Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy.
Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, Via Dodecaneso, 31, 16146, Genova, Italy.
Nat Commun. 2018 Mar 20;9(1):1141. doi: 10.1038/s41467-018-03550-z.
Colloidal nanocrystals can self-assemble into highly ordered superlattices. Recent studies have focused on changing their morphology by tuning the nanocrystal interactions via ligand-based surface modification for simple particle shapes. Here we demonstrate that this principle is transferable to and even enriched in the case of a class of branched nanocrystals made of a CdSe core and eight CdS pods, so-called octapods. Through careful experimental analysis, we show that the octapods have a heterogeneous ligand distribution, resembling a cone wrapping the individual pods. This induces location-specific interactions that, combined with variation of the pod aspect ratio and ligands, lead to a wide range of planar superlattices assembled at an air-liquid interface. We capture these findings using a simple simulation model, which reveals the necessity of including ligand-based interactions to achieve these superlattices. Our work evidences the sensitivity that ligands offer for the self-assembly of branched nanocrystals, thus opening new routes for metamaterial creation.
胶体纳米晶体可以自组装成高度有序的超晶格。最近的研究集中在通过配体表面修饰来改变纳米晶体的相互作用，从而改变其形态，以获得简单的颗粒形状。在这里，我们证明了这一原理可以转移到甚至丰富一类由 CdSe 核和八个 CdS 荚组成的支化纳米晶体的情况，即所谓的八荚体。通过仔细的实验分析，我们表明八荚体具有不均匀的配体分布，类似于包裹单个荚体的圆锥体。这诱导了位置特异性相互作用，再加上荚的纵横比和配体的变化，导致在气液界面上组装了一系列广泛的平面超晶格。我们使用一个简单的模拟模型来捕捉这些发现，该模型揭示了包含基于配体的相互作用以实现这些超晶格的必要性。我们的工作证明了配体在支化纳米晶体自组装中的敏感性，从而为超材料的创造开辟了新途径。
