Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.
ACS Nano. 2011 Dec 27;5(12):9755-60. doi: 10.1021/nn203273e. Epub 2011 Nov 2.
The nucleation of noble metal nanoparticles on oxide surfaces can lead to dramatic enhancements in catalytic activity that are related to the atomic-scale formation of the nanoparticles and interfaces. For the case of submonolayer Pt deposited on the 2×1 SrTiO(3)(001) surface atomic-force microscopy shows the formation of nanoparticles. We use X-ray standing wave (XSW) atomic imaging to show that these nanoparticles are composed of Pt face-centered-cubic nanocrystals with cube-on-cube epitaxy laterally correlated to the substrate unit cell. The phase sensitivity of the XSW allows for a direct measurement of the interface offset between the two unit cells along the c-axis. Different Pt coverages lead to differences in the observed XSW image of the interfacial structure, which is explained by a proposed model based on the Pt-Pt interaction becoming stronger than the Pt-substrate interaction as the global coverage is increased from 0.2 to 0.6 ML.
在氧化物表面上形成贵金属纳米颗粒的成核会导致催化活性的显著增强，这与纳米颗粒和界面的原子尺度形成有关。对于亚单层 Pt 在 2×1 SrTiO(3)(001)表面上的沉积情况，原子力显微镜显示出纳米颗粒的形成。我们使用 X 射线驻波（XSW）原子成像来表明这些纳米颗粒由 Pt 面心立方纳米晶体组成，其具有与衬底单元晶格侧向相关的立方对立方外延。XSW 的相位灵敏度允许直接测量沿 c 轴的两个单元晶格之间的界面偏移。不同的 Pt 覆盖率导致观察到的界面结构的 XSW 图像存在差异，这可以通过基于 Pt-Pt 相互作用变得比 Pt-衬底相互作用更强的模型来解释，因为全局覆盖率从 0.2 增加到 0.6 ML。
