节点文献

介孔SiO2/Fe3O4中空微球的可控制备及磁性能研究

Controllable Preparation and Magnetic Capability Research of Mesoporous SiO2/Fe3O4 Hollow Microspheres

【作者】 解林艳

【导师】 王志宏;

【作者基本信息】 北京工业大学 , 材料科学与工程, 2011, 硕士

【摘要】 具有高比表面积、高饱和磁化强度和良好单分散性的介孔二氧化硅磁性复合材料有望成为良好的酶固定化和药物控释载体。介孔二氧化硅的表面形貌和孔径大小决定了负载粒子的尺寸,磁性颗粒的尺寸决定了其磁性能的优劣。本文围绕着介孔材料的制备和孔径调节、磁性颗粒微观结构调整以及介孔二氧化硅/磁性复合材料的组装等系列问题展开研究,实现了具有不同微观形貌和性能的介孔二氧化硅磁性材料的可控制备。主要研究结果如下:在碱性环境下,以正硅酸乙酯(TEOS)为前驱体,阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)为结构导向剂,通过100℃水热处理和添加扩孔剂1, 3, 5-三甲苯(TMB)实现孔径的调变和孔道取向的控制。在没有TMB的情况下,水热处理可以提高介孔材料的结晶度,孔径稍有增大,且会使介孔材料的孔道取向由平行分布转变为径向分布,颗粒尺寸也有较大增长。不经过水热处理,在室温陈化2h的条件下,介孔材料的孔径随着TMB加入量的增加而增大,样品孔径由3.00nm增大到了6.49nm,同时样品的比表面积与孔容也有较大的增长。而对样品水热处理后,TMB的加入不仅使得介孔材料的结晶度降低而且孔径变化不大,说明晶化过程削弱了TMB的扩孔作用。具体讨论了反应pH值、干燥方式与焙烧过程对磁性空心球微观形貌及磁性能的影响。随着溶液pH的增加,纳米磁性颗粒的尺寸增大,饱和磁化强度和矫顽力随之增大,但过大的矫顽力会降低颗粒的再分散性。本论文所制得的纳米结构核壳和空心微球具有良好的单分散性、均匀性、稳定性以及较高的饱和磁化强度和低的矫顽力,实现了磁性微球的可控制备。采用两步包覆法和模板法,成功制备得到介孔SiO2/Fe3O4中空磁性复合微球。通过调整磁性核心粒子浓度、TEOS的加入量和氢氧化钠浓度来制备表面形貌均匀、介孔二氧化硅层厚的复合颗粒。实验表明在TEOS为0.053mol·L-1、NaOH浓度为0.122mol·L-1、磁性核心粒子浓度为4g·L-1时制备得到的介孔SiO2/Fe3O4中空磁性微球尺寸均一约为390nm,比表面积为693m2·g-1,孔体积为0.63cm3·g-1,平均孔径为3.6nm且孔径分布窄,有利于对负载粒子的选择吸附。复合微球整体密度低,具有良好的单分散性。介孔SiO2/Fe3O4中空磁性微球的饱和磁化强度可达13.6emu·g-1,满足了药物输送的要求,且低的矫顽力利于颗粒的再分散,为其实际应用奠定了基础。

【Abstract】 Mesoporous silica magnetic composite material have become good enzyme immobilization and drug carrier due to they possess high surface area, high saturation magnetization and good monodisperse. The surface morphology and pore size of the mesoporous silica determine the size of loading particles and the size of magnetic particles determine their magnetic properties. This thesis focuses on the synthesis of mesoporous silica with different pore size, the adjustment of the sructure of magnetic particles and the preparation of mesoporous silica/magnetic composite core-shell microspheres. A novel method for the preparation of mesoporous silica magnetic composites is proposed. More detail is dicussed as follows:The control of pore size and orientation can be achieved by hydrothermal treatment using tetraethyl orthosilicate(TEOS) as precursor, cationic surfactant cetyltrimethyl ammonium bromide(CTAB) as structure directing agent and 1, 3, 5-trimethyl benzene(TMB) as pore size expansion agent under basic conditions. Hydrothermal treatment of mesoporous materials without TMB at 100℃can improve the degree of mesoscopical order, increase the pore size , vary the channel arrangment of mesoporous silica from a parallel orientation to a radial distribution and increase the size of particles. The introduction of TMB leads to a tunable pore size of mesoporous silica from 3.00nm to 6.49nm when sample is aged for 2h at room temperature in basic solution, and the BET surface area and pore volume increase with the increasing amount of TMB. The addition of TMB decreases the order of mesoporous materials and have inefficacy to the expanse of pore size, so the process of hydrothermal treatment impairs the effect of TMB.The effect of pH, dry method and calcination on the morphology and magnetic properties of hollow spheres is discussed in detail. The size of nano-magnetic particles increases with increasing solution pH, which cause the increasing of saturation magnetization and coercivity, but high coercivity will influence the redispersion of particles. In this thesis, core-shell nanostructural and hollow microspheres have good monodispersity, uniformity, stability and high saturation magnetization with low coercivity, which provides the foundation for the controllable synthesis of magnetic microspheres.Mesoporous SiO2/Fe3O4 hollow magnetic microspheres have been successfully synthesized by two-step coating and templating method. Mesoporous silica composite particles with uniform morphology are obtained via adjusting the concentration of magnetic cores, TEOS and sodium hydroxide. Experiments show that the concentration of 0.053mol·L-1, 0.122mol·L-1, and 4g·L-1 for TEOS, NaOH and core particles respectively, results in mesoporous SiO2/Fe3O4 hollow microspheres with a uniform size of about 390nm, a high specific surface area of 693m2·g-1, a pore volume of 0.63cm3·g-1 and a narrow pore size distribution centered at 3.6nm. The composite microspheres exhibit a low density and good monodispersity. For the mesoporous SiO2/Fe3O4 hollow microspheres, a saturation magnetization up to 13.6emu·g-1 can meet the requirements for drug delivery, and a low coercivity is beneficial to the redispersion of particles and the practical application in the field of drug controllable release.

【关键词】 介孔硅磁性孔径空心微球
【Key words】 mesoporous silicamagneticpore sizehollow microsphere
节点文献中: 

本文链接的文献网络图示:

本文的引文网络