A new quinoline-based fluorescent-colorimetric chemosensor for sensitive and selective “on–off” detection of Pb2+ ions†

For the first time, a novel mono Schiff base of a quinoline-based reversible fluorescent-colorimetric receptor (L) has been designed for the detection of Pb²⁺ ions in a semi-aqueous medium. The receptor L exhibited a very good selective fluorescent-colorimetric quick on–off response when exposed to Pb²⁺. The colorimetric assay showed a sensitivity of 1.2 × 10⁻⁶ M, while the fluorescent assay exhibited a sensitivity of 9.9 × 10⁻⁷ M for Pb²⁺. A 1 : 1 stoichiometric complexation between L and Pb²⁺ was determined using ESI-MS spectra and Job's plot measurements. Pb²⁺ was successfully measured using receptor L in both real samples and in an aqueous solution of the protein bovine serum albumin, as well as in the construction of an INHIBIT-type molecular logic gate.