Green synthesis and characterization of copper nanoparticles using Azadirachta indica (neem) leaf extract and evaluation of their antimicrobial activities

Abstract

The present study demonstrates the green synthesis of copper oxide nanoparticles (CuONPs) utilizing aqueous extracts of Azadirachta indica (neem) leaves. Fresh neem leaves were processed to obtain the extract, which served as a bioreducing and stabilizing agent for the synthesis of CuONPs via a simple aqueous-phase method using copper nitrate. The formation of CuONPs was indicated by a colour change from brown to sea green and confirmed through X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analyses. XRD results revealed the monoclinic crystalline structure of CuO nanoparticles with an average crystallite size of approximately 3.3 nm. SEM analysis showed irregular, aggregated morphologies, while FTIR spectra identified functional groups responsible for the reduction and stabilization of nanoparticles. Antibacterial activity assessed by the well diffusion method indicated that the biosynthesized CuONPs exhibited substantial inhibitory effects against Pseudomonas aeruginosa and Klebsiella oxytoca, but no activity against Staphylococcus aureus. The findings highlight the potential application of neem-mediated CuONPs as eco-friendly antimicrobial agents, particularly targeting Gram-negative bacterial strains.