Cancellation of contact quenching: A simple concept for selective chemosensing of basic fluoride and acetate anions

Abstract

A weakly fluorescent acid-base pair formed by reacting fluorescent acridine orange with the quencher picric acid is reported for the detection of basic fluoride and acetate anions. Deprotonation by these anions causes disengagement of the fluorescent acridine orange from the quencher, picric acid. This phenomenon cancels the quenching existing in the native probe, thereby allowing for the optical signalling of fluoride and acetate anions by colour modulation as well as fluorescence switch-on response. Anions such as Br, I, Cl, NO3, SCN, HSO4, and H2PO4 offer no detectable interference even when in excess concentration.