Thesis (M.S. in enviromental science)--Washington State University, December 2009. / Title from PDF title page (viewed on Feb. 10, 2010). "School of Earth and Environmental Sciences." Includes bibliographical references (p. 33-34).

Honors thesis (Physics)--Oberlin College, 2006. / "April 2006" Includes bibliographical references (leaves 109-115)

Thesis (Ph. D.)--California Institute of Technology, 1992. UM #92-32, 184. / Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/01/2010. Includes bibliographical references.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / "[pi]" appears in the title as a symbol. Includes bibliographical references. Also available in electronic version.

Fullerenes have been the focus of significant research effort and curiosity for their unique physicochemical and photochemical properties since their discovery almost 30 years ago. C60 fullerene in particular has received tremendous attention, due to its prevalence in fullerene production and chemical stability. While ambitious prospective applications for C60 have been ubiquitous, the extremely hydrophobic nature of fullerenes and consequent aggregation at the nano scale has hampered many endeavors. Researchers, therefore, have turned their attention to the functionalization of fullerenes to add hydrophilic moieties for applications in aqueous media. It is known that functionalizing the C60 cage alters its innate physicochemical and photochemical properties, but how these changes translate to the properties of C60 aggregates, often termed nC60, is not well understood. Functionalized fullerenes present an intriguing environmental dichotomy. On the one hand C60 has excellent potential as a novel singlet oxygen producing disinfection tool, and on the other the potential toxicological effects of functionalized C60 are largely unknown. With thousands of possible functionalities, a mechanistic understanding of the effects of functionalization is essential. To explore the effects of functionalization on fullerene photochemistry in relevant systems, three types of functional groups were selected and obtained each in series of mono-, bis-, and tris-functionalized forms. Two functionalities contrasted the presence or lack of a quaternary ammonium group and the third was the sterically bulkier phenyl-C61 butyic acid methylester, which is commonly used in polymer photovoltaics. The fullerenes were characterized for innate photochemical properties in organic solvents using UV/Vis, laser flash photolysis, and photochemical degradation experiments. Aqueous aggregates of each derivative were additionally characterized for their physical and chemical properties by dynamic light scattering, transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. All derivatives were photoactive when dispersed molecularly in organic solvents, but only the cationic fullerenes showed significant photoactivity as aqueous aggregates. Differences in aggregate size or crystallinity were unable to explain the differential photoactivity between derivatives, contrary to two established hypotheses. Antimicrobial properties were probed using innate toxicity tests and photoinactivation experiments. Again, only the cationic fullerenes were found to exert photochemical action towards Escherichia coli or MS2 bacteriophages. The cationic fullerenes were also innately toxic to E. coli due to the presence of quaternary ammonium moieties. In order to establish a mechanistic understanding of the photochemistry of functionalized C60 aggregates, simulations of the molecular dynamics (MD) were employed and compared with empirical evidences. Simulations provided theoretical values for C60-O2, C60-C60, and C60-H2O interactions for each derivative. Trends observed in the MD results were compared to photochemical characterizations as described above and Raman spectroscopic measurements of C60’s effect on localized water structure. High resolution transmission electron microscopy was used to provide empirical evidence of the C60-C60 interactions. Overall, fullerene aggregate photochemistry is likely driven by aggregate morphology and by intermolecular interactions between fullerenes, water, and O2.

The resurgence of interest in properties of molecules of icosahedral symmetry follows the discovery of the C₆₀ molecule. Due to the high symmetry of the icosahedron, almost all the electronic and vibrational levels are highly degenerate, so that in dealing with properties of these systems, the Jahn-Teller interaction must almost always be allowed for. This thesis primarily explores the properties of the icosahedral G ⊗ (g ⊕ h] interaction and related subsystems in the strong coupling régime. Mappings of the adiabatic potential energy surfaces facilitate an analysis of the geometrical phase or Berry phase acquired by the quantal system on transportation around adiabatic circuits in parameter space. The Berry phase information in conjunction with an analysis of tunnelling, determines the properties of the ground state. The use of Ham factors achieves a characterization of the various coupling régimes. However, characterization of G and H Jahn-Teller systems, requires an extension of the standard definition of these Ham factors. In such cases the extended matrix elements between and within vibronic tunnelling sublevels cannot be ignored. A calculation of all the standard and extended matrix elements is presented. A further introduction of a matrix of Ham factors facilitates the description of H multiplicity within an H manifold. Finally, two problems are investigated numerically; aimed at making some allusion towards possible experimental manifestations of G ⊗(g(⊕)h). The first investigation considers the variations in the eigensystem and Ham factors of G ⊗ (g ⊕ h), as a function of the coupling to the two modes. The second investigation considers the structure in the optical absorption line shapes for the transitions from orbital singlet to quartet, G, states in an icosahedral environment. The quartet states are subject to both spin-orbit and linear Jahn-Teller interactions.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2000. / Includes bibliographical references.

While investigating strategies to prepare precursors to highly strained buckybowls, we focused our attention on the Lewis acid aldol cyclization of 1-acenaphthenone derivatives which has been shown to produce a cyclic tetramer as a byproduct. Surprisingly, despite the interesting structural and electronic properties that have recently been observed as a result of the incorporation of eight-membered rings into polycyclic aromatic hydrocarbons, this cyclic tetramer has largely been ignored. As a result of this, we set our sights on the isolation and characterization of this cyclic tetramer. The initial approach employed subjecting 1-acenaphthenone to the most common conditions used in trimerization—TiCl4 in boiling o-dichlorobenzene. Surprisingly, this resulted in exclusive formation of the cyclic tetramer, which we have named tridecacyclene. The results of these studies were promising, establishing structural characterization and supramolecular assemblies with C60 in the solid-state. The optoelectronic properties revealed a significantly lower reduction potential (~0.4 eV) than the trimeric species of 1-acenaphthenone. This is attributed to the central eight-membered ring of tridecacyclene. Reduction proceeded through two single-electron processes. Further examining the electrochemical properties, we were able to gain new insight into the relation of structure and aromaticity. Reduction of tridecacyclene with potassium metal allowed us to characterize the radical anion and dianion through NMR and UV-Vis spectroscopy. Solid-state analysis of the dipotassium adduct revealed that despite the propensity of the reduced form of cyclooctatetraene derivatives to flatten as the molecule adopts a Hückel aromatic core, tridecacyclene maintains its tub shape. Significant bond equalization was observed in the center eight-membered ring—a strong indication of a delocalized π-system. This was supported by harmonic oscillator model of aromaticity calculations of the central ring with the value increasing from 0.09 to 0.48 where a value of 1 indicates a fully aromatic ring. Tridecacyclene represents the precursor to a fragment of the fullerene C240. A broad variety of reactions to facilitate the necessary strain inducing C–C bonds to formthe fragment have been attempted. To date, we have not been able to synthesize the fragment. However, the parent molecule tridecacyclene shows great promise in the development of non-aqueous redox flow batteries and is currently being explored for this purpose in our laboratory.

The goal of this dissertation is to study the photophysics of suspensions of colloidal C₆₀ particles to determine if their nonlinear optical (NLO) response is superior in any way to benchmark NLO materials such as molecular solutions of C₆₀ and carbon black suspensions (CBS). C₆₀ in molecular form is known to exhibit strong reverse saturable absorption (RSA) and it is posited that colloidal particles composed of many C₆₀ molecules would maintain some degree of RSA behavior upon association, although some quenching is to be expected. CBS is known to have an NLO response that is dominated by nonlinear scattering resulting from a phase change due to heating of the carbon black particles by absorbed energy. Colloidal C₆₀ particles that are many nanometers in diameter are similar to CBS, so it is posited that they would also have a nonlinear scattering mechanism contributing to their NLO response. Three samples of C₆₀ colloids are characterized by several techniques, along with two carbon black suspensions and one molecular solution of C₆₀. Transmission electron microscopy is used to determine morphology. Femtosecond pump-probe spectroscopy is used to determine the absorption spectrum and the relaxation kinetics of the first excited singlet state. Nanosecond laser flash photolysis is used to determine the absorption spectrum and the relaxation kinetics of the first excited triplet state. Z-scan is used to determine triplet-triplet absorption cross-sections. An experiment is performed to determine the percentage of the input energy that is transmitted, scattered, or absorbed by each sample. Computer modeling is performed to compare the experimental results to theory. Results show that all materials that exhibit nonlinear scattering have a constant extinction coefficient in the nonlinear regime, implying a characteristic size for the scattering centers that is independent of input energy. Quenching processes in C₆₀ colloids are found to be morphology dependent, with more crystalline structures resulting in stronger quenching and less RSA. C₆₀ colloids with stronger RSA are found to result in less nonlinear scattering than strongly quenched colloids. Highly crystalline C₆₀ colloids were shown to have a stronger NLO response than the benchmark materials at medium to high energies.

Finding renewable sources of energy is becoming an increasingly important component of scientific research. Greater competition for existing sources of energy has strained the world’s supply and demand balance and has increased the prices of traditional sources of energy such as oil, coal, and natural gas. The experiment discussed in this paper is designed to identify and build an inexpensive and simple method for creating an effective organic solar cell.