Green-fabrication of CuO nanoparticles using various plant extracts and their multifaceted applications in photocatalytic cationic dye degradation and antimicrobial activities

The green approach to the synthesis of metal oxide is an alternative to conventional methods in its ability to be facile, less expensive, time-consuming, non-toxic, and suited for large-scale manufacturing. The proposed approach for the synthesis of CuO nanoparticles (NPs) was employed as a reducing agent for an extract comprising various plant parts, including flower, leaf, and peel extracts of Caesalpinia pulcherrima, Nervilia aragoana, and Manihot esculenta. The sesquiterpenoids demonstrated that two molecules of cubebene were sufficient to reduce Cu2+ ions to monoclinic CuO NPs which were investigated by UV-Vis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and X-ray diffraction. CuO NPs were used in flower, leaf, and peel extracts and they degraded at 96%, 72%, and 78% respectively. The degradation rate of CuO NPs kinetics were also calculated against the MB dye. The antimicrobial activity of CuO NPs exhibited the highest activity against Candida albicans microbe. Using the agar well diffusion method, the synthesized CuO NPs were shown to have antibacterial action against human pathogenic Escherichia coli and S. aureus bacteria. Gram-positive bacteria of S. aureus, as opposed to Gram-negative bacteria of E. coli, were more susceptible to the potential bactericidal activity of biologically produced CuO NPs.