Crown ether-bridging pyridinium tetraphenylimidazole: an effective fluorescent sensor for pesticide bromoxynil...

Pesticide bromoxynil octanoate is widely used in agriculture but might bring environmental contamination and pose risks to human health when excessive or improper application. Therefore, the simple and in-situ method on detecting bromoxynil octanoate is extremely anticipated. In this work, a crown-ether-bridged tetraarylimidazole pyridinium salt (CPT) was designed and synthesized as an effective fluorescent sensor for bromoxynil octanoate. The synthesis was simple and straightforward condensation in yield of 84%. This sensor exhibited a distinct "turn-on" blue-green fluorescence response toward bromoxynil octanoate with high selectivity over various interfering ions and pesticides in near aqueous media. The limitation of detection was as low as 1.1 × 10^-7 M. The sensing mechanism was confirmed as that bromoxynil octanoate was bound in the opening cavity of CPT via π-π stacking and hydrophobic interaction, restricting the rotation freedom of the aromatic groups and increasing the aggregates to enhance the AIE emission. The sensing capability for bromoxynil octanoate was successfully applied in paper tests, seal test and water samples, indicating its excellent potential for simple, rapid, and in-situ detection of bromoxynil octanoate in real environments.