| Real-time and reversible measurement of chemical and biological information with high sensitivity and selectivity is one of the frontiers in sensor research.In the middle of 1990's, "molecular wire" technology was proposed where a single event, the binding of an analyte, in a supramolecular polyreceptor system produces a chain of signal amplification that cannot be generated in an analogous monoreceptor system. This technique is attracting extensive attention for its signal amplifying and gradually become one of the hot points.This thesis focuses on investigating the basic issues of molecular wire functioned as fluorescence chemosensors by implementing a variety of fluorescence measurements such as quenching, enhancement, energy transfer and anisotropy. A series of new fluorescent conjugated polymers were designed and synthesized, and their emission, electrical conduction and selectivity in various sensing systems were thoroughly investigated. Effect of the content of selective sites in molecular wire was also studied, which provides some theoretically and practically useful guides for tailor-making new potential molecular wire with multiple carriers. A three-dimensional sensing mechanism and a steric selectivity theory were suggested. This might become a valuable theoretical and technical platform for the development of sensitive and selective sensors based on molecular wire. A competitive detection method for molecular wire based anion sensing was developed, which might create a new dimension for extensive application of molecular wire in the anion analysis. Several novel fluorescence chemosensors with molecular wire carriers were then developed. These sensors offered improved sensitivity, stability and bleaching resistability compared to traditional fluorescent sensors based on small molecule carriers. In addition, a fluorescence chemosensor based on high efficient fluorescence energy transfer (FET) between small molecules and conjugated polymer was proposed. This expanded the variety of FET and enriched the methods of molecular wire based sensing.The main contents of the thesis are summarized as follows:(1) A series of new conjugated polymers - pyridine substitute poly(phenylene ethynylene)s were synthesized by Sonogashira-Hagihara coupling reaction. Theimpact of structure modification on physical and spectral properties has been investigated and tunable optical and responsive properties were obtained. The quenching studies exhibited that recognition site (pyridyle group) played a major role in the quenching efficiency. Polymer with pyridyl group entrapped in the conjugated backbone had the specific and sensitive response to Pd2+ ion. The fluorescence quenching efficiency of molecular wire by Pd2+ ion was about 56 times greater than that of model monomer.(2) A new fluorescent conjugated polymer for selective and sensitive sensing of transitional metal ions has systematically investigated. It exhibited a good selectivity for Pd2+ with respect to many other metal ions including heavy metal ions and main group metal ions. The result is correlated with the aggregation of polymer by the evidence of the enhanced fluorescence anisotropy as well as absorption spectra.(3) A new method had been developed for the rapid determination of cyanide, based on the fluorescence recovery of conjugated polymer by the competitive interaction of cyanide and Pd2+, and Pd2+ quenched the polymer's fluorescence initially. It was reported for the first time that the conjugated polymer was used for the detection of anion based on the fluorescence enhancement. The optimum condition and the fundamental interaction were discussed. The linear range of CN-detection was 2X 10~4M~5X 10-6M and the detection limit was 1 X 10-7M.(4) A selective optode for o-mononitrophenol had been developed based on fluorescence quenching of a conjugated polymer - poly (2,5-dimethoxy -phenyldiacetylene) (PDPA) (399 nm/446 nm), which was incorporated in...
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