Synthesis Of New Fluorescence Carriers And Their Application In Fluorescence PH Sensor Preparation

In recent years, the development of fluorescence pH sensors has attracted consideral attention because of their potential in environmental analysis, medical diagnostics and process control. A large variety of fluorescence pH sensors have been fabricated; though the fluorescence carriers used are limited to a narrow range of chemical compounds and most fluorescence carriers are physically entrapped in various membrane materials. Although physical entrapping is a simple method for sensor membrane preparation, the leaching of fluorescence carrier is a major disadvantage. Bearing this in mind, the research interest of this work is to search new fluorescence carriers and develop new fluorescence sensors for pH measurement.In this thesis, new fluorescence carriers with terminal double bonds such as naphthalimides and porphyrins were synthesized and copolymerized under UV irradiation on the silanized glass. The prepared sensors were studied and used for pH determination. (1) N-allyl-4-(N-amino-ethyl)amino-1,8-naphthalimide (AAEAN) with proton"off-on"switch behavior was synthesized. The sensor can be used for the determination of pH in the range of pH 5.0–9.0, without interference of most commonly co-existing inorganic ions and some organic species. The sensor has been applied to the analysis of wastewater sample. (2) In order to develop a ratiometric sensor for pH measurement, two markedly different fluorophores, meso-5,1015,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP) and N-(2-methacryloxyethyl)benzo[k,l] thioxanthene-3,4-dicarboximide (MBTD)were synthesized. The sensor incorporated the pH-sensitive dye TAPP as an indicator and the pH-insensitive dye MBTD as a reference for fluorescence ratiometric measurement. Both fluorophores with the terminal double bonds were copolymerized on the silanized glass surface. The use of MBTD as a reference for the fluorescence intensity of TAPP resulted in a more stable sensor signal because it iminimized the effects of the external environment and instrumental conditions. (3) Taking account of the cumbersomeness of searching for new types of fluorophores and the difficulty of compound synthesis, we endeavored to design a ratiometric pH sensor with a pair of fluorophores, N-allyl-4-(4'-methyl- piperazinyl)-1,8-naphthalimide (AMPN) and TAPP. Our strategy for ratiometric determination of pH is based on the pH-dependent fluorescence intensities of the two fluorophores in different pH ranges. In this dual-fluorophore system, which is the first of this kind, AMPN and TAPP were served as referencing indicators for each other. The sensor covers a broad dynamic range of pH 1.5-9.0. The successful fabrication of the sensor provides an alternative concept of utilizing two or more fluorophores for the development of ratiometric sensors covering a broad range of pH.Beside the research in fluorescence sensor preparation, the development of fluorescence probes and their application in the analysis of environmental polluents are also included in this thesis. A new fluorescence carrier bearing bisthiourea were synthesized and used to develop fluorescence probe. Preliminary study showed that the fluorescence probe was selective for Hg²⁺ and Cu²⁺. The prepared sensing system presented satisfactory sensitivity and selectivity.