(142s) Hydrodynamic Behavior of Carbon Nanotubes and Characterization of Length Distributions

Single-walled carbon nanotubes (SWCNTs) are 1D, cylindrical, structures of carbon with long persistence lengths and consistent diameters. In this talk, I will discuss the use of doubly sorted SWCNTs (by buoyancy and length), which are effectively colloidal rods, to explore experimentally the effectiveness of theoretical approximations for the hydrodynamic drag of a freely rotating rod.  The objective of this work is establish and validate the use of Analytical Ultracentrifugation (AUC) as a technique to measure the length distribution of rodlike colloidal particles including SWCNT dispersions. This is necessary for real applications of nanotube dispersions, as the transport, optical, and thermal properties, as well as the toxicity of SWCNTs have all been demonstrated to depend on the length. To date however, length distributions of suspensions have most commonly been determined using Atomic Force Microscopy (AFM). Unfortunately for this purpose, AFM is time consuming, tedious, does not measure the distribution in situ, and can be biased by both the method of sample preparation as well as the image analysis. AUC would be thus advantageous because it allows the direct measurement of ensembles as they exist in the liquid phase. In this talk, I will present measurements and analysis of SWCNT samples with narrow distributions in length, diameter and buoyancy as measured through AUC and compare them against independent measurements conducted with AFM.  Using this data, the validity of hydrodynamic theory for this application is verified.