A quinoline-based fluorescence “on-off-on” probe for relay identification of Cu2+ and Cd2+ ions

A novel fluorescent probe based 8-hydroxyquinoline (8-HQ) has been designed and synthesized. The probe 1 exhibits fast relay recognition performance for Cu 2+ and Cd 2+ via a fluorescence “on−off−on” response signal. The probe 1 itself has a strong emission peak at 471 nm in EtOH/H 2 O (v/v = 1:9) solution with a blue fluorescence. The addition of Cu 2+ immediately results in the quenching of fluorescence and the limit of detection is 2.7 × 10 −8  M. Moreover, the formation of [1-Cu 2+ ] complexes can also serve as a new efficient probe system for the relay recognition of Cd 2+ with the emergence of a new fluorescence signal under the same conditions. The study also found that the probe 1 has high selectivity for target ions in the presence of other competing ions. The probe 1 has been successfully applied to detect and analyze the trace amount of Cu 2+ and Cd 2+ in environmental water samples.