Sulphur and nitrogen doped carbon dots: A facile synthetic strategy for multicolour bioimaging, tiopronin sensing, and Hg2+ ion detection

In this article, a novel and facile strategy has been developed to synthesize nitrogen (N) and sulphur (S) doped carbon dots (NSCDs) by a one-step hydrothermal method. Diethylenetriamine and thiomalic acid are used as nitrogen and sulphur sources respectively. Through the extensive study on chemical structures, morphology, and optical properties of the synthesized NSCDs, it is found that as-synthesized NSCDs exhibits good luminescence, uniform size, excellent stability, and excitation-dependent photoluminescence (PL) property. The obtained NSCDs are stable in aqueous solution with quantum yield of 17.59 %. Importantly, the fluorescence property of NSCDs has been utilized to detect tiopronin with a limit of detection (LOD) 3.8 μM (linear response concentration range 4-18 μM). Furthermore, the synthesized NSCDs are contributed for the selective detection of Hg2+ ions and multicolour cell imaging. The Hg2+ ions assay shows a linear range from 0.06 to 5 μM with a LOD 50 nM. As an efficient chemosensor, the developed NSCDs possess excellent biocompatibility, low cytotoxicity and Hg2+ ion detection in living cells.