▎ 摘　　要

A facile one-pot and environment-friendly method has been developed for the synthesis of graphene sheets. Poly(vinyl-pyrrolidone) nanoparticles with a size range of 23-57 nm are used for the exfoliation process of graphene sheets in conjunction with ultrasonication. The polymer nanoparticle size played a significant role in the exfoliation yield of the graphene sheets. The small nanoparticle size of 23 nm was found to be the most effective size for the exfoliation. Thus, high quality individualized graphene sheets were obtained and the sheet thickness was found to be 4 nm. The polymer nanoparticles contributed to stable graphene dispersions through wrapping on the surface of the sheets. The graphene sheets have been characterized by using Raman and UV-Vis spectroscopy and their morphology visualized by transmission electron microscopy. In addition, the as-prepared graphene sheets were investigated as a potential cytotoxic drug and their anti-proliferative activity was studied in vitro by the MMT assay. The results showed a remarkable lethality rate of 87% for human colon cancer cells (HCT-116) and biocompatibility to normal mouse embryonic fibroblast NIH-3T3 cells.