Synthesis and structural characterization of Eu(III)-doped Zn7Sb2O12

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

The temperature coefficient of the optical path length as a function of the temperature in different optical glasses

An interferometric technique was used to determine the temperature coefficient of the optical path length (dS/dT) as a function of the temperature in several optical glasses. The temperature range was between 25degreesC and 180degreesC. The studied samples included undoped and doped oxide glasses, such as low silica calcium aluminosilicate, phosphates, borates and also chalcogenides. The oxide glasses had dS/dT between 10 X 10(-6) K-1 and 20x10(-6) K-1, while for the chalcogenides, these were around 70 x 10(-6)K(-1). The results showed that dS/dTs increased with the temperature in all samples. For samples doped with Nd the dS/dT values were found to be independent of concentration. on the other hand, for the phosphate glass doped with Cr, dS/dT increased about 5% when compared with the Nd doped one. In conclusion, the used interferometric method, which is a considerably simpler and a lower cost technique, and is a useful tool to measure dS/dT in semi-transparent glasses as a function of the composition and temperature. (C) 2004 Elsevier B.V. All rights reserved.

Síntese, caracterização e estudo fotofísico de complexos de 4,4- diaminoestilbeno-2,2-dissulfonato com íons lantanídeos

This is a work involving fundamental studies of chemistry where the synthesis and structural characterization, as well as a possible future application of these new compounds as luminescent sensors or sunscreen agents, complexes with 4,4 diaminostilbene-2,2-disulfonic (DSD) and trivalent lanthanide ions La3+, Nd3+, Eu3+, Gd3+ and Yb3+, were synthesized in the ratio of 3 mmol: 1 mmol (DSD: lanthanides). The complexes obtained with these ions were present in powder form and were characterized by complexometric titration with EDTA CHN Elemental analysis, molecular absorption spectroscopy in the ultraviolet region, the absorption spectroscopy in the infrared, thermal analysis (TG / DTG), Nuclear Magnetic Resonance - NMR 1H and Luminescence Spectroscopy. The complexometric titration and CHN analysis, confirmed the TG / DTG which suggest that these complexes have the following general chemical formulas: [La2(C14H12S2O6N2)2(H2O)2Cl2].7H2O,[Nd2(C14H12S2O6N2)2(H2O)2Cl2].6H2O,[Eu2(C14 H12S2O6N2)2(H2O)2Cl2].7H2O,[Gd2(C14H12S2O6N2)2(H2O)2Cl2].4H2O e [Yb2(C14H12S2O6N2)2(H2O)2].6H2O. The disappearance of the bands in the infrared spectrum at 2921 cm-1 and 2623 cm-1 and the displacement of the bands in the spectra of the amine complex indicate that the lanthanide ion is coordinated to the oxygen atoms and the sulfonate groups of the nitrogens amines, suggesting the formation of the dimer. The disappearance of the signal and the displacement signal SO3H amines in the 1H NMR spectrum of this complex are also indicative coordination and dimer formation. The Thermogravimetry indicates that the DSD is thermally stable in the range of 40º to 385°C and their complexes with lanthanide ions exhibit weight loss between 4 and 5 stages. The Uv-visible spectra indicated that the DSD and complexes exhibit cis isomers. The analysis of luminescence indicates that the complexes do not exhibit emission in the region of the lanthanides but an intense emission part of the binder. This is related to the triplet states of the ligand, which are in the lowest energy state emitting lanthanide ions, and also the formation of the dimer that suppress the luminescence of ion Eu3+. The formation of dimer was also confirmed by calculating the europium complex structure using the model Hamiltonian PM6 and Sparkle

Petrologia do magmatismo tardi-brasiliano no Maciço São José de Campestre(RN/PB), com ênfase no Plúton Alcalino Caxexa

The area studied is located on the north-easternmost portion of the Borborema Province, on the so-called São José de Campestre Massif, States of RN and PB, Northeast Brazil. Field relations and petrographic, geochemical and isotope data permitted the separation of five suites of plutonic rocks: alkali-feldspar granite (Caxexa Pluton), which constitutes the main subject of this dissertation, amphibole-biotite granite (Cabeçudo Pluton), biotite microgranite, gabbronorite to monzonite (Basic to Intermediate Suite) and aluminous granitoid. The Caxexa Pluton is laterally associated to the Remígio Pocinhos Shear Zone, with its emplacement along the mylonitic contact between the gneissic basement and the micashists. This pluton corresponds to a syntectonic intrusion elongated in the N-S direction, with about 50 km2 of outcropping surface. It is composed exclusively of alkali-feldspar granites, having clinopyroxene (aegirine-augite and hedenbergite), andradite-rich garnet, sphene and magnetite. It is classified geochemically as high silica rocks (>70 % wt), metaluminous to slightly peraluminous (normative corindon < 1%), with high total alkalis (>10% wt), Sr, iron number (#Fe=90-98) and agpaitic index (0.86-1.00), and positive europium anomaly. The Cabeçudo Pluton is composed of porphyritic rocks, commonly containing basic to intermediate magmatic enclaves often with mingling and mixing textures. Petrographically, it presents k-feldspar and plagioclase phenocrysts as the essential minerals, besides the accessories amphibole, biotite, sphene and magnetite. It is metaluminous and shows characteristics transitional between the calc-alkaline and alkaline series (or monzonitic subalkaline). Its REE content is greater than those ones of the Caxexa Pluton and biotite microgranite, and all spectra have negative europium anomalies. The biotite microgranites occur mainly on the central and eastern portion of the mapped area, as dykes and sheets with decimetric thickness, hosted principally in orthogneisses and micashists. Their field relationships as regards the Caxexa and Cabeçudo plutons suggested that they are late-tectonic intrusions. They are typically biotite granites, having also sphene, amphibole, allanite, opaques and zircon in the accessory assemblage. Geochemically they can be distinguished from the porphyritic types because the biotite microgranites are more evolved, peraluminous, and have more fractionated REE spectra. The Basic to Intermediate rocks form a volumetrically expressive elliptical, kilometric scale body on the Southeast, as well as sheets in micashists. They are classified as gabbronorites to monzonites, with the two pyroxenes and biotite, besides subordinated amounts of amphibole, sphene, ilmenite and allanite. These rocks do not show a well-defined geochemical trend, however they may possibly represent a monzonitic (shoshonitic) series. Their REE spectra have negative europium anomalies and REE contents greater than the other suites. The aluminous granitoids are volumetrically restricted, and have been observed in close association with migmatised micashists bordering the gabbronorite pluton. They are composed of almandine-rich garnet, andalusite, biotite and muscovite, and are akin to the peraluminous suites. Rb-Sr (whole rock) and Sm-Nd (whole-rock and mineral) isotopes furnished a minimum estimate of the crystallization (578±14 Ma) and the final resetting age of the Rb-Sr system (536±4 Ma) in the Caxexa Pluton. The aluminous granitoid has a Sm-Nd garnet age similar to that one of the Caxexa Pluton, that is 574±67 Ma. The strong interaction of shear bands and pegmatite dykes favoured the opening of the Rb-Sr system for the Caxexa Pluton and biotite microgranite. The amphibole-plagioclase geothermometer and the Al-in amphibole geobarometer indicate minimum conditions of 560°C and 7 kbar for the Cabeçudo Pluton, 730°C and 6 kbar for the microgranite and 743°C and 5 kbar for the basic to intermediate suite. The Zr saturation geothermometer reveals temperatures of respectively 855°C, 812°C and 957°C for those suites, whereas the Caxexa Pluton shows temperatures of around 757°C. The Caxexa, Cabeçudo and microgranites suites crystallized under high fO2 (presence of magnetite). On the other hand, the occurrence of ilmenite suggests less oxidant conditions in the basic to intermediate suite. Field relations demonstrate the intrusive character of the granitoids into a tectonically relatively stable continental crust. This is corroborated by petrographic and geochemical data, which suggest a late- or post-collisional tectonic context. It follows that the generation and emplacement of those granitoid suites is related to the latest events of the Brasiliano orogeny. Finally, the relationships between eNd (600 Ma), TDM (Nd) and initial Sr isotope ratio (ISr) do not permit to define the precise sources of the granitoids. Nevertheless, trace element modelling and isotopic comparisons suggest the participation of the metasomatised mantle in the generation of these suites, probably modified by different degrees of crustal contamination. In this way, a metasomatised mantle would not be a particular characteristic of the Neoproterozoic lithosphere, but a remarkable feature of this portion of the Borborema Province since Archaean and Paleoproterozoic times.

Interface Formation and Electrical Transport in SnO2:Eu3+/GaAs Heterojunction Deposited by Sol-Gel Dip-Coating and Resistive Evaporation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The role of the Eu3+ ions in structure and photoluminescence properties of SrBi2Nb2O9 powders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

APTES-Modified RE2O3:Eu3+ Luminescent Beads: Structure and Properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis and Study of the Photophysical Properties of a New Eu3+ Complex with 3-Hydroxypicolinamide

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photolumiscent Properties of Nanorods and Nanoplates Y2O3:Eu3+

Nanorods and nanoplates of Y2O3:Eu3+ powders were synthesized through the thermal decomposition of the Y(OH)(3) precursors using a microwave-hydrothermal method in a very short reaction time. These powders were analyzed by X-ray diffraction, field emission scanning electron microscopy, Fourrier transform Raman, as well as photoluminescence measurements. Based on these results, these materials presented nanoplates and nanorods morphologies. The broad emission band between 300 and 440 nm ascribed to the photoluminescence of Y2O3 matrix shifts as the procedure used in the microwave-hydrothermal assisted method changes in the Y2O3:Eu3+ samples. The presence of Eu3+ and the hydrothermal treatment time are responsible for the band shifts in Y2O3:Eu3+ powders, since in the pure Y2O3 matrix this behavior was not observed. Y2O3:Eu3+ powders also show the characteristic Eu3+ emission lines at 580, 591, 610, 651 and 695 nm, when excited at 393 nm. The most intense band at 610 nm is responsible for the Eu3+ red emission in these materials, and the Eu3+ lifetime for this transition presented a slight increase as the time used in the microwave-hydrothermal assisted method increases.

Synthesis, characterization and photophysical properties of Eu3+ doped in BaMoO4

In this work Ba0.99Eu0.01MoO4 (BEMO) powders were prepared by the first time by the Complex Polymerization Method. The structural and optical properties of the BEMO powders were characterized by Fourier Transform Infra-Red (FTIR), X-ray Diffraction (XRD), Raman Spectra, High-Resolution Scanning Electron Microscopy (HR-SEM) and Photoluminescent Measurements. XRD show a crystalline scheelite-type phase after the heat treatment at temperatures greater than 400 degrees C. The ionic radius of Eu3+ (0.109 nm) is lower than the Ba2+ (0.149 nm) one. This difference is responsible for the decrease in the lattice parameters of the BEMO compared to the pure BaMoO4 matrix. This little difference in the lattice parameters show that Eu3+ is expected to occupy the Ba2+ site at different temperatures, stayed the tetragonal (S-4) symmetry characteristic of scheelite-type crystalline structures of BaMoO4. The emission spectra of the samples, when excited at 394 nm, presented the D-5(1)-> F-7(0, 1 and 2) and D-5(0)-> F-7(0, 1, 2, 3 and 4) Eu3+ transitions at 523, 533, 554, 578, 589, 614, 652 and 699 nm, respectively. The emission spectra of the powders heat-treated at 800 and 900 degrees C showed a marked increase in its intensities compared to the materials heat-treated from 400 to 700 C. The decay times for the sample were evaluated and all of them presented the average value of 0.61 ms. Eu3+ luminescence decay time follows one exponential curve indicating the presence of only one type of Eu3+ symmetry site.

Filmes de titânio-silício preparados por spin e dip-coating

The conditions for the preparation of luminescent materials, consisting of Eu3+ ions entrapped in a titanium matrix, in the forma of a thin film, using the sol-gel process, are described. The films were obtained from sols prepared with TEOS and TEOT, in the presence of acetylacetone as the hidrolysis-retarding agent, using the dip-coating and spin-coating techniques. The influence of these techniques on the films based on titanium and silicon are presented. The Eu3+ was used as a luminescent probe. The films have been characterized by luminescence, reflection and transmittance. The thickness of the films could be related to the preparation procedure. Transparent thin films have been prepared by dip-coating technique.

Nanocomposites materials generated from a spray

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Y2O3:Eu3+ (5 mol%) with Ag nanoparticles prepared by citrate precursor

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

Visible and near-infrared luminescent Eu3+ or Er3+ doped laponite-derived xerogels and thick films: Structural and spectroscopic properties

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

Preparação de LiNbO3 e LiNbO3:Eu3+ pelo método dos precursores poliméricos

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