Department of Physics and Astronomy and Ames Laboratory, Iowa State University , Ames, Iowa 50011, United States.
ACS Nano. 2017 Jun 27;11(6):5375-5382. doi: 10.1021/acsnano.7b02219. Epub 2017 May 19.
A number of bewildering paradoxes arise in the field of nanoparticle self-assembly: nominal low density superlattices, strong stability of low coordination sites, and a clear but imperfect correlation between lattice stability and the maximum of hard sphere packing, despite the fact that that nanocrystals themselves are, through their ligands, very much compressible. In this study, I show that by regarding nanocrystals as pseudotopological objects ("soft skyrmions"), it is possible to identify and classify the ligand textures that determine their bonding. These textures consist of interacting vortices, where the total vorticity defines a spontaneous valence (coordination). Furthermore, skyrmion interactions are governed by two simple assumptions, which lead to a set of selection rules for superlattice structure. Besides resolving all the above paradoxes, the predictions are completely supported by more than one hundred sixty experiments gathered from the literature, including a wide range of nanocrystal cores and ligands (saturated or unsaturated hydrocarbons, amines, polystyrene, etc.). How those results can be used for addressing more complex structures and guiding future experiments is also addressed.
名义上的低密度超晶格、低配位位点的强稳定性，以及晶格稳定性与硬球堆积最大值之间的明显但不完美的相关性，尽管纳米晶体本身通过配体非常可压缩。在这项研究中，我表明，通过将纳米晶体视为拟拓扑物体（“软 Skyrmions”），可以识别和分类决定其键合的配体纹理。这些纹理由相互作用的涡旋组成，其中总涡度定义了自发价（配位）。此外，Skyrmion 相互作用受两个简单假设的支配，这导致了超晶格结构的一组选择规则。除了解决上述所有悖论外，这些预测还得到了从文献中收集的一百六十多个实验的完全支持，其中包括广泛的纳米晶核和配体（饱和或不饱和烃类、胺类、聚苯乙烯等）。还讨论了如何将这些结果用于处理更复杂的结构和指导未来的实验。
