Investigations on microstructure, optical, magnetic, photocatalytic, and dielectric behaviours of pure and Co-doped ZnO NPs

In this research, an effective usage of quantum size effect is a foregrounded strategy to produce and employ excellent visible light-driven photocatalytic materials. Zn_100−xCo_xO (x = 0, 2.5, 7.5) particles at nanoscale were synthesized successfully by chemical co-precipitation method and then investigated by some complimentary analytical techniques. Physical structure and chemical states were analysed by X-ray diffraction and X-ray photoelectron spectroscopy. XRD and HRTEM analysis confirmed the formation of wurtzite-type structure without any traces of secondary phase. XPS spectra exhibited the incorporation of Co²⁺ ions into ZnO lattice. Optical spectra of Zn_100−xCo_xO nanoparticles (NPs) indicated that bandgap is significantly narrowed with increasing Co concentration. Ferromagnetic behaviour was observed at room temperature in pure and Co-doped ZnO, due to the effect of quantum confinement and of Co²⁺ ions incorporation. The frequency and composition dependence of dielectric constant and dielectric loss have been analysed in detail using Maxwell–Wagner model and Cole–Cole plots. The activity of synthesized photocatalysts under simulated sunlight irradiation was characterized through decomposition of methylene blue (MB) dye in aqueous suspension, which revealed that Co²⁺ ions incorporation in ZnO greatly enhanced the photocatalytic degradation efficiency and hence employable in environmental cleaning.