Comparative study on structural and photocatalytic activity of rare earth and transition metal doped ZnO: Nd-doped versus Ni-doped ZnO

Zinc oxide, rare earth (Nd), and transition metal (Ni) doped zinc oxide were synthesized by facile and low cost hydrothermal method. Structural, microstructural, and optical properties, as well as photocatalytic activity of these nanoparticles, were investigated by various characterization techniques. The X-ray diffraction (XRD) pattern of nanoparticles showed a pure-phase with a hexagonal structure with an average crystallite size of 23.3 nm. The microstructural study by scanning electron microscopy (SEM) confirmed that all synthesized nanoparticles had spherical morphology and particle size was smaller for doped samples. The optical properties of ZnO and doped-ZnO were determined by UV–vis spectroscopy. Furthermore, the band gap of the samples was calculated by absorption spectra that resolved the excitonic or interband (valence-conduction band) transition. Nd-doped ZnO nanoparticles had the smallest band gap. The photocatalytic activity of ZnO, Ni-doped ZnO, and Nd-doped ZnO was studied by comparing the degradation rate of methyl blue (MB) under UV-light irradiation. The results show that Nd ions have more effect on improving the photocatalytic activity of ZnO than Ni ions.