Visible-light activate mesoporous WO3 sensors with enhanced formaldehyde-sensing property at room temperature

The formaldehyde (HCHO) sensing properties of mesoporous WO3 sensors were investigated via being activated by the visible light at room temperature. It is found that the response of the mesoporous WO3 sensors to HCHO (100 ppm) reached to 1.3 × 10−7 (Ωs)−1 under white light (100 W/m2) and 9.5 × 10−8 (Ωs)−1 under blue light (100 W/m2), respectively, which are 4 times and 9 times as much as the response of the commercial WO3, mainly due to the high surface area and the existence of the mesopores. Moreover, the response of the WO3 sensors is linearly increased with the increase of the light intensity and the formaldehyde concentration, and high humidity significantly decreases the gas sensing properties of the mesoporous WO3 under visible light. Also, compared to the sensors made by commercial WO3 material, the mesoporous WO3 sensors exhibit high sensitivity to acetone and toluene. Enhancement of the gas sensing properties of the mesoporous WO3 is attributed to the higher surface interaction rate among photoelectron, photoinduced oxygen ion and target gas.