Graphene quantum dots (GQDs) have attracted a great deal of interest from the viewpoints of both fundamental studies and applications. Photoluminescence (PL) is one of the intriguing properties of GQDs, however, the mechanism of the PL in GQDs is not fully understood. In the present study, a drastic change in the PL from UV to red light region is reported among GQDs separated by size-exclusion …