The N-GQDs were synthesized by carbonization of CA (99%,
Sigma-Aldrich) with ammonia through hydrothermal treatment.
In brief, 40 ml of a CA aqueous solution (1 mg/ml) and an ammonia
aqueous solution (2, 5, and 8 ml, 25 wt%) were transferred into
Teflon-lined autoclave and were heated at 200
C for 3 h.