Prev. Article Next Article Table of Contents

Article

Translational and Rotational Dynamics of Individual Single-Walled Carbon Nanotubes in Aqueous Suspension

Supporting Info

Dmitri A. Tsyboulski, Sergei M. Bachilo, Anatoly B. Kolomeisky and R. Bruce Weisman*

Department of Chemistry, Richard E. Smalley Institute for Nanoscale Science and Technology, and Center for Biological and Environmental Nanotechnology, Rice University, 6100 Main Street, Houston, Texas 77005

ACS Nano, 2008, 2 (9), pp 1770–1776

DOI: 10.1021/nn800364r

Publication Date (Web): July 29, 2008

* Address correspondence to weisman@rice.edu.

Abstract

Near-infrared fluorescence videomicroscopy has been used to study simultaneously the translational and rotational diffusion of individual semiconducting single-walled carbon nanotubes (SWCNTs) in aqueous suspension. Analysis of translational trajectories revealed diffusion coefficient values from approximately 0.3 to 6 μm²/s. The nanotube lengths deduced from these values ranged between 130 nm and 6 μm. From the minor bending motions observed in individual nanotubes several micrometers in length, we confirmed that the shorter SWCNTs of primary interest here can be considered to be rigid rods under normal conditions. Because the nanotubes act as highly rigid, photostable, steady, and anisotropic fluorophores, it was possible to monitor their rotational reorientations through fluctuations in emission intensity under linearly polarized excitation. The magnitudes of observed orientational fluctuations varied substantially among individual nanotubes. These magnitudes correlated strongly with translational diffusion coefficient, reflecting the length dependence of both types of motions. Combined translational and rotational measurements also revealed the influence of local environment on nanotube mobility.