▎ 摘　　要

A facile, low-cost and environmentally friendly method was developed to prepare processable graphene materials by direct exfoliation of expandable graphite flakes under wet ball milling conditions in ionic liquids. The graphene nano-sheets obtained in this method were characterized by AFM, Raman spectroscopy, UV-NIR. Thin-film field-effect transistors made from this graphene sheets exhibit ambipolar effect, an average hole mobility of similar to 0.29 cm(2) V-1 s(-1), electron mobility of similar to 0.57 cm(2) V-1 s(-1) was obtained.