Efficient Photocatalytic Degradation of Rhodamine B Dye by Aligned Arrays of Self-Assembled Hydrogen Titanate Nanotubes

We show that an aligned array of hydrothermally grown, multiwalled hydrogen titanate (H2Ti3O7) nanotubes—anchored to both faces of a metallic Ti foil—acts as an efficient photocatalyst. We studied the degradation of rhodamine B dye in the presence of the nanostructured photocatalyst under UV irradiation, by monitoring the optical absorption of the dye. Rhodamine B was chosen as a representative—and particularly harmful—industrial pollutant dye. The inner and outer diameters of the H2Ti3O7 nanotubes were 5 nm and 10 nm, respectively. The nanotube array catalyst is recyclable and structurally stable. Most importantly, it shows comparable or higher photodecomposition rate constant than those of both H2Ti3O7 nanotube powder and P-25 (Degussa). The enhanced photocatalytic performance may be ascribed to the nanotube array having a superhydrophilic surface with a high accessible surface area

Pressure Impact on the Stability and Distortion of the Crystal Structure of CeScO3

[EN] The effects of high pressure on the crystal structure of orthorhombic (Pnma) perovskite-type cerium scandate were studied in situ under high pressure by means of synchrotron X-ray powder diffraction, using a diamond-anvil cell. We found that the perovskite-type crystal structure remains stable up to 40 GPa, the highest pressure reached in the experiments. The evolution of unit-cell parameters with pressure indicated an anisotropic compression. The room-temperature pressure¿volume equation of state (EOS) obtained from the experiments indicated the EOS parameters V0 = 262.5(3) Å3 , B0 = 165(7) GPa, and B0¿ = 6.3(5). From the evolution of microscopic structural parameters like bond distances and coordination polyhedra of cerium and scandium, the macroscopic behavior of CeScO3 under compression was explained and reasoned for its large pressure stability. The reported results are discussed in comparison with high-pressure results from otherThe authors are thankful for the financial support to this research from the Spanish Ministerio de Economia y Competitividad, the Spanish Research Agency, and the European Fund for Regional Development under Grant Nos. MAT2016-75S86-C4-1/2-P, MAT2013-46649-C4-1/2-P, and MAT2015-71070-REDC (MALTA Consolider). D.S.P. acknowledges the Spanish government for a Ramon y Cajal grant. The authors express gratitude to F. Aguado for fruitful discussions on the high-pressure behavior of perovskites. These experiments were performed at MSPD beamline at ALBA Synchrotron with the collaboration of ALBA staff.Errandonea, D.; Santamaria-Perez, D.; Martinez-Garcia, D.; Gomis, O.; Shukla, R.; Achary, SN.; Tyagi, AK.... (2017). Pressure Impact on the Stability and Distortion of the Crystal Structure of CeScO3. Inorganic Chemistry. 56(14):8363-8371. https://doi.org/10.1021/acs.inorgchem.7b01042S83638371561

High-pressure crystal structure, lattice vibrations, and band structure of BiSbO4

"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.inorgchem.6b00503”The high-pressure crystal structure, lattice-vibrations HP crystal structure, lattice vibrations, and band , and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressure on it. They also predict a possible high-pressure phase. A room-temperature pressure volume equation of state is determined, and the effect of pressure on the coordination polyhedron of Bi and Sb is discussed. Raman- and infrared-active phonons were measured and calculated. In particular, calculations provide assignments for all the vibrational modes as well as their pressure dependence. In addition, the band structure and electronic density of states under pressure were also calculated. The calculations combined with the optical measurements allow us to conclude that BiSbO4 is an indirect-gap semiconductor, with an electronic band gap of 2.9(1) eV. Finally, the isothermal compressibility tensor for. BiSbO4 is given at 1.8 GPa. The experimental (theoretical) data revealed that the direction of maximum compressibility is in the (0 1 0) plane at similar to 33 degrees (38 degrees) to the c-axis and 47 degrees (42 degrees) to the a-axis. The reliability of the reported results is supported by the consistency between experiments and calculations.Research supported by the Spanish government MINECO under Grant Nos. MAT2013-46649-C4-1/2/3-P and MAT2015-71070-REDC. We also acknowledge the computer time provided by MALTA cluster and the Red Espanola de Supercomputacion. Experiments were performed at MSPD beamline at ALBA Synchrotron Light Facility with the collaboration of ALBA staff.Errandonea, D.; Muñoz, A.; Rodríguez-Hernández, P.; Gomis, O.; Achary, SN.; Popescu, C.; Patwe, SJ.... (2016). High-pressure crystal structure, lattice vibrations, and band structure of BiSbO4. Inorganic Chemistry. 55(10):4958-4969. doi:10.1021/acs.inorgchem.6b00503S49584969551

New polymorph of InVO4: A high-pressure structure with six-coordinated vanadium

This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Inorganic Chemestry, copyright © American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/ic402043xA new wolframite-type polymorph of InVO4 is identified under compression near 7 GPa by in situ high-pressure (HP) X-ray diffraction (XRD) and Raman spectroscopic investigations on the stable orthorhombic InVO4. The structural transition is accompanied by a large volume collapse (Delta V/V = -14%) and a drastic increase in bulk modulus (from 69 to 168 GPa). Both techniques also show the existence of a third phase coexisting with the low- and high-pressure phases in a limited pressure range close to the transition pressure. XRD studies revealed a highly anisotropic compression in orthorhombic InVO4. In addition, the compressibility becomes nonlinear in the HP polymorph. The volume collapse in the lattice is related to an increase of the polyhedral coordination around the vanadium atoms. The transformation is not fully reversible. The drastic change in the polyhedral arrangement observed at the transition is indicative of a reconstructive phase transformation. The HP phase here found is the only modification of InVO4 reported to date with 6-fold coordinated vanadium atoms. Finally, Raman frequencies and pressure coefficients in the low- and high-pressure phases of InVO4 are reported.This research supported by the Spanish government MINECO under Grant Nos. MAT2010-21270-C04-01/04 and CSD2007-00045. O.G. acknowledges support from Vicerrectorado de Investigacion y Desarrollo of UPV (Grant No. UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). S.N.A. acknowledges support provided by Universitat de Valencia during his visit to it. B.G.-D. acknowledges the financial support from MINECO through the FPI program.Errandonea, D.; Gomis Hilario, O.; García-Domene, B.; Pellicer Porres, J.; Katari, V.; Achary, SN.; Tyagi, AK.... (2013). New polymorph of InVO4: A high-pressure structure with six-coordinated vanadium. Inorganic Chemistry. 52(21):12790-12798. https://doi.org/10.1021/ic402043xS1279012798522

Tin oxide nanocrystals: controllable synthesis, characterization, optical properties and mechanistic insights into the formation process

A novel, surfactant-free, solution-phase method has been successfully developed for the synthesis of SnO2 nanocrystals using a solvothermal route. The nanocrystals having average diameters in the range 4–8 nm, have been synthesized by a non-aqueous sol–gel reaction using tin(IV) bis(acetylacetonate)dichloride, [(Sn(acac)2Cl2)] with benzyl alcohol as the reaction medium at 200 °C. The crystal structure, morphology, and sizes of the SnO2 nanocrystals have been determined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman studies. Raman peaks at 627, 768 cm−1 characteristic of the rutile phase of bulk SnO2 are observed along with broad surface vibration modes in the range 400–600 cm−1. Optical properties of the nanocrystals have been explored by optical absorption and photoluminescence (PL). A blue shift of the optical band gap of the nanocrystals is observed due to size effects. The estimated band gap of the SnO2 nanocrystals from optical absorption data is found to be 3.81 eV. The photoluminescence spectrum showed broad UV as well as visible emission. Based on the GC-MS and carbon-13 NMR analysis of the final reaction solution, a formation mechanism encompassing the ether elimination and solvolysis of acetylacetonate ligand is proposed

Interconversion of perovskite and fluorite structures in Ce−Sc−O system

CeScO3 was synthesized by a two-step synthesis route involving a combustion method followed by vacuum heating at 1100 °C in the presence of Zr sponge which acts as an oxygen getter. The compound was characterized by various techniques such as X-ray diffraction (XRD), high temperature XRD, thermogravimetry, diffuse reflectance (DR)-UV visible spectrophotometry, and Raman spectroscopy. Fluorite-type (F-type) solid solution with composition Ce0.5Sc0.5O1.75 was observed as an intermediate during the synthesis of CeScO3. Only by mere redox reaction was a reversible transformation between fluorite-type structure and perovskites structure observed. CeScO3 was found as semiconducting oxide with band gap of 3.2 eV arising mainly between O p states in the valence band and Sc d and Ce d states in the conduction band with small contributions coming from Ce f and Sc p states. First-principles potential plane-wave-based calculations were performed for the band gap and its origin in CeScO3. Photoluminescence measurement showed that CeScO3 is a potential host material giving broad blue emission. This was further confirmed by demonstrating CeScO3 doped with 2 mol % Tb3+ compound as an efficient green light emitter

Template-assisted synthesis of room-temperature ferromagnetic Mn-Doped ZnO: first example of a high-temperature synthesis using polystyrene

Mn-doped ZnO nanostructures with significant room-temperature ferromagnetism have been synthesized at high temperature for the first time using polystyrene (PS) as a template. The X-ray diffraction and transmission electron microscopy analyses of these samples showed the formation of impurity-free crystals with wurtzite ZnO structure. SEM and TEM studies of PS-treated ZnO showed predominantly rod-like microstructure, while PS-treated Zn<SUB>0.95</SUB>Mn<SUB>0.05</SUB>O showed nearly spherical aggregated particles with a flower-like morphology in the nanometer regime. Quenching of visible emission intensity observed with the doping of Mn ions into ZnO confirmed the changed defect structure in PS-treated Mn-doped ZnO lattice

Phase relations and thermal expansion studies in the ceria-yttria system

The synthesis, characterization, and bulk and lattice thermal expansions of a series of compounds with general composition Ce<SUB>1–x</SUB>Y<SUB>x</SUB>O<SUB>1–x/2</SUB> (0.0 ≤x≤ 1.0) are reported. The XRD pattern of each product was refined to learn the solid solubility limit and the homogeneity range. The solid solubility limit of YO<SUB>1.5</SUB> in CeO<SUB>2</SUB> lattice, under the conditions of slow cooling from 1400°C, is represented as Ce<SUB>0.55</SUB>Y<SUB>0.45</SUB>O<SUB>1.775</SUB> (i.e., 45 mol% of YO<SUB>1.5</SUB>). The subsequent compositions were biphase. There was no solubility of CeO<SUB>2</SUB> into the lattice of YO<SUB>1.5</SUB>. The bulk thermal expansion measurements from ambient to 1123 K, as investigated using a dilatometer, revealed that the α<SUB>1</SUB> (293–1123 K) values, within the homogeneity range, decreased on increased Y<SUP>3+</SUP> content. A similar trend was observed for average lattice thermal expansion coefficient, α<SUB>a</SUB> (293–1473 K), as investigated using high-temperature XRD. No ordered phases were obtained in this system under the used conditions. These studies on Ce<SUB>1–x</SUB>Y<SUB>x</SUB>O<SUB>1–x/2</SUB> (0.0 ≤x≤ 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu<SUB>1–x</SUB>Y<SUB>x</SUB>O<SUB>1–x/2</SUB> (0.0 ≤x≤ 1.0), because CeO<SUB>2</SUB> is widely used as a surrogate material for PuO<SUB>2</SUB>