In2O3/g-C3N4/Au ternary heterojunction-integrated surface plasmonic and charge-separated effects for room-temperature ultrasensitive NO2 detection

Light-activated gas sensors based on semiconducting metal oxides (SMOs) hold great promise for next-generation gas sensing application, due to their unique superiority including room-temperature operation, intrinsic safety, and simple device structure. However, poor visible-light absorption and fast carrier recombination of SMOs sensing film are two main barriers that seriously restrict their sensing performance of light-activated gas sensors. Herein, a visible-light activated gas sensor based on Au nanoparticles modified In2O3/g-C3N4 heterojunction nanofibers is developed. Excellent sensing response (Rg/Ra = 17.2 to 1 ppm NO2, where Ra and Rg represent the resistance of sensors when exposed to air or target gas) and fast response/recovery kinetics at room temperature are obtained, which is markedly better than the sensors based on pristine In2O3 nanofibers and In2O3/g-C3N4 nanofibers. Through the discussion and estimation of experimental results, the improved gas sensing properties of In2O3/g-C3N4/Au-based sensors are speculated to be related to the enhanced visible light utilization benefiting from localized surface plasmon resonance (LSPR) effect of Au nanoparticles, and the efficient separation of photo-generated carriers enabled by heterojunctions between In2O3, Au, and g-C3N4 components. The current work will provide a universal strategy to develop high-performance light-activated gas sensor and a deep understanding about the sensing principle of this novel type of gas sensor.