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 CO2 drying of nanostructures can eliminate the effect of capillary (or interfacial tension) forces on the final morphology and enable the unique properties and potential applications of these novel materials to be realized. © 2003 Elsevier B.V. All rights reserved.

Duke Scholars

Author Brian R. Stoner Electrical and Computer Engineering