Method for the preparation of graphene

A method for the preparation of graphene, comprising:

• (a) oxidizing a graphite material to form graphite oxide;
• (b) dispersing graphite oxide into water to form an aqueous suspension of graphite oxide;
• (c) adding a dispersing agent to the aqueous suspension of graphite oxide;
• and (d) adding an acidic reducing agent to the aqueous suspension of graphite oxide, graphite oxide being reduced to graphene by the acidic reducing agent, graphene being further bonded with the dispersing agent to form a grapheme dispersion including a surface-modified graphene,
• wherein the dispersing agent has two terminal ends, and has a cholic acid group at its one terminal end, and has a phenyl group at its another terminal end, the cholic acid group at one terminal end of the dispersing agent is bonded to the surface of graphene, and thereby the surface of graphene is modified by the presence of the phenyl group at another terminal end of the dispersing agent, and the acidic reducing agent is selected from the group consisting of ascorbic acid, citric acid, and polyphenol.