AVS 51st International Symposium
    Surface Science Friday Sessions
       Session SS1-FrM

Paper SS1-FrM10
Interaction of Glycine with Ice Nanolayers@footnote *@

Friday, November 19, 2004, 11:20 am, Room 210B

Session: Hydrated Surface Phenomena
Presenter: G. Tzvetkov, University of Graz, Austria
Authors: G. Tzvetkov, University of Graz, Austria
M.G. Ramsey, University of Graz, Austria
F.P. Netzer, University of Graz, Austria
Correspondent: Click to Email
The interaction of amino acids with ice surfaces is of interest in a variety of scientific disciplines, ranging from the chemistry in interstellar space and in stratospheric clouds to processes in the geosphere and biosphere. Thin films of ice grown on crystalline substrates under ultrahigh vacuum conditions have been recognised as excellent model systems to study the surface chemistry of molecules on ice. Here we report a study of the interaction of glycine, the simplest amino acid, with ultrathin films of amorphous and polycrystalline ice, as obtained by TPD, XPS, and work function measurements. Thin ice films (@<=@50 layers) have been condensed at 110 K and at 150 K on a hydrophilic single crystalline aluminium oxide surface to produce nanolayers of low-density amorphous and polycrystalline cubic ice, respectively. Glycine overlayers have been prepared by physical vapour deposition at 110 K onto the ice surfaces and mixed glycine-ice layers by codeposition of water and glycine. Whereas the TPD of glycine at 300-350 K remains unaltered by its previous history on ice, the desorption kinetics of water in the temperature range 155-200 K is significantly influenced by the presence of glycine on the ice surfaces, with TPD peaks shifting to lower and higher temperatures with respect to those from the pristine ice surfaces. It is proposed that, on the one hand, the glycine molecules restrict the crystallisation tendency of amorphous to crystalline ice at around 140-160K, and that, on the other hand, the glycine overlayers stabilise the ice surface. The N 1s XPS spectra of the glycine molecules in the monolayer show evidence of a H-bonding interaction of the glycine amino groups with the surface O-H species. The work functions of pristine amorphous and crystalline ice surfaces and the work function changes during glycine adsorption are reported and discussed. @FootnoteText@ @footnote *@ Supported by the Austrian Science Funds.