Eco-friendly synthesis of silver-doped zinc oxide nanocomposites with enhanced antibacterial performance

Abstract

Abstract This study presents the use of extracts of Searsia lancea in the synthesis of zinc oxide nanoparticles (ZnONPs), silver nanoparticles (AgNPs), and silver-doped zinc oxide nanocomposites (Ag/ZnO) at different dopant concentrations of 0, 1, 5, 10, and 20%, given composites denoted as 1%Ag/ZnO, 5%Ag/ZnO, 10%Ag/ZnO, and 20%Ag/ZnO, respectively. The synthesized ZnONPs, AgNPs, and Ag/ZnO nanocomposites were characterized using spectroscopic and microscopic techniques, and their antibacterial activities were evaluated against common bacterial pathogens. The UV–vis spectroscopy and XRD results reveal successful formation of ZnONPs, AgNPs, and Ag/ZnO nanocomposites with improved structural and optical properties. The TEM results confirmed particle sizes of 49.75, 32.91, 30.95, 29.29, and 26.00 nm for 1%Ag/ZnO, 5%Ag/ZnO, 10%Ag/ZnO, and 20%Ag/ZnO, respectively, indicating a decrease in particle size with increasing Ag ion concentration. The pure AgNPs showed strong antibacterial activity, with MIC values of 0.25 mg ml −1 against E. coli and P. aeruginosa , and 0.062 mg ml −1 against S. aureus and S. pyogenes . In contrast, pristine ZnONPs (0%Ag/ZnO) exhibited higher MIC values of 1.00, 0.50, 0.25, and 0.25 mg ml −1 against E. coli , P. aeruginosa , S. aureus and S. pyogenes , respectively. Notably, 1%Ag/ZnO and 5%Ag/ZnO nanocomposites displayed moderate activity, with MIC values in the range 0.125 to 0.50 mg ml −1 across all strains. The 10%Ag/ZnO nanocomposite showed consistent MIC values of 0.125 mg ml −1 for all tested organisms. The 20%Ag/ZnO nanocomposite exhibited the highest antibacterial potency among all synthesized samples, with MIC values of 0.062 mg ml −1 against E. coli and P. aeruginosa , and 0.031 mg ml −1 against S. aureus and S. pyogenes. The enhanced antibacterial activities shown by Ag/ZnO nanocomposites compared to pure ZnONPs, with efficiency increasing with the concentration of Ag highlights the potential of plant-mediated silver-doped zinc oxide nanocomposites as eco-friendly and efficient antimicrobial agents.