Turn‐On Fluorescence Sensing of Cyanide Ions in Aqueous Solution at Parts‐per‐Billion Concentrations

Abstract

A few parts per billion are enough to turn on a novel fluorescent cyanide sensor in aqueous solutions. Because of its inherent electron deficiency, the cationic boron moiety of this sensor not only serves as a high-affinity anion binding site, but also quenches the fluorescence of the pendant fluorophores (see figure; PET=photo-induced electron transfer). Anion binding to the boron center neutralizes the electron-accepting properties of the phosphonium borane unit, leading to a revival of the fluorescence of the pendant fluorophore.