Fluorescent Carbon Quantum Dots with Fe(III/II) Irons as Bridge for the Detection of Ascorbic Acid and H2O2

Nitrogen-sulfur co-doped carbon quantum dots (N, S-CQDs) with good photoluminescence properties were prepared by hydrothermal method using citric acid (CA) and methionine (Met) as precursors. Co-doping with N and S facilitates the electron transfer rate and coordination interaction between N,S-CQDs and Fe(III) ions which acts as a quencher of fluorescence. Based on a simple redox principle, a highly sensitive and selective method for the detection of ascorbic acid (AA) and H 2 O 2 was successfully developed. The calibration curves obtained are linear for the current versus AA and H 2 O 2 concentration over the range 50–500 μM and 10–140 μM, respectively. And the detection limits for AA and H 2 O 2 are 4.2 μM and 1.9 μM, respectively. The quantitative analysis of AA and H 2 O 2 in various juices and H 2 O 2 disinfectant with Fe 3+ /CQDs or Fe 2+ /CQDs gave the recoveries of 87.8%–117.5% and 99.2%–106.4% with relative standard deviations ( RSD ) of 1.6–5.1% and 1.7–3.1%, respectively, showing satisfactory results for the determination of AA and H 2 O 2 in actual application. The proposed strategy may provide a new pathway to developing inexpensive and sensitive way for the detection of various redox reaction–involved system.