Research On SiO₂ Compolex Nanoparticles With The Properties Of Enzymatic Catalysis And Optical Oxygen Sensing

Optical fiber biosensing technology is developing rapidly. Fiber optic biosensors have many advantages such as high sensitivity, fast response, immunity from electrical and magnetic interference, long distance sensing, and low cost compared with electrical sensors and electrochemical sensors. As a branch of fiber optic sensor, the enzyme based fiber optic biosensors have great application potential in many fields. However, these sensors often suffer from the drawback of nature enzymes such as poor stability, complicated preparation and impossibility of reuse. To overcome these shortages, the immobilized enzymes offers several advantages including its reuse, possibility of better control of reactions, ease removal from the reaction medium and improved stability. As a good immobilized carrier, SiO2 nanoparticles are highly compatible with enzymes and were used for fabrication of glucose sensor. Most of the reported sensing materials for fiber optic biosensor based on enzyme catalysis usually consist of two parts, the optical sensing part and catalytic enzyme part. If the SiO2 nanoparticles containing photosensitizer are used to immobilize enzyme to form the biofunctional SiO2 complex nanoparticles with the properties of enzymatic catalysis and optical oxygen sensing, the catalysis effect of enzyme can arrive at the photosensitizer directly, which will improve the performance of fiber optic biosensor. Furthermore, by preparing different immobilized enzyme on luminescent sinica nanoparticles, it will be possible to develop the multi parameter fiber optic biosensor based on enzyme catalysis and oxygen consumption.The main work in this thesis includes:(1) Preparation of bifunctional fluorescent SiO2/porous fluorescent SiO2 complex nanoparticlesUsing the improved St?ber method, fluorescence SiO2 complex nanoparticles and fluorescence SiO2 porous complex nanoparticles were prepared and characterized. The surface of these nanoparticles was modified for immobilization of different enzymes(GOD/COD). The preparation conditions for these nanoparticles were studied. The nanoparticles were characterized by field emission scanning electron microscopy(SEM), X-ray diffraction analysis, fluorescence spectrophotometer, infrared spectrum and the nitrogen adsorption desorption. The influence of immobilization conditions on the properties of immobilized enzymes was studied and the optimal immobilization conditions were obtained.(2) Study of the enzymatic performance and oxygen sensing property of bifunctional complex nanoparticles.Using UV-visible spectrophotometer instrument, the enzymatic properties of immobilized GOD and immobilized COD were obtained. The optimal reaction conditions for the catalysis of immobilized enzymes were studied. The thermal stability, storage stability and operation stability of the immobilized enzymes were studied and compared with free enzymes, the results indicate that the immobilized enzymes are more stable than free enzyme.The fiber optic detection system for O2 sensing was designed and fabricated. The detection was performed with lock-in technology. The sensing properties of the bifunctional complex nanoparticles were studied. The relative phase shift function tan? 0 /tan ? has an obvious linear relationship with O2 concentration. The corresponding equation is y = 0.0005916 + 1.00 x,(R2=0.9617) with the response time of 20 s. They have good repeatability and reversibility.