Iron Oxide Nanoparticles
Iron oxides are abundantly found in nature since iron is one of the most abundant materials in the earth's crust and easily form various compounds with oxygen. There are approximately 16 identified iron oxides. However, the most prevalent iron oxide nanoparticles are magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (α-Fe2O3). Fe3O4 and γ-Fe2O3 show superior magnetic properties in comparison to α-Fe2O3. These iron oxides are ferromagnetic materials and are widely used in biomedical applications such as diagnostic magnetic resonance imaging (MRI),hyperthermia treatment of solid tumors, gene therapy tissue regeneration,and drug delivery. Non-toxic nature and biocompatibility of iron oxides are also important for these biomedical applications. α-Fe2O3 is found to be the most stable form of iron oxides. It shows n-type semiconductor properties (Eg=2.1eV) under ambient conditions. Nanoparticles ofα-Fe2O3 are used as electrode material in photoelectrochemical cells, catalysts, and sensing elements in gas sensors and humidity sensors.