A highly selective fluorescent sensor for ratiometric detection of cyanide in aqueous solution and solid states

Abstract Designing fluorescent sensors for selective detection of CN− in aqueous and even solid states are still rarely reported due to the aggregation-caused quenching (ACQ) effect. In this paper, we report a novel fluorescent probe C-1. Due to the AIE effect, C-1 displayed obvious orange-red fluorescence with emission peak centered at 597nm in aqueous solution and solid state. Under the influence of electron withdrawing cyano and ester groups, the vinyl C=C bond was easy to be attacked by nucleophilic CN−, which destroyed the conjugated bridge and also blocked the ICT process between the donor and the acceptor. The emission band shifted from 597 nm to 475 nm consequently. Other anions have no effect on the fluorescence of C-1. Thus, C-1 could be used as a selective CN− sensor. The UV-visible and fluorescent measurement confirmed the interactions between C-1 and CN−. 1H NMR titration method further demonstrated the detection mechanism. The sensitivity and detection limit of C-1 were measured to be 5.97 × 104 M−1 and 1.2 μM respectively. Due to the solid-state emission nature, C-1 immersed test strip was prepared and used as an effective test kit to detect CN¯ ion.