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Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-23Bitstream added on 2014-06-13T19:38:11Z : No. of bitstreams: 1 macario_lr_me_araiq.pdf: 2041175 bytes, checksum: 961d5ba845b7c11a8a6b7a00c583a3b4 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A necessidade de materiais com emissão luminescente tem aumentado continuamente com o desenvolvimento tecnológico. Para isto, torna-se necessária a obtenção de novos materiais, a fim de acompanhar esta crescente demanda. A criação de novos dispositivos depende, em geral, da obtenção de materiais que possam ser sintetizados, sem que haja a necessidade de utilização de condições especiais de síntese. Com isso, neste trabalho foram obtidas estruturas cristalinas de titanatos e zirconatos de bário dopados com a terra rara európio (Eu) por intermédio do método Hidrotérmico Assistido por Micro-ondas (HAM). Foram utilizadas as técnicas de caracterização, Difração de Raios X (DRX), Microscopia Eletrônica de Varredura (MEV), Espectroscopia Raman (FT-Raman), Espectroscopia de Reflectância no Ultravioleta e Visível (UV-Vis) e Fotoluminescência (FL), com intuito de verificar a influência do dopante Eu sobre as características ópticas e estruturais nos materiais. Assim, foi realizado um estudo correlacionando as técnicas de caracterização que permitiram uma avaliação das propriedades fotoluminescentes e da organização estrutural destes materiais. Os espectros de DRX mostraram que ambos os compostos podem ser obtidos, na fase cristalina a partir de um minuto de tratamento em HAM, sendo o zirconato de bário (BZ) de fase cúbica e o titanato de bário (BT) de fase tetragonal. A espectroscopia Raman foi uma ferramenta importante para caracterizar os compostos a curta distância de acordo com os tempos de síntese das amostras e da concentração de Eu. Por intermédio das medidas de UV-Vis verificou-se a presença de estados intermediários na região do “gap” gerados por defeitos estruturais nos compostos e a inserção dos íons Eu3+ nas redes cristalinas de BZ e BT. Os materiais sintetizados quando excitados em 350,7 nm apresentaram emissões de banda larga na região... / The need for materials with luminescence increases with technological development, which grows every day. For this, it becomes necessary the obtention of new materials in order to follow this growing demand. The creation of new devices depends, in general, from obtaining materials that can be synthesized without the need to use special conditions of synthesis. Thus, in this work crystal structures of barium titanate and barium zirconate doped with rare earth europium (Eu) were obtained through the hydrothermal method assisted by microwave (HAM). The characterization techniques used were X-Ray Diffraction (XRD), Scanning Electron Microscopy (EMS), Raman Spectroscopy (FT-Raman), Reflectance Spectroscopy on Ultraviolet and Visible (UV-Vis) and Photoluminescence (FL), in order to verify the influence of doping on the synthesized materials. Thus, a study correlating the characterization techniques that have allowed an evaluation of the photoluminescent properties and structural organization of these materials was necessary. XRD spectra showed that both materials can be obtained in crystalline phase from one minute of treatment on HAM, giving barium zirconate (BZ) in cubic phase and barium titanate (BT) in tetragonal phase. Raman spectroscopy has been an important tool to characterize the compounds in short distance according to the time of synthesis and Eu concentrations. By means of UV-Vis measurements the presence of intermediate states were observed in the region of gap generated by structural defects in the compounds and the insertion of Eu3+ ions in the crystalline lattice of BZ and BT. The synthesized materials, when excited at 350.7 nm, showed a broadband emission in the visible region, with a variation of intensity of broad bands relative to the luminescence of the matrices by varying the concentration of Eu3+, as well as intensity variations on emissions from the rare earth in question... (Complete abstract click electronic access below)

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Luminescent lanthanide coordination complexes have attracted significant attention due to their unique optical properties. The poor absorption of a lanthanide ion can be resolved by so-called antenna effect and improve the intensity of its luminescence. Three bidentate chromophores: phosphate-pyridine chromophore, 1,2-Hydroxy pyridone (1,2-HOPO) and 2-thenoyltrifluoroacetone (TTA), functioned as both chelator and sensitizer, their energy levels are well matched with the excited state energy levels of the Eu(III) and Sm(III).. To get highly luminescent and stable lanthanide complex, we designed and synthesized various Eu(III) complexes with different backbones to compare different parameters that will affect the sensitizing efficiency of the chromophores, such as rigidity, geometry and coordination saturation.. In chapter two we combined the phosphate-pyridine chromophore with the well-studied cyclen-based chelator to fulfil the requirement of high stability and brightness. We designed a nine-coordinate europium(III) complex as platform, through coupling reactions to realise fast screen of the chromophores energy transfer efficiency.. Chapter three focuses on the structure modifications based on the chromophore of 1,2-HOPO, different chelators and backbones were compared, a europium complex EuL4 with the highest quantum yield with this chromophore was obtained and it could goes into cells and localized on lysosome very fast. Two-phonon in vitro imaging was done which showed its high potential bioapplications.. Chapter four focuses on the structure modification based on the chromophore of TTA. Different backbone directly determined the europium complexes saturation number and sensitization efficiency, therefore, their quantum yields.

A systematic study has been done on the absorption and luminescence spectra of transition metal complexes with low-spin electronic configuration d⁶, in order to clarify the spectroscopic behavior of these complexes. The spectra have been measured in solutions and crystals at temperatures between 4 K and room temperature. The lifetimes of the luminescence were measured, too, as an aid to the assignments of the bands. Suitable equipment has been designed and assembled for these measurements. The series of transition metal complexes with different metal atoms and ligands was chosen in order to cover a large range of ligand field strengths and bonding characteristics. Some complexes of Co(lll), Ru(ll), Rh(lll), Os(ll), Ir(lll) and Pt(lV) have been found to luminesce. Other complexes have been investigated and even the absence of luminescence was important for the general understanding of the phenomenon. The results of this investigation show that for the complexes here studied the luminescence originates from the electronic transition ³T₁g, ↦ ¹A₁g , i.e. a transition of d-d type. Also, a luminescence of charge-transfer type has been reported in the literature for some d⁶ complexes. From our data and from the information already-available, some empirical rules were formulated for the luminescence of d⁶ low-spin complexes. A priori use of these rules enables us to prognosticate the presence and the characteristics of the luminescence of other d⁶, low-spin complexes. / Science, Faculty of / Chemistry, Department of / Graduate

Indolyl hydroperoxides have been discovered to be chemiluminescent in presence of potassium t-butoxide in dimethyl sulphoxide. A number of derivatives of indole and the corresponding peroxide have been prepared in an effort to elucidate the mechanism of chemiluminescence of this class of compound. The chemiluminescent reaction of two of the brightest hydroperoxides (X11A and XV111A) yielded a major product, the amides (Xlla and XVllla), in about 70% yield. The emitter has been identified as the amide product based on spectroscopic data. It was found that electron-donating substituents enhance the chemiluminescence intensity. A study of 2-(p-phenyl) substituted indolyl hydroperoxides shows a Hammett correlation with δ for 7 of the compounds. The chemiluminescence of compounds (XllA and (XV111A) shows a pseudo first order dependence on the concentration of (X11A and XV111A) (in excess base). Energy transfer has been observed to occur in the thermochemiluminescence of 11-tetrahydroperoxyindolenine (XXVA). / Science, Faculty of / Chemistry, Department of / Graduate

An investigation into the potential of time-wavelength resolved luminescence spectroscopy for the analysis of inorganic powders was performed. A time-wavelength resolved luminescence spectrometer consisting of an excimer laser, scanning monochromator, and gated integrator was constructed. The spectrometer had wavelength coverage from 265 nm to 800 nm, it was capable of measuring lifetimes between 100 ns and 500 ms. Sample excitation was done at 193 nm and 248 nm. A luminescence system model of first order decay in the time domain and a Gaussian function for the emission band was assumed. The time-wavelength resolved luminescence spectrum was described by the parameters: lifetime, peak maxima, peak halfwidth, and intensity factor. Parameter estimation was done with an algorithm employing a linear algebra construct and simplex optimization. The algorithm's performance on highly overlapped spectra was evaluated. For two component mixtures having a 1 % RSD noise level, overlaps greater than 0.3 halfwidths in the spectral domain and lifetime ratios greater than 1:1.3 were resolved with all parameter estimates having an error of less than ±2%. The luminescence spectra of CaMo0₄, SrMo0₄, BaMo0₄, ZnMoO₄, CdMo0₄, PbMoO₄, CaWO₄, SrW0₄, BaWO₄, ZnWO₄, CdW0₄ and PbWO₄ consisted of broad featureless bands showing simple exponential decay. Mixed crystals of Ca(MOxW₁-x)O₄ and Sr(MOxW₁-x)0₄ were examined. Tungstate emission was quenched by molybdate, the molybdate emission dominated when x was greater than 0.15. The tungstate lifetime was found to be proportional to molybdate concentration. The luminescence spectra of CaZrO₃, SrZr O₃, BaZr O₃ CaHfO₃ SrHfO₃, BaHfO₃, CaO, SrO, and BaO as pure compounds and doped with T1, Pb, Sb, and Bi were studied. The pure zirconates and hafnates showed short lived (<100 ns) luminescence with 248 not excitation; no readily discernible luminescence was observed with 193 nm excitation. Doped compounds tended to show luminescence characteristic of the dopant ion. / Science, Faculty of / Chemistry, Department of / Graduate