Effect of nitrogen doping on the photoluminescence intensity of graphene quantum dots.

We have developed a facile, fast, and one-step synthetic method to prepare graphene quantum dots (GQDs) simultaneously with nitrogen (N) doping via pulsed laser ablation. The N-doped GQDs (N-GQDs) with an average size around 3 nm and an N/C atomic ratio of 33% have been obtained. The N-GQDs emit blue photoluminescence (PL), where the PL intensity enhances as the N doping increases. The PL enhancement for the N-GQDs with a factor as high as 25 has been achieved as compared to GQDs. The origin of the PL enhancement in GQDs after N doping is attributed to the increased densities of pyridinic and graphitic N.