One-pot fabrication of FRET-based fluorescent probe for detecting copper ion and sulfide anion in 100% aqueous media

The design of effective tools for detecting copper ion (Cu2+) and sulfide anion (S2-) is of great importance due to the abnormal level of Cu2+ and S2- has been associated with an increase in risk of many diseases. Herein, we report on the fabrication of fluorescence resonance energy transfer (FRET) based fluorescent probe PF (PEI-FITC) for detecting Cu2+ and S2- in 100% aqueous media via a facile one-pot method by covalent linking fluorescein isothiocyanate (FITC) with branched-polyethylenimine (b-PEI). PF could selectively coordinate with Cu2+ among 10 metal ions to form PF-Cu2+ complex, resulting in fluorescence quenching through FRET mechanism. Furthermore, the in situ generated PF-Cu2+ complex can be used to selectively detect S2- based on the displacement approach, resulting in an off-on type sensing. There is no obvious interference from other anions, such as Cl-, NO3-, ClO4-, SO42-, HCO3-, CO32-, Br-, HPO42-, F- and S2O32-. In addition, PF was successfully used to determine Cu2+ and S2- in human serum and tap water samples. Therefore, the FRET-based probe PF may provide a new method for selective detection of multifarious analysts in biological and environmental applications, and even hold promise for application in more complicated systems.