Stilbene-based fluorescent chemosensor for selective detection of cyanide ion in DMSO medium and its application in cell-imaging, fingerprint, and food sample analysis.

We designed a new cyanide sensing probe by one-step synthesis and evaluated it using UV-vis and fluorescent techniques. The active moiety of (Z)-3-(4-(methylthio) phenyl)-2-(4-nitrophenyl) acrylonitrile (NCS) demonstrated fluorescence. The probe NCS showed turn-off fluorescence in the presence of cyanide (CN¯), which has a higher selectivity and sensitivity than other anions. The cyanide group (CN¯) nucleophilically attacks the double bond between the cyano vinyl groups of the probe, disrupting the intramolecular charge transfer (ICT) process, which accounts for the response mechanism of NCS towards CN¯. The mechanism behind the observed photophysical changes was further studied using 1HNMR titration, FT-IR, Jobs plots, DFT calculation, and mass spectroscopy. The experiments on absorption and emission showed that it was very selective. Job's plots to find the stoichiometry between NCS and CN¯ are 1:1, and the detection limit was 1.14 μM. Moreover, the test strip experiment provides a wide application prospect for the receptor for detecting poisonous cyanide and biological systems in live cell images and latent fingerprint applications.