New insights into size-controlled reproducible synthesis of anisotropic Fe3O4 nanoparticles: The importance of the reaction environment

Synthesis of size-controlled anisotropic magnetite (Fe3O4) nanoparticles allows designing next-generation magnetic nanosystems with predetermined magnetic properties suited for particular applications in the biomedical, information, and environment fields. In this work, we report a reproducible and economical approach for fabricating anisotropic Fe3O4 nanoparticles via the thermal decomposition method. Controlling the reaction environment, i.e. the degassing pressure, is essential to obtain the reproducible synthesis of anisotropic Fe3O4 nanoparticles along with monodispersity in the size and shape. At low degassing pressure, Fe3O4 nanocubes are formed, and an increase in degassing pressure leads to the formation of Fe3O4 octahedral nanoparticles. To achieve good reproducibility (with respect to size and shape) between different batches, our finding reveals the importance of maintaing the same degassing pressure. The size of the anisotropic Fe3O4 nanoparticles can be varied by changing the heating rate and the solvent amount. The amount of solvent has also an influence on the shape of the nanoparticles, and Fe3O4 nanoparticles of flower morphology are obtained at a high solvent amount. The work also provides new conceptual fundamental insights into understanding the growth mechanism of anisotropic Fe3O4 nanoparticles and thus advancing the field of materials chemistry for rationally designing anisotropic nanoparticles with tunable magnetic properties.