Self-assembly and self-orientation of truncated nano-octahedra of   magnetite
  Monodispersed magnetite (Fe3O4) nanoparticles were synthesized. Transmission electron microscopy study shows that the nanoparticles are in the shape of Wagner-Seitz crystals. The magnetite nanoparticles self-assemble into body-centered cubic superlattice, in which the nanoparticles have the same crystallographic orientations. Shape plays a very critical role in controlling the orientation of the nanoparticles in the superlattice. Both the self-assembly and self-orientation of nanoparticles are important for technical applications. This can also act as a complement to conventional lithography techniques. 
R. K. Zheng, Hongwei Gu, Bing Xu, K. K. Fung and X. X. Zhang