Sum frequency vibrational spectroscopy was used to study the structure of water/α-Al 2 O 3 (11̅02) interfaces at different pH values. The OH stretch spectra are dominated by interfacial water contributions at lower frequencies and by bonded hydroxyls on the Al 2 O 3 surface at higher frequencies. Protonation and deprotonation of various oxide functional groups at the α-Al 2 O 3 surface as pH varies can be monitored quantitatively by changes of the spectrum, allowing extraction of their p K reaction values. The point of zero charge of the interface is found to be at pH ∼6.7.
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Sung et al. (2011) studied this question.
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