Brown Paul A, Kołacz Jakub, Fischer Sean A, Spillmann Christopher M, Gunlycke Daniel
Chemistry Division, United States Naval Research Laboratory, Washington, DC 20375, USA.
Center for Bio/Molecular Science and Engineering, United States Naval Research Laboratory, Washington, DC 20375, USA.
Molecules. 2022 Mar 3;27(5):1664. doi: 10.3390/molecules27051664.
Interfacial interactions between liquid crystal (LC) and two-dimensional (2D) materials provide a platform to facilitate novel optical and electronic material properties. These interactions are uniquely sensitive to the local energy landscape of the atomically thick 2D surface, which can be strongly influenced by defects that are introduced, either by design or as a byproduct of fabrication processes. Herein, we present density functional theory (DFT) calculations of the LC mesogen 4-cyan-4'-pentylbiphenyl (5CB) on graphene in the presence of a monovacancy (MV-G). We find that the monovacancy strengthens the binding of 5CB in the planar alignment and that the structure is lower in energy than the corresponding homeotropic structure. However, if the molecule is able to approach the monovacancy homeotropically, 5CB undergoes a chemical reaction, releasing 4.5 eV in the process. This reaction follows a step-by-step process gradually adding bonds, inserting the 5CB cyano group into MV-G. We conclude that this irreversible insertion reaction is likely spontaneous, potentially providing a new avenue for controlling both LC behavior and graphene properties.
液晶（LC）与二维（2D）材料之间的界面相互作用提供了一个平台，有助于展现新颖的光学和电子材料特性。这些相互作用对原子级厚度的二维表面的局部能量格局具有独特的敏感性，而这种格局会受到有意引入或作为制造过程副产物的缺陷的强烈影响。在此，我们展示了在存在单空位（MV-G）的情况下，液晶基元4-氰基-4'-戊基联苯（5CB）在石墨烯上的密度泛函理论（DFT）计算。我们发现单空位增强了5CB在平面排列中的结合力，且该结构的能量低于相应的垂直排列结构。然而，如果分子能够垂直接近单空位，5CB会发生化学反应，在此过程中释放4.5电子伏特的能量。该反应遵循逐步过程，逐渐添加化学键，将5CB的氰基插入MV-G中。我们得出结论，这种不可逆的插入反应可能是自发的，这有可能为控制液晶行为和石墨烯特性提供一条新途径。
