Simultaneous stripping determination of cadmium and lead ions based on the N-doped carbon quantum dots-graphene oxide hybrid

In the present work, a new electrochemical sensor using anodic stripping voltammetry from N-doped carbon quantum dots-graphene oxide hybrid (NCQDs-GO) for the simultaneous determination of cadmium ion (Cd2+) and lead ion (Pb2+) is developed. In the hybrid, both the NCQDs and GO have large electroactive surface areas and abundant oxygen-containing functional groups, which supply active sites for the efficient adsorption of heavy metal ions by electrostatic interaction to improve the sensor sensitivity. The NCQDs homogeneously distribute on the surface of GO and play an important role in re-oxidizing metals into ions for stripping analysis. Based on these excellent advantages, the electrochemical Cd2+ and Pb2+ sensor using a NCQDs-GO hybrid modified glassy carbon electrode (NCQDs-GO/GCE) exhibits superior analysis performance than those using just NCQDs on GCE (NCQDs/GCE) and just GO on GCE (GO/GCE), such as wide linear range (11.24–11241 μg/L for Cd2+ and 20.72–10360 μg/L for Pb2+, respectively), low detection limit (7.45 μg/L for Cd2+ and 1.17 μg/L for Pb2+, respectively), good reproducibility and selectivity. Moreover, satisfactory testing recoveries are obtained for the simultaneous detection of Cd2+ and Pb2+ in lake water and tap water, suggesting that NCQDs-GO hybrid is a promising material for the fabrication of electrochemical heavy metal ion sensor.