A simple benzothiazolium-based sensor for cyanide detection: Applications in environmental analysis and bioimaging
Sisay Uota, Bor-Jang Hwang, Ray J. Butcher, Roger J. Mullins, James Wachira, Yousef M. Hijji, Fasil A. Abebe
Abstract
• A new benzothiazolium-based CN − fluorescent and colorimetric sensor has been designed and synthesized using microwave irradiation. • The sensor exhibits excellent sensitivity, selectivity, large Stokes shift and low detection limit to CN − in aqueous and solid state. • The sensing mechanism includes formation of deprotonation and nucleophilic addition reaction. • SU-1 can be applied to determine CN − in environmental water samples with a LOD of 0.27 nM and detect intracellular CN − in live cells. A new sensor based on Ethylbenzothiazolium-2-hydroxynaphthaldehyde conjugate-based fluorescent sensor, (E)-3-ethyl-2-(2-(2-hydroxynaphthalen-1-yl) vinyl) benzo[d]thiazol-3-ium iodide ( SU-1 ) was designed and synthesized. The structure of SU-1 was confirmed by 1 H NMR, 13 C NMR, HRMS, and single crystal XRD spectral analysis. SU-1 displayed a colorimetric and fluorometric response in a DMSO:H 2 O (1:1,v/v) matrix, changing color from pale yellow to colorless visible to the naked eye, accompanied by a ∼ 120 nm red-shift in the absorption spectra upon CN − addition. This shift, due to formation of deprotonation followed by the nucleophilic attack on the benzothiazolium ring’s double bond, disrupts π-conjugation, blocking intramolecular charge transfer within SU-1 . However, competitive anions showed negligible interference while detecting CN − . The Limit of detection for CN − was determined to be 0.27 nM, significantly below the WHO’s permissible CN − concentration in drinking water (1.9 μM). Job’s plot analysis shows that the binding stoichiometry of SU-1 to CN − is a 1:1, with a stability constant (Ka) of 1.58 x 10 4 M −1 . The sensor demonstrated practical applications in environmental water samples and fluorescence imaging of intracellular CN − in CAD cell line.