| A conjugated system is a system of connected p-orbitals with delocalizedelectrons in compounds with alternating single and multiple bonds, which in generalmay lower the overall energy of the molecule and increase stability, which attractsmore and more interest. The first chapter of this thesis outlines the history anddevelopment of conjugated polymer, the structure and classify. The fluorescencequench mechanism and the research method were discussed. For CPs application,the reported fluorescent sensors based on CPs were listed (ion detection,biomolecular detection, explosive substance detection and bio-imaging applications).And the research significance of this work is discussed.We used a facile sysnthetic route for preparing fluorescent conjugated polymerPPESO3in chapter two, which avoided the dealkylation step with BBr3. We alsoinvestigated the fluorescence spectroscopy and absorption spectroscopy of PPESO3.Both fluorescence enchance and quenching of PPESO3were studied detailedly which is a preparation for later study in the thesis.In chapter three, a sensitive and simple detecting system was developed forquantitative analysis of both hydroquinone (H2Q) and hydrogen peroxide (H2O2),based on the successful combination of horse radish peroxidase (HRP) andwater-soluble conjugate fluorescence polymers PPESO3. In the presence of HRP andH2O2, H2Q could be oxidized to1,4-benzoquinone (BQ), an intermediate, which playsthe main role in the enhanced quenching of the photoluminescence (PL) intensity ofPPESO3. The quenching PL intensity of PPESO3(I0/I) was proportional to theconcentration of H2Q and H2O2in the range of1.0×10-6to2.0×10-3mol/L (R2=0.996)and6.0×10-6to2.0×10-3mol/L (R2=0.999), respectively. The detection limit for H2Qand H2O2was5.0×10-7mol/L and1.0×10-6. The present fluorescence quenchingmethod was successfully applied for the determination of H2Q in the lake water,rainwater, tap-water and chemical plant waste water samples. Compared withprevious reports, the fluorescence quenching approach described in this work issimple and rapid with high sensitivity, which has a potential application for detectingvarious analytes which can be translated into quinone.The above study indicates that the enzymatic reaction product ofhydroquinone–quinone can efficiently quench the photo-luminescence intensity ofPPESO3. Considering that dopamine is a catecholamine that contains adihydroxybenzene group, we developed a sensitive water-soluble fluorescentconjugated polymer biosensor for catecholamine (dopamine DA, adrenaline AD andnorepinephrine NE) in chapter four. In the presence of horse radish peroxidase (HRP) and H2O2, catecholamine could be oxidized and the oxidation product ofcatecholamine could quench the photoluminescence (PL) intensity of PPESO3. Thequenching PL intensity of PPESO3(I0/I) was proportional to the concentration of DA,AD and NE in the concentration ranges of5.0×10-7to1.4×10-4,5.0×10-6to5.0×10-4,and5.0×10-6to5.0×10-4mol/L, respectively. The detection limit for DA, AD and NEwas1.4×10-7mol/L,1.0×10-6and1.0×10-6mol/L, respectively. The PPESO3-enzymehybrid system based on the fluorescencequenching method was successfully appliedfor the determination of catecholamine in human serumsamples with good accuracyand satisfactory recovery. The results were in good agreement with thoseprovided bythe HPLC-MS method.In chapter five, we developed a new one-step turn-on sensor for the sensitive andselective detection of glutathione (GSH) and cysteine (Cys). The photoluminescenceintensity of PPESO3could be quenched by Cu(II) due to the strong electrostaticinteraction and electron transfer between PPESO3and Cu2+. In the presence ofbiothiols, such as GSH and Cys, Cu(II) preferred to react with biothiols to form theCu(II)-S bond due to the strong affinity between Cu(II) and thiols. The recovered PLintensity of PPESO3(Ir/I0) was proportional to the concentration of GSH or Cys in theconcentration ranges of1.0×10-7～1.5×10-5mol/L and2.0×10-7～2.0×10-5mol/L,respectively. The detection limit for GSH and Cys were4.0×10-8and4.5×10-8mol/L, respectively. In addition, the established method showed a high selectivity forbiothiols among other twelve amino acids without biothiols. Furthermore, thePPESO3-Cu(II) system as a fluorescence probe was successfully used for fluorescence imaging of biothiols in the HepG2cells, which presents a potential application inbioimaging field.
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