Fluorescence “Turn-On” Indicator Displacement Assay-Based Sensing of Nitroexplosive 2,4,6-Trinitrophenol in Aqueous Media via a Polyelectrolyte and Dye Complex

A water-soluble nonfluorescent cationic conjugated polyelectrolyte poly(1,1'-((1,4-phenylenebis(oxy))bis(propane-3,1-diyl))bis(pyridin-1-ium)bromide) (PPPy) was specifically synthesized via an economical method of oxidative coupling polymerization in high yields. PPPy selectively recognized nitroexplosive picric acid (PA) by fluorescence "turn-on" in the presence of closely related nitroexplosive compounds, namely, 2,4,6-trinitrotoluene, 2,4-dinitrophenol, and 4-nitrophenol via fluorescence indicator displacement assay (IDA) technique in water at pH 7.0. The polymer PPPy was characterized by NMR spectroscopy, gel permeable chromatography, UV-vis spectroscopy. The polymer PPPy forms an electrostatic complex with uranine dye. This ensemble scheme was utilized to detect PA with a limit of detection value of 295 nM (solution state) and 0.22 ppm (vapor state) through IDA, a phenomenon that is very different from the widely reported Förster resonance energy transfer, photoinduced electron transfer, ground-state charge transfer and inner filter effect based probes used for nitroexplosive PA detection.