Achieving specific selectivity and high sensitivity for the colorimetric recognition of copper(II) ion in aqueous media over a complex background of potentially competing metal ions is inherently challenging in sensor development. Thus, a novel azo-azomethine receptor (L) based on the combination of 2-amino-3-(5-bromo-2-hydroxybenzylamino)maleonitrile and azo-coupled salicylaldehyde scaffold has been designed and synthesized for the naked-eye detection of Cu2+ ion at trace level in a wide pH range. Accordingly, the devised chemosensor distinguished Cu2+ from other metal ions by distinct color change from light yellow to light brown without any expensive equipment. The binding stoichiometry between Cu2+ and L has been investigated using Job’s plot and MALDI-TOF mass analysis. Remarkably, the current sensor can detect Cu2+ ion even at 1.07 μM level, which is lower than the World Health Organization (WHO) permissible level (30 μM) in drinking water. Furthermore, sensor L was successfully utilized in the preparation of test strip for the detection of copper(II) ion from aqueous environment.
