A ratiometric fluorescent chemodosimeter for Cu(II) in water with high selectivity and sensitivity

[Display omitted] ► A coumarin-based ratiometric chemodosimeter for the detection of Cu(II) is facilely synthesized by three steps reactions. ► Cu(II) catalyzes the hydrolysis of chemodosimeter with ratiometric fluorescence signal greatly amplified. ► Detection of Cu(II) can be performed in water at neutral pH with high sensitivity. ► The chemodosimeter exhibits remarkably selective fluorescence enhancement to Cu(II) over other metal ions. Coumarin derivative 1 was synthesized as an efficient ratiometric chemodosimeter for the detection of Cu(II) in 99% water/DMSO ( v/ v) at pH 7.0. Mechanism studies suggested that 1 formed a complex with Cu(II) at 2:1 ratio accompanied by quenching of green fluorescence at 524 nm; when the solution was heated to 50 °C for 30 min, Cu(II)-promoted hydrolysis of coumarin lactone moiety of 1 occurred with bright blue fluorescence at 451 nm emerged. With fluorescence intensity ratio detection at 451 nm and 524 nm, 1 features an excellent sensitivity with the detection limit of 15 nmol L −1 toward Cu(II) and a good selectivity over other metal ions.