(518e) Assembly of Suspending Agents On Single-Walled Nanotube Surface and Its Effect On Separation Processes

Single-walled carbon nanotubes are materials with a large number of potential applications. However, it is necessary to overcome the challenges posed by SWNT polydispersity to take advantage of their outstanding physical properties in most applications. Two of the most recent post-synthesis methods to separate SWNTs are density gradient ultracentrifugation (DGU) and selective adsorption onto agarose gel. The DGU method has been used to attain separations by diameter, type, handedness and length. Separation with agarose gel has been used to separate SWNTs mainly by type. Both of these methods take advantage of the specificity of the assembly of suspending agents on the surface of SWNTs. We have investigated the mechanism underlying the separation by the agarose gel method. Different strategies were used to show that separation depends on the state of the surfactant shell around SWNTs. The results suggest that SDS assembly on SWNTs is influenced by the type and diameter of the SWNT species as suggested by recent theoretical and experimental results. Finally, we show that both the adsorption onto agarose and DGU can be used as analytical tools to assess the surfactant structure. These methods have been used to study the effect of concentration, temperature and co-suspending agent on the structure of the surfactant shell around SWNTs.