Green synthesis of ZnO, CuO and NiO nanoparticles using Neem leaf extract and comparing their photocatalytic activity under solar irradiation

In this study, a facile, green, and eco-friendly approach was conducted for the synthesis of zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO) nanoparticles (NPs) using the leaf extract of the Azadirachta indica (neem) plant. The biosynthesized nanoparticles were characterized by X-ray diffraction (X-RD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive x-ray (EDX), scanning electron microscopy (SEM), and ultraviolet-visible spectroscopy (UV-Vis). The X-RD showed that the synthesized ZnO, CuO, and NiO NPs were of high purity, mostly hexagonal, monoclinic, and cubic in shape, with an average crystalline size in the range 25.26-10.50 nm. The EDX confirms the presence of different elements: Zn, Cu, Ni, and O. Morphology of the nanoparticles was investigated with SEM. The presence of Zn-O, Ni-O, and Cu-O stretching vibration bands was revealed in FT-IR spectrum. The optical band gaps were in the range of 2.59-1.67 eV. The photocatalytic activity of NPs was evaluated by carrying out the degradation of methylene blue under solar irradiation. Among, the biosynthesized nanoparticles, CuO NPs showed excellent photocatalyst performance compared to ZnO and NiO NPs.