Highly sensitive and selective NO<inf>2</inf>sensor based on Au-impregnated WO<inf>3</inf>nanorods

Abstract

© 2017 Elsevier B.V. In this work, Au-impregnated WO3nanorods with high-aspect-ratio were synthesized by a modified precipitation/impregnation method and systematically investigated for NO2detection. Characterizations by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy revealed the formation of 5–20 nm spherical and oval Au nanoparticles loaded on the surface of polycrystalline WO3nanorods. WO3sensing films with varying Au loading levels from 0 to 2 wt% fabricated by powder pasting and spin coating were tested towards NO2over operating temperatures ranging from 25 to 350 °C. It was found that an optimal Au loading of 0.5 wt% led to significant enhancement of NO2-sensing performances. In particular, the optimal Au-loaded WO3sensing film exhibited the highest response of 836.6 with response time of 64.2 s to 5 ppm NO2at the optimal operating temperature of 250 °C. Moreover, the sensor displayed high NO2selectivity against NO, N2O, C2H5OH, CO, NH3, SO2and H2. The observed enhancement could be attributed to the formation of metal-semiconductor ohmic junctions and electronic sensitization effects of Au nanoparticles on the porous network of WO3nanorods. Therefore, the Au-impregnated WO3nanorods are highly potential for sensitive and selective NO2detection.