Polythiophene based fluorimetric insight into minute styrene concentration in solution and gas phase

Water immiscible organic solvents dispersed in aqueous phase raise concerns due to persistence in environment and high toxicity. Fast and operation-simple approaches to assess their contents outside specialized laboratories are required. In this work an original approach allowing quantification of minute amounts of styrene present in solution or in gas phase is proposed. Polythiophene - poly[3-(ethyl-6-hexanoate)thiophene-2,5-diyl] (PeHT) - nanoparticles were applied as probes, offering an increase of emission intensity upon the rise of styrene contents in the sample. The response mechanism is based on the interaction of the polymer dye with analyte; at lower concentrations, the increase of emission at wavelengths typical for nanoparticles emission suggests interactions of the analyte with polymer chains in nanostructural form and offers selectivity. On the other hand, with increasing styrene contents in solution, polythiophene tends to form nano-dispersion droplets in the analyte resulting in appearance of emission peak characteristic for solvent dispersed polymer. A linear dependence of emission intensity on styrene concentration in solution was observed within the range from 0 to 200 ppm. The proposed approach benefits from full reversibility of sensors, upon spontaneous evaporation of styrene from solution. Finally, the nanoparticle suspension allows to detect the presence of styrene also in the vapor phase due to its solubilization in water (Henry's Law). Emission changes were observed in case of 0–2100 ppm of styrene vapor in the probe headspace, corresponding to 0–80 ppm styrene in solution. For the sake of comparison another polythiophene derivative, poly(3-octylthiophene-2,5-diyl) (POT), was investigated showing no changes in fluorescence emission spectra in the presence of styrene up to 200 ppm.