Bonding and structure of glycine on ordered Al2O3 film surfaces.
The interaction between glycine (NH2CH2COOH) layers and an ultrathin Al2O3 film grown epitaxially onto NiAl(110) was studied by temperature-programmed desorption, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, work function measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. At monolayer coverages at 110 K, there are two coexisting molecular forms: the anionic (NH2CH2COO-) and the zwitterionic form (NH3+CH2COO-) of glycine. As deduced from the photoemission data, the buildup of multilayers at 110 K leads to a condensed phase predominantly in the zwitterionic state. In contrast to the monolayer at 110 K, the monolayer formed at 300 K consists primarily of glycine molecules in the anionic state. The latter species is adsorbed with the oxygen atoms of the carboxylic group pointing toward the substrate. The polarization-dependent C K- and O K-edge NEXAFS spectra indicate that the glycinate species in the monolayer at 300 K is oriented nearly perpendicular to the surface, with the amino group pointing away from the surface.
Tzvetkov
G
G
Institut für Experimentalphysik, Karl-Franzens-Universität Graz, Universitätsplatz 5, A-8010 Graz, Austria. george.tzvetkov@uni-graz.at
Koller
G
G
Zubavichus
Y
Y
Fuchs
O
O
Casu
M B
MB
Heske
C
C
Umbach
E
E
Grunze
M
M
Ramsey
M G
MG
Netzer
F P
FP
D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry*; D008567:Membranes, Artificial; D012680:Sensitivity and Specificity; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013499:Surface Properties; D013696:Temperature
D008567:Membranes, Artificial; D000537:Aluminum Oxide; D005998:Glycine