Efficient exfoliation of MoS2 with volatile solvents and their application for humidity sensor.

Liquid-phase exfoliation is likely to be feasible for practical fabrication of few-layer MoS2 nanosheets in large quantities. However, this method generally involves the organic solvents with high boiling point; new strategy using low-boiling-point solvents to obtain high MoS2 concentration is still highly required. In this study, using the strategy of Hansen solubility parameters (HSP), a method based on exfoliation of MoS2 in chloroform/acetonitrile mixtures is demonstrated to fabricate high concentration MoS2 nanosheet solution. The highest concentration of few-layer MoS2 nanosheets and nanoparticles up to 0.4 mg/ml is achieved with the optimum composition of mixture. The MoS2 nanosheet thin film is also investigated in terms of their sensing properties towards humidity. The exfoliated MoS2 based thin film sensor exhibited excellent sensitivity, quick response and recovery, and good reproducibility comparing to their bulk counterpart. The excellent sensing performance of exfoliated MoS2 is generally attributed to the high surface-to-volume-ratio and increased ratio of edge sites and basal plane sites after exfoliation.