A highly selective photoelectrochemical" sensor was fabricated for the detection of Cu2+ ions based on the Cu+ catalyzed click reaction. Firstly, 11-Azido-3,6,9-trioxaundecan-1-amine was immobilized on the CdS modified ITO electrode by classic 1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide reaction, then the propargyl-functionalized Au NPs were binding to electrode through the cycloaddition reaction between azides and alkynes, which catalyzed by Cu+ (acquired from the reduction of Cu2+ by ascorbic acid), making the Au NPs close to the CdS QDs. Upon light irradiation, energy transfer between the CdS QDs and Au NPs would lead to the decrease of photocurrent Under optimized condition, the percentage of photocurrent decrement was linearly proportional to the concentration of Cu2+ ions, ranging from 1.0 x 10-9 to 1.0 x 10(-6) M, with a detection limit of 2.0 x 10(-19) M, the novel strategy could provide a sensitive and selective platform for Cu2+ detection. (C) 2016 Elsevier B.V. All rights reserved.