289 resultados para Híbridos inorgânico-orgânicos

em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"


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Pós-graduação em Ciências Farmacêuticas - FCFAR

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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

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Pós-graduação em Ciências Farmacêuticas - FCFAR

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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In this work were studied associations of ZnO with the natural products caffeic and feluric acids. Two preparation methods were used, that is, the sol-gel and a reflux procedure. In the sol-gel method, ZnO is produced by the basics hydrolysis of precursors in the presence of the organic filters (caffeic and feluric acids), which results in 30 nm (or less) ZnO particles with the organic filters (in dissociated form) bonded to the surface of ZnO. In the reflux method, a dispersion of ZnO in a water/ethanol mixture was kept under reflux (50oC/4h) in the presence of the organic acids. The ZnO particles used in the reflux method have a higher diameter than sol-gel ZnO particles, but the prepared associated product ZnO/Organic acids were similar. Despite of the difference in relation to crystallinity between the products, the preparation methods resulted in analogous associations with respect to the interaction of the organic filters with the ZnO surface. The caffeic/ZnO associations presented low photostability, which lead to the degradation of the organic filter. The other associations (feluric acid/ZnO) presented satisfactory results. The FT-IR spectroscopy confirmed the formation of the association, and the nature of the bond formed compared with the Zn-O bond in Zn2+/Felutic acid complexes. The isolated organic and inorganic filters, along with the associations were analyzed by diffuse reflectance spectroscopy and Uv-vis spectroscopy. The absorption edges and the critical wavelengths were analyzed and the effects of Zn-O bonds in feluric acid/ZnO associations described as a function of the relative position of the π/π* system of the organic filter. Finally the performance of the hybrid filters were investigated in terms of the absorption of UVA and UVB radiations, with the UVA/UVB ratio, an efficiency parameter largely used in the description of solar filters, sunscreen and suncare products

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Organic- inorganic hybrid (HOI) are materials prepared with the combination of inorganic and organic components. The properties of a hybrid material are unique, not being the sum of each individual component added. This occurs because there is a synergism that depends of the chemical nature of organic and inorganic components, of the size and morphology of their domains. The sodium carboxymethylcellulose (CMC) it's an anionic polymer obtained of the cellulose, very soluble in water in which forms both solutions themselves and gels. The sodium polyphosphate (NaPO3)n, known commercially as Graham Salt is the only polyphosphate soluble in water, and it's the polyphosphate with the longest chain. At the present work it was prepared and characterized new phosphate organic- inorganic hybrids films of carboxymethylcellulose / sodium phosphate and luminescent films of CMC/NaPO3 doped with europium chloride (EuCl3). The films where prepared in several proportions. At first, it was set the amount of water to be used and the amount of carboxymethylcellulose, changing the concentrations of sodium polyphosphate and europium chloride. After pre-establishing concentrations, for each film, the components were submitted to constant agitation and subsequent drying. The inorganic-organic hybrid films were characterized by, TG, DR-X, DMA, FT-IR, UV-Vis-NIR, RMN 31P e 13C and at last, a study of luminescence was made. The hybrid films obtained are transparent and macroscopically homogeneous, however, the MET measures showed the formation of micro-islands of polyphosphate along the material, this fact indicates a bigger fragmentation of the films and this is verified by DMA analysis which shows a smaller resistance of the film with the increase of the concentration of phosphate. Both spectrum FT-IR and RMN analysis of the films, don't show the formation of new bands of their precursors, CMC e NaPO3,....

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Química - IQ