A novel colorimetric chemosensor for the sequential detection of Ni²⁺ and CN⁻ in aqueous solution

A new colorimetric chemosensor 1 for the sequential detection of Ni²⁺ and CN⁻ was designed and synthesized. The presence of Ni²⁺ led to a distinct naked-eye color change from colorless to yellow in a near-perfect aqueous solution. To examine the binding mechanism of 1 with Ni²⁺, UV3–vis spectroscopy, ESI-mass spectrometry analysis and DFT calculations were conducted. The detection limit of 1 for Ni²⁺ was down to nanomolar concentration (57 nM). Also, the sensing ability of 1 for Ni²⁺ was successfully carried out in real water samples (tap, drinking and sewage water). Moreover, the resulting 1-Ni²⁺ complex acted as an efficient colorimetric chemosensor for CN⁻ via a color change from yellow to colorless. Therefore, chemosensor 1 can be employed as a practical colorimetric chemosensor for detecting of both Ni²⁺ and CN⁻.