Ultrasensitive NO₂ Gas Sensor at Room Temperature Based on a Glycerol-Cross-Linked PEDOT:PSS-MoS₂ Nanocomposite

Nitrogen dioxide (NO2) is a tremendously toxic environmental pollutant that can be lethal to humans and extremely dangerous to the environment. NO2, being a highly volatile gas, undergoes photochemical reactions that can cause acid rain or generate ozone. Exposure to extremely low concentrations of NO2 can severely impact human health, primarily damaging lung tissues. Thus, fabricating highly sensitive and portable sensors for room-temperature detection of NO2 gas with a very low response/recovery time is extremely important for environmental monitoring and human safety. To address the above challenges, we have fabricated an extremely sensitive and highly selective NO2 gas sensor based on a glycerol-cross-linked PEDOT:PSS/MoS2 nanocomposite using two-dimensional MoS2 nanosheets. The deposition of the gas sensor over the substrate was facilitated by increasing the roughness of the substrate and the adhesion of the conducting polymeric films. Increased roughness facilitated better gas adsorption, which in turn increased the gas sensing capacity of the sensor. Three different nanocomposites were prepared using different concentrations of MoS2 nanosheets, and the sensor with the greatest responsivity to NO2 gas was optimized. The sensor material showed an N-type semiconducting behavior in the presence of NO2 gas with swift response and recovery times of 10.2 and 5.5 s in the presence of 100 ppb NO2 gas. The fabricated gas sensor gave a superior response to extremely low concentrations of NO2 gas even at room temperature. The sensor showed a response of 500.3% to 50 ppm of NO2 and 22.1% to 100 ppb of NO2 gas, and the detection limit was 40.02 ppb. The highly selective sensor shows a zero or very low response toward other oxidizing/reducing gases. Moreover, room-temperature gas sensing is an additional advantage because it reduces the power consumption of the device. The large surface area of the polymeric nanofilms is proposed to help enhance the charge transfer phenomenon between the N-type electron-rich semiconductor and the electron-accepting oxidizing gas, resulting in their excellent gas-sensing performance. This study proposes potential semiconducting nanostructured sensor materials with prospects for real-time NO2 detection for human protection and environmental safety.