Schnedlitz Martin, Fernandez-Perea Ricardo, Knez Daniel, Lasserus Maximilian, Schiffmann Alexander, Hofer Ferdinand, Hauser Andreas W, de Lara-Castells Maria Pilar, Ernst Wolfgang E
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz, Austria.
Instituto de Estructura de la Materia (C.S.I.C.), Serrano 123, E-28006 Madrid, Spain.
J Phys Chem C Nanomater Interfaces. 2019 Aug 15;123(32):20037-20043. doi: 10.1021/acs.jpcc.9b05765. Epub 2019 Aug 5.
Structural changes of Ni-Au core-shell nanoparticles with increasing temperature are studied at atomic resolution. The bimetallic clusters, synthesized in superfluid helium droplets, show a centralized Ni core, which is an intrinsic feature of the growth process inside helium. After deposition on SiN , the nanoparticles undergo a programmed temperature treatment in vacuum combined with an in situ transmission electron microscopy study of structural changes. We observe not only full alloying far below the actual melting temperature, but also a significantly higher stability of core-shell structures with decentralized Ni cores. Explanations are provided by large-scale molecular dynamics simulations on model structures consisting of up to 3000 metal atoms. Two entirely different diffusion processes can be identified for both types of core-shell structures, strikingly illustrating how localized, atomic features can still dictate the overall behavior of a nanometer-sized particle.
在原子分辨率下研究了随着温度升高镍 - 金核壳纳米颗粒的结构变化。在超流氦滴中合成的双金属团簇显示出一个集中的镍核，这是氦气内部生长过程的一个固有特征。沉积在氮化硅上后，纳米颗粒在真空中进行程序升温处理，并结合原位透射电子显微镜对结构变化进行研究。我们不仅观察到在远低于实际熔点的温度下完全合金化，还观察到具有分散镍核的核壳结构具有显著更高的稳定性。通过对由多达3000个金属原子组成的模型结构进行大规模分子动力学模拟给出了解释。对于这两种类型的核壳结构，可以识别出两种完全不同的扩散过程，这显著说明了局部的原子特征如何仍然能够决定纳米尺寸颗粒的整体行为。
