中文摘要：

采用化学共沉淀法制备Fe3O4，将正硅酸四乙酯水解在Fe3O4粒子表面制得Fe3O4／SiO2核壳磁微球，制备好的微球经红外光谱、X射线粉末衍射和磁强计考察其结构和磁性。在微球表面用3-氨丙基三胺乙基硅烷修饰上氨基，经戊二醛活化以偶联的方式将过氧化物酶固定在磁微球上。固定后的酶催化过氧化氢的同时使氨基二乙基苯胺硫酸盐显色，产生的有色物质在551nm处有最大吸收，以此建立检测过氧化氢的方法。结果表明，包裹SiO2层的磁微球不改变其核的结构，磁性降低但是不改变超顺磁状态。在最佳条件下，过氧化氢的线性范围是1．29～64．5μmol／L，检出限为8．5×10-7mol／L。固定后的酶可反复使用5次，放置于4℃至少两个月不影响催化效果。

英文摘要：

The Fe3O4 nanoparticles were obtained by the co-precipitation method. We coated silica on superparamagnetic nanoparticles by hydrolysis and the polycondensation of tetraethyl-orthosilicate. The magnetic microspheres were characterized by fourier transform infrared spectroscopy, X-ray diffraction and Vibrating Sample Magnetometer. The silica layer was tested by grafting （3-aminopropyl） triethoxysilane onto the nanoparticles. Following this, the surface of chemically modified maghemite nanoparticles was further subjected to activation with the crosslinker, glutaraldehyde. Then the peroxidase fixed on magnetic beads. The immobilization peroxidase was prepared and used for the determination of hydrogen peroxide. It was able to able to activate H2O2 and oxidize N, N-diethyl-p-phenylenediamine sulfate to a colored product with a strong absorption maximum at 551 nm. The results show that the magnetic microspheres coated by SiO2 layer maintained their nuclear structure, reduced but did not change the magnetic super-paramagnetic. Because of the SiO2 layer, it was easy to immobilized enzyme. Under optimized conditions, the absorbance of the product responded linearly to H2O2 concentration in the range from 1.29 to 64.5 μmol/L with a detection limit as low as 8.5×10-7 mol/L. The immobilized enzyme activity remained when it was reused for 5 times or stayed in 4 ℃ at least two months.