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

Abstract

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 160nm 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 519nm. 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 9.204nM, 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.