title: Hydrodynamic characterization of surfactant encapsulated carbon nanotubes using an analytical ultracentrifuge.
abstract: The hydrodynamic properties of surfactant encapsulated single-walled carbon nanotubes (SWNTs) have been characterized by optically measuring their spatial and temporal redistribution in situ in an analytical ultracentrifuge. The measured redistribution profiles are fit to the Lamm equation, thus determining the sedimentation, diffusion, and hydrodynamic frictional coefficients of the surfactant encapsulated SWNTs. For sodium cholate encapsulated SWNTs, we demonstrate that the technique of analytical ultracentrifugation can be utilized to determine the linear packing density of surfactant molecules along the length of the SWNTs, 3.6 +/- 0.8 nm(-1), and the anhydrous molar volume of the surfactant molecules on the SWNT surfaces, 270 +/- 20 cm(3) mol(-1). Additionally, analytical ultracentrifugation is used to measure and compare the sedimentation rates of bundled and isolated carbon nanotubes. This study should serve as a guide for designing centrifuge-based processing procedures for preparing samples of SWNTs for a wide variety of applications and studies. Additionally, the results obtained here should aid in understanding the hydrodynamic properties of SWNTs and the interactions between SWNTs and surfactants in aqueous solution.
authors.affiliation: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Arnold
authors.forename: Jin
authors.initials: J
authors.lastname: Suntivich
authors.forename: Samuel I
authors.initials: SI
authors.lastname: Stupp
authors.forename: Mark C
authors.initials: MC
authors.lastname: Hersam
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000379:methods; D017666:Deuterium Oxide / Q000737:chemistry; D015233:Models, Statistical; D008962:Models, Theoretical; D008968:Molecular Conformation; D009038:Motion; D009068:Movement; D036103:Nanotechnology / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D055095:Optics and Photonics; D020358:Sodium Cholate / Q000737:chemistry; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature; D014461:Ultracentrifugation / Q000295:instrumentation*
chemical_list: D037742:Nanotubes, Carbon; D013501:Surface-Active Agents; D017666:Deuterium Oxide; D020358:Sodium Cholate