Surface faceting and compositional evolution of Pd@ Au core- shell nanocrystals during in situ annealing
Surface faceting and compositional evolution of Pd@ Au core- shell nanocrystals during in situ annealing
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原位退火过程中 Pd@ Au 核壳纳米晶的表面刻面和成分演化
DOI：
10.1039/c8cp07576j
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发表时间：
2019
影响因子：
3.3
通讯作者：
Wang Yong
中科院分区：
文献类型：
--
作者：
Wu Zhemin;Tang Min;Li Xiaoyan;Luo Sai;Yuan Wentao;Zhu Beien;Zhang Hui;Yang Hangsheng;Gao Yi;Wang Yong
双金属核壳纳米粒子因其独特的光学、磁学和催化性能而备受关注。然而，在环境条件下，这些性质将因其结构和/或组成的变化而显著改变。因此，研究核壳纳米粒子在高温下的复杂转变路径具有重要意义。在本工作中，通过配备能量色散X射线成像系统的像差校正扫描电子显微镜，显示了从设计良好的Pd@Au核壳纳米粒子到均匀的合金粒子的完整转变过程。结果表明，这一转变过程经历了表面重构、颗粒再球化和完全合金化三个阶段。结合发展的原子动力学蒙特卡罗模拟，我们发现表面能是形状变化的驱动力，表面扩散和体迁移的不同原子活化势垒导致了多步转变路径。我们的研究结果为理解双金属核壳纳米粒子的结构演化提供了重要信息，有利于合理设计具有动力学稳定性的纳米粒子。
Bimetallic core–shell nanoparticles have received considerable attention for their unique optical, magnetic and catalytic properties. However, these properties will be dramatically modified under ambient conditions by their structure and/or composition change. Thus, it is of primary importance to study the complex transformation pathway of core–shell nanoparticles at an elevated temperature. In this work, by using an aberration-corrected scanning transmission electron microscope equipped with an energy dispersive X-ray mapping system, the complete transformation process from a well-designed Pd@Au core–shell nanoparticle to a uniform alloy particle was visualized. It is revealed that this transformation process went through three steps, i.e., surface refacetting, particle resphering and complete alloying. Combining with a developed atomic kinetic Monte Carlo simulation, we found that surface energy is the driving force for shape variation, and the different atomic activation barriers of surface diffusion and bulk migration result in the multistep transformation pathway. Our results offered important information for understanding the structure evolution of bimetallic core–shell nanoparticles, which is beneficial for the rational design of nanoparticles with kinetic stability.