Institute of Atomic and Molecular Physics, Sichuan University, Sichuan 610065, China.
Engineering Research Center in Biomaterials, Sichuan University, Sichuan 610065, China.
Nat Commun. 2017 Jun 5;8:15467. doi: 10.1038/ncomms15467.
Little is known about the induction period before the nucleation and growth of colloidal semiconductor quantum dots. Here, we introduce an approach that allows us to probe intermediates present in the induction period. We show that this induction period itself exhibits distinct stages with the evolution of the intermediates, first without and then with the formation of covalent bonds between metal cations and chalcogenide anions. The intermediates are optically invisible in toluene, while the covalent-bonded intermediates become visible as magic-size clusters when a primary amine is added. Such evolution of magic-size clusters provides indirect but compelling evidence for the presence of the intermediates in the induction period and supports the multi-step nucleation model. Our study reveals that magic-size clusters could be readily engineered in a single-size form, and suggests that the existence of the intermediates during the growth of conventional quantum dots results in low product yield.
关于胶体质点的成核和生长前的诱导期知之甚少。在这里，我们介绍了一种可以探测诱导期内中间产物的方法。我们表明，诱导期本身具有不同的阶段，伴随着中间产物的演变，首先是金属阳离子和硫属阴离子之间没有形成共价键，然后是形成共价键。在甲苯中，中间产物是光学不可见的，而当添加伯胺时，形成共价键的中间产物会变成可见的“魔术大小”团簇。这种“魔术大小”团簇的演化提供了中间产物存在于诱导期的间接但令人信服的证据，并支持多步成核模型。我们的研究表明，“魔术大小”团簇可以很容易地以单一尺寸形式进行工程设计，并表明在传统量子点生长过程中中间产物的存在会导致产物产率低。
