Fabrication of highly selective NO2 gas sensor for low ppm detection

Nitrogen dioxide (NO
2
) is one of the most harmful and highly toxic gas, and it is continuously released into the environment from automotive emissions, industrial emissions, and agriculture activities. According to the American Conference of Governmental Industrial Hygienists (ACGIH), the threshold limit value (TLV) of NO
2
is up to 3 ppm for 8 h time-weighted average and 5 ppm for 15 min period. Therefore, the efficient detection of low concentration of NO
2
gas is significant for monitoring human health in the near above-mentioned sources. In this aspect, transition metal dichalcogenides (TMDs) based gas sensor holds a promising potential for detecting the toxic gas due to their inherent properties such as, high surface to volume ratio and small intrinsic dimension. Among TMDs, tin disulfide (SnS
2
) has become a promising sensing material in gas sensing applications, owing to its physical affinity, planar crystal structure, and high specific surface area. Herein, SnS2 was synthesized by hydrothermal method and characterized by X-ray diffraction (XRD) and Raman spectroscopy. Subsequently, the chemiresistive gas sensor was fabricated by depositing SnS
2
on the glass substrate which has gold (Au) interdigitated electrode pattern. The fabricated sensor was explored for detecting various gases such as CO, CO
2
, SO
2
, NH
3
, and NO
2
at different temperatures (27°C, 60°C, 100°C, 150°C, 200°C, and 250°C) and a maximum response of 24.5% was obtained for 6 ppm NO2 gas at a temperature of 100°C, which demonstrates that the sensor is a highly selective among the other gases. Furthermore, the sensor was utilized to detect the range of NO
2
concentrations from 1.5 ppm to 6 ppm at an optimum temperature of 100°C and the results revealed that the experimental detection limit is 1.5 ppm, and the response of the sensor was also observed to be a power law behavior. In addition, the plausible sensing mechanism was explored by use of surface charge transfer to NO
2
gas and energy barrier modulation at the surface of SnS
2
.