表面羧基化Fe3O4磁性纳米粒子的快捷制备及表征

亲水性磁性纳米颗粒在生物科学领域有着广泛应用，本研究提出了一种快速对磁性纳米粒子表面进行羧基化的方法. 首先使用氯化铁和氯化亚铁为原料, 以油酸为表面活性剂, 通过共沉淀法制得油酸包覆的亲油性磁性纳米粒子, 然后用高锰酸钾进行原位氧化, 将覆盖在粒子表面的油酸中的C＝C键氧化成-COOH, 从而得到单层羧基功能化的亲水性磁性纳米粒子. 利用透射电镜(TEM)、X射线衍射(XRD)、傅利叶红外光谱仪(FT-IR)、热重分析仪(TGA)、振动样品磁强计(VSM)、Zeta电位分析仪等对其进行表征. 结果表明磁性纳米粒子表面被成功羧基化，粒子的平均直径约为9 nm，饱和磁化值为64.5 emu/g，剩磁和矫顽力近似为零，具有典型的超顺磁性. 羧基化磁性纳米粒子可在pH7-10的水溶液中形成稳定分散的磁流体，保存6周无沉淀出现.

Convenient Preparation and Characterization of Surface Carboxyl-functioned Fe_3O_4 Magnetic Nanoparticles

Hydrophilic magnetic nanoparticles have been widely applied in biological sciences. In this work, we propose a convenient method to synthesize surface carboxylic magnetic nanoparticles. Firstly, hydrophobic magnetic nanoparticles coated with oleic acid were prepared from ferric chloride and ferrous chloride by co-precipitation method, with oleic acid as surfactant. Then the C＝C bond of oleic acid coated on the surface of particles was oxidized into -COOH by KMnO4 solution in situ, thereby gaining hydrophobic magnetic nanoparticles with monolayer carboxylic groups functioned. The magnetic nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), Zeta potential analyzer and so on. The results showed that magnetic nanoparticles surface was successfully carboxyl-functioned. The average diameter and the saturation magnetization of the nanoparticles were about 9nm and 64.5emu/g, respectively. The remnant magnetization and coercivity of the nanoparticles were nearly to be 0, which demonstrated it was classic superparamagnetic. The carboxyl-functioned magnetic nanoparticles can be dispersed into water to form ferrofluid, which are stable for more than 6 weeks without precipitation in the pH range of 7-10.