Direct Electrodeposition of Carbon Dots Modifying Bismuth Film Electrode for Sensitive Detection of Cd2+ and Pb2+

A sensitive, selective, and stable sensor for the simultaneous determination of Cd 2+ and Pb 2+ in aqueous solution has been developed based on the carbon dots (CDs) and Nafion-modified bismuth film glassy carbon electrode (GCE). High graphitized CDs prepared by the sulfuric acid-assisted hydrothermal synthesis were directly electrodeposited on the GCE surface by cyclic voltammetry. Compared with the conventional bismuth film electrodes, CDs greatly improved the electrochemical activity of the bismuth film electrode for the detection of Cd 2+ and Pb 2+ . After decorating CDs, the surface impedance of the GCE was decreased from 10.9 kΩ to 4.84 kΩ. Meanwhile, the corresponding response currents of the Bi/GCE were increased over 7.4 and 2.4 times for Cd 2+ and Pb 2+ with a wide linear range of 0.05–0.50 mg l −1 , respectively. High sensitivity was obtained with the detection limits of 3.1 μ g l −1 (Cd 2+ ) and 2.3 μ g l −1 (Pb 2+ ). Moreover, good stability was obtained for the simultaneous determination of Cd 2+ and Pb 2+ in the practical underground water with the relative standard deviations less than 10%. The results indicated that the CDs-modified bismuth film electrode could potentially be applied to detect the heavy metal ion concentrations in practical environment.