Separation of single-walled carbon nanotubes via electrophoresis


Monica L. Usrey,, Woo-Jae Kim,, and Michael S. Strano, Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 104 Roger Adams Laboratory, 600 South Mathews Avenue, Urbana, IL 61801
Single-walled carbon nanotubes (SWNT) exhibit unique electronic, mechanical, and optical properties, making them the subject of intense investigation. Individual carbon nanotubes are semiconducting or metallic. The separation of SWNT by electronic structure remains an important hurdle in their widespread application. Recently, an electronic structure selective chemistry was demonstrated using an aryl diazonium salt to selectively react metallic nanotubes. Using this chemistry with a deprotonateable moiety allows for the control of metallic SWNT formal charge depending upon the extent of covalent reaction. In this work, we investigate the separation of carbon nanotubes using both gel and free solution electrophoresis. Electrophoretic mobility is dependent upon both the charge of a particle, which promotes mobility, and its hydrodynamic drag, which resists movement. A model based upon flexible rod diffusion theory is used to study both the effect of covalent reaction upon the net charge as well as the magnitude of the frictional resistance.