Ultrasensitive ammonia sensor with excellent humidity resistance based on PANI/SnS2 heterojunction

The analysis of human exhaled gas is crucial for early and noninvasive diagnosis. However, the complex composition and high-humidity of exhaled gas pose significant challenges to the application of gas sensors. This research focuses on the development of a chemiresistive ammonia sensor based on the polyaniline/tin disulfide (PANI/SnS 2 ) heterojunction, which is fabricated by hydrothermal and in-situ polymerization techniques. The sensor demonstrates significantly enhanced gas sensing capabilities manifested by increased responsiveness, improved selectivity, and stability for detecting 0.5–100 ppm ammonia at ambient temperature. Notably, the sensor exhibits a marked enhancement in response at high humidity levels. When exposed to 30 ppm of ammonia, the sensor's response value increases by 167 % at a relative humidity (RH) of 80 %, compared to 128 % at 50 % RH. This significant improvement can be attributed to the unique interaction between water molecules and the sensor material, which enhances the overall charge transfer processes at the PANI/SnS 2 interface. Furthermore, in-situ techniques as well as theoretical calculations are utilized to gain insight into the sensitization mechanism. The proposed PANI/SnS 2 heterojunction sensor shows great promise for applications in high-humidity environment at ambient temperature.