Selective and Dual Naked Eye Detection of Cu2+ and Hg2+ Ions using a Simple Quinoline–carbaldehyde Chemosensor

Abstract

A new colorimetric chemosensor based on diethylaminoquinolinecarbaldehyde (AQC) was designed and its sensing behavior towards various metal ions has been investigated through photophysical, IR and NMR techniques. Interestingly, this probe can selectively detect both Cu2+ and Hg2+ ions with an easy, well defined naked-eye visible color changes from yellow to colorless and pink, respectively. The uniqueness of this system is that it forms stable 1:1 stoichiometric complexes involving diethylamino moiety for the selective recognition of Cu2+ ions with a detection limit of 25 ppb. For the selective recognition of Hg2+ ions, it forms a 2:1 stoichiometric complex involving quinoline nitrogen and aldehyde functionality and shows a detection limit of 360 ppb. The association constants for both Cu2+ and Hg2+ complexes were determined and are found to be ca. 2.1 ± 0.1 × 104 M−1 and 1.29 ± 0.2 × 108 M−2, respectively. Uniquely, this probe can be coated on a glass surface to fabricate a simple solid-state dipstick device that can be used for the easy visual detection and analysis of Cu2+ and Hg2+ ions in the aqueous medium.