Fabrication and characterization of ZnO and Ag/ZnO nanoparticles for efficient degradation of crystal violet dye in aqueous solution

ZnO nanoparticles (ZnO NPs) were efficiently synthesized using three different methods: hydrothermal (ZnOhyd), solvothermal (ZnOsol), and co-precipitation (ZnOcop). The resulting ZnO NPs were further decorated with Ag NPs through photoreduction. All ZnO NPs and Ag/ZnO NPs were characterized by X-ray diffraction (XRD), highresolution transmission electron microscopy (HRTEM), Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption-desorption at -196 degrees C for porous structure analysis, UV-Visible spectroscopy, and photoluminescence (PL) measurements. The results confirmed that all ZnO NPs have a wurtzite hexagonal structure and that Ag NPs were successfully incorporated into the ZnO crystal lattice. The BET surface area of Ag/ZnOcop (150 m2/g) is much higher than that of undecorated ZnOcop (34 m2/g), confirming the successful incorporation of Ag nanoparticles. A redshift in the spectral absorption towards the visible light region and a reduction in the band gap, from 3.1 eV to 2.7 eV, was observed for the Ag/ZnOcop sample. The photocatalytic activities of ZnO NPs synthesized with different methods and Ag/ZnOcop NPs were assessed by their ability to degrade crystal violet (CV) in an aqueous solution when exposed to UV light. The Ag/ ZnOcop sample had the highest degradation rate (95 %) than pure ZnOcop NPs (88.9 %). This degradation process relies on dye oxidation by highly reactive hydroxyl radicals, and several factors can affect its efficiency. The reduced PL intensity of Ag/ZnOcop compared to ZnOcop indicated that Ag NPs inhibit electron-hole recombination, enhancing photocatalytic activity by promoting charge separation.