Study of the Antibacterial, Antifungal and Photodegradation Performance of Zinc Oxide and Mg/Ag-Zinc Oxide Nanoparticles

Abstract

Microbial infectious diseases remain a persistent threat to global public health. In this context, Nanotechnology has emerged as a powerful platform for contemporary technology. In this study, we synthesized pure zinc oxide (ZnO) and magnesium-silver co-doped ZnO nanoparticles (Mg/Ag-ZnO NPs) and evaluated their antibacterial and antifungal activities against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Candida albicans using the broth microdilution method to determine minimum inhibitory concentrations (MICs). Additionally, the photocatalytic performance of NPs was assessed by monitoring the degradation of methylene blue (MB) dye under UV irradiation. Results demonstrated that Mg/Ag-ZnO NPs exhibited significantly enhanced photocatalytic activity compared to undoped ZnO, achieving 85.6% MB degradation after 180 min, attributable to the synergistic effects of Ag and Mg doping, which promote charge separation and reactive oxygen species generation. Antimicrobial assays revealed that co-doping markedly improved efficacy, MIC values for Staphylococcus epidermidis were 160, 80, 40, and 40 µg/mL, and for Staphylococcus aureus were 80, 40, 40, and 20 µg/mL, corresponding to ZnO, Mg/Ag1-ZnO, Mg/Ag2-ZnO, and Mg/Ag4-ZnO, respectively. Against the more resistant Pseudomonas aeruginosa and Candida albicans, MICs decreased from >5120 µg/mL (ZnO) to 320 µg/mL and 1280 µg/mL, respectively, with the highest doping level (Mg/Ag4-ZnO). These findings indicate that silver plays a dominant role in inhibiting Gram-positive bacteria, while combined Ag/Mg doping progressively enhances activity against Gram-negative bacteria and fungi, likely through intensified oxidative stress.