Effect of the order and disorder of BaMoO4 powders in photoluminescent properties

The study of the photoluminescent properties affected by order and disorder of the BaMoO4 powders is the principal objective in this work. BaMoO4 compounds were prepared using soft chemical process called Complex Polymerization Method. In this work, different deagglomeration types and different heating rates were used to promote different disorder degrees. Scheelite type phase (BaMoO4) was determined by X-ray Diffraction (XRD), Fourier Transformed Infra-Red (FTIR) and Raman spectroscopy after heat treating the sample at 400 degrees C. The room temperature luminescence spectra revealed an intense single-emission band in the visible region. Based on XRD and Raman data it was observed that the transition between the completely disordered structure to completely ordered structure is a good condition for photoluminescence (PL) emission. The best PL emission is obtained when the material possesses short range disorder, i.e., is periodically ordered (XRD), but some disorder as measured by Raman spectroscopy. The excellent optical properties observed for disordered BaMoO4 suggested that this material is a highly promising candidate for optical applications.

Reflux synthesis and hydrothermal processing of ZrO2 nanopowders at low temperature

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Crystallization study of SrSnO3:Fe

Alkaline earth stannates have recently become important materials in ceramic technology due to its application as humidity sensor. In this work, alkaline earth stannates doped with Fe3+ were synthesized by the polymeric precursor method, with calcination at 300 A degrees C/7 h and between 400 and 1100 A degrees C/4 h. The powder precursors were characterized by TG/DTA after partial elimination of carbon. Characterization after the second calcination step was done by X-ray diffraction, infrared spectroscopy, and UV-vis spectroscopy. Results confirmed the formation of the SrSnO3:Fe with orthorhombic perovskite structure, besides SrCO3 as secondary phase. Crystallization occurred at 600 A degrees C, being much lower than the crystallization temperature of perovskites synthesized by solid state reaction. The analysis of TG curves indicated that the phase crystallization was preceded by two thermal decomposition steps. Carbonate elimination occurred at two different temperatures, around 800 A degrees C and above 1000 A degrees C.

The characterisation of the protective film formed by benzotriazole on the 90/10 copper-nickel alloy surface in H2SO4 media

The nature of the protective film formed by benzotriazole (BTAH) on the surface of the 90/10 CuNi alloy in deaerated 0.5 mol L-1 H2SO4 solution containing Fe(III) ions as oxidant was investigated by weight-loss, calorimetric measurements, and by surface-enhanced Raman spectroscopy (SERS). The SERS measurements show that the protective film is composed by the [Cu(I)BTA](n), polymeric complex and that the BTAH molecules are also adsorbed on the electrode surface. A modification of the BET isotherm for adsorption of gases ill solids is proposed to describe the experimental results obtained from weight-loss experiments that suggest an adsorption in multilayers. Electrochemical studies of copper and nickel in 0.5 mol L-1 H2SO4 in presence and absence of BTAH have also been made as an aid to interpret the results. The calculated adsorption free energy of the cuprous benzotriazolate on the surface of the alloy is in accordance with the value for pure copper. (C) 2007 Elsevier Ltd. All rights reserved.

MEH-PPV hypsochromic shifts in halogenated solvents induced by gamma-rays

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Cluster Coordination and Photoluminescence Properties of alpha-Ag2WO4 Microcrystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Characterization of dense lead lanthanum titanate ceramics prepared from powders synthesized by the oxidant peroxo method

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Drug-matrix interaction of sodium diclofenac incorporated into ureasilpoly(ethylene oxide) hybrid materials

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural deformation monitored by vibrational properties and orbital modeling in (Pb,Sm)TiO3 systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Crystallization at room temperature from amorphous to trigonal selenium as a byproduct of the synthesis of water dispersible zinc selenide

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of TiO2 surface modification in Rhodamine B photodegradation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Indium hydroxide nanocubes and microcubes obtained by microwave-assisted hydrothermal method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermo-reversible sol-gel transition of TiO2 nanoparticles with surface modified by p-toluene sulfonic acid

In this paper an unprecedent thermo-reversible sol-gel transition for titania nanoparticles dispersed in a solution of p-toluene sulfonic acid (PTSH) in isopropanol is reported. The sol formed by the thermo-hydrolysis at 60 degrees C of titanium tetraisopropoxide (Ti((OPr)-Pr-i)(4)) reversibly changes into a turbid gel upon cooling to room temperature. Turbidimetric measurements performed for samples containing different nominal acidity ratios (A = [PTSH]/[Ti]) have evidenced that the gel transformation temperature increases from 20 to 35 degrees C as the [PTSH]/[Ti] ratio increases from 0.2 to 2.0. SAXS results indicate that the thermo-reversible gelation is associated to a reversible aggregation of a monodisperse set of titania nanoparticles with average gyration radius of approximate to 2 nm. From the different PTSH species evidenced by Raman spectroscopy and TG/DTA of dried gels we proposed that the then-no-reversible gelation in this systems is induced by the formation of a supramolecular network, in which the protonated surface of nanoparticles is interconnected through cooperative hydrogen bonds between -SO3 groups of p-toluene sulfonic acid. (C) 2009 Elsevier Ltd. All rights reserved.

Synthesis, Characterization, Anisotropic Growth and Photoluminescence of BaWO4

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural and properties of nanocrystalline WO3/TiO2-based humidity sensors elements prepared by high energy activation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)