1. Fig. 1 presents the process used to synthesize N-GQDs, where the CA is carbonized and converted into N-GQDs in the presence of ammonia through the hydrothermal process at 200
C for 3 h, followed by a further purification process to obtain an aqueous
solution of N-GQDs.
2. Typically, when 40 ml of a CA aqueous solution (1 mg/ml) and 8 ml of an ammonia aqueous solution were used here, we obtained the N-GQDs aqueous solution with concentration of 4.91 mg/ml.
3. N atoms from ammonia were introduced into the graphene lattice through the high temperature hydrothermal process.
4. When CA was solely used without the addition of ammonia, the undoped GQDs were obtained from the hydrothermal process.