A new FRET ratiometric fluorescent chemosensor for Hg²⁺ and its application in living EC 109 cells.

On the basis of fluorescent resonance energy transfer, a new fluorophore dyad (L) bearing rhodamine B and naphthalimide was developed as fluorescent ratiometric chemosensor for Hg(2+) in aqueous solution. L exhibited high selectivity and excellent sensitivity towards Hg(2+) with a broad pH span (1.0-8.0) and the detection limit of L was 2.11×10(-8) M. Sensor L for the detection of Hg(2+) was rapid and the recognizing event could complete in 2.5 min. A significant change in the color could be used for naked-eye detection. The selective fluorescence response of L to Hg(2+) is due to the Hg(2+)-promoted ring opening of spirolactam of rhodamine moiety, leading to a cyclization reaction of thiourea moiety. In addition, fluorescence imaging experiments of Hg(2+) in living EC 109 cells demonstrated its value of practical applications in biological systems.