Biogenic Synthesis of Photocatalytically Active Nickel Oxide (NiO) Nanoparticles using Catharanthus roseus Leaf Extract

Abstract

A simple and environmentally friendly method was employed to synthesize Nickel oxide (NiO) nanoparticles (NPs) using the leaf extract of Catharanthus roseus via the sol-gel method. Nickel sulfate hexahydrate was utilized as a precursor, with the leaf extract of Catharanthus roseus serving as both a reducing agent and a stabilizing agent. Various characterization techniques including X-ray diffraction, Fourier transfer infrared spectroscopy, Ultraviolet diffused reflectance spectroscopy (UV-DRS), Scanning electron spectroscopy, Energy dispersive X-ray analysis, Transmission electron microscopy, and Vibrating sample magnetometer were employed to investigate the structural and characteristic properties of the NiO NPs. The synthesized NiO NPs showed super paramagnetic behaviour at room temperature with saturated magnetization
(M_s= 47.22×10^-3 emu). Methylene blue is one of the industrial dyes that make water unfit for    irrigation or drinking. It is a toxic, carcinegic and recalcitrant dye which causes a severe threat to human health. As the dye is difficult to be degraded, a biological eco-friendly method is followed in the present study. NiO NPs had a band energy gap of 3.6 eV and a strong potential to be used as photocatalysts in wastewater treatment to rapidly degrade textile dyes. Almost complete photocatalytic degradation of methylene blue dye was achieved using NiO NPs, which also exhibited high stability and reusability for three additional cycles without any significant decrease in efficacy.