Development of PM-IRRAS to Study Small Molecules on Au(111) Electrodes.
LE3 .A278 2011
2011
Roscoe, Sharon Zamlynny, Vlad
Acadia University
Master of Science
Masters
Chemistry
Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) is a technique which can facilitate the study of molecules on surfaces. This work develops PM-IRRAS to study soluble molecules in situ on electrode surfaces. Pyridine was used as the model molecule. Experimental conditions were simulated using an in-house software program “Fresnel1” to identify IR regions where the greatest signal/noise ratio can be achieved. The electrode-prism distance was investigated both experimentally and via simulations and found to strongly affect PM-IRRAS features. Use of smaller apertures ensured that experimental results were congruent with simulations. It was also found that the diffusion of the molecule out of the electrode-prism space can adversely affect PM-IRRAS. This effect is particularly strong at negative potentials and low bulk solution concentrations when all molecules are desorbed from the electrode surface. To offset this effect, concentrations less than 510 and potential ranges above desorption potential (ca. -0.5 V vs. standard calomel electrode (SCE)) must be used to ensure that the molecules remain within the electrode-prism space for the duration of the experiment. Comparison of PM-IRRAS and subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) results show that PM-IRRAS can be used as a surface analytical technique to determine the orientation of water-soluble molecules on metal electrodes.
The author retains copyright in this thesis. Any substantial copying or any other actions that exceed fair dealing or other exceptions in the Copyright Act require the permission of the author.
https://scholar.acadiau.ca/islandora/object/theses:186