Single-walled carbon nanotubes: Functionalization, characterization and application
Barron, Andrew R.
Doctor of Philosophy
With extraordinary material and physical properties, single-walled carbon nanotubes (SWNTs) attract a lot of research interest for both fundamental science and emerging applications. However, their realistic application has been hindered by difficulties with processing and characterization. This thesis reports our investigation into the functionalization and characterization of SWNTs for biological and materials applications. Carboxylic acid-functionalized SWNTs were prepared via the reaction of an amino acid, NH2(CH2)nCO 2H, with fluoronanotubes (F-SWNTs). The aqueous solubility of functionalized SWNTs over a wide pH range can be tailored through substituent chain length (i.e., n). These amino-acid functionalized SWNTs were characterized by Raman, IR, TGA, XPS, AFM and TEM. However, these methods even in combination do not provide a full characterization. In particular, they do not uniquely demonstrate the covalent attachment of the amino acid nitrogen to the SWNT sidewall. An alternative technique that potentially provides a more detailed description is NMR. We have used solid-state 13C NMR to characterize these nano-scale materials. We have observed the sp3 fluorine-substituted (C-F) carbon atoms on the sidewall of F-SWNTs. Correlation of quantification of F-SWNTs by NMR, XPS, and Raman shows that NMR provides a better quantification than Raman at high level of functionalization. Solid state NMR was also used to investigate a more complicated system: amino acid functionalized SWNTs. Our results show that increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp3 carbons (C-N) and thus provides direct evidence for covalent sidewall functionalization of SWNTs. NMR also suggests that longer side chains appear to be better at separating the SWNTs and have more motional freedom than short chains. Lastly, two applications of amino acid functionalized SWNTs are discussed: cell viability and toxicity of functionalized SWNTs for biological application and a convenient route to the covalent attachment of SWNTs to a Silicon surface for electronic and material applications.
Inorganic chemistry; Organic chemistry