Cost-effective approach to detect Cu(ii) and Hg(ii) by integrating a smartphone with the colorimetric response from a NBD-benzimidazole based dyad

A new optical chemosensor N1 was designed and synthesized by condensing 4-chloro-7-nitrobenzofurazan with 2-aminophenylbenzimidazole. In CH₃OH : H₂O (1 : 1, v/v) medium, sensor N1 exhibited high selectivity and sensitivity towards Cu²⁺ and Hg²⁺ ions by showing a distinct colour change from pale yellow to pink due to the internal charge transfer occurring between the sensor N1 and the Cu²⁺/Hg²⁺ ions upon complexation in 1 : 1 stoichiometry.