Manipulation of 3D nanocarbon hybrids toward synthesis of N-doped graphene quantum dots with high photoluminescence quantum yield

Synthesis of heteroatom-doped graphene quantum dots (GQDs) via a top-down approach is still challenging. Herein, we conveniently synthesized nitrogen-doped GQDs (N-GQDs) via an electrochemical method. In that, the N-containing 3D nanocarbon hybrids were prepared as the carbon and nitrogen sources, which were cut into small fragments in ammonia solution as the electrolyte. Interestingly, N-atoms from the 3D nanocarbon hybrids were successfully retained or converted into other types of N in the obtained GQDs, resulting to a highly doped N content up to 12.3% even after excluding the amino- and pyrrolic N at edges of the N-GQDs. As a matter of fact, the synthesized N-GQDs showed highly crystallized structure, and demonstrated a high photoluminescence quantum yield of ∼19.3%, among the highest values of top-down approach synthesized GQDs. Moreover, it can be also used for adjusting the absorption range of GQDs. Overall, we developed a new strategy to synthesize N-doped GQDs by controlling the carbon source, which opens a new avenue toward achieving other types of heteroatom-doped GQDs.