Key Laboratory for Ultrafine Materials of Ministry of Education and Shanghai Key Laboratory of Advanced Polymeric Materials, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China.
State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China.
ACS Nano. 2020 Aug 25;14(8):9594-9604. doi: 10.1021/acsnano.9b10173. Epub 2020 Aug 5.
A mechanistic understanding of the growth of multiply twinned nanoparticles (MTPs), such as decahedra (Dh) and icosahedra (Ih), is crucial for precisely controlled syntheses and applications. Despite previous successes, no consensus has been reached regarding the multiple competing growth pathways for MTPs proposed thus far, in part due to the lack of information about their nucleation and growth dynamics. Here, we used decahedral and icosahedral gold nanoparticles as a model system in conjunction with liquid cell transmission electron microscopy (LCTEM) to investigate the nucleation and growth dynamics of MTPs in aqueous solution; two growth pathways were successfully identified: (A) nucleation-based layer-by-layer growth from a rounded multiply twinned seed and (B) the successive twinning and growth of tetrahedra. The LCTEM results enabled us to directly and conclusively identify the growth behaviors of intermediate products. The internal strain relaxation mechanisms and growth kinetics differ for the two pathways: in pathway A, a MTP grew by the opening and closing of re-entrant grooves at the twin boundaries, which was not found in pathway B. We also analyzed different MTP growth pathways from an energetic perspective and discussed how the preferred pathway (A or B) is related to factors, such as the initial seed yield and the size- and morphology-dependent formation of MTPs. Our results contextualize the current understanding of MTP formation mechanisms and provide insightful guidance for the precisely controlled synthesis of MTPs for practical applications.
对于多孪晶纳米颗粒（MTPs）的生长机制的理解，如十面体（Dh）和二十面体（Ih），对于精确控制的合成和应用至关重要。尽管之前已经取得了一些成功，但迄今为止，对于 MTPs 提出的多种竞争生长途径，尚未达成共识，部分原因是缺乏关于其成核和生长动力学的信息。在这里，我们使用十面体和二十面体金纳米颗粒作为模型系统，结合液相细胞透射电子显微镜（LCTEM），研究了 MTP 在水溶液中的成核和生长动力学；成功识别了两种生长途径：（A）从圆形多孪晶种子逐层成核生长，以及（B）四面体的连续孪晶和生长。LCTEM 结果使我们能够直接且明确地识别中间产物的生长行为。两种途径的内部应变松弛机制和生长动力学不同：在途径 A 中，MTP 通过在孪晶边界处的凹口和闭合来生长，而在途径 B 中则没有发现这种情况。我们还从能量的角度分析了不同的 MTP 生长途径，并讨论了首选途径（A 或 B）如何与初始种子产量和与尺寸和形态相关的 MTP 形成等因素有关。我们的结果使我们对 MTP 形成机制的现有理解更加深入，并为精确控制 MTP 的合成提供了有价值的指导，以满足实际应用的需求。
