The combination of heterogeneous inorganic nanocrystals provides novel nanometer-scale architectures for exploration of novel functions. In the present study, heterogeneous bilayers, such as BaTiO-FeO and MnO-CeO, are fabricated via layer-by-layer stacking of several rectangular nanoblocks 5-23 nm in size by evaporation-driven self-assembly. Specific heterojunctions between inorganic crystals are constructed by nanoscale simple brick work through spontaneous adjustment of the crystallographic orientations of the nanoblocks in the lower and upper layers.

The coercivity of magnetic nanoparticles is enhanced by the exchange coupling effect at the interface of ferrimagnetic and antiferromagnetic self-assembled monolayers.

Uniformly sized building units are generally required to construct highly elaborate architectures over a wide range. Defined nanocubes of Co 3 O 4 evolved from deformed precursor nanograins 2−5 nm in diameter through direct oriented attachment in a nonpolar medium. Uniformly sized primary nanocubes ∼8 nm on a side with {100} faces were formed by adjusting the coverage of the oxide nanograins with oleic acid. Larger nanocubes 20−40 nm on a side were produced with further direct oriented attachment of the primary nanocubes. Ordered arrays, such as superlattices, were found to be constructed by the indirect oriented attachment of the primary and larger nanocubes covered with organic molecules.

As children play with wooden building blocks, we would like to construct elaborate architectures through the one-by-one accumulation of nanocrystals.

Enhanced oxide-ion conductivities were observed on mesocrystalline structures that were produced by evaporation-induced self-assembly of rare earth-doped CeO2 nanocubes 4–5 nm in size.