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

Abstract

ZnO nanoparticles (ZnO NPs) were efficiently synthesized using three different methods: hydrothermal (ZnO hyd ), solvothermal (ZnO sol ), and co-precipitation (ZnO cop ). 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), high-resolution transmission electron microscopy (HRTEM), Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption-desorption at −196 °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/ZnO cop (150 m 2 /g) is much higher than that of undecorated ZnO cop (34 m 2 /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/ZnO cop sample. The photocatalytic activities of ZnO NPs synthesized with different methods and Ag/ZnO cop NPs were assessed by their ability to degrade crystal violet (CV) in an aqueous solution when exposed to UV light . The Ag/ZnO cop sample had the highest degradation rate (95 %) than pure ZnO cop 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/ZnO cop compared to ZnO cop indicated that Ag NPs inhibit electron-hole recombination, enhancing photocatalytic activity by promoting charge separation.

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