n -alkane adsorption to polar silica surfaces

The structures of medium-length n -alkane species ( C 8 - C 11 ) adsorbed to a hydrophilic silica/vapor interface were examined using vibrational sum frequency spectroscopy. Experiments sampling out-of-plane orientation show a clear pattern in vibrational band intensities that implies chains having...

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Bibliographic Details
Published in:The Journal of chemical physics 2010-03, Vol.132 (11), p.114701-114701-6
Main Authors: Brindza, Michael R., Ding, Feng, Fourkas, John T., Walker, Robert A.
Format: Article
Language:English
Subjects:
Adsorption
Alkanes - chemistry
Molecular Conformation
Silicon Dioxide - chemistry
Spectrum Analysis
Stereoisomerism
Surface Properties
Vibration
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Summary:The structures of medium-length n -alkane species ( C 8 - C 11 ) adsorbed to a hydrophilic silica/vapor interface were examined using vibrational sum frequency spectroscopy. Experiments sampling out-of-plane orientation show a clear pattern in vibrational band intensities that implies chains having primarily all- trans conformations lying flat along the interface. Further analysis shows that the methylene groups of the alkane chains have their local symmetry axes directed into and away from the surface. Spectra acquired under different polarization conditions interlock to reinforce this picture of interfacial structure and organization. Variation in signal intensities with chain length suggests that correlation between adsorbed monomers weakens with increasing chain length. This result stands in contrast with alkane behavior at neat liquid/vapor interfaces where longer length alkanes show considerably more surface induced ordering than short chain alkanes.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.3336727