A simple quinoline-thiophene Schiff base turn-off chemosensor for Hg2+ detection: spectroscopy, sensing properties and applications

A new Schiff base probe (QT) consisting of 8-aminoquinoline (Q) and thiophene-2-carboxaldehyde (T) moieties has been synthesized. QT undergoes chelation-enhanced fluorescence quenching when exposed to Hg2+ due to coordination by the sulfur and nitrogen atoms of QT thus forming a facile turn-off sensor. The formation of the chelation complex was confirmed by UV-visible absorption and emission spectral measurements, H-1 NMR titration and density functional theory calculations. These studies revealed that the probe exhibits high selectivity and sensitivity towards Hg2+ in the presence of other common metal ions. A low detection limit of 23.4 nM was determined and a Job plot confirmed a 2:1 stoichiometry between QT and Hg2+. The potential utility of QT as a sensor for Hg2+ ions in human HeLa cells was determined by confocal fluorescence microscopy, and its suitability for use in the field with environmental samples was tested with Whatman filter paper strips. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The new Schiff base probe QT shows high selectivity and sensitivity towards Hg2+ detection, even in the presence of other common metal ions. It has potential applications in both laboratory settings and field testing with environmental samples.