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

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.