▎ 摘　　要

A gram-scale approach has been developed to prepare highly pure graphene quantum dots (GQDs) from Vulcan XC-72 carbon black refluxed with concentrated nitric acid using a home-built experimental system. The weight of the GQDs is high, up to 1.2 g in each run with a yield of 75 wt%, and the purity is 99.96 wt%. The results show that the GQDs exhibit multicolor photoluminescence from green to light red under different excitation wavelengths.