A unique dual-excitation carbon quantum dots: Facile synthesis and application as a dual-“on-off-on” fluorescent probe

A dual-"on-off-on" fluorescent probe based on nitrogen-doped carbon quantum dots (BG-NCDs) with the dual-excitation property was developed, which had a blue emission peak at 398 nm and a green emission peak at 518nm when excited at 298nm and 404nm, respectively. BG-NCDs were characterized by TEM, XPS, and FT-IR. The results showed that (1) the Fe (III) and ascorbic acid (AA) could “turn off/turn on” the blue fluorescence of BG-NCDs, the blue fluorescence of BG-NCDs was used as an “on-off-on” fluorescent probe to detecting the Fe (III) and AA in the linear ranges of 0.04–20.00 mg/L and 0.57–10.00 mg/L, the LODs were as low as 0.012 mg/L and 0.19 mg/L; (2) the presence of Cu (II) and glutathione (GSH) could “turn off/turn on” the green fluorescence of BG-NCDs, the “on-off-on” process of green fluorescence of BG-NCDs could be established as a fluorescence probe to detecting Cu (II) and GSH in the linear ranges of 1.08–16.00 mg/L and 2.46–32.00 mg/L, with LODs of 0.36 mg/L and 0.86 mg/L. The method was applied to determination analytes in real samples with satisfactory results. BG-NCDs displayed low cytotoxicity and was multicolored imaging DU145 cells successfully.