Lokteva Irina, Koof Michael, Walther Michael, Grübel Gerhard, Lehmkühler Felix
Deutsches Elektronen-Synchrotron (DESY) , Notkestraße 85 , 22607 Hamburg , Germany.
The Hamburg Centre for Ultrafast Imaging (CUI) , Luruper Chaussee 149 , 22761 Hamburg , Germany.
J Phys Chem Lett. 2019 Oct 17;10(20):6331-6338. doi: 10.1021/acs.jpclett.9b02622. Epub 2019 Oct 4.
We study the in situ self-assembly of faceted PbS nanocrystals from colloidal suspensions upon controlled solvent evaporation using time-resolved small-angle X-ray scattering and X-ray cross-correlation analysis. In our bulk-sensitive experiment in transmission geometry, the superlattice crystallization is observed in real time, revealing a hexagonal closed-packed (hcp) structure followed by formation of a body-centered cubic (bcc) superlattice. The bcc superlattice undergoes continuous tetragonal distortion in the solvated state shortly after its formation, resulting in the body-centered tetragonal (bct) structure. Upon solvent evaporation, the bct superstructure becomes more pronounced with the still coexisting hcp phase. These findings corroborate the existing simulations of assembling cuboctahedral-shaped particles and illustrate that we observed the predicted equilibrium states. This work is essential for a deeper understanding of the fundamental forces that direct nanocrystal assembly including nanocrystal shape and ligand coverage.
我们使用时间分辨小角X射线散射和X射线互相关分析，研究了在可控溶剂蒸发条件下，从胶体悬浮液中原位自组装多面体PbS纳米晶体的过程。在我们的透射几何结构的体敏感实验中，实时观察到了超晶格结晶，揭示了一种六方密堆积（hcp）结构，随后形成了体心立方（bcc）超晶格。bcc超晶格在形成后不久的溶剂化状态下会经历连续的四方畸变，形成体心四方（bct）结构。随着溶剂蒸发，bct超结构与仍然共存的hcp相一起变得更加明显。这些发现证实了现有的关于组装立方八面体形状颗粒的模拟，并表明我们观察到了预测的平衡状态。这项工作对于更深入理解指导纳米晶体组装的基本力至关重要，这些力包括纳米晶体形状和配体覆盖度。
