Needle superstructure

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 . 

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