Tiberi Matteo, Baletto Francesca
Physics Department, King's College London Strand WC2R 2LS UK.
Cambridge Graphene Centre, University of Cambridge Cambridge UK.
RSC Adv. 2024 Aug 28;14(37):27343-27353. doi: 10.1039/d4ra04100c. eCollection 2024 Aug 22.
We compare the assembly of individual Au nanoparticles in a vacuum and between two Au(111) surfaces classical molecular dynamics on a timescale of 100 ns. In a vacuum, the assembly of three nanoparticles used as seeds, initially showing decahedral, truncated octahedral and icosahedral shapes with a diameter of 1.5-1.7 nm, evolves into a spherical object with about 10-12 layers and a gyration radius ∼2.5-2.8 nm. In a vacuum, 42% show just one 5-fold symmetry axis, 33% adopt a defected icosahedral arrangement, and 25% lose all 5-fold symmetry and display a face-centred-cubic shape with several parallel stacking faults. We model a constrained version of the same assembly that takes place between two Au(111) surfaces. During the dynamics, the two Au(111) surfaces are kept fixed at distances of 55 Å, 55.5 Å, 56 Å, and 56.5 Å. The latter distance accommodates 24 Au layers with no strain, while the others correspond to nominal strains of 1.5%, 2.4%, and 3.3%, respectively. In the constrained assembly, each individual seed tends to reorganize into a layered configuration, but the filament may break. The probability of breaking the assembled nanofilament depends on the individual morphology of the seeds. It is more likely to break at the decahedron/icosahedron interface, whilst it is more likely to layer with respect to the (111) orientation when a truncated octahedron sits between the decahedron and the icosahedron. We further observe that nanofilaments between surfaces at 56 Å have a >90% probability of breaking, which decreases to 8% when the surfaces are 55 Å apart. We attribute the dramatic change in probability of breaking to the peculiar decahedron/icosahedron interface and the higher average atomic strain in the nanofilaments. This experiment can shed light on the understanding and control of the formation of metallic nanowires and nanoparticle-assembled networks, which find applications in next-generation electronic devices, such as resistive random access memories and neuromorphic devices.
我们通过经典分子动力学在100纳秒的时间尺度上比较了单个金纳米颗粒在真空中以及在两个金（111）表面之间的组装情况。在真空中，用作种子的三个纳米颗粒的组装，最初呈现出直径为1.5 - 1.7纳米的十面体、截角八面体和二十面体形状，演变成一个具有约10 - 12层且回转半径约为2.5 - 2.8纳米的球形物体。在真空中，42%的颗粒仅显示一条五重对称轴，33%呈现出有缺陷的二十面体排列，25%失去所有五重对称性并呈现出具有多个平行堆垛层错的面心立方形状。我们对在两个金（111）表面之间发生的相同组装的受限版本进行了建模。在动力学过程中，两个金（111）表面保持固定在55 Å、55.5 Å、56 Å和56.5 Å的距离。后一个距离可容纳24层金且无应变，而其他距离分别对应1.5%、2.4%和3.3%的名义应变。在受限组装中，每个单独的种子倾向于重新组织成层状结构，但细丝可能会断裂。组装好的纳米细丝断裂的概率取决于种子的个体形态。它在十面体/二十面体界面处更有可能断裂，而当截角八面体位于十面体和二十面体之间时，它相对于（111）取向更有可能分层。我们进一步观察到，表面间距为56 Å时纳米细丝断裂的概率大于90%，而当表面间距为55 Å时，该概率降至8%。我们将断裂概率的显著变化归因于特殊的十面体/二十面体界面以及纳米细丝中较高的平均原子应变。该实验有助于理解和控制金属纳米线和纳米颗粒组装网络的形成，这些在下一代电子器件中具有应用，例如电阻式随机存取存储器和神经形态器件。
