Conjugated Polymers Modified With Diazobenzene And Nitroaromatics: Synthesis And Biosensing

As a class of promising fluorescence probes,conjugated polymers have been widely used in biology,chemistry and material science.In this thesis,two series of new conjugated polymers were synthesized and demonstrated a promising future in biosensing application.New diazobenzene-containing conjugated polymers could be used as excellent dark quenchers,while nitroaromatics-containing conjugated polymers showed obvious fluorescence response to reduction and hydrolysis.A new conjugated polymer azo-PPE-CO2 H and its precursor azo-PPE-CO2 R with azo funtionality in backbone was synthesized via Sonogashira reaction,which have broad absorption band and no fluorescence emission.These diazobenzene-containing conjugated polymers could quench organic fluorophores with high quenching efiiciency.A biosensing demonstration of dsDNA using AO and azo-PPE-CO2 H suggested that these conjugated polymers have potential applications as dark quenchers in biosensing.Besides,four poly(phenylene ethynylene)s with pendant nitroaromatics,PPET,PPEF,PPNT and PPNF,were synthesized,which have strong UV-Vis absorption from 300 nm to 500 nm and show weak fluorescence.When the pendant nitrogroup was hydrolyzed or reduced,the fluorescence of PPNT was enhanced,which indicated that these conjuagted polymers with nitroaromatics may potentially be used for nitroreduction detection,hypoxia tumor cell imaging and tumor diagnosis.Molecular weight,molecular weight distribution and end-group information of seven conjugated polyelectrolytes(CPEs)were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS).The effects of molecular weight of CPEs on optical and quenching properties were also studied.Mass spectra with high resolution were obtained by “drie d droplet” method with 2,5-dihydroxybenzoic acid as matrix(M)and Ag TFA as cationization reagent(CR)at the optimum volume mixing ratios(CPE/M/CR),which was 5/5/1 and 5/50/1 for anionic polymer and cationic polymer,respectively.In this study,CPEs showed an obvious red-shift in UV absorption spectra and enhanced amplified fluorescence quenching due to the increased conjugation lengths.A sensor array consisting of six cationic CPEs was designed for detecting nine NACs.The varying binding affinity gave rise to a distinct fluorescence response via polymer–nitroaromatic interactions and fluorescence quenching.Nine NACs were differentiated successfully in aqueous solution both at a concentration of 1.0 ?M and at a fixed absorbance of 0.05 at 300 nm by using 2-D discriminant patterns.Furthermore,our six-CPE sensor array provided a practical and efficient method to determine unknown samples with 100% accuracy.