Korea University: The Tunable Assembly of Magnetite Mesocrystals, a Natural Compass

Professor Kim Young-keun’s group in the Department of Materials Science and Engineering at the College of Engineering conducted a joint study with Dr. Kim Young-kwang’s group at Virtual Lab Inc. and investigated the change of a mesocrystalline microstructure in the process of generating iron oxide mesocrystals in the presence of the surface ligand oxalate, proposing a new approach to controlling the magnetic properties of nanocrystalline materials.
* Mesocrystals : Mesocrystals refer to aggregates of very small unit crystals. They are drawing attention for potential industrial applications because they show collective properties that are not found in single unit crystals.
* Ligands : Ligands refer to the molecules or ions bound to a material, and they play critical roles in determining the properties of those materials.

The results of the research were published online in Nature Communications, a multidisciplinary journal dedicated to publishing high-quality research in all areas of the biological, health, physical, chemical and Earth sciences, on March 3.

Nano-sized iron oxide particles are highly valuable because their magnetic properties can be adjusted according to specific applications in biomedicine and electronic engineering. Because the properties of iron oxide mesocrystals are dependent upon not only the properties of the unit crystals but also on their methods of binding, it is necessary to accurately understand the mesocrystal formation process. Several theoretical pathways have been suggested, but none has been verified experimentally because an oriented attachment is difficult to control during the chemically performed mesocrystal synthesis.

The research team was able to control the alignment of unit crystals in the mesocrystal formation process by controlling the type of ligand that is attached onto the surface of the iron oxide unit crystals. The researchers found that the misalignment of the unit crystals makes it difficult to mutually combine their magnetic properties for producing mesocrystals with the desired magnetic properties in comparison with well-aligned unit crystals. In addition, they analyzed the impacts of ligands on the alignment of the unit crystals by using the density functional theory.

The research team explained the significance of their research: “In the process of assembling the iron oxide unit crystals into mesocrystals, we controlled the degree of oriented attachment by using the ligands. In addition, we showed the impacts of the crystallographic alignment of iron oxide mesocrystals on their magnetic properties through the experiment. We are now able to design the materials according to their fields of application.”

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