Efficient Liquid Nitrogen Exfoliation of MoS2 Ultrathin Nanosheets in the Pure 2H Phase

Clean and efficient exfoliation of bulk MoS2 into single- or few-layered nanosheets in the pure semiconducting hexagonal phase (2H phase) remains a great challenge and becomes a bottleneck for the intensive studies and applications of MoS2-based nanomaterials. Here, a new method for the scalable synthesis of 2H-MoS2 nanosheets using liquid nitrogen (L-N-2) exfoliation has been developed. After five heating/L-N-2 immersion cycles, the produced MoS2 nanosheets are primarily fewer than three layers in the pure 2H phase after the evaporation of the exfoliation reagent of L-N-2. Impressively, two-dimensional (2D) van der Waals heterostructures by accommodating organic semiconductive nanoaggregates on the surface of semiconducting 2H-MoS2 nanosheets exhibit excellent electronic rectification effects for a nonvolatile write-once-read-many-times memory behavior with an ON/OFF ratio of over 10(5). This work with the novel heating/L-N-2 exfoliation strategy to prepare clean and pure 2H-MoS2 nanosheets would open up tremendous potential opportunities for the fundamental studies and practical applications of semiconducting 2D nanomaterials.