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Langmuir. 2007 Oct 23;23(22):10995-9. Epub 2007 Sep 19.

ATR-FTIR observations of water structure in colloidal silica: implications for the hydration force mechanism.

Author information

1
Department of Chemistry, Bucknell University, Lewisburg, Pennsylvania 17837, USA.

Abstract

Attenuated total internal reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was used to probe the change in water structure in silica colloids as a function of particle density. The absorption index (k) spectra were calculated from the ATR spectra using the subtractive Kramers-Kronig transform in order to avoid the effects of the density-dependent refractive index on the raw spectra and allow direct comparison of the different chemical environments. Normalized difference spectra were obtained by subtracting the k spectrum of bulk water from those of the silica colloids. At low particle densities, these difference spectra reveal the presence of a strongly hydrogen-bonded hydration layer at the surface of the colloidal particles. At higher particle densities, the hydrogen-bonding network is increasingly disrupted. The results provide direct experimental evidence of hydrogen-bond breaking as the mechanism for the hydration force, which provides the extraordinary stability of colloidal silica.

PMID:
17880116
DOI:
10.1021/la701700p

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