Enhancement of photocatalytic and antibacterial activities of zinc oxide nanoparticles through in-situ loading of well-dispersed silver nanoparticles

As a photocatalytic antibacterial material, its poor visible-light absorption and rapid charge recombination lead to low photocatalytic efficiency under visible light irradiation. Incorporating silver nanoparticles (Ag NPs) can enhance both photocatalytic activity and antibacterial performance in visible light. Notably, the dispersion methodology of Ag NPs critically determines the overall effectiveness of nanoparticle-doped systems. This study demonstrates an in situ synthesis of ZnO/Ag NPs (ZA-1) featuring uniformly dispersed Ag NPs on ZnO through Sn 2+ -mediated interfacial bonding and reduction. A comparative ZnO/Ag heterogeneous nanostructures (ZA-2) was concurrently prepared via conventional hydrothermal synthesis to establish methodological contrast. The synthesized NPs underwent characterization through X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS) to systematically evaluate their structural characteristics and optical properties. The results showed that both ZA-1 and ZA-2 exhibited broadened and redshifted surface plasmon resonance (SPR) bands. Notably, ZA-1 demonstrated significantly reduced bandgap energy compared to ZA-2 and pristine ZnO. Photocatalytic evaluation under visible light revealed ZA-1′s superior performance in degrading methyl orange (MO) (from 38.85 % to 91.20 %) and methylene blue (MB) (from 60.08 % to 93.60 %). Antimicrobial validation through Ag + release kinetics (0.026 ppm accumulated over 72 h) and inhibition zone assays (17 mm E. coli and 16.5 mm S. aureus ) confirmed ZA-1′s dual functionality as an efficient photocatalytic biocide meeting food-contact material standards.