▎ 摘　　要

The preparation, structure and optical properties of single- or few-layer graphene sheets obtained by liquid phase exfoliation of natural graphite in task-specific alkyl-3-methylimidazolium peroxydisulfate ionic liquids (TSILs) were studied. The coordinated action of oxidation of the anion and the intercalation of the cation in TSILs resulted in efficient exfoliation of graphite layers and provided single- or few-layer graphene sheets with a relatively low concentration of defects and oxygen-containing groups. The optical transmittance of the thin film comprising the as-prepared graphene sheets reached up to 91% in the near infrared region. Electrochemical impedance spectroscopic analysis indicated that the prepared graphene sheets possessed higher conductance. These facts illustrate that such graphene sheets with low defect density may have great potential in optoelectronic applications.