Synthesis and Characterization of ZnO Nanoparticles for Antibacterial and Antifungal Properties

Abstract

Zinc oxide (ZnO) nanoparticles (NPs) were synthesized via chemical and green (plant-extract-mediated) methods and characterized using XRD and SEM/FESEM. The NPs typically exhibited a hexagonal wurtzite crystal structure with average crystallite sizes ranging from ~10–60 nm and morphologies including spherical like. ZnO NPs demonstrated strong, concentration- and size-dependent antibacterial activity against both Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria, as well as antifungal activity against Candida albicans, Aspergillus niger, and related species. Activity was evaluated mainly by disc/well diffusion (zones of inhibition often 14–22+ mm), MIC, and MBC assays. Smaller particles and higher-surface-area morphologies generally showed superior efficacy. Key mechanisms include reactive oxygen species (ROS) generation, Zn²⁺ ion release, and direct membrane disruption. Green synthesis routes provide eco-friendly alternatives with comparable or enhanced performance due to phytochemical capping. These results highlight ZnO NPs as promising, biocompatible antimicrobial agents for biomedical, agricultural, and environmental applications, while underscoring the need for further toxicity and scalability studies.