WS2 coating and Au nanoparticle decoration of ZnO nanorods for improving light-activated NO2 sensing

ZnO-based heterogenous nanostructures are considered as excellent active materials for fabricating highly sensitive and selective gas sensors. In this work, nanocomposite WS2/Au/ZnO nanorods were synthesized by covering WS2 thin coatings on the surface of ZnO nanorods and embedding Au nanoparticles between the WS2 coatings and the ZnO nanorods, and the light activated sensing performance of the sensor using the WS2/Au/ZnO nanorods as the sensing material was evaluated. With an average ZnO nanorod diameter of 60 nm, WS2 coating thickness of 10 nm, and Au nanoparticle diameter of 5 nm, the WS2/Au/ZnO nanorods present high photoactivity because of widened photoresponse region, increased light absorption, and quenched photoluminescence. The performance for sensing NO2 gas of the WS2/Au/ZnO nanorod-based sensor under 365, 455 or 655 nm light activation was compared with that of a bare ZnO nanorod-based sensor. The WS2/Au/ZnO nanorod-based sensor exhibits better sensing performance than the bare ZnO nanorod-based sensor under 365 or 455 light activation, with the response to 20 ppm NO2 of the former 40% higher than that of the latter. The improved sensing performance is attributed to the co-sensitization of semiconductors and metals.