The local adsorption geometry and electronic structure of alanine on Cu{1 1 0} |
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Authors: | G. Jones F. Thibault-Starzyk E.A. Seddon S.J. Jenkins |
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Affiliation: | a University of Cambridge, Department of Chemistry, Lensfield Road, Cambridge CB2 1EW, UK b CCLRC Daresbury Laboratory, Warrington, UK c Surface Science Research Centre and Department of Chemistry, University of Liverpool, UK d Laboratoire Catalyse & Spectrochimie, CNRS ENSICAEN, Université de Caen, France |
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Abstract: | The adsorption of alanine on Cu{1 1 0} was studied by a combination of near edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). Large chemical shifts in the C 1s, N 1s, and O 1s XP spectra were found between the alanine multilayer and the chemisorbed and pseudo-(3 × 2) alaninate layers. From C, N, and O K-shell NEXAFS spectra the tilt angles of the carboxylate group (≈26° in plane with respect to and ≈45° out of plane) and the C-N bond angle with respect to could be determined for the pseudo-(3 × 2) overlayer. Using this information three adsorption geometries could be eliminated from five p(3 × 2) structures which lead to almost identical heats of adsorption in the DFT calculations between 1.40 and 1.47 eV/molecule. Due to the small energy difference between the remaining two structures it is not unlikely that these coexist on the surface at room temperature. |
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Keywords: | Alanine Biological molecules (amino acids) Copper Near edge X-ray adsorption fine structure (NEXAFS) X-ray photoelectron spectroscopy (XPS) Density functional calculations (DFT) Chemisorption Surface structure |
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