Iron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxide. The uses of these various oxides and hydroxides are tremendously diverse ranging from pigments in ceramic glaze, to use in thermite.

Iron oxide nanoparticles

Superparamagnetic iron oxide nanoparticles with appropriate surface moiety have recently attracted a great deal of attention due to their potential biological applications, such as, bio separation, wastewater treatment, biosensor, biocatalysis, hyperthermia, MRI image contrasting and specific cell labeling and tracking. The humic acid coated super paramagnetic Fe3O4 nanocrystals with large numbers of functional groups have potential applications in biological and environmental science.

Chunjiao Zhou and other researchers of China prepared super paramagnetic Fe3O4 nanocrystals by the chemical co-precipitation of ferrous and ferric salts in a basic aqueous solution coated with humic acid and used them as magnetic resonance imaging (MRI) contrast agents and adsorbents for removal of cationic organic dye Methylene blue (MB) from neutral water. Researchers state in a study of self-assembly of inorganic magnetic nanocrystals that the ordering of nanocrystals at the mesoscopic scale in 3D super lattices, called supra crystals, is not simply an aesthetic arrangement but is in fact a new generation of materials. The nanocrystal ordering on long distance in supra crystals permits the emergence of collective intrinsic properties, which was not expected. The shape of the organization at the mesoscopic scale also induces new physical properties.

Young-wook Jun and other researchers of Korea report that the use of magnetic nanocrystals as probes for biomedical system is attractive and they present a synthetically controlled magnetic nanocrystal model system that correlates the nanoscale tunabilities in terms of size, magnetism, and induced nuclear spin relaxation processes. This system further led to the development of high-performance nanocrystal−antibody probe systems for the diagnosis of breast cancer cells via magnetic resonance imaging.

Mihály Pósfai and other researchers of Denmark report that ferrimagnetic nanocrystals are present in virtually every organism. They are used by bacteria, algae, mollusks, insects, and vertebrates either for navigating in the geomagnetic field or for hardening their tissues. Studies reveal the complex interplay between the physical and magnetic properties and biological functions of ferrimagnetic nanocrystals in bacteria.