Green Synthesis, Characterization, and Evaluation of Antimicrobial and Antioxidant Activities of CuO, Co3O4, and CuO-Co3O4 Composite Nanoparticles using leaf Extracts of Moringa stenopetala

Abstract

The present work reports the green synthesized CuO NPs, Co3O4 NPs, and CuO-Co3O4 composite nanoparticles using an extract from Moringa stenopetala leaves, which were designed as agents for antioxidant and antimicrobial purposes. The nanoparticles were thoroughly analyzed using various spectroscopic methods such as XRD, UV-Vis, SEM, FT-IR, and TGA. Based on the UV-Vis data, the energy band gaps of the CuO NPs, Co3O4 NPs, and CuO-Co3O4 composite NPs were determined to be 3.32eV, 3.36 eV, and 3.66 eV, respectively. The XRD analysis revealed that the CuO NPs had a monoclinic crystal structure with a spherical shape and an average crystallite size of 11.59 nm. Additionally, the Co3O4 NPs exhibited a cubic crystal structure with a spinel structure and an average crystallite size of 12.25 nm. Meanwhile, the CuO-Co3O4 nanocomposites had an average crystal size of 9.53 nm. The SEM images revealed CuO NPs has heterogeneous composition with large granular particles due to aggregation or overlapping, while Co3O4 NPs is non-uniform cubic shape and size, with agglomeration due to encapsulation and hydrogen bonding, and for CuO-Co3O4 composite NPs, inhomogeneity of particles, with both spherical and irregular geometries and different sizes. The FT-IR confirms the bioactive molecules such as flavonoids, tannins, terpenoids, steroids, glycosides, saponins, and phenols, that were actively involved during the synthesis process. The antibacterial effects of the produced nanoparticles were tested against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) bacterial strains using the agar-well diffusion method. CuO-Co3O4 composite NPs showed better inhibitory activity than CuO NPs and Co3O4 NPs against the selected bacterial species (Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes). Similarly, the antioxidant activities of the synthesized NPs were evaluated using DPPH assays. The results confirmed that the CuO Co3O4 composite NPs have excellent inhibitory activity compared to CuO NPs and Co3O4 NPs. The results of this study suggest that the CuO-Co3O4 composite NPs hold great potential for various applications, given their superior inhibitory and radical inhibitory activity