Boundary Layer Dynamics in Mixed Hydrocarbon Thin Films on Metal Surfaces
Bishop, Adeana Richelle
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/84442
Description
Title
Boundary Layer Dynamics in Mixed Hydrocarbon Thin Films on Metal Surfaces
Author(s)
Bishop, Adeana Richelle
Issue Date
1999
Doctoral Committee Chair(s)
Nuzzo, Ralph G.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Inorganic
Language
eng
Abstract
Hydrocarbon bilayers on Pt(111) are an ideal model system for studying the dynamics of molecules in organic thin films. These adsorbates form a well-ordered and well-defined molecular assembly. While maintaining a crystalline-like structure, molecules in this assembly are able to diffuse distances comparable to the lengths of the molecules. Utilizing spectroscopic methods, these dynamic processes are evidenced and quantified. Due to the selectivity of reflection absorption infrared spectroscopy, both identification of chemical species and determination of the position and orientation of each component in the assembly can be accomplished. Vibrational spectroscopy of these adsorbates and the origin of specific vibrational features are discussed in detail. Using isotopic labeling of one component in the bilayer allows the dynamics of each component to be differentiated, demonstrating the mobility of the molecules as a function of temperature. Temperature programmed desorption spectroscopy provides quantitation of the exchange process and isotope effects observed in these systems. For equal chain length, preferential segregation of the protio species to the surface is observed, this is believed to be due to the differences in zero point energies for the adsorbates and the more exothermic adsorption process for the protio species. A variation of temperature programmed desorption spectroscopy, molecular beam isothermal scattering, allows development of a kinetic model for exchange. This barrier for exchange is found to be 1.5 kcal/mol less that the activation energies for desorption, independent of chain length. In mixed component bilayers, preferential Pt(111) surface segregation is observed for longer chain, protio, and linear hydrocarbons. The dynamic effects observed in the spectroscopic investigation of these assemblies is incorporated into a modified desorption model for linear alkanes on Pt(111).
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
