Hamachi Leslie S, Yang Haoran, Jen-La Plante Ilan, Saenz Natalie, Qian Kevin, Campos Michael P, Cleveland Gregory T, Rreza Iva, Oza Aisha, Walravens Willem, Chan Emory M, Hens Zeger, Crowther Andrew C, Owen Jonathan S
Department of Chemistry , Columbia University , New York , New York 10027 , USA . Email:
The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA.
Chem Sci. 2019 Jun 5;10(26):6539-6552. doi: 10.1039/c9sc00989b. eCollection 2019 Jul 14.
We report a method to control the composition and microstructure of CdSe S nanocrystals by the simultaneous injection of sulfide and selenide precursors into a solution of cadmium oleate and oleic acid at 240 °C. Pairs of substituted thio- and selenoureas were selected from a library of compounds with conversion reaction reactivity exponents ( ) spanning 1.3 × 10 s to 2.0 × 10 s. Depending on the relative reactivity ( / ), core/shell and alloyed architectures were obtained. Growth of a thick outer CdS shell using a syringe pump method provides gram quantities of brightly photoluminescent quantum dots (PLQY = 67 to 90%) in a single reaction vessel. Kinetics simulations predict that relative precursor reactivity ratios of less than 10 result in alloyed compositions, while larger reactivity differences lead to abrupt interfaces. CdSe S alloys ( / = 2.4) display two longitudinal optical phonon modes with composition dependent frequencies characteristic of the alloy microstructure. When one precursor is more reactive than the other, its conversion reactivity and mole fraction control the number of nuclei, the final nanocrystal size at full conversion, and the elemental composition. The utility of controlled reactivity for adjusting alloy microstructure is discussed.
我们报道了一种在240℃下通过将硫化物和硒化物前驱体同时注入油酸镉和油酸溶液中来控制CdSeS纳米晶体的组成和微观结构的方法。从一系列转换反应反应指数（）跨度为1.3×10⁻⁵s至2.0×10⁻⁵s的化合物库中选择成对的取代硫脲和硒脲。根据相对反应活性（/），可获得核壳结构和合金结构。使用注射泵方法生长厚的外层CdS壳层，可在单个反应容器中制备克量级的明亮光致发光量子点（PLQY = 67%至90%）。动力学模拟预测，前驱体相对反应活性比小于10会导致合金组成，而较大的反应活性差异会导致界面突然变化。CdSeS合金（/ = 2.4）显示出两种纵向光学声子模式，其频率与合金微观结构的组成有关。当前驱体之一比另一个更具反应活性时，其转换反应活性和摩尔分数控制着核的数量、完全转化时的最终纳米晶体尺寸以及元素组成。讨论了控制反应活性在调节合金微观结构方面的实用性。
