柠檬酸根辅助多元醇法制备直径和磁性可控的Fe_3O_4亚微球

以柠檬酸三钠作辅助剂,用多元醇溶剂热还原法制备了纳米晶粒和微球直径可控的、单分散的超顺磁Fe3O4亚微球.发现与铁原子有强亲和力的柠檬酸根能有效吸附在还原产生的初始Fe3O4纳米粒子表面,阻碍其晶粒生长和影响其静电排斥力的大小,从而能在较大范围内调控最终产物Fe3O4亚微球的直径和饱和磁化强度.改变柠檬酸根或铁盐浓度不但可以调控初始Fe3O4纳米粒子的粒径,而且可以在220-550nm范围内调控单分散Fe3O4亚微球的直径,从而得到粒径均一的超顺磁Fe3O4亚微球.

Magnetite Sub-Microspheres with Controlled Diameter and Magnetic Properties Synthesized by the Citrate-Assisted Polyol Process

Monodispersed superparamagnetic magnetite (Fe₃O₄) sub-microspheres with controlled grain sizes and diameters were obtained by a facile polyol solvothermal method using sodium citrate as an additive. The results show that citric ions, which strongly coordinate with iron atoms on the surface of magnetite, can be effectively adsorbed onto the surface of Fe₃O₄ nanoparticles. Therefore, the growth of the initially formed Fe₃O₄ nanoparticles is restrained and the electrostatic repulsive force changes. Consequently, both the diameter and the magnetic properties of the resultant Fe₃O₄ sub-microspheres can be easily tuned over a relative large range. Simply changing the concentration of citric or ferric ions can change both the diameter of the Fe₃O₄ nanoparticles which construct the resultant sub-microspheres as building blocks and that of the resultant sub-microspheres in a range of 220 -550 nm, resulting in monodispersed superparamagnetic magnetite sub-microspheres.