A coumarin derivative as a "turn-on" fluorescence probe toward Cd 2+ in live cells.

A novel coumarin-derived Schiff base fluorescence probe (CTB) has been successfully designed and synthesized through exploiting tris-(2-aminothyl)-amine moiety as a recognition unit for the highly selective and sensitive detection of Cd2+. It is based on CN isomerization and the photo-induced electron transfer (PET) mechanism. The investigation into the sensing processes showed that CTB exhibited an excellent selectivity for Cd2+. The sensitivity exceeded that of other competing metal ions, and had a high sensitivity, a detection limit of 1.16 × 10−7 M with the association constants of 1.37 × 1011 M−2. The experiments including Job's plot, UV–Vis titration, 1H NMR titration and ESI-MS spectrum established that the probe CTB binds to Cd2+ in a 1:2 ratio. Further studies also demonstrated that probe CTB can be successfully applied to the fluorescence imaging of Cd2+ in HepG-2 cells.