An Electrochemical Sensor for Selective Detection of Cu ²⁺ by using a self-Assembled Cu Coordinated <i>β</i> -cyclodextrin- nitrogen-Doped Carbon Quantum Dots Composite

Abstract

Nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by one-step hydrothermal method using citric acid as carbon source and urea as nitrogen source. β -cyclodextrin ( β -CD) is a cyclic oligosaccharide with a unique hollow structure, which is beneficial to the enrichment of metal ions on the electrode surface while reducing the agglomeration of carbon quantum dots and maintaining conductivity. When Cu 2+ is coordinated with β -CD, it can further increase the affinity for Cu 2+ and recognize Cu 2+ more sensitively. Therefore, we coordinated Cu 2+ and β -CD to form copper ion coordinated β -cyclodextrin (Cu- β -CD). By self-assembly, the prepared N-CQDs and Cu- β -CD combined to form Cu- β -CD/N-CQDs composites. The electrochemical sensor constructed by Cu- β -Cd/N-CQDs successfully realizes the selective detection of Cu 2+ in the range of 1–125 μ mol l −1 , and the lowest detection limit is 0.094 μ mol l −1 . In the detection of actual water samples, the Recovery of Cu 2+ was between 92% and 120%, and the RSD was between 2.3% and 5.2%. Therefore, Cu- β -CD/N-CQDs composite is expected to be constructed as a non-toxic, pollution-free electrochemical sensor for selective detection of heavy metal Cu 2+ ions in water.