Fe3O4超顺磁纳米晶的超声共沉淀法制备及表征

Preparation of Fe_3O_4 Superparamagnetic Nanocrystals by Coprecipitation with Ultrasonic Enhancement and Their Characterization

利用超声强化的共沉淀法结合阴离子表面活性剂十二烷基硫酸钠(SDS)修饰技术,制备出Fe3O4超顺磁纳米晶,采用X射线粉末衍射仪(XRD)、傅立叶转换红外线光谱仪(FT-IR)、高分辨透射电子显微镜(HRTEM)、N2吸附-脱附及热重-差示扫描同步热分析仪(TG-DSC)等方法对样品进行表征,系统研究了样品的表面电性及磁学性质,并探索了超顺磁纳米晶的生长机理.结果表明:所制备的Fe3O4超顺磁纳米晶结晶完整,分散性良好,平均粒径在10nm左右;其比表面积高达91.6m2·g-1,具有优异的热稳定性,蒸馏水中等电点pHpzc=5.7;其饱和磁强度(Ms)可达65.0emu·g-1,属超顺磁性纳米材料;超声强化及SDS表面修饰,对Fe3O4超顺磁纳米晶的生长起着非常重要的作用.这种Fe3O4超顺磁纳米材料可望被较好地应用于细胞或酶的固定化等生物和医药领域.

Fe3O4 magnetic nanocrystals were prepared by coprecipitating Fe^2＋ and Fe^3＋ ions in an ammonia solution with ultrasonic enhancement and modification by the anionic surfactant sodium dodecyl sulfate （SDS）. The product was characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, high resolution transmission electron microscopy （HRTEM）, N2 absorption-desorption, and thermogravimetric-differential scanning calorimetry （TG-DSC）, respectively. The surface electrical properties and magnetic properties of the Fe3O4 magnetic nanocrystals were systematically investigated. The growth mechanism of the Fe3O4 magnetic nanocrystals was discussed. The results show that the Fe3O4 magnetic nanoparticles obtained are well-crystallized particles, with an average size of 10 nm, which have good dispersivity. The specific surface area of particles can reach as much as 91.6 m^2.g^-1. The obtained nanoparticles also have good thermostability, and the isoelectric point （IEP） under water conditions is at pHpzc = 5.7. Magnetic measurement reveals the magnetic nanoparticles are superparamagnetic with a saturation mag-netization of 65.0 emuog.g^-1. The ultrasonic enhancement and the surfactant modification play an important role in the growth mechanism of the Fe3O4 superparamagnetic nanocrystals. These superparamagnetic nanocrystals might be applied to biological and medical fields such as cell or enzyme immobilization.