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. 2008 Jun 18;130(24):7686-94.
doi: 10.1021/ja8011116. Epub 2008 May 21.

Structures and charging of alpha-alumina (0001)/water interfaces studied by sum-frequency vibrational spectroscopy

Luning Zhang  1 , Chuanshan Tian, Glenn A Waychunas, Y Ron Shen
Affiliations
Free article

Structures and charging of alpha-alumina (0001)/water interfaces studied by sum-frequency vibrational spectroscopy

Luning Zhang et al. J Am Chem Soc. .
Free article

Abstract

Sum-frequency vibrational spectroscopy in the OH stretch region was employed to study structures of water/alpha-Al2O3 (0001) interfaces at different pH values. Observed spectra indicate that protonation and deprotonation of the alumina surface dominate at low and high pH, respectively, with the interface positively and negatively charged accordingly. The point of zero charge (pzc) appears at pH approximately = 6.3, which is close to the values obtained from streaming potential and second-harmonic generation studies. It is significantly lower than the pzc of alumina powder. The result can be understood from the pK values of protonation and deprotonation at the water/alpha-Al2O3 (0001) interface. The pzc of amorphous alumina was found to be similar to that of powder alumina.

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