Controlled Aqueous Chemical Growth of Oriented Three-Dimensional Crystalline Nanorod Arrays:  Application to Iron(III) Oxides

The ability to create thin films of highly oriented anisotropic nanoparticles of transition metal oxides onto polycrystalline and single-crystalline substrates is demonstrated by the fabrication of large three-dimensional arrays of perpendicularly oriented nanorods of crystalline iron(III) oxides onto tin oxide and sapphire substrates. An enchanced control of the thermodynamics and kinetics of nucleation and growth processes allows one to grow such novel materials directly onto substrates from a simple aqueous solution of metal salts.