Dual-Action Polymeric Probe: Turn-On Sensing and Removal of Hg²⁺; Chemosensor for HSO₄^–

A tryptophan-dithiocarbamate-based fluorescent polymeric probe was synthesized, targeting selective recognition and sensing of both cation and anion in aqueous media. Upon treatment with several metal ions, the as-synthesized polymeric probe imparted an irreversible transformation only with Hg2+ ion in aqueous environment with a 5-fold enhancement of the fluorescence (quantum yield (Φ) = 0.055 → 0.250) attributed to the photoinduced electron transfer (PET) process. This unique design has an unprecedented detection sensitivity of 300 parts per trillion (ppt) for Hg2+ ions, the most effective water-soluble amino-acid-based polymeric sensor reported so far. Hg2+ ions get trapped when they were passed through a column containing polymeric probe with 94% removal capacity as confirmed by inductively coupled plasma optical emission spectrometer (ICP-OES). Intracellular detection of Hg2+ ions was achieved in human breast cancer cell line, MDA-MB-468, using our synthesized macromolecular probe. In addition, the probe can also be used to detect parts per million (ppm) level of hydrogen sulfate anion (HSO4–) in aqueous medium among various anions with high selectivity because of the hydrogen bonding interactions of the polymeric probe with the anion. Although the newly developed tryptophan-based polymeric probe has two distinct binding sites for HSO4– and Hg2+, the existence of Hg2+ influences the binding of HSO4–.