Materiais híbridos à base de sílica obtidos pelo método sol-gel

This review deals with silica based hybrid materials obtained by the sol-gel method. It involves concepts, classifications and important definitions regarding the sol-gel method that allows obtaining materials with organic and inorganic components dispersed in a molecular or nanometric level. We discuss the properties and characteristics of hybrid materials related to experimental synthesis conditions. We devote a special attention to the nanostructured materials, where the self-organization is imposed by the organic component. Finally, we present some important applications of these materials based on their specific properties.

Materiais híbridos orgânico-inorgânicos (ormosil) obtidos por sol-gel com potencial uso como filtro solar

This work aimed at the synthesis and characterization of particles of modified silica containing the organic filter dibenzoylmethane (DBM) by the hydrolytic sol-gel method, with modifications to the Stöber route. The structures of the resulting Xerogels were characterized by diffuse reflectance UV-VIS spectroscopy in the solid state, infrared absorption spectroscopy, Scanning Electron Microscopy (SEM) and 29Si Nuclear Magnetic Resonance (29Si NRM). The results showed favorable formation of hybrid organic-inorganic nanoparticles with efficient absorption/reflectance of radiation in the UV / VIS range, which enables their potential use as sunscreen.

ESTUDO DA IMOBILIZAÇÃO DE LIPASE EM SÍLICA OBTIDA PELA TÉCNICA SOL-GEL

The objective of this work was the immobilization of the enzyme Candida antarctica lipase B (CAL B) using the sol-gel method of immobilization and three different initiators of the polymerization reaction: one acid (HCl), one basic (NH4OH) and the other nucleophilic (HBr). Tetraethylorthosilicate was used as the silica precursor. The influence of the additive PEG 1500 on immobilization was assessed. The efficiency of the process was evaluated considering the esterification activity of the xerogels. The immobilization process provided enhanced thermal stability, storage and operational aspects relative to the free enzyme. Storage temperature proved one of the main variables to be considered in the process, with the xerogels stored under refrigeration showing better results in terms of residual activity (nearly 200 days with ≥ 90% residual activity of basic and nucleophilic xerogels) when compared with storage at ambient temperature (nearly 40 days). The results demonstrated the possibility of reuse of derivatives and a greater number of cycles (nine), considering a residual activity of 50%.