Reduced graphene oxide-WO3 and Ag-WO3 sensors obtained by microwave-assisted ultrasonic spray and deposited on flexible substrates for the detection of volatile organic compounds

Author(s)

Tarcísio Micheli Perfecto

• Document type: Master's Dissertation
• Press: São José do Rio Preto. 2018-03-23.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2018-03-05
• Advisor: Diogo Paschoalini Volanti

Abstract

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. (AU)

• FAPESP's process: 16/04371-1 - Sensors based on reduced graphene oxide-WO3 and Ag-WO3 obtained by microwave-assisted ultrasonic spray and deposited on paper for detection of volatile organic compounds
• Grantee: Tarcísio Micheli Perfecto
• Support Opportunities: Scholarships in Brazil - Master