Adsorption differences between low coverage enantiomers of alanine on the chiral Cu{421}R surface
Adsorption differences between low coverage enantiomers of alanine on the chiral Cu{421}R surface
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DOI：
10.1039/c7cp01844d
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发表时间：
2017-06-07
影响因子：
3.3
通讯作者：
Thomsen, Lars
中科院分区：
文献类型：
--
作者：
Gladys, Michael J.;Han, Jeong Woo;Thomsen, Lars
使用异质方法进行手性分离一直是人们所追求的。手性金属表面有可能使使用小氨基酸（蛋白质的构建块）来模拟这些系统成为可能。对吸附在Cu{421}(R)上的丙氨酸对映体的亚单层浓度的比较表明，与饱和覆盖相比，这两种分子之间存在很大的几何差异。HR-XPS和NEXAFS观察到很大的差异，并辅以理论DFT计算。在大约三分之一的单分子层上，比较C1s的XPS信号显示甲基的位移超过300 meV，表明这两个对映体处于不同的化学环境中。NEXAFS光谱证实了XPS的变化，并显示了吸附分子取向的巨大差异。我们的DFT结果表明，l -对映体在{311}微面结构中能量最稳定。与全单层覆盖相比，这些较低的覆盖表现出更高的选择性。
Chiral separation using heterogeneous methods has long been sought after. Chiral metal surfaces have the potential to make it possible to model these systems using small amino acids, the building blocks for proteins. A comparison of submonolayer concentrations of alanine enantiomers adsorbed onto Cu{421}(R) has revealed a large geometrical differences between the two molecules as compared to the saturated coverage. Large differences were observed in HR-XPS and NEXAFS and complemented by theoretical DFT calculations. At approximately one third of a monolayer a comparison of the C1s XPS signal showed a shift in the methyl group of more than 300 meV indicating that the two enantiomers are in different chemical environments. NEXAFS spectroscopy confirmed the XPS variations and showed large differences in the orientation of the adsorbed molecules. Our DFT results show that the L-enantiomer is energetically the most stable in the {311} microfacet configuration. In contrast to the full monolayer coverage, these lower coverages showed enhanced selectivity.