School of Physics and CRANN, Trinity College, Dublin 2, Ireland.
J Chem Phys. 2018 Sep 7;149(9):094702. doi: 10.1063/1.5042524.
Solvents are an essential element in the production and processing of two-dimensional (2D) materials. For example, the liquid-phase exfoliation of layered materials requires a solvent to prevent the resulting monolayers from re-aggregating, while solutions of functional atoms and molecules are routinely used to modify the properties of the layers. It is generally assumed that these solvents do not interact strongly with the layer and so their effects can be neglected. Yet experimental evidence has suggested that explicit atomic-scale interactions between the solvent and layered material may play a crucial role in exfoliation and cause unintended electronic changes in the layer. Little is known about the precise nature of the interaction between the solvent molecules and the 2D layer. Here, we use density functional theory calculations to determine the adsorption configuration and binding energy of a variety of common solvent molecules, both polar and non-polar, on two of the most popular 2D materials, namely, graphene and MoS. We show that these molecules are physisorbed on the surface with negligible charge transferred between them. We find that the adsorption strength of the different molecules is independent of the polar nature of the solvent. However, we show that the molecules induce a significant charge rearrangement at the interface after adsorption as a result of polar bonds in the molecule.
溶剂是二维（2D）材料生产和加工的重要组成部分。例如，层状材料的液相剥离需要溶剂来防止所得单层重新聚集，而功能原子和分子的溶液则通常用于修饰层的性质。通常假定这些溶剂与层之间不会发生强烈相互作用，因此可以忽略它们的影响。然而，实验证据表明，溶剂与层状材料之间的明确原子尺度相互作用可能在剥离过程中起关键作用，并导致层中的意外电子变化。对于溶剂分子与 2D 层之间的相互作用的确切性质，人们知之甚少。在这里，我们使用密度泛函理论计算来确定各种常见溶剂分子（极性和非极性）在两种最受欢迎的 2D 材料，即石墨烯和 MoS 上的吸附构型和结合能。我们表明，这些分子在表面上是物理吸附的，它们之间几乎没有电荷转移。我们发现，不同分子的吸附强度与溶剂的极性无关。然而，我们表明，由于分子中的极性键，吸附后分子会在界面处引起显著的电荷重排。
