The synthesis of VO2(B) ultrathin nanosheets array and effects of optical radiation on room temperature NO2 gas sensing performance

Nitrogen dioxide (NO2) seriously endangers human health. Metal oxide semiconductor sensors typically suffer from long response/recovery time. A vanadium dioxide (VO2(B)) nanosheets structure at the Debye scale was proposed to reduce the response/recovery times by illumination. The experimental results show that VO2(B) ultrathin nanosheets array are obtained at temperature of 160 degrees C. The NO2 sensing performance of VO2(B) ultrathin nanosheet arrays was investigated at room temperature under the conditions of no light, 254 nm and 365 nm ultraviolet light, visible light and infrared light. At room temperature, the response of the sensor to 5 ppm NO2 was up to 2.03. The response/recovery time of the sensor under dark and UV irradiation were 21 s/157 s and 2 s/12 s, respectively. Response time reduced to one-tenth and recovery time reduced to one-thirteenth. This is mainly due to that ultraviolet light can provide energy for the adsorption and desorption of NO2 and accelerate the response and recovery speed. However, light activation deteriorates the sensitivity of the sensor when the photon energy is higher than the band gap. This is a result of the synergistic effect of the ultrathin properties of the VO2(B) nanosheets as well as the n-p conversion properties, resulting in the inability to additionally excite more electrons by UV irradiation. This work paves a novel avenue in developing high performance gas sensor based on n-p inversion metal oxide materials.