Synthesis and application of fluorescent N,S co-doped carbon dots based on on-off-on quenching mode for the collaboration detection of iron ions and ascorbic acid

Nitrogen and sulfur co-doped carbon dots (NS-CDs) were synthesized by one-step solvothermal method using oleic acid as the medium, L-cystine and citric acid monohydrate as precursors. Based on the ``on-off-on" fluorescence quenching mode, a novel method was established for determination of both Fe3+ and ascorbic acid. The synthesized NS-CDs can be employed as fluorescence chemical sensors for the direct determination of free iron in the aqueous phase and indirect determination of the ascorbic acid contents of vitamin C tablets with linear ranges of 010 mu M (n = 3) and 0-30 mu M (n = 3), and detection limits of 36.6 and 102.5 nM, respectively. These results demonstrate that the proposed method exhibits good selectivity and linearity. (C) 2020 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.