Naked-eye detection of copper(II) ions by a “clickable” fluorescent sensor

A novel “clickable” sensing platform for signal-on fluorescent detection of Cu2+ has been developed based on the high regioselectivity of Cu(I)-catalyzed azide-alkyne click reaction (CuAAC) and the aggregated AIE-active molecules (BATPE) as the signal reporters. The CuAAC reaction causes a structural change of BATPE from molecularly dispersed to aggregate state in the presence of trace Cu2+, thus inducing a dramatic fluorescence “turn-on” response which can be judged with the naked eye. Under the optimum conditions, down to 0.2 μM and 0.5 μM Cu2+ were successfully detected by fluorescence spectrophotometer and naked eye, respectively. This method is simple and low-cost without the need for expensive equipment. Thanks to the superior specificity of CuAAC reaction, our assay is capable of sensing Cu2+ in the existence of other environmentally relevant metal ions in real samples, indicating that it may serve as a promising sensor for on-site Cu2+ analysis.