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An Experimental Investigation of the Adsorption of a Phosphonic Acid on the Anatase TiO2(101) Surface

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journal contribution
posted on 10.02.2016, 20:35 by Michael Wagstaffe, Andrew G. Thomas, Mark. J. Jackman, Maria Torres-Molina, Karen L. Syres, Karsten Handrup
A combination of synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy has been used to study the adsorption of phenyl­phosphonic acid (PPA) on anatase TiO2(101) single crystal at coverages of 0.15 monolayer (ML) and 0.85 ML. The photoelectron spectroscopy data suggest that at 0.15 ML coverage PPA adsorbs in a bidentate geometry following deprotonation of both phosphonate hydroxyl groups, leaving the PO group unbound. At 0.85 ML there is a shift to a mixed bidentate/monodentate binding mode. The carbon K-edge NEXAFS spectra were recorded at two azimuths. Our calculations show that for PPA on anatase TiO2(101) the phenyl ring is oriented 65 ± 4° away from the surface plane with an azimuthal twist of 57 ± 11° away from the [101] azimuth.