Tzvetkov G, Koller G, Zubavichus Y, Fuchs O, Casu M B, Heske C, Umbach E, Grunze M, Ramsey M G, Netzer F P
Institut für Experimentalphysik, Karl-Franzens-Universität Graz, Universitätsplatz 5, A-8010 Graz, Austria.
Langmuir. 2004 Nov 23;20(24):10551-9. doi: 10.1021/la048726m.
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.
通过程序升温脱附、X射线光电子能谱、紫外光电子能谱、功函数测量以及近边X射线吸收精细结构（NEXAFS）光谱，研究了甘氨酸（NH2CH2COOH）层与在NiAl(110)上外延生长的超薄Al2O3薄膜之间的相互作用。在110 K下单层覆盖时，存在两种共存的分子形式：甘氨酸的阴离子形式（NH2CH2COO-）和两性离子形式（NH3+CH2COO-）。根据光发射数据推断，在110 K下多层膜的形成导致主要处于两性离子状态的凝聚相。与110 K时的单层不同，300 K时形成的单层主要由处于阴离子状态的甘氨酸分子组成。后一种物质以羧基的氧原子指向衬底的方式吸附。偏振相关的C K边和O K边NEXAFS光谱表明，300 K时单层中的甘氨酸盐物种几乎垂直于表面取向，氨基指向远离表面的方向。
