Detection of cyanide (CN−) ion with high selectivity and sensitivity by using ‘Turn-ON’ fluorescence strategy of Rhodamine Schiff base

Abstract

A Rhodamine based Schiff base, (E)-3′,6′-Bis(ethylamino)-2-(2-(((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methyl-ene)amino)ethyl)-2′,7′-dimethylspiro[isoindoline-1,9′-xanthen]-3-one (HL) has been synthesized and characterized by various spectroscopic data, viz. 1H and 13C NMR, ESI-MS, FT-IR and elemental analysis. It shows very weak fluorescence emission (9:1 (v/v) DMSO/H2O, HEPES buffer at pH 7.4) while it is enhanced considerably upon addition of CN− ion selectively (λem, 456 ​nm) in presence of nineteen other biologically important anions. The Limit of Detection (LOD) is 24 ​nM which is significantly lower than literature reported data. The binding interaction of the probe to CN− ion, 1:1 (HL:CN−) mole ratio has been confirmed by Job's plot, ESI-MS spectral data and 1H NMR spectral titration measurement.