Department of Physics, Campus Plaine, CP 231, Universite Libre de Bruxelles, 1050 Brussels, Belgium.
School of Engineering and Physical Sciences, James Cook University, Townsville, QLD 4811, Australia.
J Chem Phys. 2013 Dec 14;139(22):224709. doi: 10.1063/1.4839755.
The adsorption of the chiral molecule lactate on the intrinsically chiral noble metal surfaces Pt(321), Au(321), and Ag(321) is studied by density functional theory calculations. We use the oPBE-vdW functional which includes van der Waals forces on an ab initio level. It is shown that the molecule binds via its carboxyl and the hydroxyl oxygen atoms to the surface. The binding energy is larger on Pt(321) and Ag(321) than on Au(321). An analysis of the contributions to the binding energy of the different molecular functional groups reveals that the deprotonated carboxyl group contributes most to the binding energy, with a much smaller contribution of the hydroxyl group. The Pt(321) surface shows considerable enantioselectivity of 0.06 eV. On Au(321) and Ag(321) it is much smaller if not vanishing. The chiral selectivity of the Pt(321) surface can be explained by two factors. First, it derives from the difference in van der Waals attraction of L- and D-lactate to the surface that we trace to differences in the binding energy of the methyl group. Second, the multi-point binding pattern for lactate on the Pt(321) surface is sterically more sensitive to surface chirality and also leads to large binding energy contributions of the hydroxyl group. We also calculate the charge transfer to the molecule and the work function to gauge changes in electronic structure of the adsorbed molecule. The work function is lowered by 0.8 eV on Pt(321) with much smaller changes on Au(321) and Ag(321).
通过密度泛函理论计算研究了手性分子乳酸在本征手性贵金属表面 Pt(321)、Au(321)和 Ag(321)上的吸附。我们使用 oPBE-vdW 泛函，在从头算水平上包含范德华力。结果表明，分子通过其羧基和羟基氧原子与表面结合。在 Pt(321)和 Ag(321)上的结合能大于在 Au(321)上的结合能。对不同分子官能团对结合能的贡献分析表明，去质子化的羧基基团对结合能的贡献最大，羟基基团的贡献要小得多。Pt(321)表面表现出相当大的 0.06 eV 的对映选择性。在 Au(321)和 Ag(321)表面上，如果不是为零，则要小得多。Pt(321)表面的手性选择性可以用两个因素来解释。首先，它源于 L-和 D-乳酸对表面的范德华吸引力的差异，我们可以追踪到甲基结合能的差异。其次，乳酸在 Pt(321)表面上的多点结合模式对手性更敏感，也导致了羟基的结合能贡献较大。我们还计算了向分子的电荷转移和功函数，以衡量吸附分子电子结构的变化。在 Pt(321)上，功函数降低了 0.8 eV，而在 Au(321)和 Ag(321)上的变化要小得多。
