Carbon dots(CDs)with high quantum yield(QY),low toxicity and good biocompatibility are the major quests of biomedical research.In this paper,we develop a green,simple,hydrothermal approach to synthesize water-soluble,nontoxic,highly photoluminescent carbon nanodots(CNDs)from Metronidazole,which possess excellent antibacterial activity for the first time.Metronidazole was used as a sole precursor to prepare CNDs at 250(CNDs-250)for 8 h.