Nitrogen, sulfur co-doped red carbon dots for sensitive and selective detection of Sn2+ ions

Carbon dots with both red-emission and red-excitation (R-CDs) have attracted much attention due to their excellent optical property and promising application in various fields. However, most carbon dots (CDs) with red-emission are only excited with short wavelength irradiation, which heavily hinders their further applications. Herein, novel R-CDs are obtained through a hydrothermal synthesis by using p-phenylenediamine and ammonium thiocyanate as precursors. The as-synthesized R-CDs exhibit a strong red emission at 618 nm at a long excitation (598 nm). Moreover, the R-CDs are explored as a selective and sensitive “turn-off” sensor for Sn 2+ detection by the non-radiative recombination of the excitons through effective electron, charge or energy transfer between Sn 2+ and surface functional groups such as hydroxyl, carbonyl, amine, thiophene, and S O, with a detection range from 0 to 90 μM and a detection limit of as low as 17.25 nM.