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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
ENG
Relevância na Pesquisa
38.007876%
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.

Enhancement on the Europium emission band of Europium chlortetracycline complex in the presence of LDL

Teixeira, Luciane dos Santos; Grasso, Andrea Nastri; Monteiro, Andrea Moreira; Figueiredo Neto, Antonio Martins; Vieira Junior, Nilson Dias; Gidlund, Magnus Ake; Courrol, Lilia Coronato
Fonte: ACADEMIC PRESS INC ELSEVIER SCIENCE Publicador: ACADEMIC PRESS INC ELSEVIER SCIENCE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.360771%
Low-density lipoprotein (LDL) particles are the major cholesterol-carrying lipoprotein in the human circulation from the liver to peripheral tissues. High levels of LDL-Cholesterol (LDL-C) are known risk factor for the development of coronary artery disease (CAD). The most common approach to determine the LDLC in the clinical laboratory involves the Friedewald formula. However, in certain situations, this approach is inadequate. In this paper we report on the enhancement on the Europium emission band of Europium chlortetracycline complex (CTEu) in the presence of LDL. The emission intensity at 615 nm of the CTEu increases with increasing amounts of LDL. This phenomenon allowed us to propose a method to determine the LDL concentration in a sample composed by an aqueous solution of LDL. With this result we obtained LDL calibration curve, LOD (limit of detection) of 0.49 mg/mL and SD (standard deviation) of 0.003. We observed that CTEu complex provides a wider dynamic concentration-range for LDL determination than that from Eu-tetracycline previously. The averaged emission lifetimes of the CTEu and CTEu with LDL (1.5 mg/mL) complexes were measured as 15 and 46 Its, respectively. Study with some metallic interferents is presented. (C) 2010 Elsevier Inc. All rights reserved.; State of Sao Paulo Research Foundation (FAPESP); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); National institute of Science and Technology of Complex Fluids (INCT-FCx); National institute of Science and Technology of Complex Fluids (INCT-FCx); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); National Counsel of Technological and Scientific Development (CNPq)

Morphology and Blue Photoluminescence Emission of PbMoO(4) Processed in Conventional Hydrothermal

SCZANCOSKI, J. C.; BOMIO, M. D. R.; CAVALCANTE, L. S.; JOYA, M. R.; PIZANI, P. S.; VARELA, J. A.; LONGO, E.; SIU LI, Máximo; ANDRES, J. A.
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.280615%
PbMoO(4) micro-octahedrons were prepared by the coprecipitation method at room temperature without the presence of surfactants and processed in a conventional hydrothermal at different temperatures (from 60 to 120 degrees C) for 10 min. These micro-octahedrons were structurally characterized by X-ray diffraction (XRD) and micro-Raman (MR) spectroscopy, and its morphology was investigated by field-emission gun scanning electron microscopy (FEG-SEM). The optical properties were analyzed by ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectra confirmed that the PbMoO(4) micro-octahedrons are characterized by a scheelite-type tetragonal structure. FEG-SEM micrographs points, out that these structures present a polydisperse particle size distribution in consequence of a predominant growth mechanism via aggregation of particles. In addition, it was observed that the hydrothermal conditions favored a spontaneous formation of micro-octahedrons interconnected along a common crystallographic orientation (oriented-attachment), resulting in self-organized structures. An intense blue PL emission at room temperature was observed in these micro-octahedrons when they were excited with a 350 nm wavelength. The origin of the PL emissions as well as its intensity variations are explained by means of a model based on both distorted [MoO(4)] and [PbO(8)] clusters into the lattice.; CAPES; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP

Calorimetric investigations of luminescent films polycarbonate (PC) doped with europium complex [Eu(TTA)(3)(H(2)O)(2)]

FORSTER, Pedro Lima; LUGAO, Ademar Benevolo; BRITO, Hermi Felinto; PARRA, Duclerc Fernandes
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.933896%
Polymers doped with rare earth complexes are advantaged in film production for many applications in the luminescent field. In this luminescent polycarbonate (PC) films doped with diaquatris(thenoyltrifluoroacetonate)europium(III) complex [Eu(TTA)(3)(H(2)O)(2)] were prepared and their calorimetric and luminescent properties in the solid state are reported. The thermal behavior was investigated by utilization of differential scanning calorimetry (DSC) and thermogravimetry (TG). Due of the addition of rare earth [Eu(TTA)(3)(H(2)O)(2)] into PC matrix, changes were observed in the thermal behavior concerning the glass transition and thermal stability. Characteristic broadened narrow bands arising from the (5)D(0) -> (7)F(J) transitions (J = 4-0) of Eu(3+) ion indicate the incorporation of the Eu(3+) ions in the polymer. The luminescent films show enhancement emission intensity with an increase of rare earth concentration in polymeric matrix accompanied by decrease in thermal stability.; IPEN/CNEN-SP (Nuclear and Energetic Research Institute, National Commission of Nuclear Energy); IPEN/CNEN-SP (Nuclear and Energetic Research Institute, National Commission of Nuclear Energy); Eleosmar Gasparin, Department of Fundamental Chemistry from Chemistry Institute...

Estudo das propriedades estruturais e ópticas em materiais nanoestruturados a base de silício.; Study of structural and optical properties in nanostructured silicon based films.

Ribeiro, Márcia
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/05/2009 PT
Relevância na Pesquisa
37.988403%
Esta tese de doutorado tem por objetivo aprofundar as pesquisas realizadas no mestrado, a saber, da caracterização e estudo das propriedades estruturais e ópticas de filmes de oxinitreto de silício (SiOxNy:H) ricos em silício depositados pela técnica de deposição química a vapor assistida por plasma a baixa temperatura (PECVD). Os resultados obtidos no mestrado indicaram que os filmes de SiOxNy:H ricos em silício apresentam emissão luminescente na faixa do visível cuja intensidade e freqüência de emissão estão em correlação com o excesso de silício. Os resultados sugeriram que o excesso de silício na matriz do SiOxNy:H estava disposto na forma de aglomerados de silício de dimensões nanométricas responsáveis por efeitos de tamanho quântico bem como a estados radiativos na interface dos aglomerados com a matriz isolante. Neste trabalho a fim de avaliar o efeito da separação de fases, do tamanho quântico, e da interface, foram produzidos sistemas nanoestruturados a base de silício com total e parcial separação de fases para caracterizar e analisar suas propriedades ópticas e estruturais e compará-las com as dos filmes ricos em silício. Assim foram produzidas multicamadas de a-Si:H de poucos nanômetros de espessura com materiais dielétricos. Em algumas destas multicamadas foi promovida a mistura parcial das camadas por meio de bombardeamento iônico. O estudo nas estruturas de multicamadas permitiu caracterizar e analisar as propriedades estruturais e ópticas de materiais nanoestruturados com total e parcial separação de fases para posteriormente contrastá-los com as características dos filmes de oxinitreto de silício ricos em silício. A fim de analisar a influência da interface nas propriedades ópticas destes sistemas as multicamadas foram fabricadas com dois dielétricos diferentes: o óxido de silício e o ni treto de silício. A espessura das camadas dielétricas foi mantida fixa entanto que a das camadas de silício foi variada para avaliar efeitos de confinamento no silício. A caracterização foi feita utilizando técnicas de absorção óptica no UV-Vis...

Guias de onda poliméricos para sensoriamento óptico e conversão de comprimento de onda; Polymeric based waveguides for optical biosensor and wavelength conversion

Vale, Mike Melo do
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 14/06/2010 PT
Relevância na Pesquisa
28.48647%
Um Luminescent Solar Concentrators (LSC) é basicamente uma base plástica transparente ou vidro contendo centros luminescentes.Enquanto o recente avanço dos conversores de comprimento de onda tenha aberto novas possibilidades para o desenvolvimento de células solares mais eficientes, estes também abriram novas frentes de pesquisa.Uma destas frentes envolve os problemas encontrados com o uso de novos materiais. Como por exemplo, transferência de energia em polímeros. Surgem propriedades interessantes a respeito dos processos luminescentes ao longo destes sistemas planares.Por estes motivos esses sistemas podem ser aplicados como dispositivos optoeletrônicos, sensores e também em conversores de comprimento de onda. Este estudo descreve a fabricação de guias de onda planares multipoliméricos baseados em uma matrix acrílica (PMMA) dopada com polímeros emissores de luz. A função desta blenda polimérica é absorver um largo espectro de luz e re-emitir ao longo do guia de onda. Os dispositivos foram estudados em termos de suas características de absorção, emissão e excitação.Os polímeros emissores utilizados neste trabalho foram: MEH-PPV, Super Yellow, ADS-108GE, ADS-329BE, e LAPS-16. Estes materiais foram dissolvidos em tolueno e depositados pela técnica casting sobre substratos de vidro contendo filmes metálicos de alumínio.Usando esta configuração...

Estudos espectroscópicos de sistemas luminescentes hóspede/hospedeiro; Spectroscopic studies of guest/host luminescent systems

Queiroz, Thiago Branquinho de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/02/2013 PT
Relevância na Pesquisa
37.609497%
Neste trabalho apresenta-se a obtenção e caracterização de materiais luminescentes baseados em matrizes mesoporosas incorporadas com espécies moleculares altamente emissivas; o corante rodamina 6G (R6G) e o complexo de irídio (III) (N,N-trans-[Ir-(1-benzil-4-(2,4-difluorofenil)-1,2,3-triazol)2(4,4´-dimetil-2,2´-bipiridina)]+). Na incorporação da R6G foram explorados xerogéis mesoporosos sílica de composições puramente inorgânica e modificada com grupos aromáticos, além de vidros mesoporosos sódio aluminosilicato. O complexo de Irídio (III) foi incorporado somente aos vidros sódio aluminosilicato. As matrizes hospedeiras preparadas por metodologia sol-gel foram planejadas e desenvolvidas em consonância com as propriedades físico-químicas das espécies emissoras, a fim de promover maior incorporação e dispersão molecular via diferentes interações químicas. Por exemplo, no caso da sílica modificada com grupos aromáticos, espera-se que haja interação por afinidade química entre tais grupos e as ligações insaturadas das moléculas de R6G, resultando em maior taxa de incorporação e de retenção do centro emissor, bem como minimizando agregações moleculares. No caso dos vidros sódio aluminosilicato...

Luminescent multifunctional biocellulose membranes

Caiut, J. M A; Barud, H. S.; Santos, M. V.; Oliveira, U. L.; Menezes, J. F S; Messaddeq, Y.; Ribeiro, S. J L
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
37.609497%
Luminescent biocellulose membranes were obtained by incorporation of ethanolic solutions of the europium compounds [Eu(BTFAC)3(H2O)2], [Eu(BTFA) 3(DBSO)2], [Eu(BTFA)3(PTSO)2] and [Eu(BTFA)3(FSO)2] (BTFAC- 4,4,4-Trifluoro-1- phenyl-1,3-butanedione DBSO- dibenzyl sulfoxide, PTSO- p-Tolyl sulfoxide and FSO- phenyl sulfoxide). Selfsustainable semi-transparent composite membranes were obtained showing strong emission under UV exctiation. The antenna hole played by the ligands was observed to be more efficient in the composite membranes than in the precursor complexes which by themselves are also strong red emitter compounds. These new multifuctional membranes could find application in different areas as phosphors and UV→Visible energy converting devices. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Intense photoluminescence emission at room temperature in calcium copper titanate powders

Moura, F.; Simões, A. Z.; Deus, R. C.; Silva, M. R.; Varela, José Arana; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 3499-3506
ENG
Relevância na Pesquisa
37.360771%
A study was undertaken about the structural and photoluminescent properties at room temperature of CaCu3Ti4O12 (CCTO) powders synthesized by a soft chemical method and heat treated between 300 and 800 °C. The decomposition of precursor powder was followed by thermogravimetric analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements. XRD analyses revealed that the powders annealed at 800 °C are becoming ordered and crystallize in the cubic structure. The most intense PL emission was obtained for the sample calcined at 700 °C, which is not highly disordered (300-500 °C) and neither completely ordered (800 °C). From the spectrum it is clearly visible that the lowest wavelength peak is placed around 480 nm and the highest wavelength peak at about 590 nm. The UV/vis absorption spectroscopy measurements showed the presence of intermediate energy levels in the band gap of structurally disordered powders. © 2012 Elsevier Ltd and Techna Group S.r.l.

Luminescent properties of hybrid materials prepared by the polymeric precursor method

Oliveira, Larissa H.; Moura, Ana Paula de; Longo, Elson; Varela, José Arana; Rosa, Ieda L.V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 227-235
ENG
Relevância na Pesquisa
37.415068%
Rare earth complexes (RE) can be incorporated in silica matrixes, originating organic/inorganic hybrid materials with good thermal stability and high rare earth emission lines. In this work, the hybrid material was obtained by the polymeric precursor method and ultrasonic dispersed with spherical silica particles prepared by the Stöber Method. The Raman spectra indicated that the Eu3+ ions are involved in a polymeric structure formed as consequence of the chelation and polyesterification reactions of this ion with citric acid and ethylene glycol. After the ultrasonic stirring, 2-hydroxynicotinic ligand will also compose this polymeric rigid structure. The TGA/DTA analysis showed that this polymeric material was thermal decomposed at 300 °C. Moreover, this process allows the chelating process of the 2-hydroxynicotinic acid ligand to the Eu3+ ions. The 29Si NMR showed that the ultrasonic dispersion of the reactants was not able to promote the functionalization of the silica particles with the 2-hydroxynicotinic acid ligand. Moreover, heat treatment promotes the [Eu(HnicO2)3] complex particles incorporation into silica pores. At this temperature, the TGA curve showed that only the thermal degradation of ethylene glycol and citric acid used during the experimental procedure occurs. The silica and hybrid materials are composed by spherical and aggregated particles with particle size of approximately 450 nm...

Luminescent Blinking from Silver Nanostructures

Geddes, Chris D.; Parfenov, Alex; Gryczynski, Ignacy; Lakowicz, Joseph R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 18/09/2003 EN
Relevância na Pesquisa
37.858154%
Silver nanostructures deposited on glass showed luminescent blinking when excited at a high 442 nm irradiance. The irradiance required to photoactivate the silver, was dependent on the nature of the silver nanostructures. Silver fractal-like structures were found to be highly emissive, requiring only ≈30 W/cm2 for photoactivation as compared to silver island films and spin-coated silver colloids, which required a significantly higher irradiance, > 100 W/cm2, to observe similar luminescent emission. In contrast to our recent findings for gold colloids, foci with different color blinking were also observed, with an increase in luminescence intensity as a function of time. We place these findings in context with recent work from our laboratory which employs these silver nanostructures for applications in metal-enhanced fluorescence, a relatively new phenomenon in fluorescence, whereby metallic particles, colloids, and fractal-like structures can modify the intrinsic radiative decay rate of close proximity fluorescent species. These effects are a consequence of localized changes in photonic mode density around the fluorophores, and we can now report are typically observed at significantly lower illumination intensities as compared to those required to photoactivate silver. Subsequently...

Tunable Trimers: Using Temperature and Pressure to Control Luminescent Emission in Gold(I) Pyrazolate-Based Trimers

Woodall, Christopher H; Fuertes, Sara; Beavers, Christine M; Hatcher, Lauren E; Parlett, Andrew; Shepherd, Helena J; Christensen, Jeppe; Teat, Simon J; Intissar, Mourad; Rodrigue-Witchel, Alexandre; Suffren, Yan; Reber, Christian; Hendon, Christopher H; T
Fonte: WILEY-VCH Verlag Publicador: WILEY-VCH Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
47.825254%
A systematic investigation into the relationship between the solid-state luminescence and the intermolecular Au⋅⋅⋅Au interactions in a series of pyrazolate-based gold(I) trimers; tris(μ2-pyrazolato-N,N′)-tri-gold(I) (1), tris(μ2-3,4,5- trimethylpyrazolato-N,N′)-tri-gold(I) (2), tris(μ2-3-methyl-5-phenylpyrazolato-N,N′)-tri-gold(I) (3) and tris(μ2-3,5-diphenylpyrazolato-N,N′)-tri-gold(I) (4) has been carried out using variable temperature and high pressure X-ray crystallography, solid-state emission spectroscopy, Raman spectroscopy and computational techniques. Single-crystal X-ray studies show that there is a significant reduction in the intertrimer Au⋅⋅⋅Au distances both with decreasing temperature and increasing pressure. In the four complexes, the reduction in temperature from 293 to 100 K is accompanied by a reduction in the shortest intermolecular Au⋅⋅⋅Au contacts of between 0.04 and 0.08 Å. The solid-state luminescent emission spectra of 1 and 2 display a red shift with decreasing temperature or increasing pressure. Compound 3 does not emit under ambient conditions but displays increasingly red-shifted luminescence upon cooling or compression. Compound 4 remains emissionless, consistent with the absence of intermolecular Au⋅⋅⋅Au interactions. The largest pressure induced shift in emission is observed in 2 with a red shift of approximately 630 cm−1 per GPa between ambient and 3.80 GPa. The shifts in all the complexes can be correlated with changes in Au⋅⋅⋅Au distance observed by diffraction.

Luminescent emission of multi-junction InGaP/InGaAs/Ge PV cells under high intensity irradiation

PARASKEVA Vasiliki; NORTON MATTHEW; HADJIPANAYI Maria; PRAVETTONI Mauro; GEORGHIOU George
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Articles in Journals Formato: Online
ENG
Relevância na Pesquisa
48.31179%
Combined electroluminescence (EL) and photoluminescence (PL) measurements were conducted in order to investigate the presence o fluminescent emission of InGaP/InGaAs/Ge at different operating conditions of the tandem. Luminescent emission from cell samples was observed at different sun concentrations, voltage biases and temperatures. A high intensity pulsed solar simulator was used to photoexcite the device which exhibited strong radiative recombination from both the top InGaP and middle InGaAs junctions. Luminescent emission from the device was investigated under a range of voltage biases and was clearly observed at the maximum power point voltage of the sample under test indicating its presence during typical operating conditions of the solar cells. Investigation of the emission was also performed at relatively high temperatures (up to 60C ) in order to mimic the outdoor operating conditions of a solar cell device. Luminescence was detected at high temperatures indicating that significant radiative recombination is present at even higher temperatures. Outdoor measurements under actual solar spectrum demonstrated the presence of luminescent emission in agreement with indoor testing. The significant amount of radiative recombination at the band-gap edges of the top junctions observed in our measurements gives evidence that optical coupling to the lower ones may occur. Finally...

SELECTIVE ACTIVATION OF TERBIUM(III) AND EUROPIUM(III) LUMINESCENCEWITH TRIARYLBORON-FUNCTIONNALIZED CARBOXYLATE LIGANDS. AND LUMINESCENT 8-HYDROXYQUINOLINE DIPICOLYLAMINE COMPLEXES AS SENSORS FOR ZINC(II).

Varlan, MARIA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
38.182554%
The impact of a tri-substituted boron moiety on the chelate sensitization of Tb(III) and Eu(III) lanthanide luminescence and their resulting photophysical properties was investigated. Two triarylboron-functionalized carboxylate ligands 1 and 2 and their respective Tb(III) and Eu(III) complexes, 1Tb, 2Tb, 1Eu and 2Eu were synthesized and fully characterized. The photophysical properties of these compounds were studied and it was established that these three-coordinate boron ligands are highly effective in selective activation of Tb(III) and Eu(III) luminescence yielding high efficiency green and red luminescence, respectively. Potential applications of these triarylboron-functionalized chelate Tb(III) and Eu(III) complexes as luminescent sensors for dipicolinic acid (DPA), a biomarker for anthrax spores, as well as small anions such as F- and CN- in organic solution were examined by titration experiments using UV-Vis absorption and fluorescence emission measurements. Further studies were carried out into the application of the lanthanide complexes as solid substrate luminescent sensors for the same analytes. Furthermore a novel zinc-binding compound, composed of both an 8-hydroxyquinoline fluorophore and a dipyridyl metal binding site...

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
ENG
Relevância na Pesquisa
38.109302%
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
ENG
Relevância na Pesquisa
38.109302%
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)...

Efficiency enhancement of solar cells by luminescent up-conversion of sunlight

Trupke, Thorsten; Shalav, Avi; Wurfel, P; Green, Martin Andrew
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.366194%
Significant improvements in the efficiency of solar cells by combination with luminescent up- or down-converters have recently been predicted theoretically. Here, we extend the theoretical analysis of the limiting efficiency of the up-conversion (UC)-syst

Splitting of photo-luminescent emission from nitrogen-vacancy centers in diamond induced by ion-damage-induced stress

Olivero, P.; Bosia, F.; Fairchild, B. A.; Gibson, B. C.; Greentree, A. D.; Spizzirri, P.; Prawer, S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/02/2013
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We report a systematic investigation on the spectral splitting of negatively charged, nitrogen-vacancy (NV-) photo-luminescent emission in single crystal diamond induced by strain engineering. The stress fields arise from MeV ion-induced conversion of diamond to amorphous and graphitic material in regions proximal to the centers of interest. In low-nitrogen sectors of a HPHT diamond, clearly distinguishable spectral components in the NV- emission develop over a range of 4.8 THz corresponding to distinct alignment of sub-ensembles which were mapped with micron spatial resolution. This method provides opportunities for the creation and selection of aligned NV- centers for ensemble quantum information protocols.; Comment: Submitted to "New Journal of Physics" (NJP/458519/PAP/133921): 30 pages, 12 figures, 2 tables, 61 references

Cambios en las propiedades luminiscentes de un feldespato potásico inducidos por efecto térmico y exposición a infrarrojo; Variation in the luminescent properties of a potassium rich feldspar induced by thermal treatment and infrared exposure

Correcher, Virgilio; García-Guinea, Javier
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 225683 bytes; application/pdf
SPA
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[ES] Las propiedades luminiscentes del cuarzo y de los feldespatos, que son componentes mayoritarios de los materiales cerámicos tradicionales (ladrillos, azulejos o porcelanas), varían considerablemente durante el proceso de fabricación que implica un calentamiento hasta ∼900ºC en ladrillos o ∼1200ºC en porcelanas. En este trabajo se ha estudiado como varía la luminiscencia de un feldespato potásico (KAlSi3O8) perfectamente caracterizado cuando es sometido a (i) tratamientos térmicos y (ii) exposición al infrarrojo. Se ha observado que calentamientos progresivos desde 2 hasta 96 horas a una temperatura de 500ºC producen un aumento proporcional de la intensidad en las curvas de radioluminiscencia (RL) y catodoluminiscencia (CL) sin modificar su forma. Dado que no se ha apreciado cambio alguno en la estructura cristalina estudiada por difracción de rayos X, es probable que esta variación de la intensidad sea debida a una auto-difusión de los iones alcalinos (K, Li, Na o Rb) a través de las interfases de la red. Por otra parte, la emisión termoluminiscente (TL) del feldespato potásico se desplaza moderadamente hacia altas temperaturas cuando previamente es expuesto a radiación infrarroja durante 10 minutos. Es probable que este fenómeno sea debido a una transición electrónica por efecto túnel desde trampas más superficiales hacia trampas más profundas o a un mecanismo continuo en la distribución de las trampas.; [EN] Luminescence properties of quartz and feldspars...

Luminescent polystyrene films, a novel way to reduce styrofoam residues

Carmona-Téllez,S.; Alarcón-Flores,G.; Zaleta-Alejandre,E.; Rivera-Alvarez,Z.; Meza-Rocha,A. N.; Martínez-Martínez,R.; Murrieta S.,H.; Aguilar-Frutis,M.; Falcony,C.
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2015 EN
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Polystyrene (PS) films doped with blue, yellow and red organic pigments have been deposited on glass and on commercial LED chips by spray pyrolysis using recycled PS as precursor, at deposition rates between 100 and 200 Å/s. Doped films have roughness between 100 and 2500 Å depending on the kind of pigment used; the surface morphology shows that the organic pigments incorporate into the polystyrene host forming globular particles of about 2 μm in diameter. The organic pigments used have luminescent emissions peaked at 440, 509 and 590 nm. The introduction of the proper combination of pigments on the PS film deposited on the LED chips renders a white light emission with (0.29, 0.37) and (0.30, 0.33) CIE (Commission international de l' eclairage) color coordinates. It was determined that the exposure to violet light degrades the luminescent characteristics, however, blue light is not energetic enough to cause a degradation of the luminescent layer over similar period of time.