A novel dye-based colorimetric chemosensors for sequential detection of Cu²⁺ and cysteine in aqueous solution

An IDAs based chemosensing ensembles for sensitive and selective sequential detection of Cu²⁺ and cysteine (Cys) in 100% aqueous solution was designed on the basis of the complex formation between 4-(2-Pyridylazo)resorcinol (PAR). In the first step, PAR was used for colorimetric detection of Cu²⁺ in aqueous solution by the obvious color change. The detection limit (31.0 nmol L^-1) for Cu²⁺ much lower than the guideline (31.5 μmol L^-1) of WHO in drinking water. In the second step the produced ensemble (PAR-Cu²⁺), sensitively and selectively detected a low concentration of Cys via indicator displacement assay system. The detection limit for Cys was determined to be 72 nmol L^-1. The colorimetric detection operation is low-cost using PAR and copper ion and has a simple operation without any further modifications. Any enzymatic reactions, separation processes, chemical modifications, and sophisticated instrumentations are also not required in this experiment. It could find applications for the detection of analytes in environmental, biological samples based on these results, dual logic gates (IMPLICATION and INHIBIT) were obtained by controlling the chemical inputs.