2016 PhD - Chemistry - University of Arizona
University of New Hampshire
Mentor: Dr. Glen Miller, UNH Department of Chemistry
Selective Exo-hydrogenation of Single-Walled Carbon Nanotubes and Effects on Solubility and Endohedral Filling
Single-Walled Carbon Nanotubes (SWNT) are tubular structures composed of pure carbon, ranging in diameter from 1 to 20 nanometers. The structure of a SWNT is relatively simple and is often compared to a rolled sheet of graphite which is a two-dimensional sheet of pure carbon hexagonal rings. SWNTs tend to aggregate into bundles, a property related to their large surface areas and the favorable energy associated with Van der Waals forces. This aggregation behavior makes SWNTs insoluble in organic and aqueous media which limits their utility in a range of applications, such as medicine, where water solubility is required. Using harsh chesmistries, I propose to simultaneously hydrogenate and open the ends of SWCNT, exposing their hollow interior. It is hypothesized that the hydrogenated SWNTs with C-H bonds radiating from the tubes will be less inclined to aggregate and therefore show greater solubility. The possibility of introducing small molecules into the hollow interior of hydrogenated SWCNT will also be explored
Several methods have been reported in the literature to hydrogenate SWNTs including the use of an atomic hydrogen beam and hydrogen plasma. In both cases, the reactions are effective but not scalable. The method for this proposal is scalable and has proven effective for fullerene compounds and nanoonions (both closely related to SWNTs in structure). Specifically, the SWNTs will be exposed to the chemical reagent diethylenetriamine at very high temperatures (ca. 450-500 oC) in a high pressure vessel. Under these conditions, the SWNTs are expected to hydrogenate and the caps are expected to open. These hydrogenated SWNTs will be structurally characterized by a combination of transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. Attempts to fill the interior space of SWNT 'hosts' with small molecule `guests' will also be made via heating the tubes in the presence of the appropriate guest compounds.