Green Synthesis, Optimization, and Characterization of Copper Nanoparticles Using a Combined Extract of Selected Plant Seeds

Study’s Excerpt: • CuNPs were synthesized using neem, black seed, and baobab extracts through a green Taguchi method. • UV-Vis at 590.10 nm and FTIR peaks confirmed CuNPs capped with plant-based phytochemicals. • Crystalline spherical CuNPs (25.51 nm) were revealed by XRD and SEM with effective surface capping. • CuNPs inhibited E. coli (19 mm) and A. baumannii (17 mm), showing strong antimicrobial activity. • Future studies should test cytotoxicity, scale-up, and expand antimicrobial spectrum of CuNPs. Full Abstract: This work investigates a verde method involving synthesizing, optimizing, and characterizing copper nanoparticles (CuNPs) developed from black seed, neem seed, and baobab seed extracts. The optimal synthesis conditions were investigated by means of a Taguchi method. UV-Vis spectroscopy was used to confirm the formation of CuNPs, which exhibited an SPR peak of 590.10 nm (Fig. 1b), indicating the nanoparticles' presence. Characteristic peaks at 566.65, 984.04, 1088.47, 1632.62, 2117.12, and 3265.16 cm⁻¹ were observed, attributing to Cu-O and Cu-OH and Cu-O-C bonds, as well as hydroxyl and carbon dioxide functional groups, indicating an effective capping and stabilization of the nanoparticles by plant phytochemicals (FTIR analysis). The crystalline nature of CuNPs has been confirmed using X-ray diffraction analysis, which gave diffraction peaks at 22.43°, 47.07°, 67.12°, and 87.33°. The particle size was found to be 25.51 nm. The particles exhibited a mostly spherical shape with some degeneracy when analyzed by scanning electron microscopy (SEM), and the elemental composition (EDX) characterized a copper content of 45.3% and additional plant-derived stabilizing agents, such as carbon, oxygen, and trace elements. Besides, the antimicrobial assay showed potent inhibitory effects on multiple microbes that are all pathogenic. The CuNPs showed significant antibacterial activity, exhibiting maximum inhibition zones against Acinetobacter baumannii (17 mm) and Escherichia coli (19 mm). These results emphasize the potential of biogenically synthesized CuNPs as potential antimicrobial agents, which should provide a sustainable alternative for biomedical and pharmaceutical applications.