Ppb-level NO2 gas sensor based on WO3/In2S3 heterostructure by hydrothermal method: A convenient and wearable real-time detection system

Constructing heterostructures is an effective strategy to improve the performance of semiconductor metal oxide. The heterostructure exhibits strong interaction between tightly packed interfaces, showing better performance than a single structure. Therefore, indium sulfide (In2S3)/tungsten oxide (WO3) composites were synthesized with heterojunction by a simple hydrothermal method to enhance the gas sensing performance of WO3. The WO3 and In2S3 exist in the form of nanoparticles. Then the gas sensing test of the material was carried out, by exploring the performance of WO3 based on doping different amounts of In2S3, the response of WO3 based on 3 wt% In2S3 to 10 parts per million (ppm) nitrogen dioxide (NO2) is 170.1 at the optimum operating temperature of 170 °C. Compared with pure WO3, the response is enhanced by seven times. Besides, the detection limit of the sample is low. The minimum detection concentration of NO2 can reach 20 parts per billion (ppb). The reason for the improved performance can be attributed to the wider electron depletion layer or hole accumulation layer formed by the heterojunction for electron transfer. Finally, a convenient wearable NO2 Real-time Detection System is designed to detect different concentrations of NO2 in the factory, which provides an effective alarm mean for the excessive emission of industrial waste gas in the factory environment.