A simple colorimetric chemosensor with highly performance for detection of cyanide and copper ions and its practical application in real samples

Two novel and simple azo-based compounds with electron-withdrawing and electron-donating groups (M1 and M2) were synthesized by the diazotization procedure. The synthesized compounds were then applied for detection of important ions in aqueous solutions of acetonitrile. Sensor M1 with electron-withdrawing group (EWG) showed distinct colorimetric responses towards CN- (light yellow to red) and Cu2+ (light yellow to dark yellow). Through titration experiment, the detection limit (LOD) of M1 for CN- and Cu2+ ions sensing were found to be nano molar (nM) level. Job's plot based on spectroscopic data showed the complexes formation between M1 and ions has the stoichiometric ratio of 1:1 (M1-CN- and M1-Cu2+). In addition, the binding constants for M1 towards CN- and Cu2+ were determined using the Benesi-Hildebrand equation. Furthermore, the M1-based test papers strips were successfully used to the rapid detection of CN- ions in semi-aqueous medium. Importantly, sensor M1 was applied to detect CN- and Cu2+ in real water samples and apple seeds samples. However, for M2, containing electron-donating group (EDG), no clear color changes were observed in the presence of investigated ions.