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Influence of metallic nanoparticles on electric-dipole and magnetic-dipole transitions of Eu(3+) doped germanate glasses

KASSAB, Luciana R. P.; SILVA, Diego S. da; ARAUJO, Cid B. de
Fonte: AMER INST PHYSICS Publicador: AMER INST PHYSICS
Tipo: Artigo de Revista Científica
Português
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Luminescence properties of Eu(3+) doped germanate glasses containing either silver or gold nanoparticles (NPs) were investigated for excitation at 405 nm. Enhanced emissions and luminescence quenching of the Eu(3+) transitions in the range from 570 to 720 nm were observed for samples having various concentrations of metallic NPs. Electric-dipole and magnetic-dipole transitions that originate from the Eu(3+) level (5)D(0) exhibit large enhancement due to the presence of the metallic NPs. The results suggest that the magnetic response of rare-earth doped metal-dielectric composites at optical frequencies can be as strong as their electric response due to the confinement of the optical magnetic field. (C) 2010 American Institute of Physics. [doi:10.1063/1.3431347]; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) through the National Institute of Photonics; Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)

Enhanced luminescence of Tb(3+)/Eu(3+) doped tellurium oxide glass containing silver nanostructures

KASSAB, Luciana R. P.; ALMEIDA, Ricardo de; SILVA, Davinson M. da; ASSUMPCAO, Thiago A. A. de; ARAUJO, Cid B. de
Fonte: AMER INST PHYSICS Publicador: AMER INST PHYSICS
Tipo: Artigo de Revista Científica
Português
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We report on energy transfer studies in terbium (Tb(3+))-europium (Eu(3+)) doped TeO(2)-ZnO-Na(2)O-PbO glass containing silver nanostructures. The samples excitation was made using ultraviolet radiation at 355 nm. Luminescence spectra were recorded from approximate to 480 to approximate to 700 nm. Enhanced Eu(3+) luminescence at approximate to 590 nm (transition (5)D(0)-(7)F(1)) and approximate to 614 nm (transition (5)D(0)-(7)F(2)) are observed. The large luminescence enhancement was obtained due to the simultaneous contribution of the Tb(3+)-Eu(3+) energy transfer and the contribution of the intensified local field on the Eu(3+) ions located near silver nanostructures.; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); Fundacao de Amparo a Ciencia e Tecnologia de Pernambuco (FACEPE)

Photoluminescence enhancement by gold nanoparticles in Eu(3+) doped GeO(2)-Bi(2)O(3) glasses

KASSAB, Luciana R. P.; SILVA, Diego S. da; ALMEIDA, Ricardo de; ARAUJO, Cid B. de
Fonte: AMER INST PHYSICS Publicador: AMER INST PHYSICS
Tipo: Artigo de Revista Científica
Português
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We report large photoluminescence (PL) enhancement in Eu(3+)-doped GeO(2)-Bi(2)O(3) glasses containing gold nanoparticles (NPs). Growth of approximate to 1000% in the PL intensity corresponding to the Eu(3+) transition (5)D(0)->(7)F(2), at 614 nm, was observed in comparison with a reference sample that does not contain gold NPs. Other PL bands from 580 to 700 nm are also enhanced. The enhancement of the PL intensity is attributed to the increased local field in the Eu(3+) locations due to the presence of the NPs and the energy transfer from the excited NPs to the Eu(3+) ions.; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq); Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)

Synthesis and Study of the Photophysical Properties of a New Eu(3+) Complex with 3-Hydroxypicolinamide

ROSA, Ieda Lucia Viana; SOUSA FILHO, Paulo Cesar de; NERI, Claudio Roberto; SERRA, Osvaldo Antonio; FIGUEIREDO, Alberthmeiry Teixeira de; VARELA, Jose Arana; LONGO, Elson
Fonte: SPRINGER/PLENUM PUBLISHERS Publicador: SPRINGER/PLENUM PUBLISHERS
Tipo: Artigo de Revista Científica
Português
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This work reports on the synthesis and characterization of a new complex of Eu(3+) with the 3-hydroxypicolinamide ligand (Hhpa). Here we present an approach for obtaining bis[2-carbamoyl(kappa O)pyridin-3-olato(kappa O`)] lanthanide complexes, which were characterized through elemental analysis, thermal analysis, infrared and photoluminescence spectroscopies (emission, excitation, luminescence lifetimes, quantum efficiencies, Judd-Ofelt parameters and quantum yields). Although hpa can act as a bidentate ligand in different conformations, the results attest for the occurrence of a unique coordination site of low symmetry for the Eu(3+) ions, in which two anionic hpa ligands coordinate the cations through an O/O chelating system. The phosphorescence of the synthesized gadolinium complex provides the energy of the triplet state, which is determined to be at 20,830 cm(-1) over the ground state. This makes the Hhpa ligand very adequate for sensitizing the Eu(3+) luminescence, which leads to a very efficient antenna effect and opens a wide range of applications for the complex in light emitting organic-inorganic devices.; CAPES; CNPq/INCTMN/inct-INAMI; FAPESP

Visible and near-infrared luminescent Eu(3+) or Er(3+) doped laponite-derived xerogels and thick films: Structural and spectroscopic properties

TRONTO, Jairo; RIBEIRO, Sidney Jose Lima; VALIM, Joao Barros; GONCALVES, Rogeria Rocha
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
Português
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Laponite-derived materials represent promising materials for optical applications. In this work, Eu(3+)- or Er(3+)-doped laponite xerogels and films were prepared from colloidal dispersion. Homogeneous, crack-free and transparent single layers were deposited on soda-lime substrates with a thickness of 10 mu m. Structural and spectroscopic properties were analyzed by thermal analyses, X-ray diffractometry, transmission electron microscopy, infrared spectroscopy, and luminescence spectroscopy. The addition of a rare earth ion to the laponite does not promote any changes in thermal stability or phase transition. Laponite clay was identified after annealing up to 500 degrees C, with a decrease in basal spacing when the annealing temperature is changed from 100 degrees C to 500 degrees C. Enstatite polymorphs and amorphous silicate phases were observed after heat treatment at 700 degrees C and 900 degrees C. Stationary and time-dependent luminescence spectra in the visible region for Eu(3+), and (5)D(0) lifetime are discussed in terms of thermal treatment and structural evolution. In the layered host, the Eu(3+) ions are distributed in many different local environments. However, Eu(3+) ions were found to occupy at least two symmetry sites...

Luminescent Langmuir-Blodgett film of a new amphiphilic Eu(3+) beta-diketonate

GOMES, Luciano F.; OLIVEIRA, Kleber T. de; NERI, Claudio R.; SOUSA FILHO, Paulo C. de; BIANCO, Marcos J. Dal; RAMOS, Ana P.; ZANIQUELLI, Maria E. D.; SERRA, Osvaldo A.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
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This work reports on the synthesis and characterization of the ligand 3-hexadecylpentane-2,4-drone (Hhdacac) and its Eu(3+) complexes Eu(hdacac)(6) center dot 2H(2)O, Eu(hdacac)(6) center dot phen and Eu(hdacac)(6) center dot tta, where phen and tta denote 1,10-phenanthroline and thenoyltrifluoroacetone, respectively. These new compounds present long carbon chains and their expected miscibility into non-polar ambients is confirmed by the emission spectra of Eu(hdacac)6 center dot tta in hexane. Moreover, the amphiphilic properties of Eu(hdacac)6 complexes allow the obtainment of thin luminescent films by the Langmuir-Blodgett technique. In both cases (solids and films), the typical antenna effect of beta-diketonates is observed. The alluring characteristics of these compounds raise great interest in many fields of Materials Science, like photo- and electro-luminescent materials (mainly thin ""organic"" films), metal catalysts or probes in non-polar solutions, and Langmuir-Blodgett films of several compositions. For the characterization of these products, nuclear magnetic resonance spectroscopy ((1)H NMR), thermogravimetric analysis, elementary analyses (C, H), scanning electron microscopy (energy dispersive X-ray spectroscopy), absorption (UV-vis/FT-IR) and photoluminescence spectroscopies were used. (c) 2008 Elsevier B.V. All rights reserved.

Synthesis, Characterization, Luminescence and Defect Centres in CaYAl(3)O(7):Eu(3+) Red Phosphor

SINGH, Vijay; Watanabe, Shigueo; Rao, Tumkur Krishnaswamy Gundu; KWAK, Ho-Young
Fonte: SPRINGER/PLENUM PUBLISHERS Publicador: SPRINGER/PLENUM PUBLISHERS
Tipo: Artigo de Revista Científica
Português
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45.95%
CaYAl(3)O(7):Eu(3+) phosphor was prepared at furnace temperatures as low as 550A degrees C by a solution combustion method. The formation of crystalline CaYAl(3)O(7):Eu(3+) was confirmed by powder X-Ray diffraction pattern. The prepared phosphor was characterized by SEM, FT-IR and photoluminescence techniques. Photoluminescence measurements indicated that emission spectrum is dominated by the red peak located at 618 nm due to the (5)D(0)-(7)F(2) electric dipole transition of Eu(3+) ions. Electron Spin Resonance (ESR) studies were carried out to identify the centres responsible for the thermoluminescence (TL) peaks. Room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0126 is identified as an O(-) ion while centre II with an isotropic g-factor 2.0060 is assigned to an F(+) centre (singly ionized oxygen vacancy). An additional defect centre is observed during thermal annealing experiments and this centre (assigned to F(+) centre) seems to originate from an F centre (oxygen vacancy with two electrons). The F(+) centre appears to correlate with the observed high temperature TL peak in CaYAl(3)O(7):Eu(3+) phosphor.; FAPESP, Brazil; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Characterization, photoluminescence, thermally stimulated luminescence and electron spin resonance studies of Eu(3+) doped LaAlO(3) phosphor

SINGH, Vijay; Watanabe, Shigueo; RAO, T. K. Gundu; Chubaci, Jose Fernando Diniz; KWAK, Ho-Young
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
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Europium-doped lanthanum aluminate (LaAlO(3)) powder was prepared by using a combustion method. The crystallization, surface morphology, specific surface area and luminescence properties of the samples have been investigated. Photoluminescence studies of Eu doped LaAlO(3) showed orange-reddish emission due to Eu(3+) ions. LaAlO(3):Eu(3+) exhibits one thermally stimulated luminescence (TSL) peak around 400 degrees C. Room temperature electron spin resonance spectrum of irradiated phosphor appears to be a superposition of two centres. One of them (centre I) with principal g-value 2.017 is identified as an O(-) centre while centre II with an isotropic g-value 2.011 is assigned to an F(+) centre (singly ionized oxygen vacancy). An additional defect centre observed during thermal annealing around 300 degrees C grows with the annealing temperature. This centre (assigned to F(+) centre) originates from an F-centre (oxygen vacancy with two electrons) and the F-centre along with the associated F(+) centre appear to correlate with the observed TSL peak in LaAlO(3):Eu(3+) phosphor. The activation energy for this peak has been determined to be 1.54 eV from TSL data. (C) 2010 Elsevier Masson SAS. All rights reserved.

Study on the observation of Eu(2+) and Eu(3+) valence states in low silica calcium aluminosilicate glasses

SAMPAIO, J. A.; FILADELPHO, M. C.; ANDRADE, A. A.; ROHLING, J. H.; MEDINA, A. N.; BENTO, A. C.; SILVA, L. M. da; GANDRA, F. C. G.; NUNES, L. A. O.; BAESSO, M. L.
Fonte: IOP PUBLISHING LTD Publicador: IOP PUBLISHING LTD
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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The optical, magnetic and structural properties of Eu doped low silica calcium aluminosilicate glasses were investigated. The optical absorption coefficient presented two bands at 39 246 and 29 416 cm(-1), which were assigned respectively to the 4f(7) ((8)S(7/2)) -> 4f(6) (4F(J)) 5d (T(2g)), and 4f(7) ((8)S(7/2)) -> 4f(6) (4F(J)) 5d (E(g)) transitions of Eu(2+). The fluorescence measured at 300 K on a sample doped with 0.5 wt% of Eu(2)O(3) exhibited a broad band centered at 17 350 cm(-1), which is attributed to the 4f(6)5d -> 4f(7) transition of Eu(2+), whereas the additional peaks are due to the (5)D(0) -> (7)F(J) (J = 1, 2, 4) transitions of Eu(3+). From magnetization and XANES data it was possible to evaluate the fractions of Eu(2+) and Eu(3+) for the sample doped with 0.5 and 5.0 wt% of Eu(2)O(3), the values of which were approximately 30 and 70%, respectively.; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); CAPES; FAPERJ; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ); FAPESP; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Espectroscopia no infravermelho e Raman do aluminato de gadolineo puro e dopado com íons de terras raras; Raman and infrared spectrometry of gadolinium aluminates pure and doped

Bagnato, Vanderlei Salvador
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/07/1983 Português
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Realizamos medidas de transmissão no infravermelho (médio e distante) e espelhamos Raman de amostras de GdAlO3 puras e dopadas com Eu+3 para estudarmos as bandas de absorção de fonons K=0 e as transições eletrônicas nos íons Eu+3. Conhecendo-se a simetria do GdAlO3 (D162h) pudemos, utilizando o método da correlação, calcular o número e a simetria dos modos vibracionais, bem como sua classificação em internos e externos. Os resultados experimentais mostram boa concordância com os teóricos e revelam que o GdAlO3 apresenta três regiões distintas no infravermelho, compostas de várias bandas de absorção. Os modos internos estão em torno de 670cm-1 (estiramento) e 480cm-1 (flexão) enquanto que os modos externos localizam-se em torno de 200cm-1. A interação dos estados eletrônicos do Eu+3 com o campo cristalino do GdAlO3 foi estudada inicialmente supondo um campo de simetria Oh e depois introduzindo a distorção ortorrômbica (Cs) de uma maneira perturbativa. Pudemos verificar que a dita distorção levanta totalmente a degenerescência dos níveis 7FJ (J=0,1,...,6) e torna as transições 7F0 → 7FJ permitidas.; IR and Raman measurements were carried out in pure and Eu+3 - doped GdAlO3 with the purpose of understanding their K=O phonom modes and the Eu+3 electronic transitions. Starting from the GdAlO3 symmetry...

Espectroscopia de ions Eu+3 em cristais de baixa simetria; Espectroscopy of Eu+3 ions in low simmetry cristals.

Oliveira, Antonio Cesar de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 21/02/1991 Português
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Neste trabalho estudamos o íon Eu3+ no aluminato EuAlO3 e no garnet Ca3Ga2Ge3O12:Eu+3 através de espectroscopia óptica. Técnicas convencionais de absorção e fluorescência foram utilziadas, e elas nos permitiram um levantamento sistemático dos níveis eletrônicos 7FJ (J= 0,1,2,3,4) e 5DJ (J= 0,1,2) do Eu+3. A análise dos espectros de absorção feitos com luz polarizada confirma a ocupação dos íons Eu+3 em sítios de simetria C no EuAlO3. Com isso também confirmamos as regras de seleção esperadas. Efetuamos medidas da variação da largura de linha com a temperatura, da transição 7F1 → 5D0 em EuAlO3. Isso nos permitiu determinar a estatística de íons excitados termicamente ao sub-nível 7F1, cuja energia é próxima a kT para temperatura ambiente. Os espectros de fluorescência resolvida no tempo nos forneceram o comportamento do decaimento radiativo em função da temperatura para as transições 5D0 → 7FJ do Eu3+ tanto no sistema EuAlO3 quanto no garnet Ca3Ga2Ge3O12:Eu+3. Além das técnicas convencionais citadas acima, utilizamos também uma técnica espectroscópica não linear denominada Coherent antiStokes Raman Spectroscopy. Essa é uma técnica muito útil na determinação de níveis vibracionais ou eletrônicos na região de infravermelho. O processo de alinhamento e medidas preliminares foram feitos com o benzeno e a calcita (CaCO3). Na seqüência processamos a detecção e o estudo de um dos níveis 7F2 do Eu+3 no garnet.; In this work we studied the íon Eu3+ in aluminate EuAlO3 and in the garnet Ca3Ga2Ge3O12:Eu+3 through the optical spectroscopy. Conventional techniques of absorption and fluorescence were used and enabled us to study systematically the levels 7FJ (J= 0...

Espectroscopia de íons de Eu+3 como impureza em GdAlO3; Optical spectroscopy of Eu+3 dopped GdAlO3

Padua, Sebastiao Jose Nascimento de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/08/1988 Português
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Espectros de absorção, fluorescência e excitação do íon Eu+3 em GdAlO3 na região do visível são mostrados neste trabalho. Todos os níveis 7Fj (j= 0, 1, 2 e 4) e 5Dj (j= 0 a 2) foram medidos e quase todas as transições do íon, na região do visível, foram identificadas nos espectros. A abertura dos níveis de energia verificada está de acordo com a simetria C5 do campo cristalino. Medidas de absorção polarizada foram feitas com o intuito de verificar a natureza das transições de dipolo e para determinar as representações irredutíveis dos níveis de energia 7F0, 7F1 e 5Dj (j= 0 a 2). Linhas da impureza Er+3 (não intencional) foram identificadas no espectro de absorção e sua presença no cristal foi verificada através dos valores conhecidos dos níveis de energia do íon Er+3 em GdAlO3 [III-4]. Além disso, medidas dos níveis de energia 7F2 do íon Eu+3 através da técnica espectroscópica não linear CARS, foram tentadas. Medidas preliminares destes níveis e dos níveis vibracionais do benzeno e da calcita são mostrados no final da dissertação.; Absorption, fluorescence and excitation of the Eu+3 íon in GdAlO3 in the visible region are presented in this work. All of the 7Fj (j= 0, 1, 2 and 4) and 5Dj (j= 0 to 2) energy levels were measured and almost all of the transitions in the visible region of the ion were seen in the spectra. The splitting of energy levels verified is according to the C5 symmetry of the crystal field. Polarized absorption techniques are used to check the nature of the dipole transitions and to determine the irreducible representations of the 7F0...

Estudo do poder de freamento de He, Li, Eu e Bi canalizados em alvos de Si cristalino

Azevedo, Gustavo de Medeiros
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
Português
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Neste trabalho, foi realizado um estudo experimental sistemático da perda de energia de íons canalizados ao longo das direções h100i , h111i e h110i de cristais de Si. Foram abordados dois aspectos distintos, porém correlatos, do problema. No primeiro tópico, estudamos o poder de freamento de íons pesados (Eu e Bi) com energias entre 15 e 50 keV, para os quais o mecanismo predominante de perda de energia é o freamento nuclear. O segundo tópico está relacionado ao freamento de íons leves (He e Li) com energias no intervalo entre 0.3 e 8 MeV. Neste caso, os íons perdem energia, predominantemente, em colisões com elétrons. O estudo do freamento dos íons pesados foi realizado de maneira indireta, pela comparação dos perfis de concentração de Eu e Bi implantados em direção canalizada com as previsões do programa MARLOWE, que simula a interação de feixes de íons com alvos sólidos. Nós observamos pela primeira vez, em implantações em direção canalizada, o chamado efeito Z1, ou seja, a deformação das núvens eletrônicas do projétil e do alvo em colisões binárias de baixa energia. Enquanto nossos dados para implantações de Bi são muito bem reproduzidas pelo MARLOWE, os perfis de Eu apresentam caudas mais profundas que as preditas por este programa. Além disso nós demonstramos que este comportamento é explicado por cálculos ab initio de estrutura molecular baseados na Teoria Funcional da Densidade (DFT). Com relação os íons leves...

Luminescence properties of Eu(3+)- and Mg(2+)-doped LiTaO(3) obtained via the polymeric precursor method

Gasparotto, G.; Lima, S. A. M.; Davolos, M. R.; Varela, José Arana; Longo, Elson; Zaghete, M. A.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 1606-1610
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); This work reports the pure lithium tantalate (LiTaO(3)), europium (III)-doped LiTaO(3) and magnesium (II)-europium (III)-doped LiTaO(3) preparation by the polymeric precursor method, using four different powered samples of Eu(3+) ion concentrations 0.1 and 1 at%, observing their effect on the luminescent property of the material. Results indicated LiTaO(3) phase free of secondary phases at 650 degrees C and the photoluminescence (PL) emission spectra showed the characteristic sharp emission bands given by Eu(3+) ions when they are excited at a wavelength of 399 rim. An increase of dopants led its to a non-homogeneous broadening and showed a slightly larger one when Mg was added. A displacement of the transition (5)D(0) --> (7)F(0) to shorter wavelengths as function of Eu(3+) concentration was also noticed. (C) 2008 Elsevier B.V. All rights reserved.

Enhanced photoluminescence features of Eu(3+)-modified di-ureasil-zirconium oxocluster organic-inorganic hybrids

Ferreira, R. A. S.; Oliveira, D. C.; Maia, L. Q.; Vicente, C. M. S.; André, P. S.; Bermudez, V. Zea; Ribeiro, S. J. L.; Carlos, L. D.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
45.91%
In this work, a series of transparent di-ureasil hybrids containing different amounts of methacrylic acid modified zirconium tetrapropoxide (ZrMcOH) nanoclusters (5-85 mol%) and incorporating EuCl(3) and [Eu(tta)(3)(H(2)O)(2)](tta = thenoyltrifluoroacetonate) complex were prepared. These hybrids are multi-wave-length emitters due to the convolution of the host intrinsic emission (electron-hole recombinations occurring in siliceous and urea cross-linkages) Eu(3+) intra-4f(6) transitions. The ZrMcOH incorporation deviates the maximum excitation wavelength of the hybrid host intrinsic emission from the UV (365 nm) to the blue (420 nm) and enhances the absolute emission quantum yield from 6.0 +/- 0.6% to 9.0 +/- 0.9%, and contributes to an increase in the (5)D(0) lifetime values, quantum efficiency due to a decrease in the non-radiative transition probability and OH groups coordinated to the Eu(3+) ions. (C) 2010 Elsevier B.V. All rights reserved.

Propriedade fotoluminescente da ZrO2: Tb+3, Eu+3, Tm+3 obtida pelo método de polimerização de complexos

Lovisa, Laura Ximena
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Ciência e Engenharia de Materiais; Processamento de Materiais a partir do Pó; Polímeros e Compósitos; Processamento de Materiais a part
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
56.08%
Recent studies are investigating a new class of inorganic materials which arise as a promising option for high performance applications in the field of photoluminescence. Highlight for rare earth (TR +3 ) doped, which have a high luminous efficiency, long decay time and being able to emit radiation in the visible range, specific to each element. In this study, we synthesized ZrO2: Tb +3 , Eu +3 , Tm +3 nanoparticles complex polymerization method (CPM). We investigated the influences caused by the heat treatment temperature and the content of dopants in zirconia photoluminescent behavior. The particles were calcined at temperature of 400, 500 and 600 ° C for two hours and ranged in concentration of dopants 1, 2, 4 and 8 mol% TR +3 . The samples were characterized by thermal analysis, X-ray diffraction, photoluminescence of measurements and uv-visible of spectroscopies. The results of X-ray diffraction confirmed the formation of the tetragonal and cubic phases in accordance with the content of dopants. The photoluminescence spectra show emission in the region corresponding simultaneous to blue (450 nm), green (550 nm) and red (615 nm). According to the results, ZrO2 particles co-doped with rare earth ions is a promising material white emission with a potential application in the field of photoluminescence; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Estudos recentes investigam uma nova classe de materiais inorgânicos que surgem como uma opção promissora em aplicações de alto desempenho no campo da fotoluminescência. Destaque para fósforos dopados com íons de terras raras (TR +3 )...

Síntese, caracterização e estudo de novos complexos de Európio(III) e Térbio (III), contendo como ligantes a [1,2,5]tiadiazolo[3,4-f][1,10]fenantrolina e derivados de pirazolonas

Girotto, Edivandro
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Dissertação de Mestrado Formato: 97 f.| il., grafs., tabs.
Português
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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Química, Florianópolis, 2010; Neste trabalho foi sintetizado o ligante [1,2,5]tiadiazolo[3,4-f][1,10]fenantrolina, TDPHEN, juntamente com os ligantes derivados da pirazolona. Com estes ligantes foram obtidos novos compostos de coordenação de íons lantanídeos (Eu3+ e Tb3+). Os mesmos foram caracterizados mediante a determinação do ponto de fusão, análise da composição elementar, voltametria cíclica, espectroscopia de absorção nas regiões UV-vis e Infravermelho e espectroscopia de emissão. Para aqueles compostos nos quais foi possível obter bons cristais, (cristais únicos ou monocristais) sua caracterização foi feita por difração de raio#X. Também foram feitas as análises termogravimétricas (TGA), para determinar a estabilidade térmica dos compostos de coordenação sintetizados. O estudo eletroquímico permitiu obter os valores de - 4,07, - 4,17, - 4,09, - 4,23 eV e # 3,34, - 3,17, - 3,32, - 3,34 eV HOMO e LUMO e de suas diferenças de energia #band gap# 0,73, 1,0, 0,77 e 0,89 eV para os complexos Eu(TDPHEN)(AMPP)3(H2O)3 20, Tb(TDPHEN)(AMPP)3(H2O) 21, Eu(TDPHEN)(AMFPP)3 22 e Tb(TDPHEN)(AMFPP)3 23. As propriedades fotofísicas foram analisadas através de seus espectros de absorção UV-vis e emissão...

Modulating the Photoluminescence of Bridged Silsesquioxanes Incorporating Eu(3+)-Complexed n,n '-Diureido-2,2 '-bipyridine Isomers: Application for Luminescent Solar Concentrators

Graffion, Julien; Cattoen, Xavier; Man, Michel Wong Chi; Fernandes, Vasco R.; Andre, Paulo S.; Ferreira, Rute A. S.; Carlos, Luis D.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.01%
Two new urea-bipyridine derived bridged organosilanes (P5 and P6) have been synthesized and their hydrolysis-condensation under nucleophilic catalysis in the presence of Eu(3+) salts led to luminescent bridged silsesquioxanes (M5-Eu and M6-Eu). An important loading of Eu(3+) (up to 11%(w)) can be obtained for the material based on the 6,6'-isomer. Indeed the photoluminescence properties of these materials, that have been investigated in depth (photoluminescence (PL), quantum yield, lifetimes), show a significantly different complexation mode of the Eu(3+) ions for M6-Eu, compared with M4-Eu (obtained from the already-reported 4,4'-isomer) and M5-Eu. Moreover, M6-Eu exhibits the highest absolute emission quantum yield value (0.18 +/- 0.02) among these three materials. The modification of the sol composition upon the addition of a malonamide derivative led to similar luminescent features but with an increased quantum yield (026 +/- 0.03). In addition, M6-Eu can be processed as thin films by spin-coating on glass substrates, leading to plates coated by a thin layer (similar to 54 nm) of Eu(3+)-containing hybrid silica exhibiting one of the highest emission quantum yields reported so far for films of Eu(3+)-containing hybrids (0.34 +/- 0.03) and an interesting potential as new luminescent solar concentrators (LSCs) with an optical conversion efficiency of similar to 4%. The ratio between the light guided to the film edges and the one emitted by the surface of the film was quantified through the mapping of the intensity of the red pixels (in the RGB color model) from a film image. This quantification enabled a more accurate estimation of the transport losses due to the scattering of the emitted light in the film (0.40)...

Modulating the photoluminescence of bridged silsesquioxanes incorporating Eu(3+)-complexed n,n '-diureido-2,2 '-bipyridine isomers: application for luminescent solar concentrators

Graffion, Julien; Cattoën, Xavier; Man, Michel Wong Chi; Fernandes, Vasco R.; André, Paulo S.; Ferreira, Rute A. S.; Carlos, Luís D.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.01%
Two new urea-bipyridine derived bridged organosilanes (P5 and P6) have been synthesized and their hydrolysis-condensation under nucleophilic catalysis in the presence of Eu(3+) salts led to luminescent bridged silsesquioxanes (M5-Eu and M6-Eu). An important loading of Eu(3+) (up to 11%(w)) can be obtained for the material based on the 6,6'-isomer. Indeed the photoluminescence properties of these materials, that have been investigated in depth (photoluminescence (PL), quantum yield, lifetimes), show a significantly different complexation mode of the Eu(3+) ions for M6-Eu, compared with M4-Eu (obtained from the already-reported 4,4'-isomer) and M5-Eu. Moreover, M6-Eu exhibits the highest absolute emission quantum yield value (0.18 +/- 0.02) among these three materials. The modification of the sol composition upon the addition of a malonamide derivative led to similar luminescent features but with an increased quantum yield (026 +/- 0.03). In addition, M6-Eu can be processed as thin films by spin-coating on glass substrates, leading to plates coated by a thin layer (similar to 54 nm) of Eu(3+)-containing hybrid silica exhibiting one of the highest emission quantum yields reported so far for films of Eu(3+)-containing hybrids (0.34 +/- 0.03) and an interesting potential as new luminescent solar concentrators (LSCs) with an optical conversion efficiency of similar to 4%. The ratio between the light guided to the film edges and the one emitted by the surface of the film was quantified through the mapping of the intensity of the red pixels (in the RGB color model) from a film image. This quantification enabled a more accurate estimation of the transport losses due to the scattering of the emitted light in the film (0.40)...

Long range antiferromagnetic order of formally non-magnetic Eu$^{3+}$ Van Vleck ions observed in multiferroic Eu$_{1-x}$Y$_{x}$MnO$_3$

Skaugen, Arvid; Schierle, Enrico; van der Laan, Gerrit; Shukla, Dinesh K.; Walker, Helen C.; Weschke, Eugen; Strempfer, Jörg
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/05/2015 Português
Relevância na Pesquisa
46.08%
We report on resonant magnetic x-ray scattering and absorption spectroscopy studies of exchange-coupled antiferromagnetic ordering of Eu$^{3+}$ magnetic moments in multiferroic Eu$_{1-x}$Y$_{x}$MnO$_3$ in the absence of an external magnetic field. The observed resonant spectrum is characteristic of a magnetically ordered $^7F_1$ state that mirrors the Mn magnetic ordering, due to exchange coupling between the Eu $4f$ and Mn $3d$ spins. This is the first observation of long range magnetic order generated by exchange coupling of magnetic moments of formally non-magnetic Van Vleck ions, which is a step further towards the realization of exotic phases induced by exchange coupling in systems entirely composed of non-magnetic ions.; Comment: 5 pages, 3 figures, to be published in Physical Review B: Rapid Communications