We present the separation of surfactant encapsulated double wall carbon nanotubes (DWCNTs) synthesized by the high pressure carbon monoxide decomposition (HiPco) process by length and electronic characteristics using density gradient ultracentrifugation (DGU). To focus only the behavior of DWCNTs, dispersed DWCNTs were first isolated following the method of Green et al. , utilizing the differences in buoyant density of DWCNTs from impurity single wall carbon nanotubes (SWCNTs) and multi wall carbon nanotubes (MWCNTs) contained in the parent soot. The controlled addition of co-surfactants is shown to allow resolution of DWCNTs by electronic structure, as demonstrated through optical absorbance, Raman spectra, and electrical conductivity measurements. Measurements of conducting films prepared from separated fractions exhibit significant property differences in the enriched materials. Additionally by increasing the density difference between the nanotubes and density gradient medium away from the isopycnic point, we further obtained narrow length distributions of DWCNTs. The length dependent intrinsic optical response of DWCNTs is consistent compared with the previously reported values for SWCNTs.
Citation: Journal of Physical Chemistry C
Pub Type: Journals
nanotubes, SWCNT, SWNT, DWCNT, DWNT, separation, length