Optical and photocatalytic properties undoped and Mn-doped ZnO nanoparticles synthesized by hydrothermal method: Effect of annealing temperature

Undoped and Mn-doped ZnO nanoparticles were successfully prepared by the hydrothermal method with different annealing temperature conditions. Structural, chemical and optical properties of the samples were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV-Vis spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The phase purity was confirmed by X-ray powder diffraction (XRD) indicating hexagonal wurtzite structure for all samples and less crystallinity with increasing annealing temperature. In addition, the average particle size was found to be 15-30 nm from SEM and XRD. It is seen that the optical band gap increases when the ZnO is doped with manganese and decreases when annealing temperature increases. The photocatalytic activity of undoped and Mn-doped ZnO nanoparticles was tested by the degradation of methyl orang (MO) under UV light and indicated that Mn-doped ZnO has higher photocatalytic activity relative to ZnO nanoparticles and photocatalytic activity decreases when annealing temperature increases.