A system based on FRET mechanism, comprising a coumarindonor and a rhodamineacceptor, was developed for the selective and quantitative detection of metal ions. Fluorescent chemosensors RCs, linked by 1,2-diethylamine, exhibit significant fluorescence enhancement and excellent selectivity toward Cu2+. Fluorescent probes CRB and CR6G, linked by hydrazide, function as ratiometric receptors for Cu2+