Calvin Jason J, Kaufman Tierni M, Sedlak Adam B, Crook Michelle F, Alivisatos A Paul
Department of Chemistry, University of California, Berkeley, CA, USA.
Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Nat Commun. 2021 May 11;12(1):2663. doi: 10.1038/s41467-021-22947-x.
Powder X-ray diffraction is one of the key techniques used to characterize the inorganic structure of colloidal nanocrystals. The comparatively low scattering factor of nuclei of the organic capping ligands and their propensity to be disordered has led investigators to typically consider them effectively invisible to this technique. In this report, we demonstrate that a commonly observed powder X-ray diffraction peak around [Formula: see text] observed in many small, colloidal quantum dots can be assigned to well-ordered aliphatic ligands bound to and capping the nanocrystals. This conclusion differs from a variety of explanations ascribed by previous sources, the majority of which propose an excess of organic material. Additionally, we demonstrate that the observed ligand peak is a sensitive probe of ligand shell ordering. Changes as a function of ligand length, geometry, and temperature can all be readily observed by X-ray diffraction and manipulated to achieve desired outcomes for the final colloidal system.
粉末X射线衍射是用于表征胶体纳米晶体无机结构的关键技术之一。有机封端配体的原子核相对较低的散射因子及其无序倾向导致研究人员通常认为该技术对它们基本不可见。在本报告中，我们证明，在许多小的胶体量子点中常见的在[公式：见正文]附近观察到的粉末X射线衍射峰可归因于与纳米晶体结合并封端的有序脂肪族配体。这一结论与先前文献给出的各种解释不同，其中大多数认为是有机材料过量所致。此外，我们证明观察到的配体峰是配体壳层有序性的灵敏探针。通过X射线衍射可以很容易地观察到配体长度、几何形状和温度变化的函数关系，并对其进行调控，以实现最终胶体系统的理想结果。
