Vaezi Mehran, Nejat Pishkenari Hossein, Ejtehadi Mohammad Reza
Institute for Nanoscience and Nanotechnology (INST), Sharif University of Technology, Tehran 11365-11155, Iran.
Mechanical Engineering Department, Sharif University of Technology, Tehran 11365-11155, Iran.
Langmuir. 2023 Mar 28;39(12):4483-4494. doi: 10.1021/acs.langmuir.3c00180. Epub 2023 Mar 16.
Controlling the maneuverability of nanocars and molecular machines on the surface is essential for the targeted transportation of materials and energy at the nanoscale. Here, we evaluate the motion of fullerene, as the most popular candidate for use as a nanocar wheel, on the graphene nanoribbons with strain gradients based on molecular dynamics (MD), and theoretical approaches. The strain of the examined substrates linearly decreases by 20%, 16%, 12%, 8%, 4%, and 2%. MD calculations were performed with the open source LAMMPS solver. The essential physics of the interactions is captured by Lennard-Jones and Tersoff potentials. The motion of C60 on the graphene nanoribbon is simulated in canonical ensemble, which is implanted by using a Nose-Hoover thermostat. Since the potential energy of C60 is lower on the unstrained end of nanoribbons, this region is energetically more favorable for the molecule. As the strain gradient of the surface increases, the trajectories of the motion and the C60 velocity indicate more directed movements along the gradient of strain on the substrate. Based on the theoretical relations, it was shown that the driving force and diffusion coefficient of the C60 motion respectively find linear and quadratic growth with the increase of strain gradient, which is confirmed by MD simulations. To understand the effect of temperature, at each strain gradient of substrate, the simulations are repeated at the temperatures of 100, 200, 300, and 400 K. The large ratio of longitudinal speed to the transverse speed of fullerene at 100 and 200 K refers to the rectilinear motion of molecule at low temperatures. Using successive strain gradients on the graphene in perpendicular directions, we steered the motion of C60 to the desired target locations. The programmable transportation of nanomaterials on the surface has a significant role in different processes at the nanoscale, such as bottom-up assembly.
控制纳米汽车和分子机器在表面的机动性对于纳米尺度下材料和能量的靶向运输至关重要。在此，我们基于分子动力学（MD）和理论方法，评估了作为纳米汽车车轮最热门候选材料的富勒烯在具有应变梯度的石墨烯纳米带上的运动。所研究的基底应变线性降低20%、16%、12%、8%、4%和2%。MD计算使用开源的LAMMPS求解器进行。相互作用的基本物理过程由 Lennard-Jones 势和 Tersoff 势描述。C60在石墨烯纳米带上的运动在正则系综中进行模拟，采用 Nose-Hoover 恒温器实现。由于C60在纳米带无应变端的势能较低，该区域在能量上对分子更有利。随着表面应变梯度的增加，运动轨迹和C60速度表明其沿着基底应变梯度的运动更具方向性。基于理论关系，结果表明C60运动的驱动力和扩散系数分别随应变梯度的增加呈线性和二次增长，这得到了MD模拟的证实。为了解温度的影响，在基底的每个应变梯度下，分别在温度为100、200、300和400 K时重复模拟。在100和200 K时，富勒烯纵向速度与横向速度的比值较大，这表明分子在低温下做直线运动。通过在石墨烯上沿垂直方向使用连续的应变梯度，我们将C60的运动引导到了期望的目标位置。纳米材料在表面的可编程运输在纳米尺度的不同过程中，如自下而上的组装，具有重要作用。
