Sequential detecting of Ni²⁺ and CN⁻ with a Chalcone-based colorimetric chemosensor in near-perfect water

As a chalcone-based colorimetric chemosensor for consecutive detection of Ni²⁺ and CN⁻, HNP ((E)-3-(2-hydroxy-5-nitrophenyl)-1-(pyridin-2-yl)prop-2-en-1-one) was developed. HNP detected exclusively Ni²⁺ through the variation of color from yellow to orange. The detection limit of HNP for Ni²⁺ was calculated to be 0.209 μM. In the competition experiment, HNP was not considerably disturbed by various metals in the sensing of Ni²⁺. Moreover, the HNP-Ni²⁺ complex showed a selective color variation from orange to yellow for CN⁻. The detection limit of the HNP-Ni²⁺ complex for CN⁻ was calculated to be 20.8 μM. In the interference test for CN⁻, HNP-Ni²⁺ complex was not significantly inhibited by other anions for detecting CN⁻. In water samples, the detecting ability of HNP for Ni²⁺ and CN⁻ was satisfactorily performed. The binding ratios of HNP to Ni²⁺ and HNP-Ni²⁺ complex to CN⁻ were determined as a 1:1 with Job plot and ESI-mass. Binding mechanisms of HNP to Ni²⁺ and HNP-Ni²⁺ to CN⁻ were demonstrated by ESI-MS, Job plot, UV–vis, FT-IR analysis, and DFT calculations.