Effect of soaking time on the photoluminescence properties of cerium oxide nanoparticles

The structural and photoluminescence properties at room temperature of CeO2 nanoparticles synthesized by a microwave-assisted hydrothermal method (MAH) under different soaking times on KOH mineralizer added to a cerium ammonium nitrate aqueous solution were undertaken. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.

Optical properties of the MoO3-TiO2 particulate system and its use as a ceramic pigment

Mo-doped TiO2 powders were prepared using a dry mixture of TiO2 and MoO3 oxides with several compositions, followed by a calcination step at several temperatures. The resulting oxide system develops yellow and green tones. The XRD patterns showed only traces of MoO 3; however, EDS results, combined with TG/DTA data, confirmed the presence of molybdenum ions, suggesting that the changes in optical properties of the oxide system is due to the incorporation of Mo ions into the TiO 2 matrix, substituting Ti+4 with Mo+6 ions. The band gap decreased with increasing of MoO3 content; on the other hand, the band gap reached a maximum value at about 850°C to 910°C when plotted as a function of the calcination temperature. The glazes produced showed that the oxide system under study is a potential material for use as abinary ceramic pigment. Copyright © 2013 Taylor & Francis Group, LLC.

Rietveld refinement, morphology and optical properties of (Ba 1-xSrx)MoO4 crystals

In this article, the structural refinement, morphology and optical properties of barium strontium molybdate [(Ba1-x Sr x )MoO4 with x = 0, 0.25, 0.50, 0.75 and 1] crystals, synthesized by the co-precipitation (drop-by-drop) method, are reported. The crystals obtained were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, and Fourier transform-Raman (FT-Raman) and Fourier transform-infrared (FT-IR) spectroscopies. The shapes of the crystals were observed by means of field-emission scanning electron microscopy (FE-SEM). The optical properties were investigated using ultraviolet-visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns, Rietveld refinement, and FT-Raman and FT-IR spectra showed that all of the crystals are monophasic with a scheelite-type tetragonal structure. The refined lattice parameters and atomic positions were employed to model the [BaO8], [SrO8] and [MoO4] clusters in the tetragonal lattices. The FE-SEM images indicate that increased x content produces a decrease in the crystal size and modifications in the crystal shape. UV-Vis spectra indicated a decrease in the optical band gap with an increase in x in the (Ba1-x Sr x )MoO4 crystals. Finally, a decrease in the intensity of PL emission is apparent with an increase in x up to 0.75 in the (Ba1-x Sr x )MoO4 crystal lattice when excited by a wavelength of 350nm, probably associated with the degree of structural order-disorder. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved.

Photoluminescence properties of praseodymium doped cerium oxide nanoparticles

The structural and photoluminescent properties at room temperature of CeO2 nanoparticles synthesized by a Microwave-Assisted Hydrothermal Method (MAH) under different praseodymium contents was undertaken. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), UV-vis Spectroscopy (UV-vis), Fourier Transform Raman (FT-Raman) and Photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure while FT-Raman revealed a typical scattering mode of fluorite type. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.

Red shift and higher photoluminescence emission of CCTO thin films undergoing pressure treatment

CCTO thin films were deposited on Pt(1 1 1)/Ti/SiO2/Si substrates using a chemical (polymeric precursor) and pressure method. Pressure effects on CCTO thin films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and optical properties which revealed that a pressure film (PF) is denser and more homogeneous than a chemical film (CF). Pressure also causes a decrease in the band gap and an increase in the photoluminescence (PL) emission of CCTO films which suggests that the pressure facilitates the displacement of Ti in the titanate clusters and the charge transference from TiO6 to [TiO5V0z], [TiO5V0z] to [CaO11V0z] and [TiO5V0z] to [CuO4]x. © 2013 Elsevier B.V. All rights reserved.

Projeto de uma referência de tensão com baixa susceptibilidade a interferência eletromagnética (EMI)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de nanopartículas e filmes finos de óxidos semicondutores

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de filmes finos de ZnO dopados com Al e Mn depositados em substrato vítreo pelo método de Spray Pirólise

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo no grau de ordem-desordem no 'SR''BI IND 2''NB IND 2''O IND.9 pela influência do íon 'EU IND.3'/' e tratamento térmico por microondas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo teórico - experimental do titanato de cálcio - 'CA''TI''OIND.3'

Pós-graduação em Química - IQ

Preparação e caracterização de filmes finos Sr1-xMexTiO3(Me=Fe, Ni)

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Degradação fotocatalítica de efluente simulado de refinaria de petróleo e monitoramento de sua toxicidade com microrganismos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Otimização das propriedades fotoluminescentes de nanoestruturas preparadas via síntese hidrotérmica assistida por micro-ondas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Microcompósitos fotocatalíticos a base de 'Ti' 'O IND.2' modificados com 'Ag'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise morfológica de filmes finos de óxido de zinco

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