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 redemission 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 Sn2+ detection by the non-radiative recombination of the excitons through effective electron, charge or energy transfer between Sn2+ and surface functional groups such as hydroxyl, carbonyl, amine, thiophene, and S=O, with a detection range from 0 to 90 mu M and a detection limit of as low as 17.25 nM.

Automated summary

Novel R-CDs with strong red emission were successfully synthesized and utilized as a selective and sensitive turn-off sensor for Sn2+ detection. The R-CDs demonstrated effective electron, charge or energy transfer between excitons and Sn2+ through non-radiative recombination, enabling detection with a high range and low limit.