Ind. Eng. Chem. Res., 2013, 52, 4379–4382

A facile and general approach was developed to exfoliate layer materials to produce two-dimensional atomic　crystals. A single and few layers of BN, MoS₂, and WS₂ were obtained via directly exfoliating their powder materials using　supercritical CO₂ assisted with ultrasound. The effects of supercritical CO₂ coupled with ultrasound play a key role in the　exfoliation process. The layer numbers and sizes of the BN, MoS₂, and WS₂ can be easily controlled by adjusting the power and　the time of ultrasonication. The AFM images suggest single-layered BN, MoS₂, and WS₂ were produced, respectively. Their　lateral sizes are about 0.5−2 μm, and almost 90% of the BN sheets are less than five layers. The electric diffraction patterns　demonstrate that the crystallinities of the produced samples remained the same as that of the raw material during the exfoliating　process. This novel technique is cost-effective and scalable, and can be widely used in the production of two-dimensional atomic　crystals with high quality.

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http://pubs.acs.org/doi/full/10.1021/ie303633c