The  organization of water at the interface with silica and alumina oxides has been analysed using Density Functional Theory-based molecular dynamics simulations (DFT-MD).  The interfacial hydrogen bonding is investigated in detail and related to the chemistry of the oxide surfaces by computing the surface charge acidity (pKa of surface sites). We find that water molecules hydrogen bonded to the surface have different orientations  depending on the strength of the hydrogen bonds. This is used in conjunction with a vibrational analysis of the O-H stretching movements of water at the interfaces in order to explain the vibrational features in the surface vibrational spectra measured by Sum Frequency Generation Spectroscopy (experiments of Shen et al.). In particular, ``ice-like'' and ``liquid-like'' features in these spectra are interpreted as the result of hydrogen bonds of different strengths between surface silanols/aluminols and water and in terms of H-bond donors and acceptors at the interface.

Oxide/water interfaces: How the surface chemistry modifies interfacial water properties

243rd National Meeting (2012)

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