A novel barbituric-based fluorescent probe with aggregation induced emission for the highly sensitive ratiometric detection of cyanide anions

Abstract

A new tetraphenylethylene-based barbituric acid derivative (TPEB) with an aggregation induced emission effect is synthesized as a fluorescent probe for CN−. The fluorescence spectra of TPEB in a DMSO–H2O mixture changed with different water fractions (fw). Nano-aggregates of TPEB are formed with the strongest fluorescence emission when fw beyond 60%. TPEB displays high selectivity and anti-interference toward CN− in DMSO–H2O (fw 70%) system at pH around 6, even in the presence of other competitive anions (AcO−, F−, Cl−, Br−, I−, NO3−, SO42−, ClO4−, PO43−, SCN−, HS−, S2− and H2O2). The linear curve is excellently matched between the fluorescence intensity and CN− concentration at 500 nm. By the equation 3σ/S, the limit of detection of TPEB for CN− reaches 0.767 × 10–6 mol L−1. The probe TPEB operates via intramolecular charge transfer mechanism, attributed to the unique nucleophilic addition reactions between TPEB and CN−, which is further confirmed by LC–MS spectra, Job's plot and DFT calculations. By colorimetry and fluorescence approach, CN− ions can be easily detected by the TPEB testing strip. The probe can be used to distinguish the acidity and basicity of the solution qualitatively.