One-pot hydrothermal synthesis of self-assembled MoS2/WS2 nanoflowers for chemiresistive room-temperature NO2 sensors

Transition metal dichalcogenides (TMDs) based heterostructures are becoming hotspots of gas-sensing applications due to the high electronic mobility, high surface-volume ratio, and abundant adsorption sites. However, the preparation of TMDs-based heterostructures is usually required multiple steps or higher synthesis temperatures (>= 500 degrees C). Herein, the flower-like MoS2/WS2 composites were firstly prepared by a facile one-pot hydrothermal method to effectively detect NO2 at room temperature. The WS2 molecules prefer to grow on the edge of as nucleated MoS2 to form the MoS2/WS2 nanosheets, and then they can grow by layer-by-layer self-assembly to form the MoS2/WS2 heterostructure. The optimized MoS2/WS2 heterostructured composite exhibits the very high sensitivity to NO2 at room temperature, involving high response, good reproducibility, excellent selectivity and long-term stability. Specially, the responses (Delta R/Rg) of MoS2/WS2-0.5 composite to 5 and 100 ppb NO2 are 6.1% and 23.1%, respectively. Moreover, a plausible gas sensing mechanism was proposed from viewpoints of electron transfer and gas adsorption by combining multiple experiments and DFT calculations. This work provides a facile process for synthesis of TMDs-based heterostructures, but also a prospective gas sensing material for room temperature NO2 detection.