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), 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/ZnOcop (150 m
2
/g) is much higher than that of undecorated ZnOcop (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/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.