Aluminato de lantânio no planejamento de sistemas core@shell luminescentes funcionalizados contendo os íons Eu3+ e Tb3+ para aplicação em dispositivos conversores de luz
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Data
2019-03-01
Autores
Garcia, Alessandro Bruno Silva
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho desenvolveu-se novos materiais híbridos inorgânico-orgânico do tipo multi shell com potencial aplicação em dispositivos conversores de luz. Como componente inorgânico utilizou-se um sistema do tipo core/shell composto por LaAlO3 dopado com Tb3+ como core, uma primeira camada de óxido de lantânio dopado com Eu3+ e uma segunda camada de SiO2 aminofuncionalizada. A matriz aluminato de lantânio foi preparada a partir da metodologia Pechini modificado, sendo que um estudo sistemático variando a porcentagem de dopante foi realizado, tanto para dopagem com Tb3+ quanto com Eu3+, determinando-se a concentração ótima como sendo 9% e 11%, respectivamente. O recobrimento com SiO2 aminofuncionalizada, por sua vez, foi realizado via método Stöber modificado. A partir de reação dos grupos amino na superfície da sílica houve o ancoramento de bases de Schiff as quais foram coordenadas ao íon terra rara (Eu3+); moléculas de água desativadoras da luminescência coordenadas aos íons metálicos foram então substituídas por ligantes do tipo βdicetonas. Todas as etapas envolvidas na preparação dos sistemas híbridos foram monitoradas por técnicas de caracterizações elucidativas e adequadas a cada sistema, tais como análises térmica, difração de raios X, microscopia eletrônica de varredura e de transmissão, espectroscopia vibracional de absorção na região do IV e luminescência. A metodologia Pechini produziu com sucesso os sistemas multishell planejados, sendo o híbrido final constituído de um core de aluminato de lantânio dopado a 5% com térbio(III) com diâmetro médio entre 20 a 60 nm, recoberto com duas camadas de natureza não cristalina dopada com európio(III) também a 5%, e por fim uma camada de sílica aminofuncionalizada a 5% com espessura total de quase 2 nm. A presença de Eu3+ na camada e Tb3+ no core viabilizou a modulação de cor conforme a excitação. Já a funcionalização e ancoramento de complexos com Eu3+ foi também bem sucedida, sendo possível detectar emissões do sistema core@shell e também do complexo ancorado. Desta forma os materiais produzidos são promissores para aplicação em dispositivos emissores de luz.
In this work, new multi shell type inorganic-organic hybrids with potential application in light converters were developed. As an inorganic component, a core@shell system composed of LaAlO3 doped with Tb3+ as core, a first layer of lanthanum oxide doped with Eu3+ and a second layer of aminofunctionalized SiO2 was used. The lanthanum aluminate matrix was prepared from the modified Pechini methodology, and a systematic study of the percentage of dopant was performed for both Tb3+ and Eu3 + doping, and the optimum concentration was determined to be 9% and 11%, respectively. The amino functionalized SiO2 coating, in turn, was performed by the modified Stöber method. From the reaction of the amino groups on the surface of the silica there was the anchoring of Schiff bases which were coordinated to the rare earth ion (Eu3+); water molecules coordinated to the metal ion were then replaced by β-diketone type ligand. All steps involved in the preparation of the hybrid systems were monitored by suitable characterization techniques appropriated to each system, such as thermal analysis, X-ray diffraction, scanning and transmission electron microscopy, vibration absorption spectroscopy in the IR region and photoluminescence. The Pechini methodology successfully produced the planned multishell systems, the final hybrid consisting of a lanthanum aluminate 5% doped with terbium(III) as core with an average diameter between 20 and 60 nm, covered with two non-crystalline layers doped with 5% of europium(III), and finally a 5% aminofunctionalized silica layer with a total thickness of almost 2 nm. The presence of Eu3+ in the shell and Tb3+ in the core facilitated the modulation of color according to the excitation. The functionalization and anchoring of complexes with Eu3+ was also successful, being possible to detect emissions of the core@shell system and also of the anchored complex. In this way, the materials produced are promising for application in light emitting devices.
In this work, new multi shell type inorganic-organic hybrids with potential application in light converters were developed. As an inorganic component, a core@shell system composed of LaAlO3 doped with Tb3+ as core, a first layer of lanthanum oxide doped with Eu3+ and a second layer of aminofunctionalized SiO2 was used. The lanthanum aluminate matrix was prepared from the modified Pechini methodology, and a systematic study of the percentage of dopant was performed for both Tb3+ and Eu3 + doping, and the optimum concentration was determined to be 9% and 11%, respectively. The amino functionalized SiO2 coating, in turn, was performed by the modified Stöber method. From the reaction of the amino groups on the surface of the silica there was the anchoring of Schiff bases which were coordinated to the rare earth ion (Eu3+); water molecules coordinated to the metal ion were then replaced by β-diketone type ligand. All steps involved in the preparation of the hybrid systems were monitored by suitable characterization techniques appropriated to each system, such as thermal analysis, X-ray diffraction, scanning and transmission electron microscopy, vibration absorption spectroscopy in the IR region and photoluminescence. The Pechini methodology successfully produced the planned multishell systems, the final hybrid consisting of a lanthanum aluminate 5% doped with terbium(III) as core with an average diameter between 20 and 60 nm, covered with two non-crystalline layers doped with 5% of europium(III), and finally a 5% aminofunctionalized silica layer with a total thickness of almost 2 nm. The presence of Eu3+ in the shell and Tb3+ in the core facilitated the modulation of color according to the excitation. The functionalization and anchoring of complexes with Eu3+ was also successful, being possible to detect emissions of the core@shell system and also of the anchored complex. In this way, the materials produced are promising for application in light emitting devices.
Descrição
Palavras-chave
Terra rara, Base de schiff, Caroço-casca, Aluminato de lantânio, Hibrido inorgânico-orgânico, Rare earths, Schiff base, Core-Shell, Lanthanum aluminate, Inorganic-organic hybrid