Helium Droplet-Mediated Deposition and Aggregation of Nanoscale Silver Clusters on Carbon Surfaces
Helium Droplet-Mediated Deposition and Aggregation of Nanoscale Silver Clusters on Carbon Surfaces
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DOI：
10.1021/acs.jpcc.7b08109
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发表时间：
2017-10-12
影响因子：
3.7
通讯作者：
Pilar de Lara-Castells, Maria
中科院分区：
文献类型：
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作者：
Fernandez-Perea, Ricardo;Gomez, Luis F.;Pilar de Lara-Castells, Maria
我们提出了室温下嵌入氦滴中的银簇沉积和聚集到无定形碳表面的实验和计算。还对石墨烯表面上的沉积进行了计算。它们涉及碳原子与银和氦原子相互作用的势，由从头计算提供。数值模拟针对几纳米大小的银团簇（包括多达 5000 个 Ag 原子）和含有多达 10(5) He-4 原子的 He 液滴进行。 He-4 液滴的流体性质是通过 He-He 相互作用势的重整化来解释的。数值结果与每个 4He 液滴平均有 3000 个银原子的沉积实验一致，表明银簇在碳表面的聚集是由二次液滴撞击介导的。他们还揭示了载体液滴内银簇的非平凡动力学，显示出向液滴表面漂移的趋势。这些发现对于理解为每个液滴平均银原子数在百万范围内的非常大的液滴开发的异质沉积模式（大的分枝岛）具有相关性。最后，石墨烯上大型（5000 个原子）银簇沉积的模拟揭示了强烈的超扩散行为。与此形成鲜明对比的是，无定形碳表面上的扩散可以忽略不计。
We present experiments and calculations of the deposition and aggregation of silver clusters embedded in helium droplets onto an amorphous carbon surface at room temperature. Calculations were also performed for deposition onto a graphene surface. They involve potentials for the interaction of carbon atoms with silver and helium atoms, provided by ab initio calculations. The numerical simulations were performed for few-nanometer-sized silver clusters including up to 5000 Ag atoms and He droplets with up to 10(5) He-4 atoms. The fluid nature of the He-4 droplet is accounted for by the renormalizationof the He-He interaction potential. The numerical results are consistent with deposition experiments with an average number of 3000 Ag atoms per 4He droplet and indicate that the aggregation of the silver clusters on the carbon surface is mediated by secondary droplet impacts. They also reveal nontrivial dynamics of the Ag clusters within the carrier droplet, showing a tendency to drift toward the droplet surface. These findings are of relevance in understanding the heterogeneous deposition patterns (large ramified islands) developed for very large droplets with an average number of Ag atoms per droplet within the million range. Finally, the simulations of large (5000 atoms) Ag cluster deposition on graphene reveals strong superdiffusive behavior. In stark contrast, the diffusion is negligible on the amorphous carbon surface.