Mechanochemical synthesis of fluorescein-based receptor for CN ion detection in aqueous solution and cigarette smoke residue.

A facile green method for the mechanochemical synthesis of Schiff base phenylhydrazono-N-methylene fluorescein (PHMF) with 95% yields has been established. The synthesized receptor assists in the naked-eye detection of CN ions in organic and aqueous media, and F ions in acetonitrile over a series of anions with a color transfer from colorless to pink. A redshift of 160 nm of PHMF-CN complex in the absorbance spectrum and a turn-on response in the fluorescence spectrum were observed, respectively, at λmax 345 to 515 and 519 nm. A strong interaction of PHMF with CN and F ions forming a 1:3 binding stoichiometry has been noted in this study. In an aqueous medium for CN ion, the lower limit of detection (LOD) is defined as 9.204 nM, which is quite better in terms of sensitivity. In addition, PHMF's paper-strip sensor for rapid real-time CN ion sensing was found to be sufficiently sensitive to successfully detect CN ion in water and a solid state, resulting in a portable device for detecting cyanide ions. In acetonitrile, the receptor's ability to detect CN ion in cigarette smoke residue was also satisfactorily achieved. Graphical Abstract.