Supercritical fluid preparation of copper nanotubes and nanowires using mesoporous templates

Supercritical fluid decomposition of copper precursors in the presence of hexagonal mesoporous silica matrices are used to prepare ordered copper metal nanowire and nanotube arrays. Evidence is presented which shows that the pore-filling process is accompanied by large expansions of the pore-to-pore distance induced by the inclusion process. Preparation of these materials requires strict control as copper appears to catalyze the collapse of the mesoporous structure. The copper nanostructures exhibit the normal face-centred cubic crystal structure although there is a strong variation of the lattice parameter with size. UV-visible absorption spectra of copper nanowires within the mesoporous matrix as a function of copper loading exhibit effects related to the low dimensionality of the nanowires formed. Transmission electron microscopy images and changes in the surface area and pore size of the materials as a function of copper content suggest that the growth mode is radial rather than a random nucleation and growth mechanism.