, we have chosen various plant parts of M. oleifera, including leaves, stem bark and seeds, to synthesize copper-based nanomaterials. The prepared materials were thoroughly characterized using several techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis spectrophotometry. Finally, the prepared materials were tested for antimicrobial activity, antioxidant activity, and Eriochrome Black T (EBT) degradation.

Moringa oleifera leaves, seeds and stem bark were purchased from the local market in Chennai and washed thoroughly in tap water, followed by double-distilled water. The samples were then air-dried at room temperature (25 °C ± 2 °C) and ground into fine powder. The powder was stored in an air-tight container till further use. They were labelled as ML (Moringa Leaf), MB (Moringa Stem Bark), and MS (Moringa Seed).

Chemicals and solvents

Copper (II) Sulphate (CuSO 4.5H 2 0; 99% purity), gallic acid (3,4,5-trihydroxybenzoic acid), tannic acid, quercetin and Folin-Ciocalteu’s reagent (colourimetric mixture of phosphomolybdic and phosphotungstic acids) were purchased from Loba chemicals. Ammonia (NH 3, 25% purity) and Eriochrome Black-T (C 20 H 12 N 3 NaO 7 S) were purchased from Merck. Milli-Q Water (Grade I) was used for sample preparation. The Gram-positive strains (Staphylococcus saprophyticus MTCC 6155, Staphylococcus aureus MTCC 737), Gram-negative (Salmonella typhimurium MTCC 3231, Escherichia coli MTCC 1687), strains were procured from MTCC (Microbial Type Culture Collection), Chandigarh, India, for the antibacterial study, and other solvents were analytical grade.

Preparation of plant extracts

Accurately, 10 g of ML powder was weighed and transferred, and 100 mL of Milli-Q water was added. The extract was allowed to stand for 24 h. The next day, the extract was filtered through Whatman filter paper 1, and the aqueous extract was stored in a refrigerator for further analysis. Similarly, MB and MS aqueous extracts were prepared and stored.

Phytochemical screening

Phytochemical screening of aqueous extracts of leaves, seeds, and stem bark of Moringa oleifera was performed to identify various secondary metabolites in them (Chandan and Krishna, 2024; Woisky and Salatino, 1998).

Total phenol estimation

Total phenol estimation was performed for the leaves, seeds, and stem bark of M. oleifera. The analysis was carried out by measuring the reaction between the sample solution and Folin-Ciocalteu reagent (FCP) under alkaline conditions (AOAC, 2020; Singleton et al., 1999). For the analysis, the blank was prepared by adding 2.5 mL of Folin-Ciocalteu reagent, 2 mL of 20% Na 2 CO 3, and making up to 10 mL with distilled water. Next, the standards were prepared by adding 200, 400, 600, 800, and 1000 µL of standard gallic acid solution (100 μg/mL) to 2.5 mL of Folin-Ciocalteu reagent, 2 mL of 20% Na 2 CO 3, and making up to 10 mL with distilled water. For the sample analysis, 100 µL each of stem bark and seed aqueous extracts, and 50 µL of M. oleifera leaf aqueous extract were separately added to 2.5 mL of Folin–Ciocalteu reagent and 2 mL of 20% Na 2 CO 3 solution. The mixtures were then made up to a final volume of 10 mL with distilled water. The solutions were kept at room temperature (25 °C ± 2 °C) for 30 min, and the absorbance was measured at 760 nm using a UV-spectrophotometer.

Tannins estimation

For the tannins estimation, the blank is prepared by adding 2.5 mL Folin-Ciacalteu reagent, 2 mL 20% Na 2 CO 3 and made-up to 10 mL using distilled water. The standards are prepared by adding 200, 400, 600, 800, and 1000 µL of standard tannic acid solution (100 μg/mL) to 0.5 mL Folin-Ciocalteu reagent, 1 mL 35% Na 2 CO 3, and finally making up to 10 mL with distilled water (Medini et al., 2014). For the reaction mixtures, 100 µL of each Moringa extract was combined with Folin-Ciocalteu reagent and sodium carbonate solution, diluted to 10 mL, and incubated for 30 min. The absorbance was then measured at 700 nm using a UV-spectrophotometer.

Flavonoids estimation

The amount of flavonoids was determined based on the formation of a stable flavonoid–aluminium complex in the presence of potassium acetate (Chang et al., 2002). The blank consisted of methanol, aluminium chloride solution, potassium acetate, and distilled water. The standards are prepared by adding 200, 400, 600, 800, and 1000 µL of standard quercetin solution (100 μg/mL) separately in volumetric flasks. For the extracts, 100 µL of each was mixed with methanol, aluminium chloride, and potassium acetate, then brought to 10 mL with distilled water. After incubating for 30 min, the absorbance of the yellow solutions was measured at 415 nm against the blank using a UV-visible spectrophotometer.

Biosynthesis of copper-based nanomaterials

For nanomaterial synthesis, 10 mL of the ML aqueous extract (pH∼6.8) was added to 5 mL of 20, 50, and 100 mM CuSO 4 solutions at the optimised 2:1 ratio, separately. Then, 10 mL of 2% aqueous ammonia solution (pH∼12) was added dropwise, and the mixture was stirred at 700–750 rpm at room temperature (25 °C ± 2 °C) for 180 min. The colour changes from green to dark green indicate the formation of a nanomaterial, which occurred at pH ∼10.5. The solution was collected in centrifuge tubes and centrifuged at 4500 rpm for 10 min. It was then washed with Milli-Q water to remove all untreated materials. The obtained sample was collected, dried at 105 °C for a minimum of 6 h, ground into a fine powder, and stored for further use. Similarly, copper oxide nanomaterials were prepared from MB aqueous extract (pH ∼6.2) and MS aqueous extract (pH∼6.5). During this, the solution colour changed from a mild yellow to dark green. Here, with 100 mM CuSO 4, only a considerable amount of material was yielded. The yield of the nanomaterial prepared using 100 mM, 50 mM, and 20 mM CuSO 4 solutions is in the order 100 mM > 50 mM > 20 mM. The synthesis procedure is outlined in Figure 1.

Materials characterization

The XRD data were acquired in the 2θ range of 10°–80° using a Bruker D8 Advance A25 at a scanning speed of 4°min −1, with Cu Kα radiation (λ = 1.54 Å) and a Ni filter. The applied current and accelerating voltage are maintained at 40 mA and 40 kV, respectively, during the measurement. The average size of the crystalline domains (D) of the prepared materials was estimated with the help of the Scherrer Equation 1 using the XRD data. where D denotes the crystallite size, the X-ray wavelength (1.54 Å), K the particle shape factor taken as 1, the peak width (FWHM, full width at half maximum) in radians and the Bragg diffraction angle. The morphology of the prepared samples was investigated using a field-emission scanning electron microscope (FE-SEM) with a Carl Zeiss UHR FESEM - Model GEMINI SEM 500 KMAT. Transmission electron microscopy (TEM) studies were conducted using a JEM-F200 with an accelerating voltage of 200 kV. A Fourier transform infrared (FT-IR) spectrum of the samples was recorded using a Bruker alpha spectrometer at room temperature over the range 400–4000 cm −1. The secondary metabolites were quantified over 800–200 nm using a UV-Visible spectrophotometer (Shimadzu UV-1900i).

Activity studies

Anti-microbial activity

The antimicrobial activity of the prepared materials evaluated using the agar well diffusion assay (Chávez-Esquivel et al., 2021). Fresh bacterial cultures- Staphylococcus aureus MTCC 737, Staphylococcus saprophyticus MTCC 6155, Escherichia coli MTCC 1687, and Salmonella typhimurium MTCC 3231 were prepared. Then, Muller-Hinton Agar (MHA) (HiMedia, India) plates were prepared according to the manufacturer’s instructions, and 6 mm diameter holes were created using a cork borer. The plates were incubated at 37 °C for 24–48 h. Gentamycin (1 mg/mL) and DMSO were used as positive and negative controls, respectively.

Antioxidant activity

The antioxidant activity was assessed using the DPPH scavenging assay according to Equation 2. Equal quantities of nanomaterial extract, DPPH, and ethanol were mixed in a microwell plate and incubated in the dark at room temperature for 30 min. After which, the absorbance was measured at 517 nm using a UV-spectrophotometer (Kochadai et al., 2022). The ethanol-DPPH mixture served as the control, and ethanol alone served as the blank. The IC50 value was also calculated using a four-parameter logistic model using the AAT Bioquest online service (AAT Bioquest, 2025).

Eriochrome Black-T (EBT) dye degradation

Photocatalytic Eriochrome Black-T (EBT) dye degradation was performed under ambient laboratory lighting at room temperature (25 °C ± 2 °C) for 180 min. The light source used standard cool-white LED ceiling lamps that emit a broad spectrum of visible light (400–700 nm). They typically provide an illuminance of approximately 500–1000 lux at the working surface (Minna et al., 2025). In a typical run, 0.03 g of prepared materials was added individually to 50 mL of a 0.05 mg/mL and 0.1 mg/mL EBT solution, respectively, in a beaker. The pH of the EBT solution was ∼7.5. During the reaction, small aliquots were collected every 15 min, centrifuged at 5000 rpm, and the catalyst particles were separated. Thereafter, EBT concentration was estimated using a UV-Vis spectrophotometer at 570 nm.

The catalytic degradation efficiency (η) of EBT was obtained with the help of Equation 3. where C is the concentration of the EBT solution at the reaction time t, and C 0 is the initial concentration of EBT (at reaction time 0).

Secondary metabolite estimation

The initial phytochemical screening shows the presence of various phytochemicals in different plant parts (Table 1). Among them, we quantified total phenols, flavonoids, and tannins in the leaves, seeds, and stem bark of M. oleifera.

Total phenols, flavonoids and tannins estimation

Calibration plots of standards are shown in Figure 2. The amount of phenols was analysed for the different plant part extracts. Gallic acid was used as a standard (Figure 2a). Among the extracts, the total phenol content is higher for Moringa leaf extract (ML) as seen in Table 2. The higher presence of phenol compounds can be correlated to the formation of nanomaterials and antioxidant activity.

The amount of tannin compounds was analysed for the different plant part extracts. Tannic acid was used as a standard (Figure 2b). Among the extracts, the total tannin compounds for Moringa leaf extract (ML) were higher compared to Moringa stem bark extract (MB) and Moringa seed extract (MS), as seen in Table 2.

Similarly, the amount of flavonoids was analysed for the different plant part extracts. Quercetin was used as a standard (Figure 2c). Among the extracts, the total flavonoid compounds for Moringa leaf extract (ML) were higher compared to other extracts (Table 2).

Among the extracts, the amounts of phenols, tannins, and flavonoids follow the order ML > MS > MB. Higher levels of phenols, flavonoids, and tannins influence material synthesis, antioxidant and antimicrobial activity, and EBT degradation.

Characterization of copper-based nanomaterials

The XRD patterns of the synthesised materials are presented in Figure 3. The nanomaterial derived from the stem bark aqueous extract (Figure 3a) typically shows a mixed phase of crystalline Cu 2 O and metallic copper (c-Cu 2 O/Cu). Prominent peaks were observed at 29.8°, 36.42°, 42.3°, 61.74°, and 73.52°, corresponding to the (110), (111), (220), and (311) planes of Cu 2 O. This matches well with JCPDS Card No. 05–0667. The sharp peaks observed at 43.35° and 50.65° correspond to the (111) and (200) planes of metallic copper (Nguyen, et al., 2022). The crystallite size of the prepared materials (Figure 3a) was calculated using the Scherrer equation, yielding an average size of 33.27 nm. In Figure 3b, the materials prepared using leaf aqueous extract at different concentrations of CuSO 4 (20, 50, and 100 mM) displayed a very broad feature, indicating the amorphous nature of the copper oxide material. With increasing precursor (CuSO 4) concentration, crystallinity was observed. The material prepared with 100 mM CuSO 4 shows very low crystallinity, consisting of tiny nanocrystallites embedded in an amorphous matrix. Similarly, the XRD pattern of the material prepared from the seed aqueous extract, shown in Figure 3c, indicates amorphous copper oxide with very low crystallinity. From the results, it was observed that the materials prepared with 100 mM CuSO 4 and different extracts ranged from low to good crystallinity. The crystallite sizes were not determined for the materials derived from the leaf and seed aqueous extracts (Figures 3b,c). These materials are amorphous, indicating a lack of long-range atomic order. Therefore, crystallite size calculation was not applicable for these samples.

FT-IR analysis was performed to support the formation of nanomaterials using the plant extract, which serves as a reducing and capping agent. Figure 4a shows the FT-IR spectrum of the plant powder sample, and Figure 4b shows the prepared nanomaterials along with the CuSO 4 salt. Figure 4a exhibited several absorption bands at 3322, 2910, 1610, 1030 cm −1, etc., which can be attributed to the stretching vibrations of hydroxyl (–OH) groups and N–H bonds, indicating the presence of phenolic compounds and amide groups. The peaks appearing around 2920–2850 cm −1 correspond to C–H stretching vibrations of aliphatic–CH 2 and–CH 3 groups. Also, distinct absorption bands in the 1600–1650 cm −1 region are typically assigned to C=O stretching vibrations of amide groups or to C=C stretching vibrations of aromatic rings, indicating the presence of proteins and polyphenolic structures. The bands in the region of 1000–1200 cm −1 are attributed to C–O stretching and C–O–C stretching asymmetric vibration. It demonstrates the presence of various functional groups in the plant extract, respectively.

Figure 4b represents the prepared copper-based nanomaterials using different extracts along with the CuSO 4 salt. The peak observed around 610 cm −1 in c-MB100-Cu 2 O/Cu corresponds to the Cu–O stretching vibration in the cubic lattice, strongly supporting the formation of cuprous oxide (Cu 2 O). Additionally, a less intense band was observed around 490 cm −1, attributed to a copper-oxygen vibration, indicating the formation of copper oxide as an amorphous impurity (Manohar and Bhalchandra, 2016). Conversely, in a-ML100-CUO and a-MS100-CUO samples, we observed bands in the 400–600 cm −1 region, corresponding to Cu(II)-O stretching vibrations, confirming the formation of copper oxide (Sathish et al., 2019; Elango et al., 2017; Arun et al., 2015; Djamila et al., 2022). The peak observed at 2920–2850 cm −1 in Figure 4a was absent in Figure 4b, and the absorption bands in the 1600–1650 cm −1 region (Figure 4a) were less intense in Figure 4b. These results support the formation of copper-based nanomaterials. The other bands observed at 3200–3400 cm −1 and 1000–1200 cm −1 correspond to stretching vibrations of alcohols, phenols, and polysaccharides, highlighting the contribution of carbohydrate-based compounds to the capping and stabilisation of copper-based nanomaterials. The materials were prepared at room temperature and dried at 105 °c. Based on XRD and IR analyses, we confirmed that the aqueous extract of the stem bark mainly produced a crystalline mixed phase of Cu 2 O/Cu. In contrast, extracts from leaves and seeds yielded amorphous copper oxide nanomaterials under these experimental conditions. This difference may be due to the higher levels of polyphenols, tannins, flavonoids, and other phytochemicals in the leaves and seeds, which likely form a dense capping layer that prevents crystallisation, leading to amorphous structures. Conversely, in stem bark, phytochemicals like lignins act as templates, facilitating a more organized reduction process and producing stable crystalline Cu 2 O/Cu materials (Mashrafi et al., 2025).

Figure 5 shows the SEM images of the prepared materials obtained from aqueous extracts of leaf, seed and stem bark, separately, at magnifications of 50 KX and 10 KX. All materials exhibit irregular particle sizes, with an average particle size of 50–150 nm.

Figure 6a shows the TEM image of a-ML100-CUO nanomaterial. The particles aggregate into larger particles of roughly 50–150 nm. Figure 6b shows the selected-area electron diffraction (SAED) pattern, which consists of a few randomly oriented nanocrystallites. This confirms that a-ML100-CUO is a polycrystalline material.

Antimicrobial activity

For the antimicrobial activity, a-ML100-CUO nanomaterial inhibited Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Staphylococcus saprophyticus in agar well diffusion with a clear concentration–response, yielding zones at 100 mM of 13 and 15 mm respectively, with stepwise reductions to 11, 12, and 10.5 mm for a-ML50-CUO nanomaterials and to 10.5, 11, 11.5, and 11.5 mm for a-ML20-CUO for the same organisms, confirming a monotonic decline a-ML100-CUO > a-ML50-CUO > a-ML20-CUO across all species. For a-MS100-CUO and c-MB100-Cu 2 O/Cu nanomaterials inhibited all four test organisms: a-MS100-CUOnanomaterial produced zones of 11.5 mm (S. aureus), 13.5 mm (S. typhimurium), 11.5 mm (E. coli), and 10 mm (S. saprophyticus), while c-MB100-Cu 2 O/Cu nanomaterial produced 10.5 mm, 13.5 mm, 10 mm, and 10 mm in the same order, indicating consistent, broad-spectrum but moderate activity with the largest effects against S. typhimurium.

Representative plates (Figure 7) align with the tabulated measurements (Table 3), visually corroborating the absence of DMSO activity, robust gentamicin inhibition, and the concentration-dependent pattern observed for the prepared copper-based nanomaterials across all organisms. Additionally, the results showed that the DMSO vehicle produced no inhibition, whereas gentamicin generated larger zones, validating the assay performance and benchmarking the potency. The data showed that the copper-based nanomaterials prepared from the three different extracts (ML, MB, MS) exhibited activity, and the a-ML100-CUO nanomaterial had the highest inhibitory activity among all samples. All tests were conducted in duplicate, and a two-way ANOVA was performed in GraphPad Prism version 10.6.1. A p-value of <0.0001 was observed, indicating significance.

Anti-oxidant activity

Antioxidant activity was assessed for the prepared nanomaterials according to the literature (Kochadai et al., 2022), and the results were tabulated in Table 4. Among the prepared materials, a-ML100-CUO showed the best concentration-dependent DPPH scavenging activity across the tested range (0.39–100 mg/mL). At the lowest concentration, the radical-scavenging activity was 5.22%, which gradually increased to 95.54% at 100 mg/mL, indicating that maximum activity was observed at higher doses. The nanomaterials a-MS100-CUO and c-MB100-Cu 2 O/Cu showed lower antioxidant activity at 100 mg/mL, i.e., 38.62% and 27.2%, respectively, which is significantly lower than the potency of the leaf extract. The DPPH activity data were fit to a four-parameter logistic model, yielding an IC50 of 13.20 mg/mL for the leaf extract, consistent with the transition region observed between 6.25 and 12.5 mg/mL, where %RSA crosses the 50% threshold.

The results were well correlated with the amount of phenol content (Table 2). Amorphous materials (a-ML100-CUO and a-MS100-CUO) exhibited better antimicrobial and antioxidant activity compared to crystalline material(c-MB100-Cu 2 O/Cu). This is mainly due to a greater abundance of plant-derived capping agents, which provide a higher density of active surface sites that facilitate more chemical interactions than the stable, low-energy facets of crystalline materials like c-MB100-Cu 2 O/Cu.

Eriochrome Black-T (EBT) degradation activity

The dye-degradation reaction has environmental benefits. The reaction can be analysed for the degradation of pollutants in water bodies, including lab and other industrial wastes that, when released untreated, can cause serious ecological problems (Pradhan et al., 2001; Singh et al., 2010). In addition to antimicrobial and antioxidant studies, the prepared materials were evaluated for their suitability in environmental applications. For this purpose, we selected the degradation of Eriochrome Black-T as a model reaction (Figure 8). Here, we employed amorphous materials, such as a-ML100-CUO and a-MS100-CUO, and crystalline materials, such as c-MB100-Cu 2 O/Cu, for the degradation of 50 and 100 ppm EBT solutions, respectively. The reaction was performed at room temperature for 180 min, the aliquots were collected every 15 min and analysed using a UV-Vis spectrophotometer.

The results show that the prepared copper-based nanomaterials can degrade dye, but with notable variations in efficiency. In this, amorphous materials demonstrated better activity than crystalline materials. Among the three systems, the a-ML100-CUO nanomaterial exhibited the highest degradation activity, followed by a-MS100-CUO and

c-MB100-Cu 2 O/Cu. The time-dependent UV-Vis absorption spectra of EBT dye degraded by the prepared nanomaterials at different amounts are shown in Figure 9. At 50 and 100 ppm concentrations of EBT, the a-ML100-CUO nanomaterial degraded EBT by upto 40%, whereas in other cases it was lower than 20% (Figure 10). The observed trend aligns well with the overall phenolic content and antioxidant capacity of the respective plant extracts. It is proposed that the higher levels of phenols, flavonoids, and tannins in the leaf extracts, as confirmed by FT-IR and UV analyses, facilitate the formation of a dense phytochemical capping layer. This layer inhibits crystal growth and maintains a high density of active surface defects. These surface characteristics improve the adsorption of dye molecules and accelerate electron transfer, ultimately enhancing degradation efficiency. For c-MB100-Cu 2 O/Cu nanomaterial, copper atoms exist in the stable oxidation states (I) and (0), resulting in reduced antimicrobial, antioxidant, and EBT-degradation activity (Sonam et al., 2025). The dye-degradation results highlight the significant influence of the phytochemical nature of the plant extracts used in nanomaterial synthesis, emphasising the advantages of green-synthesised amorphous nanomaterials for environmental cleanup.

A plausible mechanistic pathway for the catalytic degradation of EBT under visible-light irradiation is illustrated in Figure 11(Kousik et al., 2024; Vinodkumar et al., 2019). When the visible light irradiates on the catalytic material, electrons (e‾) are excited from the valence band (VB) to the conduction band (CB), creating an equal number of holes (h +). These holes in the valence band react with adsorbed water to produce hydroxyl radicals (OH •). Simultaneously, the electrons in the conduction band react with dissolved oxygen to produce superoxide radicals (O 2 −•). These reactive species (h +, OH •, and O 2 −•) then react with EBT molecules adsorbed on the catalyst surface, thereby degrading the EBT.

Reusability studies

Among the prepared materials, the leaf extract-derived copper oxide (a-ML100-CUO) showed better activity. Therefore, we reused this material by recovering the catalyst via centrifugation, washing with water and ethanol, and drying in a hot-air oven at 80 °C overnight. Subsequently, we performed reusability studies for EBT degradation (100 ppm). The experiment was conducted over four cycles. From the 1st to the 4th cycle, the degradation percentage slightly changed from 40% to 37%. This indicates that the material remains stable throughout the four runs. To support this, the spent catalyst was characterized with FT-IR and presented in Figure 12 alongside the fresh catalyst.

This work demonstrates a sustainable, green synthesis of copper-based nanomaterials using different parts of Moringa oleifera (leaf, seed, or stem bark), with the phytochemical profile of each plant part dictating the structural and functional properties of the resulting material. Phytochemical analysis confirmed that leaf and seed extracts, rich in phenols, tannins and flavonoids, facilitate the formation of amorphous nanomaterials (a-ML100-CUO and a-MS100-CUO). In contrast, stem bark extract yields a crystalline mixed-phase of Cu 2 O/Cu nanomaterial. Which are further confirmed through the XRD and FT-IR analysis. The amorphous materials exhibited higher antimicrobial, antioxidant, and catalytic (EBT degradation) activities compared to the crystalline material. This is attributed to a higher density of surface defects and a more robust coating of bioactive capping agents, which provide more active sites for biochemical and catalytic interactions. Among the prepared copper-based nanomaterials, a-ML100-CUO exhibited the highest efficacy, correlating strongly with its superior phenolic content. These results highlight the importance of the phytochemical composition, which influences crystalline growth and, in turn, catalytic activity. Future research should focus on the long-term stability, reusability, and environmental safety of these amorphous materials to facilitate their transition into practical, large-scale applications.