Interactions Between Organized, Surface-Confined Monolayers and Vapor- Phase Probe Molecules. 7. Comparison of Self-Assemblying Organomercaptan Monolayers Deposited on Gold from Liquid and Vapor Phases
Rept. for 1 Aug 1992-31 Jul 1993
NEW MEXICO UNIV ALBUQUERQUE DEPT OF CHEMISTRY
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We report a comparative study of the structure and chemistry of methyl-terminated n-alkanethiol self-assembling monolayers SAMs formed from liquid and vapor phases. Three different SAMs are considered AuHSCH2nCH3, n5, 11, and 15. Liquid-phase-deposited films were prepared by exposure of Au substrates to dilute ethanol solutions of the n-alkanethiols followed by ethanol rinsing, and vapor-phase-deposited SAMs were prepared by exposure of the Au surface to 10-of-saturation n-alkanethiol vapors followed by N2 purging, which removes loosely bound n-alkanethiol molecules from the surface. The matrix of 6 organic surfaces were studied by FTIR external reflectance spectroscopy FTIR- ERS, ellipsometry, and cyclic voltammetry, which provide information about the average structure of the SAMs, and a newly developed scanned tunneling microscope STM-based method, which provides information about individual SAM defect structures. FTIR-ERS and ellipsometry indicate no detectable differences between liquid- and vapor-phase-deposited SAMs. Data obtained using cyclic voltammetry and STM show that the barrier properties of SAMs depend on the ambient phase from which the SAM assemblies, the length of the n-alkanethiol, and the chemical nature of the molecular probe used to evaluate the monolayer structure.
- Organic Chemistry
- Physical Chemistry
- Atomic and Molecular Physics and Spectroscopy