A selective, fluorescent probe for Hg²⁺ detection in aqueous solution

A novel fluorescent probe, 5-(2-benzothzaole)-2-thiophene boronic acid (1), for Hg²⁺ detection in aqueous solution was synthesized. (1) exhibited very strong fluorescence emission (φ{symbol} = 0.92) in tris-HCl (pH 7.42) buffer aqueous solution. It was found that the fluorescence emission of (1) was quenched significantly upon addition of Hg²⁺ in buffer aqueous solution, whereas no marked fluorescence quenching was detected with addition of other metal ions (Ba²⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Mg²⁺, Fe²⁺, Fe³⁺, Ni²⁺, Pb²⁺, Zn²⁺, Na⁺, K⁺) expect for Fe²⁺ and Fe³⁺, for which a small fluorescence quenching was detected in same condition. Competition experiment showed that no obvious interference was observed in its fluorescence while (1) performed the titration with Hg²⁺ in the different mixtures of metal ions.