Síntese e caracterização do compósito SnO2/TiO2 nanoestruturado
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Data
2014-06-26
Autores
Breve, Joelma Cristina de Souza [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O nanocompósito faz parte de um tipo de material o qual, apesar de ser obtido pela junção de dois ou mais materiais, não possui simplesmente a união das propriedades individuais de cada componente, mas possuui novas propriedades resultantes da interação entre as fases, justificada pela enorme interface entre estes materiais. Neste trabalho o método Poliol foi utilizado para preparar nanocompósitos SnO2/TiO2, formados de óxidos semicondutores de grande interesse no cenário atual da tecnologia sendo ambos de grande versatilidade para aplicações. Estes óxidos podem apresentar-se com uma mesma estrutura cristalina, a tetragonal do tipo rutila. Porém, apresentam diferentes estruturas eletrônicas e band gaps de energia, conferindo propriedades diferenciadas relacionadas à absorção de luz e à aplicação como sensores de gás. O compósito nanoestruturado e os óxidos sintetizados isoladamente foram caracterizados estruturalmente (DRX, FEG-MEV), por meio de análises térmicas (TG/DTA) e por espectroscopia de absorção de luz na região do ultravioleta, visível e infravermelho. As análises térmicas aliadas à difração de raios X revelaram que a síntese conjunta dos óxidos modifica o precipitado reduzindo a proporção de compostos orgânicos e intermediários e antecipando a formação das fases cristalinas do dióxido de titânio. Na análise por FEG-MEV observou-se que o compósito formado no aquecimento a 500ºC é constituído de nanoportículas de SnO2 suportados por placas maiores de TiO2 e este material, quando submetido à espectroscopia na região UV-Vis, apresentou maior absorção na região do ultravioleta. Foram realizados ensaios fotocatalíticos de descoloração do corante Rodamina B, os quais indicaram que o nanocompósitos possui atividade catalítica intermediária quando comparada aos óxidos isolados. Essa mesma amostra foi submetida a caracterizações elétricas que levaram à proposta de um modelo...
The nanocomposite is part of a class of materials which, despite being obtained by joining two or more materials, it has not simply the sum of the individual properties of resulting from the interaction between the phases, justified by the enormous interface between these materials. In the present work Polyol method was used to prepare SnO2/TiO2 nanocomposites, formed of semiconductor oxides of great interest in today's technology being of great versatility for applications. These oxides may present the same crystal structure, the tetragonal rutile type. However, they present different electronic structures and energy band gaps, giving different properties related to light absorption and application as gas sensors. The synthesized nanostructured composite as well as the isolate oxides were structurally characterized (XRD, FEG-SEM), using thermal analysis (TG/DTA), and light absorption spectroscopy within ultraviolet, visible and infrared regions. The combination of thermal analysis and X ray diffraction revealed that the simulataneous synthesis of two metals modified the precipitate, reducing the proportion of organic and intermediates compounds and anticipating the formation of crystalline phases of titanium oxides. By FEG-SEM analysis it was found that te composite treated at 500ºC consists of SnO2 nanoparticles suported by large plates of TiO2 and this material present highest uptake in the ultraviolet region. Testing photocatalytic discoloration of the dye Rhodamine B indicated that the nanocomposite has an intermediate catalytic activity when compared to the isolate oxides. The same sample was subjected to electrical characterization which led to a simplified model of electron transport in which it is assumed that the existing barrier between TiO2 particles is reduced due to the presence of SnO2 on the their surfaces
The nanocomposite is part of a class of materials which, despite being obtained by joining two or more materials, it has not simply the sum of the individual properties of resulting from the interaction between the phases, justified by the enormous interface between these materials. In the present work Polyol method was used to prepare SnO2/TiO2 nanocomposites, formed of semiconductor oxides of great interest in today's technology being of great versatility for applications. These oxides may present the same crystal structure, the tetragonal rutile type. However, they present different electronic structures and energy band gaps, giving different properties related to light absorption and application as gas sensors. The synthesized nanostructured composite as well as the isolate oxides were structurally characterized (XRD, FEG-SEM), using thermal analysis (TG/DTA), and light absorption spectroscopy within ultraviolet, visible and infrared regions. The combination of thermal analysis and X ray diffraction revealed that the simulataneous synthesis of two metals modified the precipitate, reducing the proportion of organic and intermediates compounds and anticipating the formation of crystalline phases of titanium oxides. By FEG-SEM analysis it was found that te composite treated at 500ºC consists of SnO2 nanoparticles suported by large plates of TiO2 and this material present highest uptake in the ultraviolet region. Testing photocatalytic discoloration of the dye Rhodamine B indicated that the nanocomposite has an intermediate catalytic activity when compared to the isolate oxides. The same sample was subjected to electrical characterization which led to a simplified model of electron transport in which it is assumed that the existing barrier between TiO2 particles is reduced due to the presence of SnO2 on the their surfaces
Descrição
Palavras-chave
Dioxinas, Estanho, Dióxido de titânio, Materiais nanoestruturados - Propriedades opticas, Eletrons - Transporte, Dioxins
Como citar
BREVE, Joelma Cristina de Souza. Síntese e caracterização do compósito SnO2/TiO2 nanoestruturado. 2014. 118 f. Dissertaçao (mestrado) - Universidade Estadual Paulista Julio de Mesquita Fiho, Faculdade de Ciências, 2014.