▎ 摘　　要

The van der Waals corrected first-principles approach within density functional theory is performed to investigate the mechanism of direct exfoliation of graphite into graphene by pyrene-based molecules. Our results show that the interaction energies between pyrene-based molecules and graphene are larger than the interlayer inaction energy of bilayer graphene. However, the frictions of pyrene-based molecules on graphene are lower than the interlayer friction of bilayer graphene. The comparisons of adsorption energies and frictions for different molecules on graphene indicate that the size of friction can be affected by the length and type of the additional chain of pyrene-based molecule. These studies illustrate that the PCA can bond to graphene from adsorption energy view, and can slide on the graphene easily, which explains the experiment very well and provides a few of alternative molecules to produce the aqueous dispersions of graphene flakes according to different demands.