Fluorescence turn-on detection of cyanide anion based on viologen-quenched water-soluble hyperbranched polymer

The synthesis of an anionically-functionalized, hyperbranched conjugated polymer with sulfonic acid end groups is presented. Due to the presence of sulfonate groups in the hyperbranched polymer, the electrostatic interaction with viologen-based cation has a major impact on the quenching of the polymer. The electrostatic complex dissociates into individual molecules upon addition of cyanide anions, due to the more favorable interaction between the viologen-based cations and cyanide anions, resulting in the restoration of fluorescence. This change in fluorescence can be employed as a highly selective and sensitive sensing signal for the presence of cyanide anions.