Sensores à base de óxido de grafeno reduzido-WO3 e Ag-WO3 obtidos por spray ultrassônico assistido por micro-ondas e depositados em substratos flexíveis para detecção de compostos orgânicos voláteis
Carregando...
Data
2018-03-05
Autores
Perfecto, Tarcísio Micheli
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O presente trabalho estuda a influência da combinação dos métodos de nebulização por spray ultrassônico (NSU) e hidrotérmico assistido por microondas (HAM) para a síntese de materiais com fase cristalina ortorrômbica de WO3·0.33H2O e de seus compósitos com nanopartículas de prata ou óxido de grafeno reduzido (RGO), na proporção de 1, 5 e 10% em massa em relação a WO3·0.33H2O, sendo aplicados como sensores para diferentes compostos orgânicos voláteis, em destaque isopropanol, na faixa de partes por milhão (ppm). As amostras sintetizadas foram caracterizadas por difratometria de raios X (DRX), espectroscopia na região do infravermelho com transformada de Fourier (FTIR), análise termogravimétrica (TG), microscopia eletrônica de varredura com canhão de emissão de campo (FEG-MEV) e microscopia eletrônica de transmissão (MET). Os resultados de DRX, FEG-MEV e MET ajudaram a compreender o mecanismo de formação e crescimento dos materiais, bem como sua pureza. Com as técnicas TG e FTIR, foi possível estudar a estabilidade térmica dos materiais, bem como verificar a presença do RGO nos materiais. Para estudar o desempenho dos materiais como sensor, foi realizada a confecção de eletrodos interdigitais em polietileno tereftalato (PET), e a deposição dos materiais nesses eletrodos. Os materiais foram expostos a acetona, etanol, isopropanol, ácido acético e metanol, para determinar sua seletividade. Os materiais apresentaram boa seletividade para isopropanol. Foi realizado teste de sensibilidade dos materiais expondo-os a isopropanol em uma faixa de concentração de 1 – 200 ppm em condições de temperatura ambiente e 55% U.R. (umidade relativa). Pode-se concluir que o compósito 5%-RGOWO3 ·0.33H2O apresentou a maior sensibilidade, com resposta (Resistênciavoc/Resistênciaar) de 1,2 para 1 ppm e de 8,6 para 200 ppm e que o compósito 1%-Ag-WO3·0.33H2O apesar de apresentar sensibilidade inferior ao compósito de RGO (1,13 para 1 ppm e 5,97 para 200 ppm), apresentou a melhor seletividade frente a diferentes VOCs.
The present work studies the influence of a combination of the ultrasonic spray nozzle (USN) and microwave-assisted hydrothermal (MAH) methods for the formation of new materials with the single orthorhombic crystalline phase of WO3·0.33H2O. The composites of this materials with silver or reduced graphene oxide(RGO) was studied, in the proportion of 1, 5 and 10% by mass in relation to the material. The materials (WO3·0.33H2O, RGO-WO3·0.33H2O, and Ag- WO3·0.33H2O) was applied as sensors for different volatile organic compounds, in particular, isopropanol, in the parts per million (ppm) range. The synthesized samples were characterized by X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The results of XRD, FE-SEM and TEM helped to understand the growth mechanism of the material as well as their purity. With the TG and FTIR techniques, it was possible to study the thermal stability of the materials, as well as to verify the presence of the RGO in the materials. To investigate the performance of the materials as a sensor, we made the interdigital electrodes in polyethylene terephthalate (PET), and the deposition of the materials in these electrodes. The materials were exposed to acetone, ethanol, isopropanol, acetic acid and methanol to determine their selectivity. The materials showed good selectivity for isopropanol. Sensitivity testing of the materials was carried out by exposing them to isopropanol in a concentration range of 1 - 200 ppm at ambient temperature and 55% U.R. It can be concluded that the composite of 5%-RGOWO3 ·0.33H2O presented the highest sensitivity, with a response of 1.2 to 1 ppm and 8.6 to 200 ppm. The composite of 1%-Ag-WO3·0.33H2O despite having lower sensitivity to RGO composite (1.13 to 1 ppm and 5.97 to 200 ppm), showed the best selectivity against different VOCs.
The present work studies the influence of a combination of the ultrasonic spray nozzle (USN) and microwave-assisted hydrothermal (MAH) methods for the formation of new materials with the single orthorhombic crystalline phase of WO3·0.33H2O. The composites of this materials with silver or reduced graphene oxide(RGO) was studied, in the proportion of 1, 5 and 10% by mass in relation to the material. The materials (WO3·0.33H2O, RGO-WO3·0.33H2O, and Ag- WO3·0.33H2O) was applied as sensors for different volatile organic compounds, in particular, isopropanol, in the parts per million (ppm) range. The synthesized samples were characterized by X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The results of XRD, FE-SEM and TEM helped to understand the growth mechanism of the material as well as their purity. With the TG and FTIR techniques, it was possible to study the thermal stability of the materials, as well as to verify the presence of the RGO in the materials. To investigate the performance of the materials as a sensor, we made the interdigital electrodes in polyethylene terephthalate (PET), and the deposition of the materials in these electrodes. The materials were exposed to acetone, ethanol, isopropanol, acetic acid and methanol to determine their selectivity. The materials showed good selectivity for isopropanol. Sensitivity testing of the materials was carried out by exposing them to isopropanol in a concentration range of 1 - 200 ppm at ambient temperature and 55% U.R. It can be concluded that the composite of 5%-RGOWO3 ·0.33H2O presented the highest sensitivity, with a response of 1.2 to 1 ppm and 8.6 to 200 ppm. The composite of 1%-Ag-WO3·0.33H2O despite having lower sensitivity to RGO composite (1.13 to 1 ppm and 5.97 to 200 ppm), showed the best selectivity against different VOCs.
Descrição
Palavras-chave
Grafeno, Micro-ondas, Trióxido de tungstênio, Spray ultrassônico, Sensores flexíveis, Diagnóstico de baixo custo, Graphene, Microwave, Tungsten trioxide, Ultrasonic spray, Flexible sensors, Low cost diagnostics