Highly sensitive and selective NO2 sensor based on Au-impregnated WO3 nanorods

In this work, Au-impregnated WO3 nanorods with high-aspect-ratio were synthesized by a modified precipitation/impregnation method and systematically investigated for NO2 detection. 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 WO3 nanorods. WO3 sensing films with varying Au loading levels from 0 to 2 wt% fabricated by powder pasting and spin coating were tested towards NO2 over operating temperatures ranging from 25 to 350 degrees 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 WO3 sensing film exhibited the highest response of 836.6 with response time of 64.2 s to 5 ppm NO2 at the optimal operating temperature of 250 degrees C. Moreover, the sensor displayed high NO2 selectivity against NO, N2O, C-2 H-5 OH, CO, NH3, SO2 and H-2. 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 WO3 nanorods. Therefore, the Au-impregnated WO3 nanorods are highly potential for sensitive and selective NO2 detection. (C) 2017 Elsevier B.V. All rights reserved.