Reversible multi-control fluorescent switch and molecular logic gate based on selective recognition of Fe3+ and its application to multiplex detection

Abstract

A novel chemosensor, 2-hydroxy-4-(pyridin-2-ylmethyleneamino)benzoic acid (PA) has been developed and found to be a selective fluorescent detector of Fe³⁺ over a wide range of treated metal ions. Because of the presence of carboxyl in PA, the fluorescence of this Schiff base could be reversibly controlled by alternately adding OH⁻ and H⁺. In addition, because Fe³⁺ selectively quenches the fluorescence of PA, the quenched fluorescence can be recovered by adding EDTA as a competitor or NH₂OH × HCl as a reducing agent. As a result, the fluorescence intensity of PA could be reversibly turned by H⁺/OH⁻ or Fe³⁺/EDTA or NH₂OH × HCl/K₂S₂O₈ in an aqueous solution. These results demonstrated that PA along with a PA–Fe³⁺ system can perform not only as a reversible multi-control fluorescent switch, but also as a “NOR,” “OR” and “INHIBIT” logic gates. Furthermore, analytical application of this fluorescent probe was investigated and achieved promising and satisfying results.