Vaezi Mehran, Nejat Pishkenari Hossein, Ejtehadi Mohammad Reza
Institute for Nanoscience and Nanotechnology (INST), Sharif University of Technology, Tehran, Iran.
Mechanical Engineering Department, Sharif University of Technology, Tehran, Iran.
Phys Chem Chem Phys. 2022 May 18;24(19):11770-11781. doi: 10.1039/d2cp00667g.
Understanding the motion characteristics of fullerene clusters on the graphene surface is critical for designing surface manipulation systems. Toward this purpose, using the molecular dynamics method, we evaluated six clusters of fullerenes including 1, 2, 3, 5, 10, and 25 molecules on the graphene surface, in the temperature range of 25 to 500 K. First, the surface motion of clusters is studied at 200 K and lower temperatures, in which fullerenes remain as a single group. The trajectories of the motion as well as the diffusion coefficients indicate the reduction of surface mobility as a response to the increase of the fullerene number. The clusters show normal diffusion at the temperature of 25 K, while they follow the super-diffusion regime at higher temperatures. The separation of fullerenes occurs at 300 K and higher temperatures. Due to the increase of vdW attraction with the increase of the fullerene number, the separation of fullerenes in larger clusters occurs at higher temperatures. The thermal energy at 500 K is sufficient to divide the large C60 clusters into smaller clusters. This energy level is related to the saturation of the interaction energy experienced by individual fullerenes, which can be estimated from the potential energy analysis. The results of simulations reveal that the separation occurs at the edge of clusters. Moreover, we studied the thermal stability of multilayer fullerene clusters on graphene. The simulation results indicate the tendency of multilayer clusters to locate on the surface, which implies the wetting property of C60s on the graphene layer.
了解富勒烯团簇在石墨烯表面的运动特性对于设计表面操纵系统至关重要。为此,我们使用分子动力学方法,在25至500 K的温度范围内,评估了石墨烯表面上包含1、2、3、5、10和25个分子的六个富勒烯团簇。首先,研究了200 K及更低温度下团簇的表面运动,此时富勒烯保持为单个基团。运动轨迹和扩散系数表明,随着富勒烯数量的增加,表面迁移率降低。团簇在25 K时表现出正常扩散,而在较高温度下遵循超扩散机制。富勒烯在300 K及更高温度下会发生分离。由于范德华吸引力随富勒烯数量的增加而增加,较大团簇中的富勒烯在更高温度下发生分离。500 K时的热能足以将大的C60团簇分成较小的团簇。这个能量水平与单个富勒烯所经历的相互作用能的饱和有关,这可以通过势能分析来估计。模拟结果表明,分离发生在团簇的边缘。此外,我们研究了石墨烯上多层富勒烯团簇的热稳定性。模拟结果表明多层团簇倾向于定位在表面,这意味着C60在石墨烯层上具有润湿性。