Visual‐Detection of Cu²⁺ in DMSO aAqueous Solution Based on Benzimidazole Azo‐dye as a Colorimetric Chemosensor

In this work, a novel colorimetric chemosensor ( BIAD ) containing azo chromophore, 1,5dihydroxynaphthalene, and benzimidazole was synthesized and characterized by using IR, 1 H, 13 C NMR, and mass spectral data, and elemental analysis. The cation recognition studies (including fourteen metal cations) exhibited that the synthesized azo dye can act as a rapid, sensitive, and selective colorimetric chemosensor for detecting Cu 2+ ions. The addition of Cu 2+ ions to the BIAD solution, changed immediately the solution color from purple to blue‐green, which could be observed by the naked eye. Comparison of the UV/Visible spectra of BIAD and ( BIAD +Cu 2+ ) revealed a red shift from 543 nm to 616 nm, which confirms the formation of a complex between Cu 2+ cations and BIAD molecules. The result of Job's plot indicated that the stoichiometry binding ratio of BIAD to Cu 2+ is 1 : 1. The limit of detection (LOD) was found for BIAD toward Cu 2+ ion to be 0.10 μM. Furthermore, the BIAD ‐based test paper strips were successfully used for the rapid detection of Cu 2+ ions (<1 sec) in the aqueous solution (H 2 O‐DMSO, 9 : 1).