Efficient exfoliation of MoS₂with 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.