Title

The separation and substrate independent organization of single-wall carbon nanotubes

Date of Completion

January 2003

Keywords

Chemistry, Polymer|Engineering, Materials Science

Degree

Ph.D.

Abstract

Learning how to separate, purify and manipulate single wall carbon nanotubes (SWNTs) presents a unique challenge in material science. The processing-related difficulties of these long nano-fibers stem from their high aspect ratio, rigidity and the profound hydrophobic attractions along their tubular walls. Shortening them into discrete segments, with lengths from tens to hundreds of nanometers, presents a viable methodology to alleviate the shape-induced intractability. The thesis presents a route for the length fractionation of shortened-S WNTs, and most importantly provides a venue by which substantial separation of single wall carbon nanotubes (SWNTs) according to type (metallic versus semiconducting) has been achieved for HiPco and laser-ablated SWNTs. Herein I argue that stable dispersions of SWNTs with octadecylamine (ODA) in tetrahydrofuran (THF) originate from the physisorption and organization of ODA along the SWNT sidewalls in addition to the originally proposed zwitterion model. Furthermore, the reported affinity of amine groups for semiconducting SWNTs, as opposed to their metallic counterparts contributes additional stability to the physisorbed ODA. This provides a venue for the selective precipitation of metallic SWNTs upon increasing dispersion concentration, as indicated by Raman investigations. In addition, the thesis provides a novel metal-assisted self-organization of these nanosized objects into nano-forest geometries with dense perpendicular surface grafting, and demonstrates that such nanosized objects hold significant promise for the development of nanoscale sensors. Additionally, this dissertation provides a method for the complete elimination of catalytic impurities from SWNTs. Electrochemical actuators using such purified SWNTs have been characterized. ^