Thesis (Ph. D.)--School of Physics, Georgia Institute of Technology, 2005. Directed by Walt A. de Heer. / Whetten, Robert L., Committee Member ; Conrad, Edward H., Committee Member ; First, Phillip N., Committee Member ; de Heer, Walt A., Committee Chair ; Gaylord, Thomas K., Committee Member. Includes bibliographical references.

Thesis (M.S.)--University of Louisville, 2009. / Department of Physics. Vita. "May 2009." Includes bibliographical references (leaves 57-58).

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 112-123). Also available in electronic version. Access restricted to campus users.

Les matériaux hybrides nanotubes de carbone remplis par des matériaux ferromagnétiques (NTCFM) présentent un fort potentiel pour des applications en électronique de spin. Leurs propriétés magnétiques dépendent fortement de la qualité de leur synthèse : densité, orientation et efficacité de remplissage. Deux méthodes d’élaboration des (NTC-FM) ont été utilisées : i) synthèse ex-situ après ouverture mécanique des nanotubes élaborés par arc électrique et in-situ pendant la synthèse par arc électrique, ii) synthèse par dépôt vapeur chimique assisté par plasma (PECVD) en présence de catalyseurs Co et Co/Pd. Les deux approches de confinement des nanotubes de carbone avec des métaux ferromagnétiques ont été comparées. La première méthode de synthèse des nanotubes hybrides a montré que l’approche par arc électrique in-situ est plus efficace surtout par l’ajout d’un promoteur comme l’yttrium (Y) et le soufre (S). Les différentes proportions catalytiques au cours de la synthèse ont été variées et leur influence sur la production des nanotubes hybrides étudiée. La qualité et la quantité des nanotubes obtenus ainsi que les rendements disponibles au cours de la synthèse ont été améliorés. La réponse magnétique est également meilleure. La synthèse des nanotubes hybrides par PECVD a révélé que l’adjonction d’une couche de palladium comme catalyseur avec le cobalt conduit à une nette amélioration de la densité, du remplissage et de l’alignement des nanotubes. Les mesures magnétiques ont mis en évidence la contribution d’une anisotropie de forme que l’on peut associer à une meilleure orientation géométrique des nanotubes par rapport au substrat. / Hybrid materials as carbon nanotubes filled with ferromagnetic materials (FMCNT) have great potential for spintronic applications. Their magnetic properties strongly depend on their density,orientation and filling efficiency. Two preparation methods of (FMNTC) were used: i) ex-situ synthesis where mechanical opening of the nanotubes produced by electrical arc is first achieved and in-situ during the synthesis by electrical arc discharge, ii) synthesis by chemical vapor deposition enhanced by plasma (PECVD) in the presence of cobalt Co and Co / Pd catalysts. Our results showed that the arc in-situ approach is more effective especially with the addition of a filling promoter such as yttrium (Y) and sulfur (S). Different proportions of catalyst were varied and their influence on the yield of hybrid nanotubes studied. The quality and quantity of obtained nanotubes as well as their yields and magnetic properties were improved. The PECVD synthesis revealed that the addition of a thin layer of palladium (~6 nm) as a co catalyst with the cobalt leads to a significant improvement inthe density of the filler and the alignment of the nanotubes. Magnetic measurements thereby demonstrated the contribution of a shape anisotropy that can be associated with a better geometric orientation of the nanotubes to the substrate.

abstract / Chemistry / Doctoral / Doctor of Philosophy

Single walled carbon nanotubes (SWCNTs) have unique physical, optical and electronic properties. Current production methods provide SWCNTs as a polydisperse mixture, with respect to helicity, diameter and length, and cannot be tuned to yield a discrete SWCNT isomer. A bottom up approach would yield a single SWCNT, which would allow for a better understanding of how chemical modification affects a carbon nanotube’s properties. Synthesis by this route has yet to be accomplished. Phenylene ethynylene macrocycles were synthesized by a stepwise linear fashion and cyclooligomerization. These macrocycles are Diels-Alder cycloaddition precursors for a rational synthesis of a (9,0) SWCNT segment. Additionally, these macrocycles are of interest due to their highly conjugated two dimensional networks, which gives rise to high quantum efficiency. Therefore, the optical properties of these macrocycles were studied in several of solvents. In addition, a novel reductive imination was examined and used to synthesize a series of phenylene imine macrocycles. These systems could be precursors towards organic N-doped SWCNTs by either a hetro-Diels-Alder cycloaddition or pyrrole ring formation.

Carbon nanotubes (CNTs) have attracted significant attention as novel one-dimensional nanomaterials due to their unique structures and properties. Aggregate properties of CNTs such as high surface area, length, or chemical composition are further tailored to enhance their potential application in nanomedicine, through post synthesis chemical modification procedures. These modifications simultaneously alter their aggregate physiochemical properties and this has a direct impact on cytotoxicity of CNTs in cells. A lot of research has been done towards the toxicity of CNTs, however, there is need for results that are consistent and standardized if the application of CNTs in nanomedicine is to be a reality. Indeed the toxicology study of CNTs has been compromised by conflicting toxicity results due to lack of physiochemical characterization, regulation of the synthesis and standardized cytotoxicity assays. Herein, the effects of the physiochemical characteristics of riluzole loaded CNTs on their toxicity in neuronal cells is evaluated to elucidate a better understanding of CNTs toxicity. Furthermore the cellular uptake and overall efficacy of riluzole loaded CNTs is evaluated. As prepared multiwalled carbon nanotubes (MWCNTs) synthesized by the Catalytic Chemical Vapor Deposition (CCVD) method were initially acid oxidized using strong acids at different temperature and reaction time so as to remove impurities whilst introducing carboxylic groups on to the surface. The drug riluzole was then conjugated to the oxidized MWCNTs via carbodiimide activated amidation. The purification and functionalization led to the isolation of physicochemical properties as characterized by the Transmission Electron Microscopy (TEM), Raman spectroscopy, BET surface area analysis and Thermogravimetric Analysis (TGA). These physiochemical properties i.e. length, surface area, degree of fictionalization and amount of chemical impurities were key determinants of the drug loaded MWCNTs’ cytotoxicity. The data from this study supports the hypothesis that physiochemical modifications of MWCNTs that occur due to the functionalization of the drug to its surfaces alter their toxicity in neuronal systems. The riluzole loaded MWCNTs with <15% metallic residue, 500-2000nm length, and high surface area (30-76 m2/g) were found to cross the cell membrane without causing toxic effects as all the cells were viable compared to the untreated cells control. Covalently linking riluzole to MWCNTs and the consequent changes in the physiochemical properties did not lead to the generation of toxic effects in cells. Furthermore chemically binding riluzole to the MWCNTs did not deactivate the drug and reduce its ability to be antiglutamate. The identification of specific physiochemical properties governing CNTs toxicity presents the opportunity for carbon nanotube based drug delivery system designs or applications that reduce human and environmental impacts.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Kwon, Young W. Second Reader: Pollak, Randal D. "December 2009." Description based on title screen as viewed on January 29, 2010. Author(s) subject terms: Carbon nanotubes, CNTs, MWNTs, nanocomposites, carbon fiber composite, adhesive strength, crack propagation, Mode II, functionalized carbon nanotubes, carboxyl. Includes bibliographical references (p. 38-40). Also available in print.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 183-202).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 91-92). Also available in electronic version. Access restricted to campus users.