Naveen Kumar Veldurthi

Synthesis, Characterization and Photocatalytic Activity of KAl0.33W1.67O6 and Sn0.5Al0.33W1.67O6xH2O

Nano sized defect pyrochlore, KAl0.33W1.67O6 (KAW), is prepared through sol–gel method. Divalent tin‐doped KAW is obtained at room temperature by ion exchange method using acidified SnCl2 and parent KAW. These materials are characterized by powder X‐ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy—energy dispersive spectra (SEM‐EDS), Raman Spectroscopy and X‐ray photo electronic spectroscopy. The composition of tin‐doped KAW is obtained from chemical analysis, SEM‐EDS and TGA methods and written as Sn0.5Al0.33W1.67O6 xH2O (x = 1.4–1.5) (SnAW). It crystallizes in cubic lattice with Fd3¯m space group. The band gap energies are found to be 2.82 and 2.21 eV for KAW and SnAW respectively. The observed reduction in the band gap with the introduction of Sn2+ in defect pyrochlore lattice is due to mixing of 5s state of Sn2+ with O 2p states leading to an upward shift in the valence band. The Raman spectra of these materials gave more bands than the number expected for defect pyrochlores due to substitutional disorder in 16c sites and displacive disorder of A ions. The photoactivity of SnAW is higher compared to KAW.

Metathesis synthesis, characterization, spectral and photoactivity studies of Ln2/3MoO4 (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er and Y)

Abstract Rare earth ortho-oxomolybdates of composition Ln2/3MoO4 (Ln=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er and Y) were prepared by metathesis reaction. All these materials were characterized by powder X-ray diffraction, Fourier transform-infrared spectroscopy (FT-IR) and UV-Vis diffuse reflectance spectra. The Rietveld analysis of all the samples was carried out to obtain the unit cell parameters and reliability factors. All the materials were crystallized in tetragonal lattice with I41/a space group. The infrared spectra of all the samples were characterized by bands due to MoO42– units. The bandgap energies of all the samples were obtained from UV-Vis DRS spectra. The luminescence spectra of Ln2/3MoO4 (Ln=Pr, Eu and Dy) showed characteristic transitions of the rare earth ions. The visible light photocatalytic activity of all the samples was studied against degradation of methylene blue.

Antimony potassium tartrate

Single source precursor, antimony potassium tartrate, was used for the preparation of Sb2O3, KSb3O5, K0.51Sb0.67IIISb2VO6.26, and KSbO3. Antimony trioxide (Sb2O3) was prepared by hydrothermal method, while potassium antimony oxides (KSbO3, K0.51Sb0.67IIISb2VO6.26, and KSbO3) were obtained from the thermal decomposition of antimony potassium tartrate. All the compounds were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectra, and scanning electron microscopy (SEM). The decomposition process of antimony potassium tartrate with temperature was given. The product formation at different temperatures of thermal decomposition was monitored by PXRD and FT-IR. The TG profile of antimony potassium tartrate shows mass loss at three regions. The infrared spectra of parent and decomposed products gave characteristic Sb-O bands. The band gap energy of decomposed products was obtained. The SEM diagrams of Sb2O3 show different morphologies. Direct solid state preparation of KSb3O5 and K0.51Sb0.67IIISb2VO6.26 under identical experimental conditions was unsuccessful.

Photocatalytic and Conductivity Studies of Bi3+Substituted La2Zr2O7

ABSTRACT Trivalent bismuth substituted La2Zr2O7 pyrochlores of compositions La2-xBixZr2O7 (x = 0.2, 0.4 and 0.6) have been prepared by sol-gel method. All the samples were characterized by powder X-ray diffraction, IR spectroscopy, and SEM-EDS. These materials were found to crystallize in cubic lattice with space group . The unit cell parameters were deduced from the Rietveld refinement. The dc conductivity of all samples was measured in the temperature range 200–700°C. The photocatalytic activities of the samples were studied against methylene blue decomposition under sunlight. La2-xBixZr2O7 compounds showed enhanced photoactivity compared to La2Zr2O7.

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

Synthesis, Characterization and Photocatalytic Activity of Ag+ - and Sn2+ -Doped KTi0.5 Te1.5 O6

Fd\bar 3m

Synthesis and Catalytic Performance of Na2HfM(PO4)3 and Ag2−xNaxHfM(PO4)3 (M = Fe and Al and 0.07 ≤ x ≤ 0.13)

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

In this study, the photocatalytic dye degradation efficiency of KTi0.5Te1.5O6 synthesized through solid‐state method was enhanced by cation (Ag+/Sn+2) doping at potassium site via ion exchange method. As prepared materials were characterized by XRD, SEM‐EDS, IR, TGA and UV–Vis Diffuse reflectance spectroscopic (DRS) techniques. All the compounds were crystallized in cubic lattice with Fd3¯m space group. The bandgap energies of parent, Ag+‐ and Sn+2‐doped KTi0.5Te1.5O6 materials obtained from DRS profiles were found to be 2.96, 2.55 and 2.40 eV, respectively. Photocatalytic efficiency of parent, Ag+‐ and Sn+2‐doped materials was evaluated against the degradation of methylene blue (MB) and methyl violet (MV) dyes under visible light irradiation. The Sn+2‐doped KTi0.5Te1.5O6 showed higher activity toward the degradation of both MB and MV dyes and its higher activity is ascribed to the lower bandgap energy compared to the parent and Ag+‐doped KTi0.5Te1.5O6. The mechanistic degradation pathway of methylene blue (MB) was studied in the presence of Sn2+‐doped KTi0.5Te1.5O6. Quenching experiments were performed to know the participation of holes, super oxide and hydroxyl radicals in the dye degradation process. The stability and reusability of the catalysts were studied.

Photocatalytic degradation of organic dyes with Sn2

Materials belonging to NASICON family of compositions Na2HfM(PO4)3 and Ag2−xNaxHfM(PO4)3 (M = Fe and Al and 0.07 ≤ x ≤ 0.13) are prepared by sol-gel and ion exchange methods, respectively. The IR spectra are characterized by bands belonging to PO4 groups. The band gap energy of all compositions is obtained from their UV-vis DRS profiles. All these materials are used as catalysts in the degradation of methylene blue and methyl orange under visible light irradiation. The silver compounds have shown good catalytic activity compared to their sodium analogues. The catalysts are stable even after the third cycle of photodegradation.