| Conjugated polymer is a kind of semiconductor polymer with the conjugated main chain; electron could transfer on the main chain of the conjugated polymers. Conjugated polymers have entered numerous fields of applications such as light-emitting diodes, solar cells, and recently also the important field of chemical and biological sensing. Especially, the conjugated polyelectrolytes are typically soluble in water and other polar solvents and have superquenching effect. The water soluble anionic fluorescence conjugated polyelectrolytes have an advantage in detecting metal ions, organic ions, biomolecules, and biopolymers. Conjugated polyelectrolytes also have some problems such as low stability, reliability strongly depends on the environments and low fluorescence quantum yield in water solution and solid state. Although much success in demonstrating the application of surfactant to improve the emissive properties of conjugated polymers, but to the best of our knowledge, nobody has yet utilized surfactants to improve the photostability of conjugated polyelectrolytes.In order to solve the problems, we choose the PPESO3 as the model compound, studied how to improve the stability and fluorescence quantum yield of conjugated polymers. We also studied the application of conjugated polyelectrolytes in the detection of free radicals. The main contents include:In chapter one, development, category and electronic structures of conjugated polymers are introduced. We also introduced the application of conjugated polymer in the fields of light-emitting diodes, solar cells, and chemical and biological sensing. And then we talk about the problems of conjugated polymers: such as poor stability and low fluorescence quantum yields. At last we introduced some methods, which could improve the defeats of conjugated polymers.In chapter two, we introduced the synthetic route for the preparation of monomer and the final conjugated polymer PPESO3 used in our experiment. We also introduced the fluorescence spectroscopy and absorption spectroscopy of PPESO3 in different solutions.In chapter three, the interaction between the water-soluble anionic fluorescence conjugated polyelectrolyte PPESO3 and various surfactants has been studied in aqueous solution by UV-vis absorption spectra and fluorescence spectra. With the addition of surfactants, the aggregations of polymers are broken up. For eliminating the self-quenching effect of the fluorescent polymers, the photoluminescence quantum yield of PPESO3 is dramatically enhanced. The PL quantum yield of PPESO3 can be enhanced 6 to 12-fold with the addition of different surfactants. And at higher concentration of surfactants, the photostability of PPESO3 is also highly increased. A"micelle incorporation model"is proposed to explain the enhancement of photostability. To deeply understand the interaction processes between PPESO3 and surfactants, we systematically studied the fluorescence spectra changes of PPESO3 and the dynamic processes at different CTAB concentrations. All results prove the surfactants can simultaneously enhance the PL quantum yield and photostability of water-soluble conjugated polyelectrolytes and this method is very simple and powerful.In this work, we studied the fluorescence quenching of the anionic conjugated polyelectrolyte PPE.SO3 by the paramagnetic species 2,2,6,6-tetramethylpiperidine-ntroxide free radical (TEMPO) in aqueous solution. At low quencher concentration the Stern.Volmer constant is 94 M-1. Ascorbic acid is used to reduce TEMPO to the corresponding hydroxylamine and the PPE.SO3 fluorescence is fully recovered. Under a large excess of ascorbic acid over TEMPO the rise of fluorescence followed pseudo.first.order kinetics. The second.order rate constant calculated from this time course is 0.7 M-1 s-1. |
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