Facile synthesis and morphology evolution of magnetic iron oxide nanoparticles in different polyol processes

A series of magnetic iron oxide nanoparticle clusters and porous nanoparticles with high magnetization are synthesized using the polyols with different reductive abilities. To investigate the morphology evolution in a polyol process, HRTEM is used to study the products. When ethylene glycol is used as the solvent, iron oxide nanoparticles form and then self-assemble into compact nanoparticle clusters (ca. 300 nm) through oriented attachment growth with a few misarranged nanoparticles in the clusters. At last these clusters develop into flower-like clusters with single crystal-like diffraction. When 1,2-propylene glycol is employed as the solvent, iron oxide nanoparticles quickly self-assemble into nanoparticle clusters (ca. 50 nm) with many misarrangements. As the reaction time extends, these clusters collapse and split into porous nanoparticles. According to the morphology evolution of iron oxide nanoparticles in different polyols, we propose our reasonable supposition on the whole process. These findings may help to understand the role of the polyol as solvent and obtain the novel secondary structures of nanoparticles in a polyol process.