A Bright Nitrogen-doped-Carbon-Dots based Fluorescent Biosensor for Selective Detection of Copper Ions

In this work, a novel fluorescent biosensor has been constructed for rapid detection of Cu(II) via the interaction between the fluorophore groups on the surface of nitrogen-doped-carbon-dots (N-CDs) and ·OH produced from the catalytic reaction between Cu (II) and cysteine (Cys). Specifically, Cu (II) can catalyze the oxidation of Cys to form cystine (Cys–Cys) and hydrogen peroxide (H 2 O 2 ), and Cu (II) can also catalyze the decomposition of H 2 O 2 to produce hydroxyl radicals (·OH) by the Fenton-like reaction. ·OH can oxidize and destroy the surface structure of N-CDs, resulting in the fluorescence quenching of the N-CDs. Under the optimal experimental conditions, the linear range of Cu (II) is determined to be 0.05–25 μmol L −1 , and the limit of detection is 23 nmol L −1 with the limit of quantitation of 77 nmol L −1 . Besides, some characterizations are provided to verify the proposed principle. The method has been successfully applied for the detection of Cu (II) in human serum and environmental water with high sensitivity and higher selectivity.