Green-Synthesized ZnO Nanoparticles: Mechanisms, Properties, and Antimicrobial Performance
Background: Green synthesis of metal oxide nanoparticles provides a simple and sustainable alternative to conventional chemical synthesis methods. Plant-derived extracts can act as biological reducing and stabilizing agents during nanoparticle formation. Objective: This study aimed to synthesize zinc oxide nanoparticles (CL-ZnO) using aqueous extract of Citrus limetta peel and evaluate their physicochemical characteristics and antibacterial activity. Methods: Dried C. limetta peel powder was extracted in deionized water and used as a biological medium for the synthesis of ZnO nanoparticles from zinc acetate dihydrate. The synthesized CL-ZnO nanoparticles were characterized using UV–visible spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), and zeta potential analysis. Antibacterial activity was evaluated against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. Results: XRD analysis confirmed the formation of crystalline ZnO with a wurtzite structure, with an average crystallite size of approximately 24 nm. The zeta potential was measured as −24 mV, indicating a negatively charged nanoparticle surface. CL-ZnO exhibited antibacterial activity against the tested bacterial strains. This activity may be associated with nanoparticle–cell membrane interactions, oxidative stress generation, and the possible release of Zn²⁺ ions. Conclusion: The findings demonstrate that C. limetta peel can serve as a sustainable biological source for the green synthesis of ZnO nanoparticles with antibacterial properties. This approach offers a simple and environmentally friendly route for producing ZnO nanoparticles with potential applications in antibacterial materials and related biomedical fields.