Synthesis of Cobalt Oxide Nanotubes from Colloidal Particles Modified with a Co(III)-Cysteinato Precursor

The fabrication of cobalt oxide nanotubes (length 3-4 μm, width 200-400 nm) was achieved by a colloidal templating approach. In this approach, a Co(III)-cysteinato complex [Co(en)2(S-cys)]2(BF4) was employed as the precursor of cobalt oxide. The infiltration behavior of the precursor into polyelectrolyte multilayers was studied with a quartz crystal microbalance which showed that the amount of the precursor incorporated increased with the number of polyelectrolyte (PE) layers. After incorporation of the precursor into PE multilayers precoated onto submicron-sized polystyrene latex particles via the layer-by-layer deposition, the resulting composite colloidal particles became threaded in a pearl necklace-like structure. Upon calcination at an elevated temperature, cobalt oxide nanotubes were observed by transmission electronic microscopy (TEM) and atomic force microscopy. High-resolution TEM, electron diffraction, energy-dispersive X-ray spectroscopy, and X-ray diffraction showed that these nanotubes were composed of spinel polycrystalline Co3O4. The preparation of such cobalt oxide nanotubes affords a new avenue for the application of metal complexes and represents a promising route for the synthesis of novel inorganic nanotubes.