Enhanced dual gas sensing performance of MoS2/MoO3 nanostructures for NH3 and NO2 detection

Highly sensitive p-MoS2/n-MoO3 nanocomposite-based chemo-resistive gas sensors are synthesized by varying the reducing agents using hydrothermal synthesis followed by thermal annealing in an Ar environment for NH3 and NO2 detection at 50 °C. Structural characterizations confirmed the existence of MoS2 nanoflakes and MoO3 nanoplatelets and the appearance of abundant oxygen adsorption sites and sulfur vacancies in the nanocomposites. The MoS2:MoO3-based sensor (without any reducing agent) showed preferential detection of NH3 with 52% sensor response for 5 ppm gas concentration having response/recovery times of 28 s/97 s with n-type sensing behavior dominated by MoO3 charge carriers. On the contrary, NO2 gas attracts electrons from the MoS2 surface, exhibiting p-type sensing behavior with a sensor response of 42 % consisting of response/recovery times of 56 s/116 s with 5 ppm concentration at 50 °C. More interestingly, different adsorption sites and conductive channels play a huge role in the MoS2:MoO3 nanocomposite for exhibiting opposite sensing behaviours upon exposure to NH3 and NO2 gases. Enhanced sensitivity is dedicated to synergistic effects appearing due to the construction of p-n heterojunction to strengthen carrier transport by enhancing the sensor response. The present work provides a unique methodology for constructing MoS2:MoO3-based sensors and the effect of reducing agents on various MoS2:MoO3-based sensors. Moreover, our study recommends the plausible use of the MoS2:MoO3 composite-based heterojunctions to provide a constructive strategy for improving the performance of gas sensors.