Colorimetric recognition of Cu2+ and fluorescent detection of Hg2+ in aqueous media by a dual chemosensor derived from rhodamine B dye with a NS2 receptor

Abstract A rhodamine B derivative bearing a NS 2 -containing receptor ( L ) is developed as a dual chemosensor for detection of Cu 2+ and Hg 2+ in aqueous media. L shows highly sensitive colorimetric response to Cu 2+ and selectively turn-on fluorescent response to Hg 2+ with very low detection limits of 1.63 and 2.36 μM, respectively. The significant absorption enhancement (251-fold) accompanied with a visual color change from colorless to purple upon interaction with Cu 2+ , making L a suitable “bare-eye” indicator for Cu 2+ . By means of Job's plot, 1 H NMR titration and ESI-MS studies, both 1:1 binding modes ( L /Cu 2+ and L /Hg 2+ ) are confirmed and a possible sensing mechanism is further proposed. The response behaviours of L toward Cu 2+ and Hg 2+ are pH independent in a wide range (pH 4.0–9.0). Proof-of-concept experiment demonstrates the potential application of L for trace Cu 2+ and Hg 2+ detection in complicated environmental water samples. More importantly, the turn-on fluorescent chemosensor L with good membrane-permeable property is successfully applied to microscopic imaging for the detection of Hg 2+ in PC3 cells.