Solvent-induced morphology in nano-structures
Solvent-induced phenomena sometimes have undesirable influences on the morphology of carefully designed nanomaterials. The chapter basically describes the morphology of two seemingly unrelated nano-structures-arrays of multi-walled carbon nanotubes and sol-gel-templated semiconductor-oxide nanotubes-share strikingly similar responses to a high-surface-tension solvent, such as water. The chapter shows that the CNT brush morphology can be converted into a honeycomb nanostructure on silicon substrates by evaporating a dilute polymer solution in a volatile organic solvent on the brush surface. This composite CNT honeycomb morphology exhibits a combination of good electrical and mechanical properties and may have potential as a robust field emitter or other thin-film, functional polymer composites. The honeycomb morphology appears to be the result of water-induced capillary forces within the brush during drying. The same forces appear to be the origin of the collapsed or bundled morphology exhibited by sol-gel-templated processing of semiconductor nanotube arrays. Liquid and supercritical CO
