We report a visualized method for the detection of Cu²⁺ ions, which relies on the Cu(I)-catalyzed 1,3-dipolar cycloaddition of alkynes on the surface of functionalized QDs and azides on the surface of functionalized graphene oxide (GO). This click chemistry process results in self-assembly of GO-N₃ sheets into aggregates that can be observed by the naked eye. The catalyst, Cu(I), was conveniently derived from the reduction of Cu(II) in the presence of sodium ascorbate, thereby allowing the reaction to serve as a naked eye method to assay for the presence of Cu²⁺ ions.