Synthesis of a functionalized europium complex and deposition of luminescent Langmuir-Blodgett (LB) films

The synthesis, characterization and formation of Langmuir-Blodgett (LB)films for the luminescent [(C12H25)(2)(CH3)(2)N][Eu(tta)(4)] complex, where [(C12H25)(2)(CH3)(2)](N+) is didodecyldimethylammonium and the tta ligand is thenoyltrifluoroacetone, are reported. The coordination of tta ligands to the Eu3+ ion was confirmed by FTIR spectroscopy and the emission spectrum comprised bands corresponding to D-5(0) -> F-7(0-4) transitions. The lifetime (tau) from the emission state (D-5(0))was 0.41 ms, measured by monitoring the hypersensitive D-5(0) -> F-7(2) transition, with the curve being fitted with a first-order exponential function. The surface pressure-area isotherm indicated that the anionic complex may form condensed structures at the air-water interface due to the amphiphilic properties of the counter ion and the beta-diketone ligand. Y-type LB films of [(C12H25)(2)(CH3)(2)N][Eu(tta)(4)] were deposited on quartz substrates, with preserved luminescence and a band assigned to the D-5(0) -> F-7(2) transition. The molecular arrangement at the air/water interface and the preserved luminescence in LB films are consistent with theoretical predictions using a semi-empirical Sparkle/AM1 calculation method for the molecule in vacuum. These tools were used for the first time to predict the behavior of organized films.CAPESCAPESCNPqCNPqFAPESPFAPES

Efficient Dye-sensitized Solar Cells Based On The Combination Of Zno Nanorods And Microflowers.

Well-aligned ZnO nanorod films were grown onto transparent conducting substrates by using an aqueous solution route. The presence of some reflections in the X-ray diffraction pattern of the ZnO films indicates the vertical alignment of the nanorods along the c axis of the wurtzite hexagonal structure. Well-aligned ZnO nanorods were observed by scanning electron microscopy. The presence of top ZnO microflower layers over the ZnO nanorod film was observed for all growth times studied. The ZnO nanorods with ZnO microflower top layers were applied as photoelectrodes in dye-sensitized solar cells. Higher photocurrent densities and photovoltages were observed with longer nanorod growth times. The high performance of the dye-sensitized solar cells might be associated to the combination of ZnO nanorods and microflowers in the same photoelectrode.106432-

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 and morphological study of Sr2CeO4 blue phosphor prepared from oxalate precursors

Luminescent and morphological studies of Sr2CeO4 blue phosphor prepared from cerium-doped strontium oxalate precursor are reported Powder samples were prepared from 5 and 25 mol% Ce3+-doped strontium oxalate as well as from a mechanical mixture of strontium oxalate and cerium oxalate at a 4 1 ratio respectively All the samples were characterized by XRD IR PLS and SEM The luminescent and structural properties of the Sr2CeO4 material are little affected by the SrCO3 remaining from precursors The Sr2CeO4 material consists in one-dimensional chains of edge-sharing CeO6 octahedra that are linked together by Sr2+ ions The carbonate ion might be associated with oxygen ions of the linear chain and also with the oxygen atoms located in the equatorial position which consequently affects the charge transfer bands between O2- and Ce4+. As observed by SEM, the morphological changes are related to each kind of precursor and thermal treatment along with irregular powder particles within the size range 05-2 mu m (c) 2010 Elsevier B V All rights reservedFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Investigation of the systems silica and silica containing chromium in alcohol medium

The purpose of this work is to obtain micrometer sized spherical particles of silica and silica-chromium from sodium silicate. Spherical particles were prepared by sol-gel method from hydrolysis to polycondensation of aqueous sodium silicate in alcohol medium. Chromium was added to the system for some samples. Compositions and morphologies were achieved by changing the precipitation agent. X-ray diffractometry, electrophoretic mobility, infrared spectroscopy and scanning electron microscopies were carried out on these particles to identify phases, determine particle mobility, morphology, particle sizes, shapes and order at short distance. Non-crystalline silica particles with spherical shapes and micrometric size were obtained. The surface potentials of the silica particles differed from that of the silica-chromium particles. (C) 1999 Elsevier B.V. B.V. All rights reserved

Morphology of alumina: a comparison between infrared spectroscopy and X-ray diffractometry

Morphology of three samples of alumina are investigated. Infrared spectra are analysed by use of their morphology through the theory of average dielectric constant. Crystal shape is obtained from X-ray diffraction patterns by reflection intensity ratio. In the case of electron scanning microscopy, shape factor was obtained by an average axial ratio of the particles. Comparison of results show that there is agreement among these techniques and infrared spectra can be used to determine the morphology of alumina particles from 2.7 to 10 mu m, even for heterogeneous samples. (C) 1999 Elsevier B.V. B.V. All rights reserved

Spectroscopy properties and energy level location of Gd(2)O(2)S:Pr(3+),Ce(3+)

In this work we propose the study of the spectroscopy properties and the energy level location of Ce(3+) and Pr(3+) in Gd(2)O(2)S, along with the effects of Ce(4+) (Ce(2)O(2)S(2)) incorporation in Gd(2)O(2)S and Gd(2)O(2)S: Pr(3+) in order to understand the formation and position of the associated defects energy levels in relation to the band structure of Gd(2)O(2)S and Pr(3+) energy levels. Ce-, Pr(3+)-doped and Pr(3+), Ce-doped Gd(2)O(2)S were prepared by the sulfidization of a basic gadolinium carbonate with S(8) using H(2)/N(2) (3.0/97.0%) and air during the firing of the precursor. Samples were analyzed by X-ray diffraction in order to guarantee the formation of the Gd(2)O(2)S single phase. Diffuse reflectance spectroscopy and luminescent measurements (emission/excitation) were used to locate Ce(3+), Pr(3+) and defects energy levels in relation to the band structure of Gd(2)O(2)S. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Chromium-containing silica materials

Chromium-containing silica samples were obtained from soluble sodium silicate solutions in the presence of different chromium nitrate concentrations. Precipitation was carried out in ethanolic media. Gel precipitate was dried by liophylization and samples measured by transmission electron microscopy (TEM), X-ray energy-dispersive spectrometer, X-ray mapping, X-ray photoemission spectroscopy (XPS), and particle size analysis. Spherical chromium containing silica particles with 3.5% and 4.8% (at.%) of chromium were obtained. Particle size analysis results showed that with increased addition of chromium in sodium silicate solutions produces agglomerates whose sizes range from 1 to 0.2 μm. Chromium mapping and XPS results show that chromium oxide is preferentially segregated on particle surfaces. Chromium oxide was detected on particle surface with a binding energy of 576.77 ± 0.05 eV as obtained from XPS analysis. During the hydrolysis and condensation processes chromium oxide precipitates on the silica surface and it affects the silica chain size. © 2000 Elsevier Science B.V. All rights reserved