Laboratory for Ultrafast Microscopy and Electron Scattering, Lausanne Center for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
Physics Institute, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Nano Lett. 2016 Apr 13;16(4):2705-13. doi: 10.1021/acs.nanolett.6b00355. Epub 2016 Mar 12.
The design and the characterization of functionalized gold nanoparticles supracrystals require atomically resolved information on both the metallic core and the external organic ligand shell. At present, there is no known approach to characterize simultaneously the static local order of the ligands and of the nanoparticles, nor their dynamical evolution. In this work, we apply femtosecond small-angle electron diffraction combined with angular cross-correlation analysis, to retrieve the local arrangement from nanometer to interatomic scales in glassy aggregates. With this technique we study a two-dimensional distribution of functionalized gold nanoparticles deposited on amorphous carbon. We show that the dodecanethiol ligand chains, coating the gold cores, order in a preferential orientation on the nanoparticle surface and throughout the supracrystal. Furthermore, we retrieve the dynamics of the supracrystal upon excitation with light and show that the positional disorder is induced by light pulses, while its overall homogeneity is surprisingly found to transiently increase. This new technique will enable the systematic investigation of the static and dynamical structural properties of nanoassembled materials containing light elements, relevant for several applications including signal processing and biology.
功能化金纳米粒子超晶格的设计和特性需要原子分辨率的信息，包括金属核心和外部有机配体壳。目前，还没有已知的方法可以同时描述配体和纳米粒子的静态局部有序性，也无法描述它们的动态演变。在这项工作中，我们应用飞秒小角电子衍射结合角交叉相关分析，从纳米到原子尺度的范围内恢复非晶态聚集体中的局部排列。我们使用这项技术研究了沉积在非晶碳上的功能化金纳米粒子的二维分布。我们发现，涂覆在金核上的十二硫醇配体链在纳米粒子表面和整个超晶格中优先取向有序。此外，我们还研究了光激发下超晶格的动力学，发现光脉冲会引起位置无序，而其整体均匀性出人意料地发现会暂时增加。这项新技术将能够系统地研究包含轻元素的纳米组装材料的静态和动态结构特性，这些特性与包括信号处理和生物学在内的多个应用相关。
