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Tailoring the chemistry of gold surfaces with aryl Layers formed from diazonium cations Open Access


Other title
Type of item
Degree grantor
University of Alberta
Author or creator
Shewchuk, Dwayne
Supervisor and department
McDermott, Mark T. (Chemistry)
Examining committee member and department
Bélanger, Daniel (Chemistry), University of Québec at Montréal
Harrison, D. Jed (Chemistry)
Veinot, Jonathan G. C. (Chemistry)
Xu, Zhenghe (Chemical and Materials Engineering)
McCreery, Richard L. (Chemistry)
Department of Chemistry

Date accepted
Graduation date
Doctor of Philosophy
Degree level
The electrochemical reduction of para-substituted aryldiazonium cations is a convenient method of introducing chemical functional groups to a surface. The number of conductive surfaces that have been used for this purpose is rapidly expanding. The body of work presented in this thesis will serve to further investigate this method as it applies to polycrystalline gold surfaces. The stability of diazonium-derived nitroazobenzene (NAB) layers on Au was investigated by subjecting them to a variety of treatments including prolonged exposure to UV radiation, refluxing solvents, ultrasonication, chemical displacement by octadecanethiol (ODT), and the application of negative potentials to -1.5 V vs Ag/AgCl. Infrared reflection-absorption spectroscopy (IRRAS) and electrochemical blocking were used to make the assessments. The films are very resistant to ODT displacement reactions, moderately resistant to ultrasonication and refluxing; but not very resistant to the other treatments. In most cases, quantitative IRRAS measurements indicate that > 50 % of the layer resists the treatments. A direct, side-by-side comparison of the stability of nitrobenzene (NB) layers deposited electrochemically from nitrobenzene diazonium cations to self-assembled monolayers (SAMs) of mercaptonitrobenzene was made. Both types of layers are prone to removal by the various treatments. This is likely due to the presence of weakly bound, physisorbed material in addition to more strongly bound material. Immersion in an ODT solution results in complete displacement of the thiol derived nitrobenzene monolayer but does not completely displace the diazonium-derived layer. Two-component, mixed molecular layers comprised of diazonium-derived NAB and dodecanethiolate (DDT) were prepared using a sequential deposition approach. The aryl component is first deposited electrochemically, followed by immersion in a solution of DDT. We will demonstrate that control over the composition of the layers can be achieved by manipulating the concentration of NAB diazonium cations at the electrochemical grafting step. The mixed layers were characterized by reflection-absorption spectroscopy, atomic force microscopy, electrochemical blocking, and x-ray photoelectron spectroscopy. The electron transfer kinetics of hexaammineruthenium(III) chloride were examined at the mixed layer electrodes. The kinetics are highly dependent on the relative proportions of NAB and DDT present and the thickness of the NAB component. The NAB:DDT mixed films were employed as the molecular layer in molecular electronics junctions. We examined the suitability of Al2O3/Au top contacts for these junctions. Junctions for which the molecular layer was mostly comprised of DDT showed an increased failure rate.
License granted by Dwayne Shewchuk ( on 2010-06-24T21:41:50Z (GMT): Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of the above terms. The author reserves all other publication and other rights in association with the copyright in the thesis, and except as herein provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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