Citation
Lattimer, Judith Rebecca Cabelli (2014) Functionalization of Si(111) Surfaces and the Formation of Mixed Monolayers for the Covalent Attachment of Molecular Catalysts in Photoelectrochemical Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/5EJQ-5134. https://resolver.caltech.edu/CaltechTHESIS:05022014-101347718
Abstract
The functionalization of silicon surfaces with molecular catalysts for proton reduction is an important part of the development of a solar-powered, water-splitting device for solar fuel formation. The covalent attachment of these catalysts to silicon without damaging the underlying electronic properties of silicon that make it a good photocathode has proven difficult. We report the formation of mixed monolayer-functionalized surfaces that incor- porate both methyl and vinylferrocenyl or vinylbipyridyl (vbpy) moieties. The silicon was functionalized using reaction conditions analogous to those of hydrosilylation, but instead of a H-terminated Si surface, a chlorine-terminated Si precursor surface was used to produce the linked vinyl-modified functional group. The functionalized surfaces were characterized by time-resolved photoconductivity decay, X-ray photoelectron spectroscopy (XPS), electro- chemical, and photoelectrochemical measurements. The functionalized Si surfaces were well passivated, exhibited high surface coverage and few remaining reactive Si atop sites, had a very low surface recombination velocity, and displayed little initial surface oxidation. The surfaces were stable toward atmospheric and electrochemical oxidation. The surface coverage of ferrocene or bipyridine was controllably varied from 0 up to 30% of a monolayer without loss of the underlying electronic properties of the silicon. Interfacial charge transfer to the attached ferrocene group was relatively rapid, and a photovoltage of 0.4 V was generated upon illumination of functionalized n-type silicon surfaces in CH3CN. The immobilized bipyridine ligands bound transition metal ions, and thus enabled the assembly of metal complexes on the silicon surface. XPS studies demonstrated that [Cp∗Rh(vbpy)Cl]Cl, [Cp∗Ir(vbpy)Cl]Cl, and Ru(acac)2vbpy were assembled on the surface. For the surface prepared with iridium, x-ray absorption spectroscopy at the Ir LIII edge showed an edge energy and post-edge features virtually identical to a powder sample of [Cp∗Ir(bipy)Cl]Cl (bipy is 2,2 ́-bipyridyl). Electrochemical studies on these surfaces confirmed that the assembled complexes were electrochemically active.
Item Type: | Thesis (Dissertation (Ph.D.)) | ||||
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Subject Keywords: | silicon, surfaces, functionalization, hydrosilylation, ferrocene, passivation | ||||
Degree Grantor: | California Institute of Technology | ||||
Division: | Chemistry and Chemical Engineering | ||||
Major Option: | Chemistry | ||||
Thesis Availability: | Public (worldwide access) | ||||
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Thesis Committee: |
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Defense Date: | 21 April 2014 | ||||
Non-Caltech Author Email: | jlattimer (AT) gmail.com | ||||
Funders: |
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Record Number: | CaltechTHESIS:05022014-101347718 | ||||
Persistent URL: | https://resolver.caltech.edu/CaltechTHESIS:05022014-101347718 | ||||
DOI: | 10.7907/5EJQ-5134 | ||||
Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||
ID Code: | 8209 | ||||
Collection: | CaltechTHESIS | ||||
Deposited By: | Judith Lattimer | ||||
Deposited On: | 03 Jun 2014 19:30 | ||||
Last Modified: | 24 Oct 2020 00:12 |
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