Exposure of mass-selected bimetallic Pt-Ti nanoalloys to oxygen explored using scanning transmission electron microscopy and density functional theory.
Exposure of mass-selected bimetallic Pt-Ti nanoalloys to oxygen explored using scanning transmission electron microscopy and density functional theory.
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DOI：
10.1039/c8ra02449a
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发表时间：
2018-07-30
期刊：
影响因子：
3.9
通讯作者：
Palmer, Richard E.
中科院分区：
文献类型：
--
作者：
Gholhaki, Saeed;Hung, Shih-Hsuan;Cant, David J. H.;Blackmore, Caroline E.;Shard, Alex G.;Guo, Quanmin;McKenna, Keith P.;Palmer, Richard E.
纳米颗粒对暴露于环境条件，特别是氧化的响应是纳米技术应用的基础。选择的质量，30 kDa和90 kDa的双金属铂-钛纳米粒子，使用磁控溅射气体冷凝簇源和沉积到无定形碳TEM网格上。用Cs校正的扫描透射电子显微镜（STEM）以高角度环形暗场（HAADF）模式分析纳米颗粒。据观察，在完全Ti氧化之前，Pt原子分散在Ti壳内。然而，在STEM之前通过长时间暴露于环境条件而完全氧化后，较小尺寸的30 kDa颗粒形成单个Pt核，较大尺寸的90 kDa颗粒表现出多核结构。电子束退火诱导的单核心形态在较大的颗粒。采用第一性原理密度泛函理论（DFT）计算计算的最低能量结构的Pt-Ti纳米粒子的存在和不存在的氧。结果表明，随着氧浓度的增加，最低能量结构从分散的Pt到多个Pt核，最后是一个单一的Pt核，这是与实验观察到的。Ti元素氧化诱导的理论和实验形态。
The response of nanoparticles to exposure to ambient conditions and especially oxidation is fundamental to the application of nanotechnology. Bimetallic platinum–titanium nanoparticles of selected mass, 30 kDa and 90 kDa, were produced using a magnetron sputtering gas condensation cluster source and deposited onto amorphous carbon TEM grids. The nanoparticles were analysed with a Cs-corrected Scanning Transmission Electron Microscope (STEM) in High Angle Annular Dark Field (HAADF) mode. It was observed that prior to full Ti oxidation, Pt atoms were dispersed within a Ti shell. However, after full oxidation by prolonged exposure to ambient conditions prior to STEM, the smaller size 30 kDa particles form a single Pt core and the larger size 90 kDa particles exhibit a multi-core structure. Electron beam annealing induced a single core morphology in the larger particles. First principles density functional theory (DFT) calculations were employed to calculate the lowest energy structure of the Pt–Ti nanoparticles with and without the presence of oxygen. It was demonstrated that, as the concentration of oxygen increases, the lowest energy structure changes from dispersed Pt to multiple Pt cores and finally a single Pt core, which is in good agreement with the experimental observations. Theoretical and experimental morphology induced by oxidation of the Ti element.
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