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Infrared Reflection Absorption Spectroscopy Studies of Thin Organic Films Adsorbed at Gold (111) Electrode Surfaces

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dc.contributor.advisor Lipkowski, Jacek Leitch, J. Jay 2014-12-24T18:13:11Z 2014-12-24T18:13:11Z 2014-11 2014-11-25 2014-12-24
dc.description Infrared Studies of the Structure, Orientation and Conformation of Adsorbed Thin Organic Films at a Gold (111) Electrode-Solution Interface en_US
dc.description.abstract This thesis is an infrared reflection absorption spectroscopy (IRRAS) investigation of the structure, conformation and orientation of organic films adsorbed at the surface of gold (111) electrodes. The first study employed subtractively normalized interfacial Fourier transform infrared reflection spectroscopy (SNIFTIRS) to examine the adsorption behaviour of sodium dodecyl sulfate (SDS) as a function of applied voltage. The SNIFTIRS data confirmed that adsorbed SDS molecules adopt a hemicylindrical film structure at potentials ranging from −250 to 450 mV. Conversely, the calculated average angle of the transition dipole contradicted existing models of interdigitated SDS films at potentials greater than 450 mV. With this new IR data, the structure of the adsorbed SDS film could be more accurately described as a disordered, tilted bilayer. The second study examined the effects of cholera toxin B (CTB) protein bound to the outer surface of a model bilayer lipid membrane supported on the surface of a gold electrode. The binding of CTB to the membrane surface resulted in ~15o increase in the average tilt angle of the phospholipid tails with no change in the membrane capacitance. This increase in lipid disorder suggests that CTB may be forming lipid rafts on the membrane surface. The orientation of the CTB α-helices showed significant voltage-dependent changes. These changes may correspond to voltage-gated opening and closing of the central pore, supporting the translocation mechanism for cholera toxin infection. The final work examined the physical properties of self-assembled 2,3-di-O-phytanyl-sn-glycerol-1-tetraethylene glycol-D,L-α-lipoic acid ester lipid (DPTL) monolayers. The goal was to evaluate the candidacy of this molecule in creating tethered phospholipid bilayers for mimicking biological cell membranes. Polarization modulation infrared reflection spectroscopy (PM-IRRAS) spectra of the DPTL monolayer showed that the film is very stable over a wide range of potentials. In addition, the IR spectra showed that the tetraethylene glycol chains were coiled, disordered and poorly hydrated, contradicting the original tBLM design. en_US
dc.description.sponsorship NSERC en_US
dc.language.iso en en_US
dc.subject Infrared Reflection Spectroscopy en_US
dc.subject DPTL en_US
dc.subject Thin Films en_US
dc.subject SDS en_US
dc.subject SNIFTIRS en_US
dc.subject PM-IRRAS en_US
dc.subject Cholera Toxin en_US
dc.subject supported bilayers en_US
dc.subject tethered lipid bilayers en_US
dc.subject electrochemistry en_US
dc.subject chronocoulometry en_US
dc.title Infrared Reflection Absorption Spectroscopy Studies of Thin Organic Films Adsorbed at Gold (111) Electrode Surfaces en_US
dc.type Thesis en_US Chemistry en_US Doctor of Philosophy en_US Department of Chemistry en_US
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