Ultrasensitive and light-activated NO2 gas sensor based on networked MoS2/ZnO nanohybrid with adsorption/desorption kinetics study

In this work, a high-performance room temperature NO2 chemoresistive gas sensor is fabricated using a MoS2/ZnO nanohybrid. The nanohybrid is synthesized by drop-casting liquid exfoliated MoS2 nanosheets on ZnO nanorods. The uniform network-like distribution of MoS2 nanosheets on the nanorods is confirmed by various characterization techniques. Under UV-activation, the nanohybrid sensor exhibits remarkable responses of 91% and 2310% at 5 and 500 ppb NO2, respectively. In addition, full recovery to the base resistance is observed in each sensing cycle. The low concentration sensitivity is 0.135 ppb−1 and the lowest detection limit is estimated to be around 0.2 ppb. These two values are superior when compared with other reports. The adsorption/desorption kinetics has been studied in detail using the Langmuir adsorption model. The saturated response, the adsorption, and the desorption constant are determined to be 2744%, 3.52 × 10–5 ppb−1 s−1, and 3.50 × 10–3 s−1, respectively. The outstanding performance of the sensor can be attributed to the synergetic effects of MoS2 and ZnO including creation of abundant adsorption sites and fast charge carrier migration.