FRET-based ratiometric detection of Hg2+ and biothiols using naphthalimide-rhodamine dyads

A new naphthalimide-rhodamine-based dyad in CH(3)CN-HEPES (1 : 1) buffer solution exhibits fluorescence resonance energy transfer (FRET) from naphthalimide to the rhodamine moiety on addition of only Hg(2+) ions and allows ratiometric absorption and fluorimetric estimation of Hg(2+) ions between 50 nM (10 ppb) to 2 μM (0.4 ppm). FRET-induced fluorescence changes were recovered again by the subsequent addition of thiol amino acids via reverse FRET. The interconversion of probe and via the complexation/decomplexation by the modulation of Hg(2+)/Cys exhibited a selective probe for biothiols in real samples.