【作者】 常青；

【导师】 朱丽华；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2011， 博士

【摘要】 磁性纳米粒子与块体不同,具有独特的化学和物理性质,其中Fe304磁性纳米粒子具有生物相容性良好、无溶血活性、遗传毒性以及超顺磁性等特性,在生物医药、催化、环境等领域应用前景广阔。但是在实际应用时,一般要求纳米粒子尺寸均一、化学性质稳定、生物相容性和分散性好。为了解决这些问题并赋予其更多的功能,需要对其进行表面修饰。本学位论文重点研究了Fe304磁性纳米粒子及其复合物的制备以及它们在催化分析、酶固载、生物标记、环境控制领域的应用,主要集中在以下五个方面：(1)采用共沉淀法制备了Fe304磁性纳米粒子,利用其具有类似辣根过氧化氢酶的特性建立了一种快速测定H202的紫外可见分光光度法。所制备的Fe304纳米粒子可以催化活化H202产生·OH氧化N,N.二乙基对苯二胺硫酸盐(DPD), H2O2氧化DPD的表观活化能从62.5 kJ mol-1降低至21.8 kJ mol-1;DPD的氧化产物在550 nm处有很强的吸收,其吸光度A与样品中H202的浓度之间存在良好的线性关系。在优化反应条件下,H202的线性范围为0.5-150×10-6 mol L-1,检出限为2.5×10-7mol L-1。该方法已成功应用于雨水中,蜂蜜和牛奶样品中H202的测定。(2)以包覆纳米Fe304的氨基化Si02纳米颗粒(Fe3O4/SiO2)为载体固定辣根过氧化物酶(HRP),制备了固定化辣根过氧化物酶。这种以纳米Fe3O4/SiO2为载体的固定化辣根过氧化物酶较纳米Fe304和辣根过氧化物酶相比,具有高活性及高稳定性。该固定化酶可以活化H202产生·OH将无荧光对羟基苯丙酸氧化为在409 nm处有最大发射的荧光二聚体,该反应可以与葡萄糖氧化酶催化氧化葡萄糖的体系偶联,利用固定化酶的高催化活性建立快速测定H202及葡萄糖的荧光光度法。在优化条件下,H202和葡萄糖的线性范围分别为5×10-9-1.0×10-5 mol L-1和5.0×10-8-5.0×10-5 molL-1,检出限分别为2.1×10-9 mol L-1和1.8×10-8 mol L-1。固定化酶通过外加磁场可以方便地磁分离、回收及再利用。(3)采用原位沉淀法合成了Fe304／氧化石墨烯纳米颗粒,并以其为载体固定葡萄糖氧化酶。Fe3O4／氧化石墨烯纳米颗粒可催化活化由负载在其上的葡萄糖氧化酶催化氧化葡萄糖生成的H202,将其均裂为·OH,·OH将DPD氧化为在550 nm处有强吸收的DPD+,从而建立了一种一步法同时测定葡萄糖和H2O2的紫外可见分光光度法。在优化条件下,葡萄糖和H202的线性范围分别为5.0×10-7-6.0×10-4 mol L-1和1.0×10-7-1.0×10-4 mol L-1,检出限分别为2.0×10-7 mol L-1和4.0×10-8 mol L-1。(4)采用改进的Stober法合成具有磁性和荧光特性的双功能纳米粒子Fe3O4/SiO2/dye/SiO2。包覆纳米Fe304的内层Si02可防止纳米颗粒的团聚,而外层Si02可保护染料分子不受外界干扰,使其具有良好的光稳定性,硅层的厚度可通过改变前驱体正硅酸乙酯的浓度来调控。该纳米粒子具有荧光强度高,光稳定性好和超顺磁性的特点；其荧光强度随合成过程中所加入染料浓度的增加而增强。通过包覆不同的染料可调控纳米粒子的荧光波长,从而改变其发射光的颜色。与染料溶液相比,染料掺杂的荧光纳米颗粒的荧光发射光谱发生部分红移或蓝移,其原因可能是由于染料分子聚集在硅壳中或聚集态的染料分子共平面性降低所致。(5)采用超声辅助共沉淀法制备了具有典型层状结构的磁性镁铝水滑石(MLDHs),用于去除废水中氟离子的吸附材料。制备过程中超声的引入不但可加速水滑石相的形成,而且能极大缩短合成MLDHs的时间。结果表明,超声法合成的MLDHs粒径小、比表面积大,有利于吸附性能的提高,氟离子的饱和吸附容量为47.7mg g-1。吸附动力学数据和等温吸附数据分别符合准一级吸附动力学模型和Langmuir等温模型。磁性水滑石材料可有效地进行磁分离,经过解吸再生后可以重复利用。更多还原

【Abstract】 Magnetic nanoparticles are different from the bulk material with unique chemical and physical properties. Fe3O4 magnetic nanoparticles are the very promising and popular candidates because they are known to be biocompatible, displaying no hemolytic activity or genotoxicity with superparamagnetic properties, which have been widely used in biomedicine, catalysis, environment and so on. For many applications, the Fe3O4 nanoparticles are necessary to be chemically stable, well dispersed in liquid environment, biocompatible and uniform in size. This problem can be solved by modifing magnetic nanoparticles with the functional materials. We focus on the synthesis of Fe3O4 magnetic nanoparticles and their composite nanoparticles and their application in catalytic analysis, enzyme immobilization, biological imaging and environment protection. The major contents are summarized as follows:(1) Fe3O4 magnetic nanoparticles were prepared by the co-precipitation method and used as a mimetic peroxidase for the determination of hydrogen peroxide (H2O2) based on their catalytic effect on the oxidation of N, N-diethyl-p-phenylenediamine sulfate (DPD). Because of the peroxidase-like activating effect, Fe3O4 nanoparticles decreased the activation energy of the oxidation of DPD by H2O2 from 62.5 kJ mol-1 to 21.8 kJ mol-1 at room temperature, promoting greatly the oxidation of DPD by H2O2. Fe3O4 nanoparticles were found to be able to activate H2O2 and oxidize DPD to a colored product with a strong absorption maximum at 550 nm, which yielded a satisfactory linear correlation between the absorbance (A) and H2O2 concentration. The parameters for the determination of H2O2 were optimized by the investigations of the effects of reaction conditions on the absorbance of DPD+ produced by the catalytic oxidation of DPD. Under optimized conditions, the absorbance of the product responded linearly to H2O2 concentration in the range from 0.5 to 150×10-6 mol L-1 H2O2 with a detection limit as low as 2.5×10-7 mol L-1.The method was successfully applied to the determination of H2O2 in rainwater, honey and milk samples.(2) Sensitive fluorescent probes for the determination of hydrogen peroxide and glucose were developed by immobilizing enzyme horseradish peroxidase (HRP) on Fe3O4/SiO2 magnetic core-shell nanoparticles in the presence of glutaraldehyde. Compared with Fe3O4 magnetic nanoparticles and HRP, the immobilized enzyme catalyst has high activity and stability. The HRP immobilized nanoparticles were able to activate H2O2 to produce·OH radicals, which oxidized non-fluorescent 3-(4-hydroxyphenyl)propionic acid to a fluorescent dimmer with an emission maximum at 409 nm. Under optimized conditions, a linear calibration curve was obtained over the H2O2 concentrations ranging from 5.0×10-9 to 1.0×10-5 mol L-1, with a detection limit of 2.1×10-9 mol L-1. By simultaneously using glucose oxidase and HRP-immobilized Fe3O4/SiO2 nanoparticles, a sensitive and selective analytical method for the glucose detection was established. The fluorescence intensity of the product responded well linearly to glucose concentration in the range from 5.0×10-8 to 5.0×10-5 mol L-1 with a detection limit of 1.8×10-8 mol L-1. Besides its excellent catalytic activity, the immobilized enzyme could be easily and completely recovered by a magnetic separation, and the recovered HRP immobilized Fe3O4/SiO2 nanoparticles were able to be used repeatedly as catalysts without deactivation.(3) Magnetic Fe3O4/GO nanoparticles were synthesized by in situ precipitation method and used as a substrate for the immobilization of glucose oxidase. The Fe3O4/GO nanoparticles were used as an enzyme-like catalyst to activate H2O2 to produce·OH radicals by homolytic cleavage, which could be produced by the glucose oxidation with glucose oxidase-immobilized nanoparticles.·OH radicals will catalytically oxidize the substrate DPD to the radical cation DPD+ with a strong absorption maximum at 550 nm. We have developed a one-step method for determination of trace concentrations of glucose or H2O2 based on a bienzyme system. Under the optimized conditions, this method could give linear responses to glucose in a range of 5.0×10-7 to 6.0×10-4 mol L-1 with adetection limit of 2.0×10-7 mol L-1. And a linear calibration curve was obtained over the H2O2 concentrations ranging from 1.0×10-7 to 1.0×10-4 mol L-1 with a detection limit of 4.0×10-8 mol L-1.(4) Based on the Stober method, we have developed a simple and reproducible method to synthesize a novel class of Fe3O4/SiO2/dye/SiO2 composite nanoparticles. The inner silica layer is introduced to enhance the adherence of the dye-doped silica layer to the surface of magnetic Fe3O4 particles, and the outer dye-doped silica layer enables the nanoparticles with excellent fluorescent properties. The thickness of the outer shell of silica could be tuned by changing the concentration of the silicon precursor tetraethyl orthosilicate during the synthesis. These multifunctional nanoparticles were found to be highly luminescent, photostable and superparamagnetic. The luminescence intensity of the nanoparticles was increased as the dye concentration was increased in the preparation process. The color of the luminescence was successfully tuned by incorporating different dyes into the nanoparticles. The measurements of the emission spectra indicated that relative to the dye molecules dissolved in ethanol, the emission of the dye-doped nanoparticles exhibited either a red shift or a blue shift owing to the aggregation of dye molecules in the silica matrix or destroyed the coplanar.(5) A simple ultrasound-assisted co-precipitation method in combination with a calcination treatment was developed to prepare magnetic Mg-Al layered double hydroxides composite with layered structure as an adsorbent material to remove fluoride ions from aqueous solutions. The application of ultrasound in the preparation process promoted the formation of the hydrotalcite-like phase and drastically shortened the time being required for preparation of the crystalline composite. It was found that the ultrasound irradiation assistance decreased the size of the composite particles and increased the specific surface area, being favorable to the improvement of the adsorption capacity. The composite prepared under the ultrasound irradiation exhibited fairly high maximum adsorption capacity of fluoride (47.7 mg g-1). Equilibrium adsorption and kinetic data were fitted well with the Langmuir isotherm model and the pseudo-first-order kinetic model. In addition, the magnetic composite can be effectively and simply separated by using an external magnetic field, and then regenerated by desorption and calcination.更多还原