Engineering Research Center in Biomaterials, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China.
Department of Ophthalmology, West China School of Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan 610065, People's Republic of China.
Acc Chem Res. 2021 Feb 16;54(4):776-786. doi: 10.1021/acs.accounts.0c00702. Epub 2021 Feb 3.
A knowledge of colloidal semiconductor magic-size clusters (MSCs) is essential for understanding how fundamental properties evolve during transformations from individual molecules to semiconductor quantum dots (QDs). Compared to QDs, MSCs display much narrower optical absorption bands; the higher cluster stability gives rise to a narrower size distribution. During the production of binary QDs such as II-VI metal (M) chalcogenide (E) ones, binary ME MSCs observed were interpreted as side products and/or the nuclei of QDs. Prior to the current development of our two-step approach followed by our two-pathway model, it had been extremely challenging to synthesize MSCs as a unique product without the nucleation and growth of QDs. With the two-step approach, we have demonstrated that MSCs can be readily engineered as a sole product at room temperature from a prenucleation stage sample, also called an induction period (IP) sample. It is important that we were able to discover that the evolution of the MSCs follows first-order reaction kinetics behavior. Accordingly, we proposed that a new type of compound, termed as "precursor compounds" (PCs) of MSCs, was produced in an IP sample. Such PCs are optically transparent at the absorption peak positions of their MSC counterparts as well as to longer wavelengths. It is thought that quasi isomerization of a single PC results in the development of one MSC.In this Account, we provide an overview of our latest advances regarding the transformations among binary CdE MSCs as well as from binary CdTe to ternary CdTeSe MSCs. Optical absorption spectroscopy has been employed to study these transformations, all of which display well-defined isosbestic points. We have proposed that these MSC to MSC transformations occur via their corresponding PCs, also called immediate PCs. It is reasonable that the as-synthesized PC (in an IP sample) and the immediate PC (in an incubated and/or diluted sample) probably have different configurations. A transformation between two PCs may involve an intermolecular reaction, with either first-order reaction kinetics or a more complicated time profile. A transformation between one immediate PC and its counterpart MSC may contain an intramolecular reaction. The present Account, which addresses the PC-enabled MSC transformations with isosbestic points probed by optical absorption spectroscopy, calls for more experimental and theoretical attention to understand these magic species and their transformation processes more precisely.
胶体半导体魔角团簇（MSC）的知识对于理解从单个分子到半导体量子点（QD）的基本性质演变至关重要。与 QD 相比，MSC 显示出更窄的光吸收带；更高的团簇稳定性导致更窄的尺寸分布。在 II-VI 金属（M）硫属化物（E）等二元 QD 的生产过程中，观察到的二元 ME MSC 被解释为副产物和/或 QD 的核。在我们目前采用两步法和双路径模型之前，在没有 QD 的成核和生长的情况下，将 MSC 作为独特产物进行合成极具挑战性。通过两步法，我们已经证明，MSC 可以在室温下从预成核阶段样品（也称为诱导期（IP）样品）容易地作为唯一产物进行工程设计。重要的是，我们能够发现 MSC 的演变遵循一级反应动力学行为。因此，我们提出在 IP 样品中产生一种称为 MSC 的“前体化合物”（PC）的新型化合物。这种 PC 在 MSC 对应物的吸收峰位置以及更长的波长处具有光学透明性。据认为，单个 PC 的准异构化导致一个 MSC 的发展。在本报告中，我们提供了关于二元 CdE MSC 之间以及从二元 CdTe 到三元 CdTeSe MSC 的转变的最新进展概述。我们已经使用光吸收光谱研究了这些转变，所有这些转变都显示出明确的等吸收点。我们提出这些 MSC 到 MSC 的转变是通过它们相应的 PC（也称为即时 PC）发生的。可以合理地认为，合成的 PC（在 IP 样品中）和即时 PC（在孵育和/或稀释样品中）可能具有不同的构型。两个 PC 之间的转变可能涉及分子间反应，具有一级反应动力学或更复杂的时间分布。一个即时 PC 与其对应 MSC 之间的转变可能包含分子内反应。本报告讨论了通过光吸收光谱探测等吸收点的 PC 支持的 MSC 转变，呼吁更多的实验和理论关注，以更准确地理解这些神奇物种及其转化过程。
