Surface chemistry of alanine on Cu{111}: Adsorption geometry and temperature dependence
Surface chemistry of alanine on Cu{111}: Adsorption geometry and temperature dependence
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DOI：
10.1016/j.susc.2014.04.016
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发表时间：
2014-11-01
期刊：
影响因子：
1.9
通讯作者：
Held, Georg
中科院分区：
文献类型：
--
作者：
Baldanza, Silvia;Cornish, Alix;Held, Georg
研究了 L-丙氨酸在 Cu{111} 单晶表面上的吸附，作为小手性改性剂分子与密堆积金属表面之间相互作用的模型系统。基于同步加速器的 X 射线光电子能谱 (XPS) 和近边 X 射线吸收精细结构 (NEXAFS) 光谱用于确定表面分子的化学态、键配位和面外取向。丙氨酸在室温下以其阴离子形式吸附，而在低温下，覆盖层由阴离子和两性离子分子组成。 NEXAFS 光谱表现出与羧酸酯基团相关的 pi* 共振的强烈角度依赖性，这使得可以在室温下确定该基团相对于表面平面的倾斜角（48 度+/- 2 度）。低能电子衍射 (LEED) 显示 ap (2 root 13 x 2 root 13)R13 度超结构仅具有一个域，这打破了基底的镜面对称性，从而在表面诱导了全局手性。程序升温 XPS (TP-XPS) 和程序升温解吸 (TPD) 实验表明，两性离子形式在 293 K 时转化为阴离子物质（丙氨酸盐）。后者在 435 K 至 445 K 之间解吸/分解。(C) 2014 Elsevier B.V. 保留所有权利。
Adsorption of L-alanine on the Cu{111} single crystal surface was investigated as a model system for interactions between small chiral modifier molecules and close-packed metal surfaces. Synchrotron-based X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy are used to determine the chemical state, bond coordination and out-of-plane orientation of the molecule on the surface. Alanine adsorbs in its anionic form at room temperature, whilst at low temperature the overlayer consists of anionic and zwitterionic molecules. NEXAFS spectra exhibit a strong angular dependence of the pi* resonance associated with the carboxylate group, which allows determining the tilt angle of this group with respect to the surface plane (48 degrees +/- 2 degrees) at room temperature. Low-energy electron diffraction (LEED) shows ap (2 root 13 x 2 root 13)R13 degrees superstructure with only one domain, which breaks the mirror symmetry of the substrate and, thus, induces global chirality to the surface. Temperature-programmed XPS (TP-XPS) and temperature-programmed desorption (TPD) experiments indicate that the zwitterionic form converts into the anionic species (alaninate) at 293 K. The latter desorbs/decomposes between 435 K and 445 K. (C) 2014 Elsevier B.V. All rights reserved.