Sustainable Fabrication of ZnO-Based Photocatalysts for Light-Driven Degradation of Organic Dyes

Pure ZnO and Ni-doped ZnO nanoparticles with Ni concentrations of 5[Formula: see text]wt.%, 10[Formula: see text]wt.% and 15[Formula: see text]wt.% were successfully synthesized and systematically investigated for their optical, photocatalytic and antibacterial properties. UV–Vis diffuse reflectance analysis revealed a gradual narrowing of the optical band gap with increasing Ni content, indicating modification of the electronic structure due to dopant induced defect states. The photocatalytic activity was evaluated through methylene blue degradation under light irradiation, where 15[Formula: see text]wt.% Ni@ZnO exhibited the highest degradation efficiency, showing a lower normalized concentration value of 0.53 after 80[Formula: see text]min compared with 0.56 for pure ZnO. Kinetic analysis confirmed pseudo-first-order behavior, with the apparent rate constant increasing from [Formula: see text][Formula: see text]min[Formula: see text] for pure ZnO to [Formula: see text][Formula: see text]min[Formula: see text] for 15[Formula: see text]wt.% Ni@ZnO, along with an improved correlation coefficient [Formula: see text] of 0.9707. Antibacterial studies conducted using the agar well diffusion method demonstrated a pronounced enhancement in bactericidal performance with Ni doping. The maximum zones of inhibition were observed for 15[Formula: see text]wt.% Ni@ZnO, measuring 16[Formula: see text]mm against Staphylococcus aureus and 15[Formula: see text]mm against Vibrio spp., compared with 9[Formula: see text]mm and 8[Formula: see text]mm for pure ZnO, respectively. The enhanced photocatalytic and antibacterial activities are attributed to improved charge separation, increased reactive oxygen species generation and stronger interactions with bacterial cell membranes induced by Ni incorporation. These findings establish Ni-doped ZnO as an efficient multifunctional material for environmental remediation and antimicrobial applications.