Development of sulfur doped carbon quantum dots for highly selective and sensitive fluorescent detection of Fe2+ and Fe3+ 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 3+ ions in comparison with Fe 2+ and other metal ions , In the presence of adequate H 2 O 2 , Fe 2+ was completely transformed to Fe 3+ 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 H 2 O 2 was used for detection of Fe 2+ and Fe 3+ ions, respectively. Under the optimum experimental conditions, the fluorescence intensity of S-CQDs gradually decreased with increasing of Fe 3+ 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 3+ . The recoveries of Fe 2+ and Fe 3+ 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 2+ and Fe 3+ ions in oral ferrous gluconate samples, which presents potential applications in the speciation and determination of Fe 2+ and Fe 3+ ions in complex samples.