Synthesis of a highly selective indazole-based chemosensor for detecting the lethal CN− and its real-time applications in water samples

An indazole derivative, VS, was synthesized from benzo[ d ]thiazol-2-amine and 1 H -indazole-3-carboxylic acid and was found to detect the cyanide (CN − ) ion selectively. The sensor characteristics of VS were studied using UV-absorption studies in a DMSO medium. The probe VS was discovered to display a colorimetric response, from colourless to yellow colour when it reacts with the CN − ion. 1 H NMR studies were utilized to ascertain the recognition mechanism, which revealed the CN − ion-assisted deprotonation of two-N-H protons of VS. The developed probe VS was found to be sensitive towards CN − ion with a detection limit of 8.9 × 10 −6 M, and B–H plot revealed a binding constant of 9.3 × 10 −7 M. The CN − ion observed to bind with the probe VS in a 1:2 stoichiometry was confirmed by using Job's plot, and the treatment with trifluoroacetic acid makes probe VS recyclable, and also discovered that VS is capable of sensing the CN − ion in cashew fruit and drinking water samples. The probe VS was demonstrated as a colorimetric test kit using cotton swabs.