Hydrothermally synthesized MoS2-multi-walled carbon nanotube composite as a novel room-temperature ammonia sensing platform

MoS2 and its composite with mull-walled carbon nanotube (MWCNTs) were synthesized using facile hydrothermal approach. Structural and vibrational analysis revealed the presence of various defects in MoS2 and its composite with MWCNT. Two-terminal devices were made on a quartz substrate with pre-deposited silver contacts. The resulting Ag/MoS2/Ag and Ag/MoS2-MWCNT/Ag devices exhibit n-type semiconducting behavior and have shown room-temperature ammonia detection down to 12 ppm level. In case of former, the corresponding response time (t(response) = 400 s) and recovery time (t(recovery) = 280 s) are very large with limit of detection down to 1.2 ppm. The latter, i.e., Ag/MoS2-MWCNT/Ag device on the other hand exhibits faster response-recovery (65 and 70 s, respectively) features along with enhanced relative response for various ammonia concentrations ranging from 12 to 325 ppm. Further, the composite device also displays superior selectivity to its counterpart. It is argued that these differences might arise from different adsorption energy for different gas molecules on the surface of MoS2 or MoS2-MWCNT semiconducting channel. Present results suggest that composite materials such as MoS2-MWCNT may serve as a novel gas sensing platform with superior sensing characteristics and selectivity features.