Study On Preparation And Properties Of Sol-Gel Sensing Membrane For Fiber Optic Oxygen Sensor

The sol-gel method has been widely used in preparing organic-inorganic materials because of its advantages such as high purity of products, good uniformity, low processing temperature, and easily controlled reaction condition. The preparation of optically active composite is a promising alternative to obtain a kind of new and competitive sensing membrane for fiber optic sensors, and has attracted the global attention. In this thesis, the modified sol-gel sensing membranes based on fluorescence quenching have been prepared by using tetraethoxysilane (TEOS) and Dimthyldimethoxysilane (DDS) as the main material, formamide as the drying control chemical additive (DCCA), Ru(phen)3Cl2 and Ru(bpy)3Cl2 as the indicator. This kind of membranes is crack-free and has low indicator-leaking rate. The sensors with this kind of sensing membranes for the detection of gas-phase oxygen and dissolved oxygen have short response time, high detection precision and good stability and reproducibility.The work of this paper includes mainly two aspects: preparation and properties of sol-gel sensing membrane for fiber optic gas oxygen sensor; preparation and properties of organically modified sol-gel sensing membrane for fiber optic oxygen sensor. The main contents are in the following:(1) Oxygen sensing membranes based on fluorescence quenching were prepared by sol-gel method, using formamide as the drying control chemical additive, TEOS as the main material, Ru(phen)3Cl2 and Ru(bpy)3Cl2 as the indicator. The sensing membranes were characterized by FI-IR, SEM. The oxygen sensing properties of the membranes have been studied, the results indicate that the membranes with Ru(phen)3Cl2 have better oxygen-sensitivity than those with Ru(bpy)3Cl2, and the membranes with the formamide content of 16%(V/V) and Ru(phen)3Cl2 content of 2.10g/l in the precursor mixture have the best structure and quality. The fiber optic gas oxygen sensor with this sensing membrane has a detection limit of 5ppm, a response time of less than 30s,excellent reproducibility and stability.(2) A new kind of Organically modified oxygen-sensitive membrane based on fluorescence quenching was prepared by sol-gel method, using DDS and TEOS as the mixed precursor, RufchenbCla as the indicator. The sensing membranes were characterized by FI-IR, 3D optical microscope. The factors that influence the formation and sensing properties of the membranes were studied. The results indicate that, with the proper amount of DDS doped, the membranes are uniform and crack-free, and have favorable mechanical ability and good flexibility. For the detection of gas-phase oxygen, the fiber optic oxygen sensor with this sensing membrane has a detection limit of 5ppm, a response time of less than 30s. For the detection of dissolved oxygen, its detection limit is 0.5mg/l and response time is less than 50s. Compared with pure TEOS sensing membrane, modified sensing membranes have better reproducibility and stability, which is more favorable for the detection of dissolved oxygen.