ABSTRACT The migration behaviour of an ionic liquid (IL) nano-droplet on a graphene surface under temperature gradients was studied using non-equilibrium molecular dynamics (MD) simulations. 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) was used in the study. The migration of the IL nano-droplet from the hot end to the cold end of the graphene surface was observed under all temperature gradients considered in the current work. The migration was found to be faster under higher temperature gradients. Detailed analysis reveals that, instead of rolling like a ball, the IL nano-droplet migrates via a layer-based motion, in which the molecules have limited displacement in the direction perpendicular to the graphene surface. The migration of the IL nano-droplet was also found to be coupled with spreading on the graphene surface. The spatial organisation of the cations and anions within the IL nano-droplet was also analysed. It was found that the ions forming the IL nano-droplet organised themselves in layers parallel to the graphene surface, and the angles of cation rings on different layers also tend to be specific. The cation closest to the graphene surface tends to align with their rings parallel to the surface, while those away from the surface are more disordered.

中文翻译：

---

石墨烯表面离子液体纳米液滴的基于层的热迁移：分子动力学研究

摘要使用非平衡分子动力学 (MD) 模拟研究了离子液体 (IL) 纳米液滴在温度梯度下在石墨烯表面上的迁移行为。研究中使用了 1-乙基-3-甲基咪唑鎓四氟硼酸盐 ([EMIM][BF4])。在当前工作中考虑的所有温度梯度下观察到 IL 纳米液滴从石墨烯表面的热端迁移到冷端。发现在较高的温度梯度下迁移更快。详细分析表明，IL 纳米液滴不是像球一样滚动，而是通过基于层的运动迁移，其中分子在垂直于石墨烯表面的方向上的位移有限。还发现 IL 纳米液滴的迁移与石墨烯表面上的扩散有关。还分析了 IL 纳米液滴内阳离子和阴离子的空间组织。发现形成IL纳米液滴的离子在平行于石墨烯表面的层中自行组织，并且不同层上的阳离子环的角度也趋于特定。最靠近石墨烯表面的阳离子倾向于与它们平行于表面的环对齐，而远离表面的阳离子则更加无序。