Spectroscopic Studies of Carbon Nanotubes: Spectra of Bulk Swnt Suspensions, Probing Swnt Electronic Structure Via Redox Chemistry, Optical Properties of Double-walled Carbon Nanotubes

Spectroscopic studies were performed on carbon nanotubes including single-walled carbon nanotubes (SWNTs) and double-walled carbon nanotubes (DWNTs). First, we followed the reported method to obtain the individually dispersed SWNTs with the assistance of surfactants in aqueous phase. The absorption and fluorescence spectra of this surfactant/SWNTs suspension were captured and the species distribution for the semiconducting tubes was assigned as well. Afterwards, we studied how the surfactant/SWNT suspension is affected by sonication temperature, centrifugation time, pH, and the surfactant structures. Further we describe a new method to probe the absolute energy levels of SWNTs. The first conduction band edge of the semiconducting SWNTs was obtained via measuring the redox chemistry. Finally, the optical property of DWNTs was investigated collaborating with people in Dr. Jie liu¿s group in Duke University. Our current results suggest that the inner layer of a DWNT can not fluoresce, which is contrary to the conclusion in the published literature.