Modulação das propriedade ópticas de semicondutores pela incorporação de íons terras raras
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Data
2013-06-11
Autores
Souza, Glenda Gonçalves de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
ZnO tem sido extensivamente estudado devido à sua importância como semicondutor, suas inúmeras aplicações, alta abundância natural, baixo custo e alta estabilidade química e térmica. Desta forma, neste trabalho preparou-se este semicondutor contendo diferentes concentrações de Eu(III) para produzir sistemas do tipo Core/Shell no intuito de investigar e modular suas propriedades ópticas, morfológicas e estruturais com especial interesse nas propriedades elétricas (bandgap) dos sistemas obtidos, visando aplicação em dispositivos ópticos e/ou sensores químicos. Realizou-se a sistematização da metodologia via método Pechini, onde se conseguiu estabelecer uma rotina de preparo das partículas Core/Shell a partir de um controle do pH do meio para comparação com o ZnO puro. Foram obtidos três tipos de amostras, dois deles iniciando-se o recobrimento de ZnO com sucessivas camadas de Eu2O3 em 2 e 4%, respectivamente, até quatro camadas, e um terceiro tipo onde as camadas foram intercaladas entre ZnO e Eu 2O3 mantendo-se a porcentagem de 2%, até completar 3 camadas. Análises de difração de raios X confirmaram a formação das fases dos óxidos de Zn e de Eu e os parâmetros obtidos indicaram que a rede deve estar sendo comprimida com a inserção de camadas. Combinando resultados de luminescência e de difração de raios X verificou-se que o Eu(III) deve estar ocupando um retículo cristalino com simetria cúbica distorcida, além de ser muito pouco provável a transferência de energia ZnO → Eu. Já se comparando dados de luminescência com os de reflectância difusa observou-se a provável formação das camadas externas (aumento da concentração de Eu(III) após cada recobrimento) e diminuição da intensidade relativa de emissão devido ao efeito quenching ou supressão por concentração, permanecendo em todos os...
ZnO has been extensively studied because of its importance as a semiconductor, its many applications, high natural abundance, low cost and high chemical and thermal stability. Thus, in this work this semiconductor was prepared containing different concentrations of Eu(III) to produce Core/Shell type systems in order to investigate and modulate their optical properties, morphology and structure with special interest in the electrical properties (bandgap) of the obtained systems aiming their application in optical and/or chemical sensors. The methodology systematization via Pechini method was performed whereas a routine of Core/Shell particles preparation was established using a pH control for comparison with the pure ZnO. Three kinds of samples were obtained, two of them initiating the coating of successive layers of ZnO with Eu 2O3 2 and 4%, respectively, up to four layers, and a third type with the intercalation of layers between ZnO and Eu 2O3 maintaining the percentage of 2% until 3 layers. X-ray diffraction analysis confirmed the formation of the Zn and Eu oxides phases and the parameters obtained indicated that the network must be being compressed by inserting layers. Combining the luminescence and X-ray diffraction results it was showed that the Eu(III) must be occupying a distorted cubic symmetry crystal lattice, and also that it is very unlikely energy transfer between ZnO→Eu(III). The comparison among luminescence and diffuse reflectance data revealed the probable formation of the outer layers (increasing the concentration of Eu(III) after each coating) and reduced relative emission intensities due to the effect of concentration quenching, remaining in all systems studied the characteristic of semiconductor. SEM images showed that with the increase of the layers the coating occurs on the surface of the clusters... (Complete abstract click electronic access below)
ZnO has been extensively studied because of its importance as a semiconductor, its many applications, high natural abundance, low cost and high chemical and thermal stability. Thus, in this work this semiconductor was prepared containing different concentrations of Eu(III) to produce Core/Shell type systems in order to investigate and modulate their optical properties, morphology and structure with special interest in the electrical properties (bandgap) of the obtained systems aiming their application in optical and/or chemical sensors. The methodology systematization via Pechini method was performed whereas a routine of Core/Shell particles preparation was established using a pH control for comparison with the pure ZnO. Three kinds of samples were obtained, two of them initiating the coating of successive layers of ZnO with Eu 2O3 2 and 4%, respectively, up to four layers, and a third type with the intercalation of layers between ZnO and Eu 2O3 maintaining the percentage of 2% until 3 layers. X-ray diffraction analysis confirmed the formation of the Zn and Eu oxides phases and the parameters obtained indicated that the network must be being compressed by inserting layers. Combining the luminescence and X-ray diffraction results it was showed that the Eu(III) must be occupying a distorted cubic symmetry crystal lattice, and also that it is very unlikely energy transfer between ZnO→Eu(III). The comparison among luminescence and diffuse reflectance data revealed the probable formation of the outer layers (increasing the concentration of Eu(III) after each coating) and reduced relative emission intensities due to the effect of concentration quenching, remaining in all systems studied the characteristic of semiconductor. SEM images showed that with the increase of the layers the coating occurs on the surface of the clusters... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Química inorgânica, Nanotecnologia, Semicondutores, Espectroscopia de luminescencia
Como citar
SOUZA, Glenda Gonçalves de. Modulação das propriedade ópticas de semicondutores pela incorporação de íons terras raras: . 2013. 101 f. Dissertação (mestrado) - Universidade Estadual Paulista Julio de Mesquita Filho. Instituto de Biociências, Letras e Ciências Exatas, 2013.