A highly selective and sensitive fluorescent chemosensor for detection of CN−, SO32− and Fe3+ based on aggregation-induced emission

A novel fluorescence chemosensor 1 with aggregation-induced emission was designed and synthesized through a nucleophilic addition reaction between cyanide and triphenylamine. It exhibited remarkable selectivity and high sensitivity and was able to detect Fe3+, CN− and SO32− in almost pure aqueous solution with low detection limits of 1.44 μM, 9.88 nM and 0.107 μM, respectively. Job's plot and 1H NMR data showed that the binding stoichiometry of 1 with Fe3+, CN− or SO32− was 1:1. Further observations of 1H NMR titration suggested that a coordination bond was formed between two cyano of 1 and Fe3+ which resulted in fluorescence quenching of 1 after detection of Fe3+, whereas the nucleophilic addition of cyanide or sulfite to the vinyl group was responsible for the fluorescent quenching of CN− or SO32− toward 1. The biological applications of 1 were also evaluated and it was found to exhibit low cytotoxicity and membrane permeability. In addition, 1 could also be made into test strips to detect Fe3+ and CN− and was employed as a sensor for detection Fe3+ in living cells.