Desenvolvimento de heteroestruturas derivadas do óxido de tungstênio para sensores de gases

Abstract

This work explored the synthesis of materials derived from metal oxides and sulfides for applications in gas sensor devices. The focus was on studying how the introduction of heterojunctions can alter the sensor response of the material to analytes in the gas phase. Specifically, the modification of materials derived from tungsten oxide (WO3) with tin sulfide (SnS2) phases. To analyze the effect of this modification in a sensor device, the responses to gases H₂ (flammable), CO, NO₂ (toxic), and acetone (a known biomarker for diseases) were examined. The materials analyzed demonstrated high selectivity for NO₂, especially at high concentrations (50/100 ppm), with particular emphasis on the SnS₂/WO₃ (10:1) material, which achieved a sensor response of 1995 at 100°C. For gases such as H₂ and acetone, significant responses were observed at higher temperatures (300°C), while carbon monoxide (CO) showed low sensitivity across all materials. A thermal treatment was also applied to the materials to study whether there would be any changes in their overall behavior. Although the thermal treatment enhanced the sensor response for some materials, such as SnS₂/WO₃ (1:10) in acetone detection, it also brought disadvantages. At certain temperature ranges, there was a loss of sensor response, as observed in SnS₂/WO₃ (10:1) at 100°C. Furthermore, the presence of the heterojunction influenced the response and recovery times. For acetone, some materials exhibited significantly longer recovery times, while others reduced these times compared to the seed material.