Developing Carbon Dots with Room-Temperature Phosphorescence for the Dual-Signal Detection of Metronidazole

Room-temperature phosphorescent carbon dots (CDs) show the advanced property owing to their dual signal; howbeit, acquiring the efficient phosphorescence of CDs is still challengeable. Here, we proposed one type of CD doped with nitrogen through the microwave method, which exhibited the obvious blue fluorescence in aqueous solution and green phosphorescence immobilized on filter paper, while diethylenetriamine pentamethylene phosphonic acid provided the source of carbon and nitrogen. Importantly, introducing metronidazole (MNZ) into the CDs leads to their simultaneous decrease in both fluorescence and phosphorescence, and thus, we successfully established a dual-signal strategy for detecting MNZ. Likewise, this fluorescent detection showed the linear range of 2–200 μM and the phosphorescent way of 50–2000 μM. Meanwhile, the corresponding detection mechanism was also explored, and both the quenched fluorescence and phosphorescence of CDs were mainly due to the occurrence of the electron transfer and internal filtration effect between CDs and MNZ. Additionally, we employed these CDs as the fluorescent and phosphorescent inks for painting and information encryption.