Magnetic magnetite nanocrystals

The magnetite nanocrystals we discussed in Chapter 33 are used by nature in ways we do not fully understand, but they appear to allow certain species to detect the earth s magnetic field and use it to navigate. 

Kim, J. et al (2008) Multifunctional uniform nanoparticles composed of a magnetite nanocrystal core and a mesoporous silica shell for magnetic resonance and fluorescence imaging and for drug delivery. Angew. Chem., Int Ed., 47 (44), 8438-8441. 

The confinement of two species in stoichiometric amounts within the nanodroplets also allows the synthesis of mixed species. A mixture of Fe2+ and Fe3+ salts leads to the formation of magnetite, Fe304. The final dispersion with a particle size of 200 nm is black and shows magnetic properties. As is seen in the TEM pictures (Fig. 23b), the superstructure composed of 10-nm nanoparticles as determined by WAXS is anisotropic (lemon shaped), and constituting needle shaped nanocrystals, can be identified inside the particles, arranged as bundles along the main axis of the lemons . 

When nanocrystals of magnetite are precipitated in a glassy phase, FARG becomes a magnetic material. 

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