Ligand-Mediated Phase Control in Colloidal AgInSe2 Nanocrystals,Chemistry of Materials

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Ligand-Mediated Phase Control in Colloidal AgInSe2 Nanocrystals
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-03-19 , DOI: 10.1021/acs.chemmater.9b05163
Bryce A. Tappan ₁ , Matthew K. Horton ₂ , Richard L. Brutchey ₁

Affiliation

Synthetic studies of colloidal nanoparticles that crystallize in metastable structures represent an emerging area of interest in the development of novel functional materials, as metastable nanomaterials may exhibit unique properties when compared to their counterparts that crystallize in thermodynamically preferred structures. Herein, we demonstrate how phase control of colloidal AgInSe₂ nanocrystals can be achieved by performing reactions in the presence or absence of coordinating ligands that can act as cation exchange mediators (i.e., oleylamine or 1-dodecanethiol). These coordinating ligands play a crucial role in the formation of metastable AgInSe₂ nanocrystals, as they mediate in situ topotactic conversion of an orthorhombic Ag₂Se intermediate to a metastable orthorhombic phase of AgInSe₂. We provide a detailed mechanistic crystal chemistry description of this process to structurally elucidate how the orthorhombic phase of AgInSe₂ forms. Density functional theory calculations suggest that the metastable orthorhombic phase of AgInSe₂ is metastable by a small margin, at 10 meV/atom above the thermodynamic ground state. In the absence of oleylamine or 1-dodecanethiol, Ag₂Se nanocrystal intermediates convert through kinetically slow, nontopotactic conversion processes to yield the thermodynamically preferred chalcopyrite structure of AgInSe₂. On the basis of these discoveries, we offer new insights into the prediction of novel metastable multinary nanocrystal phases that do not exist on bulk phase diagrams.

中文翻译：

胶体AgInSe ₂纳米晶体中的配体介导的相控制

在亚稳态结构中结晶的胶体纳米颗粒的合成研究代表了新型功能材料开发中的一个新兴领域，因为与在热力学上优选的结构中结晶的同行相比，亚稳态纳米材料可能表现出独特的性能。在本文中，我们证明了在存在或不存在可以充当阳离子交换介质（即油胺或1-十二烷硫醇）的配位体存在或不存在的情况下，通过反应可以实现胶体AgInSe ₂纳米晶体的相控制。这些配位配体在亚稳态AgInSe ₂纳米晶体的形成中起着至关重要的作用，因为它们介导正交晶体Ag _2的原位到正离子转化。硒介于AgInSe ₂的亚稳正交相中。我们提供了此过程的详细机械晶体化学描述，以在结构上阐明AgInSe ₂的正交晶相是如何形成的。密度泛函理论计算表明，AgInSe ₂的亚稳态斜方晶相在热力学基态上方10 meV /原子处以很小的幅度是亚稳的。在不存在油胺或1-十二烷硫醇的情况下，Ag ₂ Se纳米晶体中间体通过动力学缓慢的非等规转变过程进行转化，从而生成热力学上优选的AgInSe ₂黄铜矿结构。在这些发现的基础上，我们为新的亚稳态多元纳米晶体相的预测提供了新见解，而这些相在体相图上不存在。

更新日期：2020-04-23

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