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 degrees 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 degrees 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.