Thiazole-containing conjugated polymer as a visual and fluorometric sensor for iodide and mercury

A neutral conjugated polymer poly-p-phenylene (PPP) derivative, poly(1,4-bis-(8-(4-phenylthiazole-2-thiol)-octyloxy)-benzene) (PPT), was prepared using a simple and economical method of oxidative polymerization reaction. This newly synthesized polymer PPT was characterized by means of Fourier transform infrared spectroscopy (FT-IR), (1)H nuclear magnetic resonance ((1)H NMR), ultraviolet-visible (UV-Vis), and fluorescence spectroscopy. PPT displays fluorescence "turn-off/turn-on" characteristics and colorimetric responses to I(-) and Hg(2+). The UV-Vis and fluorescence spectra of the PPT showed a significant shift in λmax via the addition of iodides and mercury. A colorless PPT solution turns to deep yellow in the presence of iodide salts, which subsequently becomes colorless again on addition of Hg(2+) salts that could be easily detected visually by the naked eye. The Stern-Volmer constant (Ksv) value obtained for the detection of iodide is 0.13 × 10(5) M(-1), confirming very high sensitivity of this polymer for iodide salts. The detection limit of Hg(2+) salt using the PPT polymer was found to be 2.1 nM in water. The detection of both iodide and mercury was also possible in solid state by using a membrane film prepared by mixing 1% PPT in polystyrene. This membrane changes color in the presence of iodide as well as mercury salts. These results confirm that the PPT polymer can be applied for the colorimetric as well as fluorometric sensing of I(-) and Hg(2+) ions in a competent environment in solution, as well as in the solid state, using a membrane film rapidly.