▎ 摘　　要

Because of their low toxicity and excellent water-solubility, graphene quantum dots have been highly anticipated for use in cellular imaging. However, their limited optical properties are hampering this use. To address this issue, graphene quantum dots surface passivated by branched polyethylenimine (GQDs-BPEI) were proposed in this paper. We discussed optical properties when prepared under different conditions including reaction time, temperature, and pH value. The results indicate that GQDs-BPEI prepared at pH 12, at a temperature of 200 degrees C, and with a 20 h reaction in an autoclave can achieve a higher UV absorbency and better PL properties with a high quantum yield.