Ind. Eng. Chem. Res., 2014, 53, 2839–2845

A simple, cost-effective approach is presented for producing exfoliated films of pure graphene or polymer−graphene composite with high yield, high conductivity, and processability. The approach combines supercritical CO₂ with　ultrasonics. Characterization by Raman spectroscopy combined with atom force field microscopy demonstrates that the graphene　sheets were obtained with 24% as monolayers, 44% as bilayers, and 26% as trilayers. The layer number and lateral size of
graphene sheets can be controlled by adjusting the process parameters. The yield of graphene sheets with a lateral size of about　0.5−5.0 μm is about 16.7 wt % under optimum conditions, which can be easily raised to 40−50 wt % by repeated exfoliation of　the sediment that remained in the reactor. The resultant pure graphene film made by filtration has a high electrical conductivity　of 2.8 × 107 S/m. The electrical conductivity of the film of polyvinyl alcohol−graphene composite is 300 S/m.

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http://pubs.acs.org/doi/abs/10.1021/ie402889s