Development of sulfur doped carbon quantum dots for highly selective and sensitive fluorescent detection of Fe and Fe ions in oral ferrous gluconate samples.

Sulfur-doped carbon quantum dots (S-CQDs) with stable blue fluorescence were synthesized through a facile one-step hydrothermal method by using ascorbic acid and thioglycolic acid as carbon and sulfur sources. The prepared S-CQDs exhibited a sensitive and selective response to Fe ions in comparison with Fe and other metal ions, In the presence of adequate HO, Fe was completely transformed to Fe that is the determinable form of iron ions, and the difference in the change of the fluorescence intensity of S-CQDs before and after adding HO was used for detection of Fe and Fe ions, respectively. Under the optimum experimental conditions, the fluorescence intensity of S-CQDs gradually decreased with increasing of Fe concentration ranging from 0 to 200 μM. Good linearity was achieved over the range of 0-200 μM. The detection limit of the developed method was 0.050 μM for Fe. The recoveries of Fe and Fe spiked in real samples ranged from 98.2% to 112.4%. Finally, the proposed S-CQDs integrated with Fenton system was applied to the detection of Fe and Fe ions in oral ferrous gluconate samples, which presents potential applications in the speciation and determination of Fe and Fe ions in complex samples.