SnO₂ photocatalyst was successfully synthesised by novel chemical route in hydrothermal environment and annealed at two different temperatures viz 550 and 600 °C, respectively. The crystal structure, optical properties, surface and bulk morphology have been characterised using various tools like X-ray diffraction (XRD), UV visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscope (TEM) and scanning electron microscope (SEM). Cubic, spheres and porous like morphology of SnO₂ photocatalyst was successfully confirmed using SEM micrographs and TEM. In addition to this the photocatalytic activity was evaluated towards the degradation of methylene blue dye solution. SnO₂ photocatalyst annealed at 600 °C exhibits excellent photocatalytic efficiency which may be attributed to the unique morphology, high crystalline nature and charge separation. The photocatalyst efficiency was further tested towards the concentration of dye, catalyst dosage and pH of the dye. The involvement of •OH in the photocatalytic reaction was evidenced using trapping experiment by employing different scavengers. The photocatalyst was moderately active, stable upto its fifth usage and stability of the photocatalyst before and after the photocatalytic reaction was also been studied using XRD and SEM.

The present work demonstrates a new simple hand-picking technique for the 100% recovery of a CuO nanosphere photocatalyst.

A series of CdO/ZnO nanohybrids of different compositions were synthesized by a wet chemical method and investigated in detail. The nanohybrids were characterized by various techniques such as wide angle X-ray diffraction (XRD), diffuse reflectance UV-vis spectroscopy, transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The results revealed that the crystal structure and optical properties of the nanohybrids were almost the same for all the compositions. FE-SEM images showed that the morphology of CdO/ZnO was hexagonal like microspheres, and the 0.75 : 1 Cd/Zn sample had a well-proportioned morphology. Three different dyes viz crystal violet, congo red and rhodamineB were used for the photocatalytic studies in a photoreactor and monitored with a UV-visible spectrometer. The nanohybrids showed excellent photocatalytic degradation compared to pure CdO and ZnO. In particular, nanohybrids with 0.75 : 1 (Cd : Zn) composition ratio exhibited better results compared to all other CdO/ZnO nanohybrids, which may be attributed to the improved charge separation at the heterojunction interface.