Evolution of Co₃O₄ Nanocubes through Stepwise Oriented Attachment

Uniformly sized building units are generally required to construct highly elaborate architectures over a wide range. Defined nanocubes of Co3O4 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.