Suppressing of photocatalytic degradation in Ga and Bi co-doping ZnO nanopowders: Potential application in sunscreen

The chemical sol-gel method was successfully used to synthesize ZnO semiconductor nanopowders co-doped with varying concentrations of Bi and Ga. This study investigates the effect of these dopants in suppressing the photocatalytic activity of ZnO for sunscreen applications. The structural, morphological, and optical properties of Bi- and Ga-doped ZnO were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), ultraviolet-visible reflectance spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FTIR). XRD analysis confirmed the presence of the hexagonal wurtzite phase in the co-doped ZnO nanoparticles. The crystallite size, estimated using the Williamson-Hall (W-H) plot, ranged from 24 to 10 nm. SEM analysis revealed that the particle size was below 100 nm, and the co-doped ZnO exhibits a smaller size compared to undoped ZnO. This reduction in particle size leads to an increase in structural defects, which, in turn, suppresses the photocatalytic activity. The EDS analysis further confirmed these results. The UV-Vis spectrophotometer results show the bandgap increases with Bi and Ga co-doping. These increases inhibit the electron-hole pair recombination, thereby reducing the production of reactive oxygen species (ROS). Finally, FTIR analysis verified the chemical bonding of Zn-O and Bi-O. The photocatalytic activity was evaluated against Rhodamine B (Rh-B), a typical organic contaminant, under sunlight irradiation. The results demonstrated that co-doped ZnO exhibits lower photocatalytic efficiency compared to undoped ZnO, confirming its suitability for sunscreen applications.

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