Influence of Composition and Chemical Arrangement on the Kinetic Stability of 147-Atom Au-Ag Bimetallic Nanoclusters
Influence of Composition and Chemical Arrangement on the Kinetic Stability of 147-Atom Au-Ag Bimetallic Nanoclusters
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DOI：
10.1021/acs.jpcc.5b03577
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发表时间：
2015-10-15
影响因子：
3.7
通讯作者：
Catlow, C. Richard A.
中科院分区：
文献类型：
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作者：
Gould, Anna L.;Logsdail, Andrew J.;Catlow, C. Richard A.
在纳米颗粒合成中通常需要较高的煅烧温度，了解加热如何影响双金属纳米团簇的结构和化学排列对于设计有效的制造工艺至关重要。我们研究了147个原子的不同组成和化学顺序的Au-Ag纳米合金的动力学稳定性，使用集合分子动力学模拟来复制这些高温条件。富银混合合金经历了无扩散的“马氏体”结构从立方体向二十面体转变；随后的二十面体的熔化温度（T-m）取决于Au:Ag的化学计量。Core@shell化学排列不以类似的方式表现：T.强烈依赖于壳组分；此外，Au-55@Ag-92由于其二十面体Au核而表现出更高的稳定性。我们还报道了纳米簇相变对化学排列的新依赖，如银原子在Ag-55@Au-92表面的低温非马氏体原子扩散所示。这一发现说明了为什么Ag@Au化学排列尤其难以在实验中维持。总的来说，观察到的动力学现象有助于解释为什么特定的形态和化学排列在实验合成中更丰富，以及后处理如何影响结构和化学排列。
High calcination temperatures are often required in nanoparticle synthesis and an understanding of how heating affects the structure and chemical arrangement of bimetallic nanoclusters is essential to design efficient fabrication processes. We have investigated the kinetic stability of 147-atom Au-Ag nanoalloys with varying composition and chemical ordering using ensemble molecular dynamics simulations to replicate these high temperature conditions. Ag-rich mixed alloys undergo a diffusion-less "martensitic" structural transition from cuboctahedral to icosahedral; the melting temperature (T-m) of the subsequent icosahedra is dependent on the Au:Ag stoichiometry. Core@shell chemical arrangements do not behave in a similar manner: T. strongly depends on the shell component; additionally Au-55@Ag-92 exhibits increased stability as a result of its icosahedral Au core. We also report a novel dependence of nanocluster phase transitions on the chemical arrangement, as shown by low temperature nonmartensitic atomic diffusion of Ag atoms to the surface for Ag-55@Au-92. This finding establishes why Ag@Au chemical arrangements, in particular, are difficult to maintain experimentally. Overall, the kinetic phenomena observed help to explain why particular morphologies and chemical arrangements are more abundant in experimental synthesis and how postprocessing affects structure and chemical arrangement.