Visual detection of copper(ii) based on the aggregation of gold nano-particles via click chemistry

A novel, highly sensitive and selective colorimetric method for copper(II) detection through copper(I) catalyzed alkyne–azide cycloaddition reaction (CuAAC) has been developed. Copper(I) is produced by the electrochemical reduction of copper(II) via Bulk Electrolysis (BE) with coulometry. The azide- and alkyne-functionalized Au nanoparticles (AuNPs) can aggregate quickly (10 min) through CuAAC reaction, resulting in the color of the solution changing from red to purple. Furthermore, the change of color is closely related to the concentration of copper(II), and 1 nM copper(II) could be detected by the naked eye. Additionally, the proposed method has good selectivity to copper(II) in the presence of other common metal ions.