This study investigates the antibacterial activity of ZnO nanoparticles with varying particle sizes. ZnO was synthesized using two methods: base hydrolysis of zinc acetate in 2-propanol and precipitation using Zn(NO₃)₂ and NaOH. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. Bacteriological tests, including minimum inhibitory concentration (MIC) and disk diffusion, were conducted on Luria-Bertani and nutrient agar media. The results showed that ZnO nanoparticles exhibited enhanced biocidal activity compared to bulk ZnO, with the efficacy increasing with decreasing particle size. The enhanced antibacterial properties were attributed to the abrasiveness and surface oxygen species of the nanoparticles. The study also found that the smaller nanoparticles had a higher surface area to volume ratio, leading to more active oxygen species generation and better bactericidal effects. The findings suggest that ZnO nanoparticles could be effective antimicrobial agents, particularly in medical device coatings.This study investigates the antibacterial activity of ZnO nanoparticles with varying particle sizes. ZnO was synthesized using two methods: base hydrolysis of zinc acetate in 2-propanol and precipitation using Zn(NO₃)₂ and NaOH. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. Bacteriological tests, including minimum inhibitory concentration (MIC) and disk diffusion, were conducted on Luria-Bertani and nutrient agar media. The results showed that ZnO nanoparticles exhibited enhanced biocidal activity compared to bulk ZnO, with the efficacy increasing with decreasing particle size. The enhanced antibacterial properties were attributed to the abrasiveness and surface oxygen species of the nanoparticles. The study also found that the smaller nanoparticles had a higher surface area to volume ratio, leading to more active oxygen species generation and better bactericidal effects. The findings suggest that ZnO nanoparticles could be effective antimicrobial agents, particularly in medical device coatings.