Li Z Y, Young N P, Di Vece M, Palomba S, Palmer R E, Bleloch A L, Curley B C, Johnston R L, Jiang J, Yuan J
Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
Nature. 2008 Jan 3;451(7174):46-8. doi: 10.1038/nature06470.
An unambiguous determination of the three-dimensional structure of nanoparticles is challenging. Electron tomography requires a series of images taken for many different specimen orientations. This approach is ideal for stable and stationary structures. But ultrasmall nanoparticles are intrinsically structurally unstable and may interact with the incident electron beam, constraining the electron beam density that can be used and the duration of the observation. Here we use aberration-corrected scanning transmission electron microscopy, coupled with simple imaging simulation, to determine with atomic resolution the size, three-dimensional shape, orientation and atomic arrangement of size-selected gold nanoclusters that are preformed in the gas phase and soft-landed on an amorphous carbon substrate. The structures of gold nanoclusters containing 3096 atoms can be identified with either Ino-decahedral, cuboctahedral or icosahedral geometries. Comparison with theoretical modelling of the system suggests that the structures are consistent with energetic considerations. The discovery that nanoscale gold particles function as active and selective catalysts for a variety of important chemical reactions has provoked much research interest in recent years. We believe that the detailed structure information we provide will help to unravel the role of these nanoclusters in size- and structure-specific catalytic reactions. We note that the technique will be of use in investigations of other supported ultrasmall metal cluster systems.
明确确定纳米颗粒的三维结构具有挑战性。电子断层扫描需要针对许多不同的样品取向拍摄一系列图像。这种方法对于稳定和固定的结构是理想的。但是超小纳米颗粒本质上结构不稳定，并且可能与入射电子束相互作用，限制了可使用的电子束密度和观察持续时间。在这里，我们使用像差校正扫描透射电子显微镜，并结合简单的成像模拟，以原子分辨率确定在气相中预先形成并软着陆在非晶碳衬底上的尺寸选择的金纳米团簇的尺寸、三维形状、取向和原子排列。含有3096个原子的金纳米团簇的结构可以用铟十面体、立方八面体或二十面体几何形状来识别。与该系统的理论模型比较表明，这些结构与能量考虑是一致的。近年来，纳米级金颗粒作为各种重要化学反应的活性和选择性催化剂的发现引发了许多研究兴趣。我们相信，我们提供的详细结构信息将有助于揭示这些纳米团簇在尺寸和结构特异性催化反应中的作用。我们注意到，该技术将用于研究其他负载型超小金属团簇系统。
