A new beta-diketone complex with high color purity

In this work a new europium (III) complex with the following formula NH(4) [Eu(bmdm)(4)] was synthesized and characterized. The bmdm (butyl methoxy-dibenzoyl-methane) is a P-diketone molecule used as UV radiation absorber in sunscreen formulations. Coordination of this ligand to the Eu(3+) ion was confinned by FT-IR, while the Raman spectrum suggests the presence of NH(4)(+) ions. The photoluminescence spectra present narrow lines arising from f-f intra-configurational transitions (5)D(0-)(7)F(0,1,2,3,4), dominated by the hypersensitive (5)D(0)-(7)F(2) transition. In the spectrum recorded at 77 K, all transitions split into 2J + 1 lines suggesting that there is just one symmetry site around Eu(3+) ion. This symmetry is not centrosymmetric. The calculated intensity parameters are ohm(2) = 30.5 x 10(-20) cm(2) and ohm(4) = 5.91 x 10(-20) cm(2) for this complex. The CIE chromaticity coordinates (x = 0.67 and y = 0.32) show a dominant wavelength of 615 nm. The color gamut achieved by this complex is a 100% in the CIE color space. (c) 2005 Elsevier B.V. All rights reserved.

Luminescent properties of yttrium diphenylphosphinate activated by europium

The synthesis and spectroscopic characterization of yttrium diphenylphosphinates doped with europium are reported. The purity of all samples was confirmed by carbon and hydrogen micro analysis, thermal analysis, IR vibrational spectroscopy, and X-ray diffraction. Luminescence spectra indicated the presence of two or more symmetry centers. The dynamic luminescence measurements suggested that one symmetry site presented an inversion center, while the others had lower symmetry. The average quantum yield of Eu3+ emission in the yttrium, matrices was 60%. (c) 2005 Elsevier B.V. All rights reserved.

The effects of ZnGa2O4 formation on structural and optical properties of ZnO : Ga powders

Gallium-doped zinc oxide (ZnO:Ga 1, 2 3, 4 and 5 at%) samples were prepared in powder form by modifying the Pechini method. The formation of zinc gallate (ZnGa2O4) With the spinel crystal structure was observed even in ZnO:Ga 1 at% by X-ray diffraction. The presence of ZnGa2O4 in ZnO:Ga samples was also evidenced by luminescence spectroscopy through its blue emission at 430 nm, assigned to charge transfer between Ga3+ at regular octahedral symmetry and its surrounding O2- ions. The amount of ZnGa2O4 increases as the dopant concentration increases, as observed by the quantitative phase analysis by the Rietveld method. (C) 2006 Elsevier B.V. All rights reserved.

Er3+-doped germanate glasses for active waveguides prepared by Ag+/K+ <-> Na+ ion-exchange

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photoluminescence in amorphous (PbLa)TiO3 thin films deposited on different substrates

Pb1-XLaXTiO3 thin films, (X = 0.0; 13 and 0.27 mol%) were prepared by the polymeric precursor method. Thin films were deposited on Pt/Ti/SiO2/Si (1 1 1), Si (1 0 0) and glass substrates by spin coating, and annealed in the 200-300degreesC range in an O-2 atmosphere. X-ray diffraction, scanning electron microscopy and atomic force microscopy were used for the microstructural characterization of the thin films. Photoluminescence (PL) at room temperature has been observed in thin films of (PbLa)TiO3. The films deposited on Pt/Ti/SiO2/Si substrates present PL intensity greater than those deposited on glass and silicon substrates. The intensity of PL in these thin films was found to be dependent on the thermal treatment and lanthanum molar concentration. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Determination of the local site occupancy of Eu3+ ions in ZnAl2O4 nanocrystalline powders

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of the order and disorder of BaMoO4 powders in photoluminescent properties

The study of the photoluminescent properties affected by order and disorder of the BaMoO4 powders is the principal objective in this work. BaMoO4 compounds were prepared using soft chemical process called Complex Polymerization Method. In this work, different deagglomeration types and different heating rates were used to promote different disorder degrees. Scheelite type phase (BaMoO4) was determined by X-ray Diffraction (XRD), Fourier Transformed Infra-Red (FTIR) and Raman spectroscopy after heat treating the sample at 400 degrees C. The room temperature luminescence spectra revealed an intense single-emission band in the visible region. Based on XRD and Raman data it was observed that the transition between the completely disordered structure to completely ordered structure is a good condition for photoluminescence (PL) emission. The best PL emission is obtained when the material possesses short range disorder, i.e., is periodically ordered (XRD), but some disorder as measured by Raman spectroscopy. The excellent optical properties observed for disordered BaMoO4 suggested that this material is a highly promising candidate for optical applications.

Structural refinement and photoluminescence properties of irregular cube-like (Ca-1_Cu-x(x))TiO3 microcrystals synthesized by the microwave-hydrothermal method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Langmuir-Blodgett films incorporating an ionic europium complex

Langmuir-Blodgett (LB) technique is a powerful tool to fabricate ultrathin films with highly ordered structures and controllable molecular array for efficient energy and electron transfer, allowing the construction of devices at molecular level. One method to obtain LB films consists in the mixture of classical film-forming molecules, for example Stearic Acid (SA) and functional metal complex. In this work NH(4)[Eu(bmdm)(4)], where the organic ligand bmdm is (butyl methoxy-dibenzoyl-methane) or (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl)propane-1,3-dione) was used to build up Langmuir and LB films. Langmuir isotherms were obtained from (i) NH(4)[Eu(bmdm)(4)] complex and (ii) NH(4)[Eu(bmdm)(4)]/SA (1:1). Results indicated that (i) form multilayer structure; however the surface pressure was insufficient to obtain LB films, and (ii) can easily reproduce and build LB films. The dependence of number of layers in the UV absorption spectra suggest that the complex did not hydrolyze or show decomposition, UV spectral differences observed between the solution and the LB film indicate that the complex has a highly ordered arrangement in the film and the complex has an interaction with SA. Excitation spectra confirm a ligand-europium energy transfer mechanism. The transition lines of Eu(3+) ion were observed in emission spectra of all films, the photoluminescence spectra indicate a fluorescence enhanced effect with the number of LB layers. (C) 2009 Elsevier B.V. All rights reserved.

Multiwavelength visible and white light generation by upconversion emission in Ho/Tm/Yb triply doped fluorogermanate glass-ceramic

Energy transfer excited multiwavelength visible upconversion emission and white light generation is described in a single sample of PbGeO(3)-PbF(2)-CdF(2) glass-ceramic triply doped With Ho/Tm/Yb under single infrared laser excitation. Blue (475 nm), green (540 mn), and red (650 nm), upconversion luminescence signals are generated, and the emissions are assigned, respectively, to thulium ((1)G(4)-(3)H(6)), and holmium ((5)S(2);(5)F(4)) -> (5)I(8), (5)F(5) -> (5)I(8)) ions transitions, both excited via successive energy transfers from ytterbium ions. It is experimentally shown that with a proper combination of the rare earth ions contents, white light may be produced, with the simultaneous generation of fluorescence with controllable intensities at the wavelengths of the three primary colours in a single sample and using a single near-infrared excitation source.

Active planar waveguides based on sol-gel Er3+-doped SiO2-ZrO2 for photonic applications: Morphological, structural and optical properties

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

Disorder-dependent photoluminescence in Ba0.8Ca0.2TiO3 at room temperature

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

Optical, electrical, and thermochromic properties of polyazothiophene Langmuir-Blodgett films

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

Infrared-to-visible upconversion in Yb3+/Er3+ co-doped PbO-GeO2 glass with silver nanoparticles

Enhanced frequency upconversion (UC) emission was studied in Yb3+/Er3+ co-doped PbO-GeO2 glass containing silver nanoparticles (NPs). Optical excitation was achieved with a laser operating at 980 nm in resonance with the Yb3+ transition F-4(5/2)-> F-4(7/2). The intensity of the whole UC spectrum from 400 to 700 nm was intensified due to the influence of silver NPs. The green and red emissions were enhanced by more than 300%. Emission bands centered at 408 nm and 480 nm were also detected corresponding to the H-2(9/2)-> I-4(15/2) and F-4(7/2)-> I-4(15/2) transitions of Er3+ ion. An intensity enhancement of approximate to 150% due to the NPs was measured. For the first time the influence of silver NPs on the blue emission of Yb3+/Er3+ co-doped PbO-GeO2 glass is reported. The large enhancement in the whole UC spectrum is due to the increased local field in the Er3+ ions locations and the proximity between the luminescence wavelengths and the NPs surface plasmon resonance. (C) 2010 Elsevier B.V. All rights reserved.

Structural deformation monitored by vibrational properties and orbital modeling in (Pb,Sm)TiO3 systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)