Sensors based on CeO2 and reduced graphene oxide/CeO2 for the detection of CO2 or volatile organic compounds

Author(s)

Cecilia de Almeida Zito

• Document type: Doctoral Thesis
• Press: São José do Rio Preto. 2021-12-17.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2021-12-01
• Advisor: Diogo Paschoalini Volanti

Abstract

In this study, the effect of morphological control and modification with reduced graphene oxide (RGO) were evaluated on the properties of CeO2 nanostructures as chemoresistive sensors for the detection of CO2 or volatile organic compounds (VOCs). The materials were synthesized by the microwave-assisted hydro/solvothermal method and were further characterized by the techniques of X-ray diffraction, scanning and transmission electron microscopy, infrared spectroscopy, Raman spectroscopy, specific surface area analysis, X-ray photoelectron spectroscopy, and pair distribution function analysis obtained by total X-ray scattering. The detection of CO2 was performed by using the hollow yolk-shell CeO2 nanospheres to evaluate the effect of morphological control on the material’s sensing properties. The tests were carried out at 100 °C and in relative humidity (RH) between 30 and 70%. It was found that hollow CeO2 nanospheres exhibited greater sensitivity to CO2, higher stability, reversibility, and faster responses than commercial CeO2 nanoparticles. Such improvements could be attributed to the hollow and porous structure, which allows for greater diffusion of gases and higher surface area. Thus, the positive effect of morphological control on the superior performance of the CO2 sensor was shown. The tests as VOC sensors were conducted for pure CeO2 nanospheres and RGO/CeO2 nanocomposites containing different concentrations of RGO to study the impact of the modification of CeO2 with RGO. The studies were carried out at room temperature (23.7 °C) and RH between 34 and 70%. All sensors were more sensitive and selective for triethylamine when compared to other VOCs. However, the RGO/CeO2 nanocomposites showed an increase in sensitivity and selectivity compared to pure CeO2 nanospheres, showing that the modification with RGO can also be used to improve the performance of CeO2-based sensor. Thus, this study presents two different approaches to obtain sensors based on CeO2 that are highly sensitive to CO2 and VOCs, which operate under conditions of low temperatures and in the presence of humidity. (AU)

• FAPESP's process: 16/25267-8 - Graphene acid composites with hollow CeO2 and Pd-CeO2 yolk-shell structures applied as volatile organic compounds sensors
• Grantee: Cecilia de Almeida Zito
• Support Opportunities: Scholarships in Brazil - Doctorate