Hierarchical nanostructures by nanotube grafting on porous cellular surfaces

Natural biological systems make use of capillary-type hierarchical structures in order to enhance surface functionality within limited size. This paper discusses fabrication of similar synthetic structures by grafting carbon nanotubes (CNTs) on microcellular substrates such as graphitic foam. A major hurdle so far had been deposition of dense CNT layers inside uneven pores. This has been overcome in this study by pre-coating the porous surface with plasma-derived silica molecules. It is seen that the pre-coating not only increases the density of nanocatalyst attachment on the surface but also makes each nanocatalyst more effective in nucleation and growth of nanotubes. The CNT layers formed are strongly attached to the substrate, which makes them particularly suitable for use in robust hierarchical devices in the future.