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 Hg(2+) ion sensor. Addition of Hg(2+) 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 Hg(2+) 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 Hg(2+) in the range of 0.4-5 μM with a detection limit of 7.4 × 10(-8) M. The sensor Rh-C was also successfully applied to the imaging of Hg(2+) in HL-7702 cells.