High performance methane gas sensor based on the heterojunction of RGO/TiO₂ on SiNWs

This study demonstrates the development of a highly responsive sensor based on heterojunction of reduced graphene oxide (RGO) and titanium dioxide (TiO₂) on silicon nanowires (SiNWs) on a Si chip for the selective detection of methane (CH₄) as a toxic gas. In this work, SiNWs on a Si chip were prepared using a metal assisted chemical etching (MACE) process. RGO nanosheets were synthesized using modified Hummers’ method whereas TiO₂ nanoparticles were prepared using a hydrothermal technique. Various characterization techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD) and Ultraviolet–visible spectrophotometer, were employed to analyze the prepared materials. The gas sensing characteristics of the developed sensor were recorded at room temperature where the sensitivity of the sensor was measured to be 67.8% over the 0 to 2 ppm concentration range of CH₄ gas. Specifically at 1 ppm concentration of CH₄ gas, the sensor exhibited a good sensing response of 1.6, with response-recovery times of 4 s and 9.3 s, respectively. The sensor demonstrated high reproducibility under exposure to five ON/OFF cycles of CH₄ gas. It was also tested against different interfering gases and was observed to be highly selective toward CH₄. The high performance of the sensor may be attributed to the precise interaction of the analyte at the interface of the heterojunction formed by RGO/TiO₂@SiNWs on the Si chip. Consequently, this sensor offers continuous monitoring capability for CH₄ gas at low concentrations, reducing the risk of undesirable incidents. This study highlights the importance of safety measures, such as the implementation of advanced gas-detection technologies, particularly to mitigate explosion risks in sewer systems.