Scalable and atom economic preparation of red-near-infrared emitted N-doped graphene quantum dots with a high quantum yield

The development of an environmental-friendly and scalable preparation approach for graphene quantum dots (GQDs) with high quantum yield is a focus area for GQDs. Hence, we describe an atom economic green chemistry strategy for nitrogen-doped GQDs (N-GQDs). The yield of N-GQDs is 98.5%. Moreover, due to the simple reaction and processes, N-GQDs can be synthesized on a large scale (the throughput of N-GQDs is 10 g). Besides, the intrinsic bandgap PL of N-GQDs can be adjusted by size modulation. The emission wavelength of N-GQDs is modulated from 405 nm to 698 nm with a high quantum yield (0.89–0.62). Furthermore, with the general nucleophilic addition reaction of indigo, the PL response-ability of the obtained GQDs can be further tuned. Different precursors with heteroatoms (such as S and Se) can be used for the preparation of dual- heteroatoms co-doped GQDs (N, S-GQDs and N, Se-GQDs). We also confirmed the utilization of the red-near-infrared emitted N-GQDs (emission wavelength: 698 nm) with high quantum yield (0.62) in bio-imaging.