In₂O₃–ZnO/Laser-Induced Graphene Nanocomposites for a Highly Sensitive, Room-Temperature, Flexible Methane Gas Sensor

Real-time monitoring of methane can alert for explosion or health issues, but it is still difficult to detect methane with high sensitivity and low detection limit at room temperature. This work reports a highly sensitive room-temperature methane gas sensor based on heterojunction nanocomposites between n-type indium–zinc oxide (In 2 O 3 –ZnO) and p-type porous laser-induced graphene (LIG) prepared by laser direct writing and facile spray coating. The resulting In 2 O 3 –ZnO/LIG-based methane gas sensor exhibits a large response of −27.48% to 500 ppm methane room temperature, a fast response/recovery time of 48/169 s, and an experimentally demonstrated ultralow detection limit of 3 ppm. After confirming the stable response over 9 days and against bending with a radius of curvature down to 10 mm, the In 2 O 3 –ZnO/LIG gas sensors are further combined with a wireless powering and transmitting module into an integrated methane gas sensing device to wirelessly detect methane in real time for early warning and safe evacuation in mining and fertilizer plants.