Chemistry of novel nanoscale carbon materials: Nanodiamond and carbon nano-onions
Halas, Naomi J.
Doctor of Philosophy
Nanoscience is the area of science concerning materials on the level of nanometer scale. Currently much of the discussion of nanoscience is focused on carbon-based nanostructures. Tremendous studies have been carried out on fullerenes and carbon nanotubes in the past a couple of decade due to their unique chemical and physical properties. This thesis studies the chemistry of the other two novel nanostructures in the carbon family: nanodiamond and carbon nano-onions. Nanodiamond is relatively a new engineering material with particular applications for fabrication of wear-resistant surface coatings, lubricating films and prototypes field emission displays. These materials are also of interest for studies of chemical reactivity stemming from their nanoscale particle sizes. The surface fluorination of nanodiamond at various temperatures yields a fluoro-nanodiamond with up to 8.6 at. % fluorine content. The fluoro-nanodiamond was used as a precursor for preparation of the series of functionalized nanodiamonds by subsequent reactions with alkyllithium reagents, diamines, and amino acids. The fluoro-nanodiamond and all derivatives were characterized by SEM, TEM, XRD, TG-MS, FTIR, XPS, and Raman measurements. In comparison with the pristine nanodiamond, all functionalized nanodiamonds show an improved solubility in polar organic solvents, e.g., alcohols and THF, and a reduced particle agglomeration. The fluoro-nanodiamond powder was also used as a precursor for diamond coating on solid substrate surface e.g. glass. This novel approach is based on the wet chemistry process (solution reaction) occurring at low temperature and resulting in a covalent bonding of tiny nanodiamond crystals to substrate through a molecular linker, 3-aminopropyltriethoxysilane (APTES). SEM, AFM and XPS were used for evaluation of surface morphology and elemental analysis to confirm the presence of diamond particles on surface. Carbon nano-onion studied in this thesis is another new material synthesized by our collaborators. The layer-by-layer structures make it a potential candidate as lubricant materials. The nano-onions were fluorinated at various temperatures resulting in fluoro-onions with different fluorine content. The inside layered structures are damaged due to fluorination, which was characterized by Raman, XRD, TEM et al. Defluorination treatment was also performed. All the samples show improved lubricating properties according to the test carried out by our collaborators.