A fully-aqueous red-fluorescent probe for selective optical sensing of Hg²⁺ and its application in living cells

A new red-fluorescent mercury ion sensor material is designed and synthesized, which is composed of a tweezer-shaped hydrophilic probe containing bifurcated soft-base atoms N and S coupled with 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) unit. By virtue of the strong electron-accepting nature of TCF unit (as a push-pull chromophore), this designed sensor material can selectively detect Hg²⁺ over various tested metal ions in a 100% aqueous medium via naked-eye and photoluminescence (PL) observations. Theoretical and time-resolved photoluminescence measurements further confirmed the selectivity and reversibility of the probe towards Hg²⁺ via intramolocular charge transfer mechanism in this sensor material. Moreover, the living cell tests by confocal fluorescence images of this sensor material towards Hg²⁺ were also investigated. Finally, distinguished absorption changes and fluorescence quenching spectral appearances allowed us to present the selective optical indicator of Hg²⁺ via TCF moiety for the first time.