A New Rhodamine-Based "Off-On" Fluorescent Chemosensor for Hg (II) Ion and its Application in Imaging Hg (II) in Living Cells

A novel rhodamine derivative (Rh-C), synthesized by the reaction of rhodamine ethylenediamine and cinnamoyl chloride, was evaluated as a chemoselective Hg2+ ion sensor. Addition of Hg2+ to an ethanol aqueous solution of the Rh-C resulted in a color change from colorless to obvious pink color together with distinctive changes in UV-vis absorption spectrum and fluorescence spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The interaction of Hg2+ and sensor Rh-C was proven to adopt a 1:1 binding stoichiometry and the recognition process is reversible. The chemosensor displayed a linear response to Hg2+ in the range of 0.4-5 mu M with a detection limit of 7.4 x 10(-8) M. The sensor Rh-C was also successfully applied to the imaging of Hg2+ in HL-7702 cells.