This study investigates the antibacterial activity of ZnO nanoparticles with varying particle sizes. ZnO was synthesized using two methods: precipitation and base hydrolysis of zinc acetate in a 2-propanol medium. The products were characterized using XRD, TEM, and PL spectroscopy. Bacteriological tests, including MIC and disk diffusion, were performed using standard microbial methods. The results showed that ZnO nanoparticles exhibit enhanced biocidal activity compared to bulk ZnO, with smaller particles showing greater efficacy. This is attributed to the increased surface area and the generation of reactive oxygen species on the nanoparticle surface. The study also found that the bactericidal effect of ZnO nanoparticles is enhanced by their abrasive surface and the ability to release reactive species such as OH⁻, H₂O₂, and O₂²⁻. The results indicate that ZnO nanoparticles are more effective antimicrobial agents than bulk ZnO, with smaller particles showing greater activity. The study concludes that the enhanced bioactivity of ZnO nanoparticles is due to their higher surface area to volume ratio and the increased surface reactivity, which leads to more effective microbial inactivation. The findings suggest that ZnO nanoparticles could be useful in medical devices coated with nanoparticles to combat microbes.This study investigates the antibacterial activity of ZnO nanoparticles with varying particle sizes. ZnO was synthesized using two methods: precipitation and base hydrolysis of zinc acetate in a 2-propanol medium. The products were characterized using XRD, TEM, and PL spectroscopy. Bacteriological tests, including MIC and disk diffusion, were performed using standard microbial methods. The results showed that ZnO nanoparticles exhibit enhanced biocidal activity compared to bulk ZnO, with smaller particles showing greater efficacy. This is attributed to the increased surface area and the generation of reactive oxygen species on the nanoparticle surface. The study also found that the bactericidal effect of ZnO nanoparticles is enhanced by their abrasive surface and the ability to release reactive species such as OH⁻, H₂O₂, and O₂²⁻. The results indicate that ZnO nanoparticles are more effective antimicrobial agents than bulk ZnO, with smaller particles showing greater activity. The study concludes that the enhanced bioactivity of ZnO nanoparticles is due to their higher surface area to volume ratio and the increased surface reactivity, which leads to more effective microbial inactivation. The findings suggest that ZnO nanoparticles could be useful in medical devices coated with nanoparticles to combat microbes.