One of the central challenges Nanotechnology seeks to address is the ability of the materials components to self-assemble into ordered arrays that will have function and utility. Physical, chemical, optical, magnetic or electronic properties of nanostructured materials can be tuned by adjusting size, shape and surface-modification. In addition to the optimisation and search for new materials, miniaturisation of existing compounds reveals that, as soon as the respective inherent bulk-limit (generally in the nanoscale regime) is surpassed, a drastic change of properties as a function of size. In order to take advantage of the potential of such properties in nanoscale materials one obstacle to overcome is their arrangement into utilizable dimensions. This issue has been addressed for single materials applying different strategies.1-3 One approach to this issue combines the advantage of miscibility of different materials by applying solution cast methods with close vicinity in the resulting dense material (although direct contact between particles is avoided by the surfactant). We present the first formation of a bimodal three-dimensional nanocrystal superlattice isomorph to NaZn13 built up 11 nm magnetic iron oxide particles (γ-Fe2O3) forming a cubic framework of superparamagnetic spheres and 6 nm semiconducting lead selenide particles inside of the maghemite-cube forming an icosahedron with an additional particle in the middle. The crystals were obtained by self-assembly of the materials during slow evaporation of the solvent from nearly monodisperse solutions. A nanocrystal superlattice of iron oxide magnetic nanocrystals prepared by this method is shown in figure 1.
Figure 1. Transmission Electron Microscope Image
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