A chemosensor for micro- to nano-molar detection of Ag⁺ and Hg²⁺ ions in pure aqueous media and its applications in cell imaging

Abstract

The pyridine substituted thiourea derivative PTB-1 was synthesized and characterized by spectroscopic techniques as well as by single crystal X-ray crystallography. The metal ion sensing ability of PTB-1 was explored by various experimental (naked-eye, UV-Vis, fluorescence, mass spectrometry and ¹H NMR spectroscopy) and theoretical (B3LYP/6-31G**/LANL2DZ) methods. PTB-1 exhibited a highly selective naked-eye detectable color change from colorless to dark brown and UV-Vis spectral changes for the detection of Ag⁺ with a detection limit of 3.67 μM in aqueous medium. The detection of Ag⁺ ions was achieved by test paper strip and supported silica methods. In contrast, PTB-1 exhibited a 23-fold enhanced emission at 420 nm in the presence of Hg²⁺ ions with a nano-molar detection limit of 0.69 nM. Finally, the sensor PTB-1 was applied successfully for the intracellular detection of Hg²⁺ ions in a HepG2 liver cell line, which was monitored by the use of confocal imaging techniques.