School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
J Am Chem Soc. 2011 Mar 9;133(9):3131-8. doi: 10.1021/ja110454b. Epub 2011 Feb 9.
The assembly of colloidal nanocrystals (NCs) into superstructures with long-range translational and orientational order is sensitive to the molecular interactions between ligands bound to the NC surface. We illustrate how ligand coverage on colloidal PbS NCs can be exploited as a tunable parameter to direct the self-assembly of superlattices with predefined symmetry. We show that PbS NCs with dense ligand coverage assemble into face-centered cubic (fcc) superlattices whereas NCs with sparse ligand coverage assemble into body-centered cubic (bcc) superlattices which also exhibit orientational ordering of NCs in their lattice sites. Surface chemistry characterization combined with density functional theory calculations suggest that the loss of ligands occurs preferentially on {100} than on reconstructed {111} NC facets. The resulting anisotropic ligand distribution amplifies the role of NC shape in the assembly and leads to the formation of superlattices with translational and orientational order.
胶体纳米晶体（NCs）的组装成具有长程平移和取向有序的超结构，对配体与 NC 表面结合的分子相互作用敏感。我们说明了如何利用胶体 PbS NC 上的配体覆盖率作为可调参数来指导具有预定对称性的超晶格的自组装。我们表明，具有密集配体覆盖的 PbS NC 组装成面心立方（fcc）超晶格，而具有稀疏配体覆盖的 NC 组装成体心立方（bcc）超晶格，其晶格位置也表现出 NC 的取向有序。表面化学特性分析结合密度泛函理论计算表明，配体优先从 {100} 而非重构 {111} NC 面缺失。由此产生的各向异性配体分布放大了 NC 形状在组装中的作用，并导致具有平移和取向有序的超晶格的形成。
