A Simple Fluorescent Chemo-Dosimeter for Sensitive Detection of Cyanide and Hydrogen Sulfide Ions: Spectroscopic and...

The lethal potency and pervasive existence of both cyanide and hydrogen sulphide in various processes mandates their detection. In this context, a simple chemo-dosimeter (AK6) containing 2,2'-bisthiophene fluorophore moiety has been synthesized and spectroscopically characterized. The selectivity of AK6 toward CN^‒ and HS^‒ ions was fortified via fluorescence enhancement, which is attributed to the nucleophilic addition of CN^‒ and HS^‒ ions to the olefinic C-atom of the probe, as manifested by ¹H and ¹³C NMR, and mass spectral experiments. The AK6 could sense CN^‒ and HS^‒ ions with a limit of detection (LOD) values of 0.42 and 13 µM, respectively, with high selectivity without interference from other common anions and cations. The pH studies revealed that AK6 is suitable for detecting CN^- and HS in physiological and environmental conditions (pH range 4-10). The Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations substantiated the proposed mechanism, which alters the intramolecular charge transfer (ICT) transition in the probe to impart fluorescence enhancement that can be seen visually. Besides, AK6 could be utilized to assess CN^‒ and HS^‒ ions in actual water samples.