Colorimetric probe for sequential chemosensing of mercury(II) and cyanide ions in aqueous media, based on a benzoxadiazole-pyrazolin-5-one glycoconjugate with INHIBIT logic gate response

Abstract

A new and efficient water-soluble probe L for the sequential detection of Hg2+ and CN− ions has been developed by the condensation of benzoxadiazole and glycoconjugated pyrazoline-5-one. The resulting probe has a water solubility of 45 g/L at room temperature and interacts selectively with Hg2+ ions in water over other cations by changing its color from yellow to red and forming the [L/Hg2+: 2:1] complex. On the other hand, the formed complex [L/Hg2+: 2:1] reacts selectively with CN− anions in an aqueous solution. This reaction is accompanied by a blue shift in wavelength from 545 nm to 472 nm with a color change from red to yellow visible to the naked eye. These reversible and repeatable colorimetric responses of probe L towards Hg2+ and CN− ions can be represented as a molecular logic gate 'IMPLICATION', where Hg2+ and CN− ions are considered as inputs and the absorbance at 472 nm as output. The detection limit for Hg2+ and CN− ions was found to be 2.31 ppb and 4.34 ppb, respectively. From a practical point of view, probe L was used to prepare a test strip based on filter paper treated with L. The resulting test strip selectively changes color after the sequential addition of Hg2+ and CN− ions in water at pH7. These high performances in terms of selectivity and sensitivity allow the probe L to be used for the sequential detection of Hg2+ and CN− ions in aqueous media.