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-N₂) exfoliation has been developed. After five heating/L-N₂ 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-N₂. 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 10⁵. This work with the novel heating/L-N₂ 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.