Spectrofluorimetric analysis of single-walled carbon nanotubes: Instrumentation and applications

Abstract

Significant effort has centered on improving methods for producing single-walled carbon nanotubes (SWCNTs) in large quantities because of their unique electrical, mechanical, and thermal characteristics. Most production methods yield many diverse SWCNT structures, which are defined by the imaginary rolling up of a graphene sheet. The discovery of intrinsic band-gap fluorescence from semiconducting SWCNTs suspended in surfactant solutions and the subsequent assignment of the various excitation-emission features for specific SWCNT structures has opened the door to a broad range of experimental endeavors previously unavailable. This thesis describes recent progress in developing fluorimetric analysis methods and applying them to chemical problems. First, a unique turn-key SWCNT fluorescence analyzer was built and novel data analysis method was implemented for the bulk characterization of carbon nanotube samples. The instrument and analysis are illustrated by comparing deduced diameter and chirality distributions for a typical SWCNT suspension against those obtained from a general purpose spectrofluorometer system. Secondly, the use of rationally designed peptide sequences as biocompatible solubilizing agents for SWCNTs is demonstrated. This study illustrates how these peptides can be tailored to either shift the average diameter of bulk suspended SWCNTs or improve sustainable nanotube solubilization through the use of peptide crosslinking. Finally, a project is described in which the addition of diazonium salts to SWCNT suspensions quenches the intrinsic near-infrared fluorescence of the semiconducting SWCNTs through sidewall chemical reactions. Structure dependent reactivities of SWCNT species were observed in bulk measurements and variations of diazonium salt, suspending agent, and/or pH were used to moderate the reactivity trends.