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- Creators: Moore, Gary F.
Description
The molecular modification of semiconductors has applications in energy
conversion and storage, including artificial photosynthesis. In nature, the active sites of
enzymes are typically earth-abundant metal centers and the protein provides a unique
three-dimensional environment for effecting catalytic transformations. Inspired by this
biological architecture, a synthetic methodology using surface-grafted polymers with
discrete chemical recognition sites for assembling human-engineered catalysts in three-dimensional
environments is presented. The use of polymeric coatings to interface cobalt-containing
catalysts with semiconductors for solar fuel production is introduced in
Chapter 1. The following three chapters demonstrate the versatility of this modular
approach to interface cobalt-containing catalysts with semiconductors for solar fuel
production. The catalyst-containing coatings are characterized through a suite of
spectroscopic techniques, including ellipsometry, grazing angle attenuated total reflection
Fourier transform infrared spectroscopy (GATR-FTIR) and x-ray photoelectron (XP)
spectroscopy. It is demonstrated that the polymeric interface can be varied to control the
surface chemistry and photoelectrochemical response of gallium phosphide (GaP) (100)
electrodes by using thin-film coatings comprising surface-immobilized pyridyl or
imidazole ligands to coordinate cobaloximes, known catalysts for hydrogen evolution.
The polymer grafting chemistry and subsequent cobaloxime attachment is applicable to
both the (111)A and (111)B crystal face of the gallium phosphide (GaP) semiconductor,
providing insights into the surface connectivity of the hard/soft matter interface and
demonstrating the applicability of the UV-induced immobilization of vinyl monomers to
a range of GaP crystal indices. Finally, thin-film polypyridine surface coatings provide a
molecular interface to assemble cobalt porphyrin catalysts for hydrogen evolution onto
GaP. In all constructs, photoelectrochemical measurements confirm the hybrid
photocathode uses solar energy to power reductive fuel-forming transformations in
aqueous solutions without the use of organic acids, sacrificial chemical reductants, or
electrochemical forward biasing.
conversion and storage, including artificial photosynthesis. In nature, the active sites of
enzymes are typically earth-abundant metal centers and the protein provides a unique
three-dimensional environment for effecting catalytic transformations. Inspired by this
biological architecture, a synthetic methodology using surface-grafted polymers with
discrete chemical recognition sites for assembling human-engineered catalysts in three-dimensional
environments is presented. The use of polymeric coatings to interface cobalt-containing
catalysts with semiconductors for solar fuel production is introduced in
Chapter 1. The following three chapters demonstrate the versatility of this modular
approach to interface cobalt-containing catalysts with semiconductors for solar fuel
production. The catalyst-containing coatings are characterized through a suite of
spectroscopic techniques, including ellipsometry, grazing angle attenuated total reflection
Fourier transform infrared spectroscopy (GATR-FTIR) and x-ray photoelectron (XP)
spectroscopy. It is demonstrated that the polymeric interface can be varied to control the
surface chemistry and photoelectrochemical response of gallium phosphide (GaP) (100)
electrodes by using thin-film coatings comprising surface-immobilized pyridyl or
imidazole ligands to coordinate cobaloximes, known catalysts for hydrogen evolution.
The polymer grafting chemistry and subsequent cobaloxime attachment is applicable to
both the (111)A and (111)B crystal face of the gallium phosphide (GaP) semiconductor,
providing insights into the surface connectivity of the hard/soft matter interface and
demonstrating the applicability of the UV-induced immobilization of vinyl monomers to
a range of GaP crystal indices. Finally, thin-film polypyridine surface coatings provide a
molecular interface to assemble cobalt porphyrin catalysts for hydrogen evolution onto
GaP. In all constructs, photoelectrochemical measurements confirm the hybrid
photocathode uses solar energy to power reductive fuel-forming transformations in
aqueous solutions without the use of organic acids, sacrificial chemical reductants, or
electrochemical forward biasing.
ContributorsBeiler, Anna Mary (Author) / Moore, Gary F. (Thesis advisor) / Moore, Thomas A. (Thesis advisor) / Redding, Kevin E. (Committee member) / Allen, James P. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Genetically encoded non-canonical amino acids (NCAAs) have allowed researchers to access functionalities that would be otherwise unavailable with the naturally-occurring amino acids. The metal-chelating NCAA (2,2'-bipyridin-5yl)alanine (Bpy-ala) has recently been employed, in tandem with computational modeling, to drive the assembly of a homotrimeric protein complex in the presence of a metal ion, specifically Fe(II). While a successful design was identified to form a homotrimeric complex with an iron-trisbipyridyl [Fe(Bpy-ala)3]2+ core when expressed in E. coli, its subsequent utility was marred by an excessively strong protein-protein interaction thus leading to a lack of metal-dependency. This thesis describes principles of protein design and characterization used to reduce the favorability of the apo protein complex in solution, resulting in the experimental verification of a mutant that undergoes facile, reversible complex assembly and disassembly in the presence or absence of Fe(II), respectively. The addition of other metal ions, such as Co(II) or Ni(II), yields products that show some level of assembly, although not with the same efficiency as Fe(II) addition, necessitating a better description of the energetics and kinetics of the system. Current studies are ongoing to examine the redox properties of the complex, as well as the kinetics of the metal-mediated self-assembly. Attempts to nucleate the trimer with Ru(II), forming a [Ru(Bpy)3]2+ complex with its interesting photophysical, photochemical, and photoredox properties, have not been met with substantial success, as coordination of the low-spin d6 metal ion often requires harsh conditions. However, due to the unique stability of the TRI_05 complexes, many approaches are available to this end, and experiments are underway to elucidate the proper conditions.
ContributorsAlmhjell, Patrick James (Author) / Mills, Jeremy H. (Thesis director) / Moore, Gary F. (Committee member) / Department of Psychology (Contributor) / School of Molecular Sciences (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05