Highly sensitive and selective “turn-off” fluorescent probes based on coumarin for detection of Cu2+

As the third most abundant trace element in human internal environment, Cu2+ has a significant impact on organisms and ecosystems. The determination of Cu2+ is an important topic in the field of environmental protection and food safety. In this study, a coumarin-based fluorescent probe (denoted by ICTAB) was designed and synthesized. The results indicate that ICTAB is a “turn-off” fluorescent probe for Cu2+, with extremely high selectivity and sensitivity. The limit of detection is down to 0.27 μM. Mass spectroscopy and Job's plot show that ICTAB and Cu2+ form 2:1 coordinate complexes, and the specific binding sites of Cu2+ on ICTAB were determined by FTIR and 1H NMR. More importantly, the fluorescent emission of ICTAB can be repeatedly recovered by removing Cu2+ with S2−, which functions as an effective “turn-off” fluorescent probe. ICTAB demonstrated over 89% of recoveries as being applied in detecting Cu2+ in water.