▎ 摘　　要

A hydrothermal approach was developed for the synthesis of N-doped graphene quantum dots (N-GQDs) by cutting N-doped graphene. The N-GQDs obtained have a N/C atomic ratio of ca. 5.6% and diameter of 1-7 nm. The photoluminescence (PL) properties of the N-GQDs were investigated. It was found that the N-GQDs possess bright blue PL and excellent upconversion PL properties. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4750065]