Structural disorder-dependent upconversion in Er3+/Yb3+-doped calcium titanate

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sprayed films of europium complexes toward light conversion devices

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

On observation of the downconversion mechanism in Er3+/Yb3+ co-doped tellurite glass using thermal and optical parameters

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of Ag nanoparticles on the radiative properties of tellurite glasses doped with Er3+, Yb3+ and Tm3+ ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Investigations on PVP/Y3BO6:Eu3+, a red Luminescent composite for lighting devices based on near UV-LEDs

This work deals with a red phosphor. Y3BO6:Eu3+, and its corresponding poly(N-vinylpyrrolidone) (PVP)/Y3BO6:Eu3+ luminescent composite film suitable for applications in the next generation of Hg-free lamps based on near ultraviolet (UV) light emitting diodes (LEDs). Well crystallized samples of Y3BO6 powders with the Eu3+ content up to 20 mol% were prepared by the Pechini method. After structural, morphological and optical characterization, the best doping rate of Eu3+ in the matrix was determined to be 15 mol%. This optimal powder, which is highly friable, was easily ground into fine particles and homogeneously dispersed into a PVP polymer solution to give rise to a polymer phosphor composite. Structural and optical features of the composite film have been studied and compared to those of a pristine PVP film and Y3BO6:Eu3+ powder. All the characterization (XRD, SAXS, luminescence...) proved that the red phosphor particles are well incorporated into the polymer composite film which exhibited the characteristic red emission of Eu3+ under UV light excitation. Furthermore, photostability of the polymer/phosphor composite film under UV-LED irradiation was evaluated from exposure to accelerated artificial photoageing at wavelengths above 300 nm.

Infrared to visible up-conversion in biocellulose yttrium vanadate nanoparticle composite membranes. Demonstration of chloroaluminum phthalocyanine light emission under up-converted light excitation

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

Coherence characteristics of random lasing in a dye doped hybrid powder

The photon statistics of the random laser emission of a Rhodamine B doped di-ureasil hybrid powder is investigated to evaluate its degree of coherence above threshold. Although the random laser emission is a weighted average of spatially uncorrelated radiation emitted at different positions in the sample, a spatial coherence control was achieved due to an improved detection configuration based on spatial filtering. By using this experimental approach, which also allows for fine mode discrimination and timeresolved analysis of uncoupled modes from mode competition, an area not larger than the expected coherence size of the random laser is probed. Once the spectral and temporal behavior of nonoverlapping modes is characterized, an assessment of the photon-number probability distribution and the resulting second-order correlation coefficient as a function of time delay and wavelength was performed. The outcome of our single photon counting measurements revealed a high degree of temporal coherence at the time of maximum pump intensity and at wavelengths around the Rhodamine B gain maximum.

Geomorfologia e paleo-hidrologia dos megaleques dos rios Cuiabá e São Lourenço, quaternário da Bacia do Pantanal

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

EStudo fundamental da interação de nanopartículas metálicas com íons terras raras em vidros e vitrocerâmicas para aplicações na região do infravermelho

Pós-graduação em Química - IQ

Fotocromismo e luminescência de compostos a base de tungstênio e íons terras raras trivalentes via síntese hidrotérmica

Pós-graduação em Química - IQ

Geocronologia de formas deposicionais e evolução da planície interleques do Rio Negro, quartenário da Bacia do Pantanal

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

Aplicação eletroanalítica de complexos oxo-manganês biomimetizadores de centros ativos enzimáticos na determinação de espécies de interesse analítico

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

Photoluminescence of the Eu-doped thin film heterojunction GaAs/SnO2 and rare-earth doping distribution

Tin dioxide (SnO2) thin films doped with Eu3+, are deposited by the sol-gel-dip-coating process on top of GaAs films, which is deposited by resistive evaporation on glass substrate. This heterojunction assembly presents luminescence from the rare-earth ion, unlike the SnO2 deposition directly on a glass substrate, where emissions from the Eu3+ transitions are absent. The Eu3+ transitions are clearly identified and are similar to the observation on SnO2 pressed powder (pellets), thermally treated at much higher temperatures. However, in the form of heterojunction films, the Eu emission comes along a broad band, located at higher energy compared to Eu3+ transitions, which is blue-shifted as the thermal annealing temperature increases. The size of nanocrystallites points toward quantum confinement or electron transfer between oxygen vacancies, originated from the disorder in the material, and trivalent rare-earth ions, which present acceptor-like character in this matrix. This electron transfer may relax for higher temperatures in the case of pellets, and the broad band is eliminated.

Rietveld refinement and optical properties of SrWO4:Eu3+ powders prepared by the non-hydrolytic sol-gel method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Color tunability in green, red and infra-red upconversion emission in Tm3+/Yb3+/Ho3+ co-doped CeO2 with potential application for improvement of efficiency in solar cells

The preparation of Tm3+/Yb3+/Ho3+ co-doped CeO2 prepared by the precipitation method using ammonium hydroxide as a precursor is presented. By X-ray diffraction the materials show the phase-type of fluorite structure and the crystallite sizes were calculated by the Scherrer's equation. No other phase was observed evincing that the rare earth ions were inserted into the fluorite phase as substitutional or interstitial dopants. The microstrain calculated by the Williamson-Hall method do not show significant changes in their values, indicating that the inclusion of rare earths does not causes structural changes in the CeO2 used as a host matrix. All material showed intense upconversion emission at red and green region under excitation with diode laser at 980 nm. The color of emission changes from green to red with increasing excitation power pump. The materials showed suitable photoluminescent properties for applications as a laser source, solar cells, and great emitter at 800 nm. (C) 2014 Elsevier B.V. All rights reserved.