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Title:In situ studies of the binding and reactivity of small molecules at metal electrode surfaces
Author(s):Richard, Katherine Marie
Doctoral Committee Chair(s):Gewirth, Andrew A.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Analytical
Chemistry, Inorganic
Chemistry, Physical
Abstract:This thesis encompasses several studies of the behavior of aromatic molecules on Au(111) single crystal electrode surfaces. In the first study, the initial stages of the binding and oxidation of phenol at high pH were addressed. Phenoxide binds to the electrode surface through the oxygen atom and is tilted away from the surface normal prior to oxidation, as shown with surface infrared spectroscopy (IR). The phenoxide forms a $\rm(\surd3\times\surd3)R30\sp\circ$ overlayer on Au(111). At the onset of oxidation, the molecule reorients to lie with the ring relatively parallel to the electrode surface as it polymerizes. Oligomers have been observed with scanning tunneling microscopy (STM).
The continued oxidation of phenol and 2-naphthol was monitored with atomic force microscopy (AFM) and surface IR. The morphology of the growing polymer was found to depend on the constituent monomer.
The impact of ring substitution on the binding and reactivity of cyanophenols was studied using STM and surface IR. Cyanophenols substituted in the 2 or 4 position displayed an inhibition of oxidation, while 3-cyanophenol oxidized at a similar rate to phenol. Only 4-cyanophenol was found to form an ordered $\rm(\surd3\times\surd3)R30\sp\circ$ overlayer on Au(111). Steric repulsions between the molecules prevented 2- and 3-cyanophenol from forming ordered adlayers.
Finally, the adsorption of uracil on Au(111) was studied while varying concentration and pH. At neutral pH values, uracil displays strongly concentration-dependent behavior. At higher concentrations, the voltammetry displays sharp peaks which are associated with phase transitions. IR data indicates that uracil binds flat to the electrode at neutral pH. In alkaline solutions, the concentration-dependence of the adsorption is less marked, but IR data indicates that the molecule binds on-edge when it is deprotonated.
Issue Date:1996
Rights Information:Copyright 1996 Richard, Katherine Marie
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9702652
OCLC Identifier:(UMI)AAI9702652

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