A near-infrared amine/HSO3- probe with colorimetric and fluorescent ultrafast response and its application in food samples and visual evaluation of salmon freshness.

A multifunctional near-infrared fluorescent probe (Sycy) is synthesized by the one-step condensation reaction of syringaldehyde and tricyanofuran. Sycy can detect HSO3- within 150 s in the red wine and sugar samples with a low detection limit of 3.5 μM. Sycy also has an obvious response to 13 volatile amines through colorimetric and fluorescent channels. Sycy recognizes representative diethylamine (DEA) with a large stokes shift (131 nm), low detection limit (7.11 μM), ultrafast response within 5 s, and fluorescence imaging DEA in living cells. The sensing tag loaded with Sycy can monitor the freshness of salmon by observing colorimetrical and fluorescent changes of the tag with the naked eye. In addition, quantitative determination of HSO3- and evaluation of fish freshness can be achieved with smartphone assistance, improving the detection accuracy. Sycy can be prepared into fluorescent ink and be applied to the field of material and information storage.