论文标题
X射线吸收光谱法的CD魔术大小簇的原子结构
Atomic structure of CdS magic-size clusters by X-ray absorption spectroscopy
论文作者
论文摘要
魔术大小的簇是超小胶体半导体系统，由于其单分散性质和与常规量子点相比，它们的单分散性和尖锐的UV-VIS吸收峰。但是，此类簇的小尺寸（<2 nm）和较大的表面与柱比显着限制了可以利用的特征技术。在这里，我们演示了如何使用EXAF和XANE的组合来获取有关样品化学计量和群集对称性的信息。研究了两种类型的簇，这些簇在311 nm和322 nm处显示出尖锐的UV-VIS吸收峰，我们发现两个样品都具有大约2：1 CD：S的比率，并且具有相似的最近邻脉结构排列。然而，这两个样品都表现出与四面体结构排列的显着背离，平均键角确定为106.1度，显示了双重键角分布。我们的结果表明，这两个样本都是Quazi Isomers。它们的核心结构具有相同的化学成分，但具有不同的原子布置，具有不同的键角分布。
Magic-size clusters are ultra-small colloidal semiconductor systems that are intensively studied due to their monodisperse nature and sharp UV-vis absorption peak compared with regular quantum dots. However, the small size of such clusters (<2 nm), and the large surface-to-bulk ratio significantly limit characterisation techniques that can be utilised. Here we demonstrate how a combination of EXAFS and XANES can be used to obtain information about sample stoichiometry and cluster symmetry. Investigating two types of clusters that show sharp UV-vis absorption peaks at 311 nm and 322 nm, we found that both samples possess approximately 2:1 Cd:S ratio and have similar nearest-neighbour structural arrangements. However, both samples demonstrate a significant departure from the tetrahedral structural arrangement, with an average bond angle determined to be around 106.1 degree showing a bi-fold bond angle distribution. Our results suggest that both samples are quazi-isomers. Their core structure has identical chemical composition but a different atomic arrangement with distinct bond angle distributions.
