Source: Dissertation Abstracts International, Volume: 78-11(E), Section: B.

Adviser: Lisa D. Pfefferle.

Ever since carbon nanotubes were discovered, research on how to functionalize or separate their different structures has been carried out in order to use them for many applications. The work presented in this thesis focuses on these two research aspects. Particular applications of single-walled carbon nanotubes (SWCNT) require functional groups on the surface to allow for ion exchange with the environment. A good characterization method of surface functionality is Point of Zero Charge (PZC). The functional groups introduced by nitric acid or ozone treated SWCNT are characterized in the first part of this thesis. Different SWCNT batches with varying diameter distributions are functionalized and heat treated and their PZC measured. Raman Spectroscopy, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, Near Edge X-ray Absorption Fine Structure Spectroscopy, and Transmission Electron Spectroscopy are used to get a full picture of how the oxygen-containing groups vary on the surface of these different batches of SWCNT and to determine if the SWCNT structure is affected. It was found that batch diameter as well as functionalization treatment affect the PZC of SWCNT. This is an indication of how surface reactivity of different SWCNT diameters plays a role in the functionalization process.

Another characteristic of SWCNT that make them useful for applications is their electrical properties. A study of how ionic liquids (IL) affect the separation of metallic and semiconducting SWCNT using an aqueous two phase extraction (ATPE) method is done. The ATPE method uses two polymers, polyethylene glycol and dextran, that create two separate phases of different hydrophobicities. Surfactant-wrapped SWCNT partition into either of these phases because of how the surfactant wraps around SWCNT of particular chiralities or electrical properties. Salts have been shown to affect this surfactant-SWCNT interaction and change which SWCNT get partitioned into either of the two phases, but IL have never been used. A matrix of IL with different cation and anions is used to study this separation. Sonie IL cause the SWCNT to partition completely into the bottom phase, while others have shown the ability to help SWCNT partition into different phases. Good metallic and selniconductive SWCNT separation was observed. IL showed a dependence on time of vortexing or time the two phases are in contact. Ultraviolet-Visible Near Infrared Spectroscopy is used to study this partitioning.