Selective H<inf>2</inf>S gas sensors based on ohmic hetero-interface of Au-functionalized WO<inf>3</inf> nanowires

Abstract

In this present study, the fabricated sensors based on WO3 nanowires sensing films were grown by thermal oxidation method on the alumina substrates in single step and subsequently functionalized with gold nanoparticles, an excellent catalyst for gas-sensing reactions, by RF magnetron sputtering with different sputtering time of 2, 5, 10 and 15 s. Structural characterizations of sensing films by electron microscopy and X-ray analysis revealed that 5–15 nm Au nanoparticles with a single metallic state decorated the highly crystalline 20–30 nm WO3 nanowires with a monoclinic structure. The effect of Au sputtering time on gas sensing properties of WO3 sensors was systematically tested towards H2S, CO, NO2 and acetone, with different working temperatures ranging from 250 to 400 °C in dry air and humidity effects. It was found that an optimal Au sputtering time of 10 s led to significant enhancement of H2S-sensing performances compared with other tested gases. Particularly, the optimal Au-functionalized WO3 sensing film exhibited the highest response of 219 to 5 ppm H2S with the detection limit of 0.17 ppb at the optimal working temperature of 350 °C and a relative humidity of 50% (@20 °C). Therefore, the Au-functionalized WO3 nanowires are highly potential for selective H2S detection.