2-(1-Pyrenyl) benzimidazole as a ratiometric and “turn-on” fluorescent probe for iron(III) ions in aqueous solution

A highly selective and sensitive ratiometric and "turn-on" fluorescent probe for Fe3+, 2-(1-pyrenyl) benzimidazole (L), was synthesized by a one-step process. In emission spectra, the relative intensity ratio of excimer to monomer fluorescence (l(E450)/l(M387)) of L increased 510-fold upon the addition of 30 equiv. of Fe3+ with a detection limit of 0.2 mu M (11.2 ppb) in aqueous solution. Meanwhile, the fluorescence excitation spectra of L showed a fluorescent "turn-on" probe for Fe3+ with 30-fold enhancement in excitation band intensity of excimer.