Aggregation-induced emission activity of sensor TBM-C1 hybrid of methoxy-triphenylamine (OMe-TPA) and dicyanovinyl for cyanide detection in aqueous THF: Mechanistic insights and potential applications

A series fluorescent probes (TBM-C x ( x  = 1, 4, 8)) were designed based on embedding various alkoxy chains on the electron donor of triphenylamine (TPA)-based dicyanovinyl (MT) compound with an electron-deficient benzothiadiazole (BTD) for sensitive, selective, and visualizing detection of cyanide in aqueous solution. Due to the nucleophilic addition of CN − , the intramolecular charge transfer (ICT) of these probes was inhibited by the destroyed conjugated structure, exhibiting excellent “turn-on” fluorescence response toward cyanide anion (CN − ) in tetrahydrofuran (THF). However, the alkoxy chains with different lengths embedded in TPA not only enhance the sensitivity and solubility, but also regulate the emission behavior from ICT to aggregation-induced emission (AIE) characteristics. The binding mechanism and AIE sensing performances between the probes and CN − have been investigated and compared in THF/water mixture by spectral tools and theoretical calculations. The results showed that the ICT-based TBM-C1 probe with methoxy chain showed significantly turn-on fluorescence response to CN − as low as 0.077 μM in THF/water solution at high water fraction (90 %). Due to the AIE sensing process, TBM-C1 was successfully employed to determine CN − in food and water samples, image CN − in living cells and BALB/c mice, and prepare test kits for visualizing cyanide.