Synthesis and characterization of phenothiazine sensor for spectrophotometric and fluorescence detection of cyanide

A sensitive and selective phenothiazine-based sensor (PTZ) has been successfully synthesized. The sensor PTZ displayed specific identification of CN^- 'turn-off' fluorescence responses with a quick reaction and strong reversibility in an acetonitrile:water (90:10, V/V) solution. The sensor PTZ for detecting CN^- exhibits the marked advantages of quenching the fluorescence intensity, fast response time (60 s), and low value of the detection limit. The concentration that is authorized for drinking water by the WHO (1.9 μM) is far higher than the detection limit, which was found to be 9.11 × 10^-9 . The sensor displays distinct colorimetric and spectrofluorometric detection for CN^- anion due to the addition of CN^- anion to the electron-deficient vinyl group of PTZ, which reduces intramolecular charge transfer efficiencies. The 1:2 binding mechanism of PTZ with CN^- was validated by fluorescence titration, Job's plot, HRMS, ¹ H NMR, FTIR analysis, and density functional theory (DFT) investigations, among other methods. Additionally, the PTZ sensor was successfully used to precisely and accurately detect cyanide anions in actual water samples.