Kelso Meagan V, Tubbesing John Z, Chen Qingzhi, Switzer Jay A
Department of Materials Science and Engineering and Graduate Center for Materials Research , Missouri University of Science and Technology , Rolla , Missouri 65409-1170 , United States.
Department of Chemistry and Graduate Center for Materials Research , Missouri University of Science and Technology , Rolla , Missouri 65409-1170 , United States.
J Am Chem Soc. 2018 Nov 21;140(46):15812-15819. doi: 10.1021/jacs.8b09108. Epub 2018 Nov 6.
Surfaces of achiral materials exhibit two-dimensional chirality if they lack mirror symmetry. An example is the (643) surface of face-centered-cubic metals such as Au. The (643) and (6̅4̅3̅) surfaces are non-superimposable mirror images of each other. Chiral surfaces offer the possibility of serving as heterogeneous catalysts for chiral synthesis or providing a platform for chiral separation or crystallization. Here, we show the symmetry requirements for surface chirality, and we demonstrate that chiral surfaces can be produced by electrochemically depositing epitaxial films of Au onto commercially available Si(643) wafers. Au(643) is deposited onto one side of the wafer, and its enantiomer Au(6̅4̅3̅) is deposited on the other side of the wafer. In addition to the (643) orientation, the (8 14 17) orientation of Au is produced on the Si(643) wafers. The (8 14 17) orientation has a similar kinked surface to the (643) surface, but it has staggered kinks. Other metal films including Pt, Ni, Cu, and Ag that are electrodeposited onto the Au films exhibit strong in-plane and out-of-plane order. Hence, the method provides a pathway for producing chiral surfaces of a wide range of materials, and it obviates the need to work with expensive single crystals. The Ag/Au/Si(643) surface showed a preference for the electrochemical oxidation of d-glucose, whereas the Ag/Au/Si(6̅4̅3̅) surface showed preference for the oxidation of l-glucose.
如果非手性材料的表面缺乏镜像对称性，那么它们就会表现出二维手性。一个例子是面心立方金属（如金）的(643)表面。(643)表面和(6̅4̅3̅)表面是彼此不可重叠的镜像。手性表面为作为手性合成的多相催化剂或提供手性分离或结晶的平台提供了可能性。在这里，我们展示了表面手性的对称性要求，并且我们证明了可以通过将金的外延膜电化学沉积到市售的Si(643)晶片上来制备手性表面。Au(643)沉积在晶片的一侧，其对映体Au(6̅4̅3̅)沉积在晶片的另一侧。除了(643)取向之外，在Si(643)晶片上还产生了Au的(8 14 17)取向。(8 14 17)取向具有与(643)表面相似的扭折表面，但它具有交错的扭折。电沉积在金膜上的其他金属膜，包括Pt、Ni、Cu和Ag，表现出很强的面内和面外有序性。因此，该方法为制备多种材料的手性表面提供了一条途径，并且无需使用昂贵的单晶。Ag/Au/Si(643)表面对d-葡萄糖的电化学氧化表现出偏好，而Ag/Au/Si(6̅4̅3̅)表面对l-葡萄糖的氧化表现出偏好。
