▎ 摘　　要

A facile and high-efficient approach for the preparation of graphene quantum dots (GQDs) is reported. With the assistance of KO2 in the hydrothermal cutting graphene oxide (GO), a conversion rate of similar to 35 wt % from GO to GQDs is achieved. The as-prepared GQDs display rarely observed yellow emissive photoluminescence with a respectable quantum yield of 8.9% in H2O. Moreover, the GQDs are further demonstrated to perform as a potential pH probe and bioimaging agent. (C) 2017 Elsevier Ltd. All rights reserved.