Thesis (M.S.)--Brigham Young University. School of Technology, 2006. / Includes bibliographical references (p. 153-160).

Thesis (Ph.D.)--University of Melbourne, Dept. , 19. / Typescript (photocopy). Includes bibliographical references.

Thesis (Ph. D.)--University of Technology, Sydney, 2005.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 62-63). Also available in electronic version. Access restricted to campus users.

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The goal of current research is probing the relationship between catalyst features and the fuel cell performance with a range of in-depth structural analysis. The study investigated different catalyst systems including core-shell structured catalyst, catalysts with unique carbon-transition metal oxide supports. PtRu catalysts nanoparticles with unique core-shell structure, one of the most practical catalysts in PEMFC technology, have been successfully obtained with the evidence from the characterization results. It is found that the enhanced CO oxidation may be achieved through the interactions between the Pt shell and Ru core atoms, which can modify the electronic structure of the Pt surface by the presence of subsurface Ru atoms or by disrupting the Pt surface arrangement. Furthermore, the possibility of presence of the compressive strain within the Pt rich shell is proved by the lattice measurements, which could significantly affect the catalytic activity. Pt catalysts supported on complex oxide and carbon support were studied to investigate the relationship between the catalyst and its support. Observations from STEM images and HAADF and energy dispersive X-ray spectrometry demonstrate the preferential distribution of Pt nanoparticles on the hybrid supports, which include Nb2O3 / C, Ta2O5 / C, (Nb2O3+TiOx) / C, (Ta2O5+TiOx) / C, and (WO3+TiOx)/C). Such evidence indicates the interaction between the catalyst and support is based on the presence of an interconnected oxide network over the carbon support and the presence of Pt strongly connected to the oxide network. In addition, using electron energy loss spectroscopy (EELS), the electronic structure of the catalyst support under various conditions was also studied to provide further evidence of the strong metal support interaction effect. / Thesis / Doctor of Philosophy (PhD)

M.Sc. / Donor-acceptor (D-A) systems consist of a donor covalently or non-covalently linked to an acceptor. The simplest D–A system consists of a donor linked to an acceptor and is called a dyad system. Photoactive dyad systems are molecular devices designed to perform through the separation of charge separation states and the conversion of solar energy to chemical energy in analogy to photosynthesis.1 These dyad systems consist of a donor which is usually a chromophore and an acceptor. The design of these systems is guided to mimic photo-induced electron transfer (PET) and charge separation (CS), which are fundamental processes of photosynthesis. In nature, photosynthetic units are often built from dyads consisting of pigments like chlorophyll (donors), non–covalently linked to quinones, (acceptors). The donor harvests light energy and transfers the energy to the nearby pigment molecules until it eventually reaches a special region of the chlorophyll macrocycle called the reaction centre where this light energy is then converted to electrochemical energy. Photoactive dyad systems act as artificial photosynthetic models as they reproduce photo–induced electron transfer and charge separation of natural photosynthesis. In this project, dyad systems were made by covalently linking zinc pheophorbide, a modified chlorophyll derivative to double–walled carbon nanotubes (DWCNTs). Zinc pheophorbide acts as the donor and DWCNTs as the acceptors. Chlorophyll was modified by cutting the phytol chain and inserting zinc as the central metal to yield zinc pheophorbide. This derivative is stable against irradiation, has a good range of acceptor wavelength and is also a good light harvester. DWCNTs are one dimensional nanowires with two concentric tubes. They readily accept electrons because they have an extended π electron system. These electrons are then transported efficiently under ballistic conditions. DWCNTs were synthesised by catalytic chemical vapour deposition (CCVD) of methane over Mg0.99Co0.075Mo0.025O catalyst. In dyad system 1, amidated zinc pheophorbide molecules were covalently attached to oxidised DWCNTs in the presence of N–ethyl–N’–(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) \ and N–hydroxysuccinnimide (NHS) as a catalysts. Dyad system 2 was synthesized by attaching zinc pheophorbide molecules to amidated DWCNTs using the same catalysts.

Poster exhibited at GPSC Student Showcase, February 24th, 2016, University of Arizona. Recipient of the 2016 Katheryne B. Willock Library Research Award. / The nervous system is composed of two types of cells: neurons and glia. In neuronal circuits, neurons communicate through synapses and glia play a crucial modulatory role. To modulate chemical reuptake, glia send processes close to synapses and many glia directly appose or ensheathe a synapse. This structural motif is one of the elements often included in describing a vertebrate tripartite synapse, which includes a bidirectional functional neuron-glia relationship. The exact nature of this neuron-glia communication is not well understood. In the invertebrate fruit fly, we have also found that particular neurons and glia also have a bidirectional functional relationship. This allows us to ask new questions about glial morphology. Throughout multiple images, I identified particular neuronal synapses and surrounding glia. After creating a 3D reconstruction, I measured the distance between a particular neuronal synapse and its closest glial process. Interestingly, the neuronal synapses were not directly apposed or ensheathed by glia, and the distance to the closest glial process varied one-hundred-fold. With variable distance, functional communication is consistently present. These findings provide important insight into invertebrate neuron-glia communication, and offer new avenues to investigate the structural neuron-glia relationships that are required for reciprocal signaling between the two cell classes.

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