Characterization of Octadecylsilane and Stearic acid Layers on AI2O3 Surfaces by Raman Spectroscopy

Wade R. Thompson, Jeanne E. Pemberton

Research output: Contribution to journalArticle

88 Scopus citations

Abstract

Results are presented which demonstrate the use of Raman spectroscopy for the characterization of octadecylsilane, octadecyldimethylsilane,and stearic acid layers on AI2O3 surfaces without the use of surface enhancement. Unlike previous attempts to study adsorbates at AI2O3 surfaces,an enhancing Ag adlayer was not used. These results represent the first report of the use of Raman spectroscopy for the characterization of alkylsilane and stearic acid layers on AI2O3 surfaces. The spectral data are interpreted in terms of alkyl chain conformation within these layers. Raman data from the v(C-C) and v(C-H) spectral regions suggest that the alkyl chains comprising the octadecylsilane layer are moee disordered than similar films formed on silica. The octadecyldimethylsilane monolayers are less ordered, suggestingAn even greater concentration of gauche conformations in the alkyl chains of these films. The observed increase in disorder in films formed from octadecyldimethylsilane is attributed to the influence of the bulky methyl groups on bonding density which prevent the alkyl chains from packing At their van der Waals radii. The Raman spectral data from self-assembled films formed from stearic acid suggest that these films are moee ordered than the similar films from alkyl chlorosilanes. The increase in order is believed to be due to the bonding orientation of the carbonyl group At the AI2O3 surface.

Original languageEnglish (US)
Pages (from-to)1720-1725
Number of pages6
JournalLangmuir
Volume11
Issue number5
DOIs
StatePublished - Jan 1 1995

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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