Synthesis and Applications of Anisotropic Magnetic Iron Oxide Nanoparticles

Magnetic iron oxide nanoparticles have been used by human mankind since ancient times and have had the capacity to adapt to the demanding technologies in each period. Ancient applications used iron oxides from nature, since iron is one of the most abundant elements on the Earth and their oxides are easy to obtain. More recently, the rapid development of the different technologies required iron oxide particles with better properties which was fulfilled with the possibility to design artificially magnetic iron oxide nanoparticles by different synthetic routes, reaching with time an exquisite control of their size, shape and crystallinity. At the end of the last century, spherical particles were used for most of the applications except for flexible recording media. However, the number of synthetic approaches leading to anisotropic nanoparticles with appealing properties has exponentially grown in the last two decades. This chapter describes the most common synthetic routes in liquid media (colloidal synthesis) to prepare magnetic iron oxide nanoparticles with different morphologies. Then, the different applications where these anisotropic nanoparticles have been tested are described, from biomedicine to magnetic recording media, spintronics or environmental remediation.