Average molecular orientations in the adsorbed water layers on silicon oxide in ambient conditions

Anna L. Barnette, David B. Asay, Seong Kim

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

The average molecular orientation in the adsorbed water layers formed on amorphous SiO2 in ambient conditions was determined as a function of relative humidity using polarization attenuated total reflectance infrared spectroscopy (ATR-IR). The silicon oxide surface was prepared by chemically cleaning in aqueous solution, washing with water, and drying with argon. After drying, this produced a SiO2 surface with hydroxyl groups, giving rise to a water contact angle <5°. Primarily two types of vibrational peaks that correspond to liquid water and solid-like water were observed in the adsorbed water layers formed on this surface at room temperature. The average orientation of the water molecules was determined from the dichroic ratio of s- to p-polarization absorbances. At low relative humidities, the highly hydrogen bonded solid-like structure exhibits a dichroic ratio as low as ∼0.4, while the liquid water structure exhibits a dichroic ratio close to ∼1.0. As the relative humidity increases, the dichroic ratio of both water structures approaches a dichroic ratio of 0.7∼0.8, which is consistent with the random orientation of molecules of bulk water and ice.

Original languageEnglish (US)
Pages (from-to)4981-4986
Number of pages6
JournalPhysical Chemistry Chemical Physics
Volume10
Issue number32
DOIs
StatePublished - Aug 19 2008

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Molecular orientation
Silicon oxides
silicon oxides
Water
water
humidity
Atmospheric humidity
drying
Drying
Polarization
Molecules
Argon
washing
Ice
Liquids
polarization
liquids
Washing
Hydroxyl Radical
cleaning

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

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Average molecular orientations in the adsorbed water layers on silicon oxide in ambient conditions. / Barnette, Anna L.; Asay, David B.; Kim, Seong.

In: Physical Chemistry Chemical Physics, Vol. 10, No. 32, 19.08.2008, p. 4981-4986.

Research output: Contribution to journalArticle

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