Sol-gel Based Applications In Fabrication Of Optical Oxygen Sensor And Hydrogen Peroxide Biosensor

The fabrication of diverse sensors is based on the selection and immobilization of sensing elements. The applications of sol-gel technologies on immobilization of sensing elements and fabrication of chemical and biological sensing films are highlighted in this dissertation. The issues on the application of organically modified silica gels (ORMOSIL), immobilization of biomaterial and the co-utilization of chitosan and crosslinker with silica gels are reviewed according to the present researches. In the process of sol-gel, the liquid sol which is composed of metal alkoxide, water and solvent undergoes hydrolysis and codensation polymerization reactions and progressively produce the solid gel, which is a nework derived from the precursor. The solvent and functional materials such as fluoresent indicator can be encapsulated in the gel network during the formation process when they are added in the sol state. The main research work and experiments are listed as follows:1. According to the principle that the fluoresent indicator of ruthenium complex, [Ru-tris(4,7-diphenyl-1,10-phenanthroline)]2+, can be quenched by oxygen, this sensing compound is immobilized into the ORMOSIL and fromed a sensing film by sol-gel technique. The oxygen sensors composed by the sensing film and attached optical devices displays linear and fast response toward oxygen. Experiment results indicate that the utilization of the ORMOSIL remarkably imporved the texture of the gel films. Five different sol systems that employed ORMOSIL precursors are designed for the fabrication of sensing films and all produce fine gel films without crack. The employment of ORMOSIL also brings about the enhancement of hydrophobicity of the gel and induces the improvement of the sensing properties to oxygen. In particular, the oxygen sensing films derived from fluorinated precursors demonstrate the optimal preformance on oxygen sensitivity, robustness, and stability.2. As the fluoresent indicator has been successfully embedded into the film for the fabrication of optical oxygen sensor, the immobilization of biomaterial catalase into sol-gel system is designed to develop a novel optical hydrogen peroxide biosensor. Immobilizing methods involving sol-gel system, chitosan, crosslinker have been studied in detail. The properties of the developed biosensors including sensitivity, anti-interference, linear range, response time and robustness have been compared and analysed. The experiment results suggest that the addition of chitosan improves the biocompatibility of the silica gel microenvironment along with the activity of the incorporated enzyme and result in the improvement of the sensitivity. The sensing film obtained by immobilizing catalase onto chitosan by crosslinker displays faster response for it is thinner than the other two sol-gel derived films. The film obtained by immobilizing catalase with chitosan/sol-gel system demonstrates higher sensitivity towards hydrogen peroxide of low concentration. Owning to the specificity characteristics of catalase, the developed optical hydrogen peroxide sensors exhibit excellent anti-interference. The biosensors fabricated in this part offer a new approach for the detection of hydrogen peroxide with low concentration, which overcome the strict requirement on spectrometer and light source of the traditional optical methods, and avoid the influence from unknown interference in common electrochemical methods.The characteristics of sol-gel immmobilizing technology such as simple, stable, high compatible in the material preparing, target immobilizing, sensor fabricating have been well demonstrated during this research process, which promise sol-gel techonolgy with great potential in further applicaitons.