ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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Description
Increasing concentrations of carbon dioxide in the atmosphere will inevitably lead to long-term changes in climate that can have serious consequences. Controlling anthropogenic emission of carbon dioxide into the atmosphere, however, represents a significant technological challenge. Various chemical approaches have been suggested, perhaps the most promising of these is based on electrochemical trapping of carbon dioxide using pyridine and derivatives. Optimization of this process requires a detailed understanding of the mechanisms of the reactions of reduced pyridines with carbon dioxide, which are not currently well known. This thesis describes a detailed mechanistic study of the nucleophilic and Bronsted basic properties of the radical anion of bipyridine as a model pyridine derivative, formed by one-electron reduction, with particular emphasis on the reactions with carbon dioxide. A time-resolved spectroscopic method was used to characterize the key intermediates and determine the kinetics of the reactions of the radical anion and its protonated radical form. Using a pulsed nanosecond laser, the bipyridine radical anion could be generated in-situ in less than 100 ns, which allows fast reactions to be monitored in real time. The bipyridine radical anion was found to be a very powerful one-electron donor, Bronsted base and nucleophile. It reacts by addition to the C=O bonds of ketones with a bimolecular rate constant around 1* 107 M-1 s-1. These are among the fastest nucleophilic additions that have been reported in literature. Temperature dependence studies demonstrate very low activation energies and large Arrhenius pre-exponential parameters, consistent with very high reactivity. The kinetics of E2 elimination, where the radical anion acts as a base, and SN2 substitution, where the radical anion acts as a nucleophile, are also characterized by large bimolecular rate constants in the range ca. 106 - 107 M-1 s-1. The pKa of the bipyridine radical anion was measured using a kinetic method and analysis of the data using a Marcus theory model for proton transfer. The bipyridine radical anion is found to have a pKa of 40±5 in DMSO. The reorganization energy for the proton transfer reaction was found to be 70±5 kJ/mol. The bipyridine radical anion was found to react very rapidly with carbon dioxide, with a bimolecular rate constant of 1* 108 M-1 s-1 and a small activation energy, whereas the protonated radical reacted with carbon dioxide with a rate constant that was too small to measure. The kinetic and thermodynamic data obtained in this work can be used to understand the mechanisms of the reactions of pyridines with carbon dioxide under reducing conditions.
ContributorsRanjan, Rajeev (Author) / Gould, Ian R (Thesis advisor) / Buttry, Daniel A (Thesis advisor) / Yarger, Jeff (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2015
Description
Surface modification of (semi)conducting materials with polymers provides a strategy for interfacing electrodes with electrocatalysts for reactions of industrial importance. The resulting constructs create opportunities to capture, convert and store solar energy in the form of chemical bonds, generating solar fuels. This thesis describes III-V semiconductors, modified with molecular catalysts embedded in thin-film polymeric coatings. Overarching goals of this work include building protein-like, soft-material environments on solid-state electrode surfaces. This approach enables coordination of earth-abundant metal centers within the three-dimensional molecular coatings to modulate the electronic and catalytic properties of the overall assembly and provide assemblies for studying the effects of polymeric-encapsulation on electrocatalytic as well as photoelectrosynthetic performance. In summary, this work provides 1) new approaches to designing, interfacing, and characterizing (semi)conducting and catalytic materials to effectively power chemical transformations (including hydrogen evolution and carbon dioxide reduction), and 2) kinetic models for better understanding the structure-function relationships governing the performance of these assemblies.
ContributorsNguyen, Nghi Do Phuong (Author) / Moore, Gary F. (Thesis advisor) / Seo, Dong-Kyun (Committee member) / Sayres, Scott G. (Committee member) / Arizona State University (Publisher)
Created2023
Description
The discovery of DNA helical structure opened the door of modern molecular biology. Ned Seeman utilized DNA as building block to construct different nanoscale materials, and introduced a new field, know as DNA nanotechnology. After several decades of development, different DNA structures had been created, with different dimension, different morphology and even with complex curvatures. In addition, after construction of enough amounts DNA structure candidates, DNA structure template, with excellent spatial addressability, had been used to direct the assembly of different nanomaterials, including nanoparticles and proteins, to produce different functional nanomaterials. However there are still many challenges to fabricate functional DNA nanostructures. The first difficulty is that the present finite sized template dimension is still very small, usually smaller than 100nm, which will limit the application for large amount of nanomaterials assembly or large sized nanomaterials assembly. Here we tried to solve this problem through developing a new method, superorigami, to construct finite sized DNA structure with much larger dimension, which can be as large as 500nm. The second problem will be explored the ability of DNA structure to assemble inorganic nanomaterials for novel photonic or electronic properties. Here we tried to utilize DNA Origami method to assemble AuNPs with controlled 3D spacial position for possible chiral photonic complex. We also tried to assemble SWNT with discrete length for possible field effect transistor device. In addition, we tried to mimic in vivo compartment with DNA structure to study internalized enzyme behavior. From our results, constructed DNA cage origami can protect encapsulated enzyme from degradation, and internalized enzyme activity can be boosted for up to 10 folds. In summary, DNA structure can serve as an ideal template for construction of functional nanomaterials with lots of possibilities to be explored.
ContributorsZhao, Zhao (Author) / Yan, Hao (Thesis advisor) / Liu, Yan (Thesis advisor) / Chen, Julian (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2013
Description
Late first row transitional metals have attracted attention for the development of sustainable catalysts due to their low cost and natural abundance. This dissertation discusses the utilization of redox-active ligands to overcome one electron redox processes exhibited by these base metals. Previous advances in carbonyl and carboxylate hydrosilylation using redox active ligand-supported complexes such as (Ph2PPrPDI)Mn and (Ph2PPrDI)Ni have been reviewed in this thesis to set the stage for the experimental work described herein.The synthesis and electronic structure of late first row transition metal complexes featuring the Ph2PPrPDI chelate was pursued. Utilizing these complexes as catalysts for a variety of reactions gave a recurring trend in catalytic activity. DFT calculations suggest that the trend in activity observed for these complexes is associated with the ease of phosphine arm dissociation.
Furthermore, the synthesis and characterization of a phosphine-substituted aryl diimine ligand, Ph2PPrADI-H was explored. Addition of Ph2PPrADI-H to CoCl2 resulted in C-H activation of the ligand backbone and formation of [(Ph2PPrADI)CoCl][Co2Cl6]0.5. Reduction of [(Ph2PPrADI)CoCl][Co2Cl6]0.5 afforded the precatalyst, (Ph2PPrADI)Co, that was found to effectively catalyze carbonyl hydrosilylation. At low catalyst loading, TOFs of up to 330 s-1 could be achieved, the highest ever reported for metal-catalyzed carbonyl hydrosilylation.
This dissertation also reports the first cobalt catalyzed pathway for dehydrocoupling diamines or polyamines with polymethylhydrosiloxanes to form crosslinked copolymers. At low catalyst loading, (Ph2PPrADI)Co was found to catalyze the dehydrocoupling of 1,3-diaminopropane and TMS-terminated PMHS with TOFs of up to 157 s-1, the highest TOF ever reported for a Si-N dehydrocoupling reaction. Dehydrocoupling of diamines with hydride-terminated polydimethylsiloxane yielded linear diamine siloxane copolymers as oils.
Finally, dehydrocoupling between diamines and organosilanes catalyzed by a manganese dimer complex, [(2,6-iPr2PhBDI)Mn(μ-H)]2, has allowed for the preparation of silane diamine copolymers. Exceptional solvent absorption capacity was demonstrated by the solid networks, which were found to absorb up to 7 times their own weight. Furthermore, degradation of these networks revealed that their Si-N backbones are easily hydrolysable when exposed to air. The use of lightly crosslinked copolymers as coatings was also studied using SEM analysis.
ContributorsSharma, Anuja (Author) / Trovitch, Ryan J. (Thesis advisor) / Seo, Dong-Kyun (Committee member) / Moore, Gary F. (Committee member) / Arizona State University (Publisher)
Created2024