Influence of Silver Content on the Structural Characteristics and Antibacterial Activity of ZnO–Ag Nanoparticles Against Escherichia coli and Salmonella typhimurium
Abstract
Antimicrobial nanomaterials have attracted increasing attention as potential alternatives for controlling pathogenic microorganisms. In this study, pure ZnO and Ag-modified ZnO nanoparticles prepared using nominal Ag contents of 1 and 5 wt.% were synthesized using a reflux-assisted polyol method and evaluated to determine the influence of Ag content on their structural characteristics and antibacterial activity. The synthesized materials were characterized by UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). UV-Vis and FTIR analyses confirmed the characteristic optical response and chemical features of ZnO-based materials. XRD patterns revealed that all samples retained the hexagonal wurtzite structure of ZnO, while additional reflections corresponding to face-centered cubic (FCC) Ag were observed in the Ag-containing samples and increased in intensity with Ag content. Crystallite sizes estimated by the Scherrer equation were 16.9 ± 2.6 nm for ZnO, 12.9 ± 1.6 nm for ZnO-Ag 1%, and 32.6 ± 10.1 nm for ZnO-Ag 5%. HRTEM confirmed the formation of crystalline nanoparticles with average particle sizes of approximately 16 nm and 12 nm for ZnO and ZnO-Ag 1%, respectively. Antimicrobial activity was evaluated against the reference strains Escherichia coli ATCC 25922 and Salmonella typhimurium ATCC 14020. ZnO–Ag 5% exhibited the greatest antibacterial activity, with minimum inhibitory concentration (MIC) values of 250 ppm against E. coli and 750 ppm against S. typhimurium, and minimum bactericidal concentration (MBC) values of 750 and 1500 ppm, respectively. These findings demonstrate that increasing Ag content influences the structural properties of ZnO nanoparticles and enhances their antibacterial performance, highlighting the potential of ZnO-Ag nanomaterials for antimicrobial applications.