Nano Structured Ni and Ru Impregnated TiO2 Photocatalysts: Synthesis, Characterization and Photocatalytic Degradation of Neonicotinoid Insecticides.

Titania by sol gel and Ni-Ru titania catalysts by wet impregnation methods were prepared and characterized by XRD, UV-DRS, BET and TEM techniques. Catalytic activities of the photocatalysts were evaluated towards the degradation of three widely used neonicotinoids type insecticides namely acetamiprid, imidacloprid and thiamethoxam under UV, Visible and solar irradiations. The reaction parameters such as initial concentration of the insecticide, weight of the catalyst and pH of the system were found to influence the reaction rate. The results indicated that the metal impregnated catalysts were found to be more active than pure TiO2.Ni/TiO2 or Ru/TiO2 catalysts degraded all the insecticides completely even under visible irradiation. The observed visible activity of the catalysts was attributed to their lower band gap values. HPLC and TOC analyses revealed that mineralisation of the insecticides occurred through dearomatization by multiple hydroxylation and oxidation. The degradation pathway and the kinetics were also discussed in detail.

Fluorescent Biomolecules Capped ZnSe Quantum Dots and Their Photocatalytic Activities.

The preparation of semiconductor Quantum Dots (QDs) with controllable size, shape and doping remains a biggest challenge, especially the size below 10 nm. To date, only scarce attempts have been made on the synthesis of ZnSe QDs using biomolecule-assisted hydrothermal approach. Hence the current research work examines the influence of some amino acids namely L-cysteine, methionine and tyrosine as stabilizing agents in the synthesis of ZnSe nanocrystals. The ZnSe QDs exhibited strong absorption and photoluminescence properties in the region from 200-600 nm. Spectroscopic and structural properties of the as-synthesized biomolecule-capped ZnSe QDs were characterized by UV-vis absorption spectrophotometer, FT-IR, fluorescence spectrophotometer, X-ray diffractometer, Scanning Electron Microscope and EDX analysis. The stabilizing agents have played a crucial role in preparing ZnSe QDs and in determining the photoluminescence properties. The luminescence intensity was enhanced significantly when amino-acid-capped ZnSe QDs were illuminated by UV light compared to visible light. The as-synthesised ZnSe QDs were capable of effectively degrading an organic azo dye Azophlexin, under direct sunlight irradiation and exhibited good stability during photocatalytic experiments which can be attributed to the small size of amino acid capped ZnSe. The degradation mechanism is discussed. The absorbance and FT-IR measurements confirmed the biocompatibility and water-solubility of the pure ZnSe and capped ZnSe QDs.