Estrutura e propriedades luminescentes de nanocompósitos híbridos Eu3+:SiO2-PMMA preparados pelo processo sol-gel

• Ano de defesa: 2015
• Autor(a) principal: Jesus, Filipe Augusto de
• Orientador(a): Sarmento, Victor Hugo Vitorino
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Sergipe
• Programa de Pós-Graduação: Pós-Graduação em Química
• País: BR
• Palavras-chave em Português: Nanocompósitos híbridos; Íons Eu3+; Luminescência; Tratamento térmico; Concentração do dopante
• Palavras-chave em Inglês: Hybrid nanocomposites; Eu3+ ions; Luminescence; Thermal treatment; Dopant concentration
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: https://ri.ufs.br/handle/riufs/6107

Eu3+:SiO2 PMMA hybrid nanocomposites were prepared by sol-gel process aiming to study its structure and luminescent properties. Thermal treatment and dopant concentration experimental variables were sequentially altered in order to evaluate their influences on the properties of the final material. At the start, the precursors (MPTS and MMA) were studied and the process of hybrid nanocomposites formation was analyzed by FTIR and TG techniques. As regards to thermal treatments, it was noticed that its execution at 100 and 200 °C for 3 hs don´t change significantly the basic structure of samples, behavior attested by the profile of FTIR spectra and by small variations of TG/DTG curves. There was, however, changes in silicon structures of samples (noticed at 29Si NMR spectra), besides great alterations in the sites occupied by Eu3+ ions, perceptible by photoluminescence spectroscopy. Luminescent behavior indicates a change in the symmetry of lanthanide sites caused by the temperatures imposed in thermal treatments. From the values calculated for a set of spectroscopic parameters, the symmetry change was attributed to the removal of water molecules coordinated to Eu3+ ions, which could coordinate to hybrid matrix groups and so interact stronger with it. The study of Eu3+ concentration influences showed that the higher this variable the broader some bands of FTIR spectra. TG analysis indicate an increase of sample´s residue percentage, assigned to Eu2O3 formation at high temperatures. In these samples, it was noticeable luminescence quenching caused by the increase of Eu3+ concentration, which wasn´t expected owing to the presence of silica network. It was supposed that clusters were formed when Eu3+ amount increases, decreasing Eu-host interaction and quenching the luminescence by energy transfer between Eu3+ ions.