Vithal Muga

New photocatalyst for allylic aliphatic C–H bond activation and degradation of organic pollutants: Schiff base Ti(IV) complexes

Schiff base metal complexes have attracted significant attention due to their alternative applications in the environment, such as the mineralization of organic pollutants to less harmful byproducts and oxygen generation via such processes as photosynthesis. The Ti4+ complexes obtained from Schiff base ligands reacted with donor atoms such as S and N under solvothermal conditions. These complexes were characterized using microanalysis, conductivity studies, and different spectral techniques. These data reveal that the compounds show distorted octahedral geometries with ligand coordination via azomethine nitrogen and thiol sulfur atoms. Oxidation of the allylic methyl group examined the photocatalytic activity of [Ti(L)O] under ambient conditions and oxidative cyclization under visible light irradiation. The Ti(DCMPPT)O complex is a very efficient catalyst due to the very short span of time it takes to produce aldehydes from allylic compounds. Aldehydes readily react with 2-aminophenol or 2-aminobenzenethiol to produce (E)-2-styrylbenzo[d]oxazoles and (E)-2-styrylbenzo[d]thiazoles due to the suitability of the bandgap energy to the generation of ˙OH radicals during the catalytic reaction. This results in a higher oxidation rate. [Ti(DCMPPT)O] is a very efficient photocatalyst for the degradation of MB, due to its large surface area which suggests a lower recombination energy mechanism.

Photocatalytic degradation of organic dyes with Sn2+- and Ag+-substituted K3Nb3WO9(PO4)2 under visible light irradiation

Abstract A tunnel structure compositions of Ag+- and Sn2+-substituted K3Nb3WO9(PO4)2 photocatalysts were synthesized by an ion exchange method and characterized by powder XRD, SEM–EDS, UV–Vis (DRS), BET and FT-IR. The ion-exchanged products are isomorphous with parent K3Nb3WO9(PO4)2. Absorption edges of Ag+- and Sn2+-doped K3Nb3WO9(PO4)2 samples were red shifted remarkably into the visible light region. Photocatalytic activity of these materials was evaluated by studying the degradation of methylene blue, methyl violet, methyl orange and rhodamine B dyes under visible light irradiation. The photocatalytic properties of these compounds were explained based on their band gap energies, photoluminescence spectra and the amounts of ·OH radicals generated during photocatalysis. The possible photocatalytic mechanistic pathway was discussed. The stability of all catalysts during photocatalytic experiment was also investigated. Graphical Abstract

Synthesis, characterisation and photocatalytic activity of Ag+- and Sn2+-substituted KSbTeO6

Ag+- and Sn2+-substituted KSbTeO6 were prepared by a facile ion-exchange method at ambient temperature. All the samples were characterised by scanning electron microscopy, energy-dispersive spectra, thermogravimetric analysis, powder X-ray diffraction, Raman spectra and UV-VIS diffuse reflectance spectra. Both Sn2+- and Ag+-substituted KSbTeO6 were crystallised in a cubic lattice with the

Cation and Anion Substituted Potassium Manganese Phosphate, KMnP3O9: Luminescence and Photocatalytic studies

Fd\bar 3m

Luminescence studies of BaGd2O4: Tb+3 phosphor

space group. The band-gap energy of all the samples was deduced from their UV-VIS diffuse reflectance spectral profiles. The visible light-induced photocatalytic oxidation of the methylene blue (MB) dye was examined in the presence of all the as-prepared materials. The Ag+- and Sn2+-substituted KSbTeO6 exhibited a higher photocatalytic activity than the parent KSbTeO6 in degradation of the MB dye under visible light irradiation.

Photocatalytic degradation of organic dyes with Sn 2+ - and Ag + -substituted K 3 Nb 3 WO 9 (PO 4 ) 2 under visible light irradiation

Phosphates as multifunctional materials were of vital importance in the environmental and energy fields. In the present work, a new cyclophosphate, potassium manganese phosphate (KMnP3O9) (hereafter KMPO), was prepared by solid state method. Cations (Ag+ and Cu2+) and anion (N3−) were substituted into KMPO lattice via ion‐exchange and solid state methods, respectively. The as‐prepared materials were characterized by powder X–ray diffraction, SEM–EDS and UV–visible diffuse reflectance spectra. Rietveld refinement was carried out for parent material. All the prepared materials were found to crystallize in the hexagonal lattice and isomorphous with KCoP3O9. The nitrogen content in N3−‐substituted KMPO was estimated by EDS and O‐N‐H analysis. The bandgap energy of the cation‐ and anion‐substituted samples was lower compared to that of pristine KMPO. Gouy method was employed to determine the magnetic susceptibility of KMPO. The photoluminescence property of Mn2+ in all the samples was studied, and the color coordinates were calculated using CIE 1931 chromaticity. The photocatalytic activity of visible light active material, N3−‐substituted KMPO, was examined against the degradation of methylene blue and methyl violet at ambient conditions.

Photocatalytic degradation of organic dyes with Sn2

The polycrystalline BaGd2-xO4: Tbx (x = 0.00 - 0.10) phosphors have been prepared by conventional high temperature solid state reaction method. All the prepared samples were characterized by powder XRD and EDS techniques. The photoluminescence (PL) and thermally stimulated luminescence (TSL) studies of these materials were investigated. For PL studies the samples were excited with 263 nm UV light. All the samples showed strong green emission at 543 nm due to 5D4→7F5 transition of Tb3+ ions. PL peak intensity was found to increase with increasing dopant concentration. For TSL studies, these samples were γ-irradiated with different dose rates using 60Co source. TSL of these phosphors showed a sharp glow peak with peak maxima at 394 K. It is found that the incorporation of terbium activator in BaGd2O4 host lattice resulted in the increase of TSL intensity. The luminescence results of these materials shows that these are promising candidates for new green emission phosphor.

Preparation, characterization and photocatalytic studies of N, Sn-doped defect pyrochlore oxide KTi0.5W1.5O6

Abstract A tunnel structure compositions of Ag+- and Sn2+-substituted K3Nb3WO9(PO4)2 photocatalysts were synthesized by an ion exchange method and characterized by powder XRD, SEM–EDS, UV–Vis (DRS), BET and FT-IR. The ion-exchanged products are isomorphous with parent K3Nb3WO9(PO4)2. Absorption edges of Ag+- and Sn2+-doped K3Nb3WO9(PO4)2 samples were red shifted remarkably into the visible light region. Photocatalytic activity of these materials was evaluated by studying the degradation of methylene blue, methyl violet, methyl orange and rhodamine B dyes under visible light irradiation. The photocatalytic properties of these compounds were explained based on their band gap energies, photoluminescence spectra and the amounts of ·OH radicals generated during photocatalysis. The possible photocatalytic mechanistic pathway was discussed. The stability of all catalysts during photocatalytic experiment was also investigated. Graphical Abstract

Defect pyrochlore oxides: as photocatalyst materials for environmental and energy applications ‐ a review

Abstract A tunnel structure compositions of Ag+- and Sn2+-substituted K3Nb3WO9(PO4)2 photocatalysts were synthesized by an ion exchange method and characterized by powder XRD, SEM–EDS, UV–Vis (DRS), BET and FT-IR. The ion-exchanged products are isomorphous with parent K3Nb3WO9(PO4)2. Absorption edges of Ag+- and Sn2+-doped K3Nb3WO9(PO4)2 samples were red shifted remarkably into the visible light region. Photocatalytic activity of these materials was evaluated by studying the degradation of methylene blue, methyl violet, methyl orange and rhodamine B dyes under visible light irradiation. The photocatalytic properties of these compounds were explained based on their band gap energies, photoluminescence spectra and the amounts of ·OH radicals generated during photocatalysis. The possible photocatalytic mechanistic pathway was discussed. The stability of all catalysts during photocatalytic experiment was also investigated. Graphical Abstract