One-pot and template-free fabrication of dendritic and octahedral single-crystal magnetites

Abstract

Dendritic and octahedral single-crystal magnetites have been successfully fabricated by a facile one-pot hydrothermal method without any templates. The presented materials were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), selection area electron diffraction (SAED) and magnetic property measurement system (MPMS). The results showed that the prepared magnetites with different morphologies have face-centred cubic structures. When using different amounts of potassium hydroxide (KOH) and hydrazine hydrate (N₂H₄·H₂O), high yields of Fe₃O₄ with well-defined three-dimensional (3D) dendritic and octahedral shapes were obtained. Moreover, the reaction time also has an important effect on the shapes of the products. The crystal growth directions of dendritic and octahedral magnetites are oriented along [110] and [111], respectively. The formation mechanism of the magnetites with different morphologies has been discussed. The magnetic properties are closely related to the morphologies of the magnetites. Furthermore, the as-prepared products have a high saturation magnetization and low coercive force, which endow the materials with great potential for applications in biological fields.