A water-soluble cationic oligopyrene derivative: Spectroscopic studies and sensing applications

A water-soluble cationic conjugated oligomer, oligo(2-(4-(1-pyrenyl)butanoyloxy)ethyltrimethylammonium bromide) (OPBEAB) was synthesized by the combination of chemical and electrochemical synthesis techniques. The oligomer has an average repeat unit of 4 and a high quantum yield (Ф) of 0.7 in an aqueous solution containing 5.91 × 10−3 mol L−1 sodium dodecyl sulfate (SDS). In this medium, surfactant molecules formed shielding layers along the OPBEAB chains and prevented aggregation of the oligomer and also improved its fluorescence stability. The fluorescence quenching of cationic oligomer (OPBEAB) depends strongly on the mixing sequence of the probe molecule (OPBEAB), analyte (TNT), and anionic surfactant (SDS). A molecule probe based on OPBEAB can rapidly detect ultra-trace TNT in both pure aqueous solution and environmental ground water with high sensitivity. The Stern–Volmer constant (KSV) of the probe in aqueous solution was measured to be as high as 5.30 × 105 mol−1 L and the limit of detection was about 7.0 × 10−8 mol L−1 (70 ppb) under optimized conditions.