Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on March 18, 2008). Includes bibliographical references (p. 134-143).

Thesis (Ph. D.)--Ohio University, June, 2000. / Title from PDF t.p.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 50-53) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 252-253). Also available in print.

Thesis (Ph. D.)--University of North Texas, May, 2009. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis -- Departmental honors in Computer Science. / Bibliography: ℓ. 73-74.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-06Bitstream added on 2014-06-13T20:53:37Z : No. of bitstreams: 1 saliba_lf_me_ilha.pdf: 2689127 bytes, checksum: 77157443fa70337c82aeb80e43ec516e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A sílica mesoporosa do tipo MSU-4 foi sintetizada a partir do agente direcionador de estrutura Tween 20, utilizado como molde, e do precursor inorgânico tetraetilortosilicato (TEOS). Estruturas mesoporosas tem sido aplicadas em estudos luminescentes por apresentarem alto índice de organização, grande área superficial e distribuição regular de tamanho de poros. Nesse trabalho a sílica mesoporosa foi funcionalizada com 3-aminopropiltrietoxisilano (APTES) para aplicação luminescente. A sílica mesoporosa funcionalizada foi caracterizada por difração de raios-X a baixo ângulo (SAXS), espectroscopia no infravermelho (FT-IR) e adsorção e dessorção de nitrogênio (BET). O material luminescente foi preparado pela formação do complexo [Eu(tta)3] em meio metanólico e impregnado nos canais da sílica mesoporosa. Para a impregnação, o íon Eu3+ foi primeiramente encapsulado na sílica e posteriormente foi adicionado o ligante 2- tenoiltrifluoroacetona (tta). Esse procedimento foi realizado para as sílicas lavada, calcinada e funcionalizada. Uma amostra de sílica funcionalizada foi preparada com a impregnação do complexo já pronto. Todas as amostras foram caracterizadas por espectroscopia luminescente. O estudo espectroscópico foi realizado à temperatura ambiente e os espectros de excitação mostraram a absorção de energia pelo ligante tta na faixa do ultravioleta. Os espectros de emissão mostraram as transições características do íon Eu3+, dos estados de maior energia 5D0 para os de menor energia 7F0-4. Foi observado que a transferência de energia do ligante para o íon Eu3+ foi eficiente. A transição hipersensitiva 5D0→7F2 mostrou o efeito das diferentes superfícies da matriz de sílica. PALAVRAS CHAVE: Sílica mesoporosa, luminescência, európio. / MSU-4 type mesoporous sílica has been synthesized with polyoxyethylenesorbitan monolaurate (Tween 20) as structure-directing agent (MTS) as a template and tetraethyl orthosilicate Si(OEt)4 (TEOS) as silica source. The mesoporous structures have a wide application in the luminescence study because of their organization, large surface area, and size of pores. In this work, MSU-4 mesoporous silica was functionalized with 3-amino-propyl-triethoxysilane (APTES) for luminescence applications. Mesoporous silica and amino-functionalized silica was characterized by small-angle X-ray scattering (SAXS), infrared spectroscopy (FT-IR) and nitrogen adsorption/desorption isotherms at 77 K (BET). A luminescent material was prepared by formation of the complex Eu(tta)3 in methanolic medium within the channels of MSU-4 type ordered mesoporous silica. Using simple wet impregnation methods, the europium ion was first encapsulated followed by ligand 2-thenoyltrifluoracetonate (tta) addition. This process it was done for washed, calcined and functionalized mesoporous silica. Analogous one sample of functionalized silica was impregnated with the complex already ready. All samples were characterized by photoluminescence spectroscopy. The spectroscopy studies in room temperature showed the energy absorption of the ligand range ultraviolet in excitation spectra. The emission spectra this materials displayed the typical Eu3+ intra-4f6 lines ascribed to transitions between the 5D0,1 excited states and the ground multiplet (7F0-4). Negligible emission from the organic part of the encapsulated species was observed, indicating that energy transfer from the ligands to the Eu3+ ion was quite efficient. The hypersensitive 5D0→7F2 line showed the mesoporous silica effect in luminescence europium chelate.

Made available in DSpace on 2014-12-02T11:16:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-02-24Bitstream added on 2014-12-02T11:21:04Z : No. of bitstreams: 1 000781231.pdf: 1372057 bytes, checksum: e6fbde2a479b8ad06bf6fbb599cf0a45 (MD5) / Dentre os poluentes gasosos, o sulfeto de hidrogênio (H2S) e seus derivados - conhecidos como Compostos Reduzidos de Enxofre (CRE) - possuem grande destaque devido a sua alta toxicidade, propriedade corrosiva e participação em problemas ambientais diversos. Diferentes órgãos de controle de emissão ao redor do mundo estabelecem limites para a presença de H2S em diversos ambientes, variando de ppm (μg g-1) até baixo ppb (ng g-1). Para que estes limites sejam de fato cumpridos, é necessário que existam métodos analíticos que produzam resultados confiáveis para quantificar e, consequentemente, monitorar H2S em ambiente gasoso. Sensores ópticos apresentam vantagens como custo acessível, facilidade de operação, potencialidade para miniaturização e facilidade de aplicação em campo. Diversos compostos químicos com propriedades luminescentes tem sido utilizados como reagente para detecção de H2S, entretanto, a maioria é baseado em metais tóxicos (p.e. mercúrio), além de síntese complexa envolvendo várias etapas. Dentro desse contexto, a primeira parte desse trabalho envolve a síntese e caracterização de um composto inédito de paládio denominado bis (2-aminobenzóico) paládio (II), que possui comprimento de onda máximo de emissão em 410 nm quando excitado em 245 nm. Esse composto reage rapidamente com sulfetos aquosos e gasosos, liberando para o meio o ligante ácido 2-aminobenzóico, responsável pelo aumento da intensidade de fluorescência, proporcional a quantidade de sulfeto. O método desenvolvido possui limite de detecção de 0,075 μmol L-1 e 6,8 ppbv para sulfeto e H2S, respectivamente. A segunda etapa do trabalho envolveu a utilização da espectroscopia de absorção no infravermelho acoplada a uma nova geração de células gasosas, denominadas substrate-integrated hollow waveguides (i-HWG), para determinação em tempo real de H2S em matrizes gasosas. A determinação envolve a conversão imediata... / Among the gaseous pollutants, hydrogen sulfide and its derivatives – also know as Reduced Sulfur Compounds (RSC) – have been attracting attention due their high toxicity, corrosive proprieties and involvement in several environmental issues. For this reason, there are many agencies worldwide that establish limits for the presence of H2S and RSC in several environmental compartments ranging from ppm (μg g-1) to low ppb (ng g-1). In order to enable the monitoring of these compounds in air, analytical methods must provide reliable and accurate results. Optical sensors appear particularly advantageous in terms of equipment cost, simplicity, easiness of operation, and potential for miniaturization. Several chemical compounds with luminescent proprieties have been used as reagent for sulfide detection. However, most of them are based on toxic metals and, furthermore, their synthesis contains many steps and generates toxic residues. In light of this context, a new palladium chelate compound – denominate bis (2-aminobenzoic) palladium (II) – was used to determinate sulfides in aqueous and gaseous samples as described in the first part of this thesis. The compound reacts with sulfides leading to the increase of the fluorescence intensity at 410 nm, when excited at 245 nm. The method was validated and enabled the determination of 0.075 μmol L- 1 and 6.8 ppbv for aqueous sulfide and gaseous H2S, respectively. The second part of this thesis involves the use of infrared spectroscopy coupled to a new generation of hollow waveguides, so-called substrate-integrated hollow waveguides, for the real-time monitoring of H2S in gaseous samples. The determination is based on the instantly and UV-based conversion of H2S to SO2, a very strong IR absorber at 1245 cm-1. The method enables the determination of 3 ppm of H2S.

Organic light-emitting diode (OLED) technology has found multitudinous applications in the development of solid-state lighting, flat-panel displays and flexible screens. Nowadays, the phosphorescent OLEDs based on metallophosphors can reach sufficiently high efficiencies for practical application. Recently, red, green and blue (RGB) platforms of highly efficient phosphorescent emitters have been achieved and OLEDs TV is now commercialized in the marketplace. However, the design and synthesis of innovative emitter materials play an important role in commercialization of the OLED technology. The basic concept of OLED is herein discussed in chapter 1 putting main focus on phosphorescent iridium(III) complexes. In chapter 2, a series of cyclometalated iridium(III) complexes containing 2-(4-benzylphenyl)pyridine have been synthesized and different electron-donating and electron-withdrawing substituents were attached on the pyridyl ring in the ligand. The device D6 doped with 8 wt% B4 gave the excellent OLED performance with a peak of external quantum efficiency (ext) of 21.4%, power efficiency (P) of 51 lm/W and current efficiencyL) of 76.3 cd/A, which is much higher than that of commercial available fac-Ir(ppy)3 under the same operation condition. These findings draw our attention to the fact that a weak electron-donating benzyl group could alleviate intermolecular aggregation in the solid state, thus improving the device performance. The bulky moiety introduced on 2-phenylpyridine through a CH2 spacer in the ligands could suppress the triplet-triplet annihilation in their metal complexes. Cylcometalating ligands and their respective metal complexes have been fully characterized by 1H and 13C NMR spectroscopy and matrix-assisted laser desorption inoization-time of flight (MALDI-TOF) mass spectrometry. In chapter 3, a series of thiazole-based iridium(III) complexes have been synthesized and characterized. It is considered that the thiazole moiety is infrequently used for organic semiconducting materials. To have a better understanding on this functional unit, different hole-transporting groups (eg, carbazole or fluorene) are attached to the thiazole ring in the cyclometalating ligands in order to tune the HOMO and LUMO levels of the complexes. Device D29 doped with 8 wt% T2 gave the highest L of 35.8 cd/A and ext of 11.1%. This result implied that thiazole moiety is an alternative option to afford a new class of cyclometalating ligands for OLED research. In chapter 4, a series of cationic iridium(III) complexes bearing diimine ligand have been synthesized and characterized. The diimine ligands were decorated with the sterically bulky groups. As self-aggregation could deteriorate the device efficiency, this molecular design strategy can diminish the aggregation-caused quenching problems, which has been supported by the aggregation-induced emission enhancement present in complexes E2 and E3. In Chapter 5, a series of bis-tridentate iridium(III) complexes have been synthesized and characterized. Our challenging is to design two types of tridentate chelates (ie. monoanionic and dianionic ligands) for balancing the charge on the metal center. Besides, these chelates should be a good cyclometallate to coordinate with the iridium metal. Four compounds with different dianionic tridentate chelates were designed to achieve distinct color emission. Compound K4 exhibited extremely high quantum yield of 85.5%. This finding revealed that the metal complex featuring two tridentate chelates is a promising phosphorescent dye in OLED. Lastly, the concluding remarks and the experimental details of all the compounds in the previous chapters were included in Chapters 6 and 7.