The size and shape of semiconductor nanocrystals govern their optical and electronic properties. Liquid cell transmission electron microscopy (LCTEM) is an emerging tool that can directly visualize nanoscale chemical transformations and therefore inform the precise synthesis of nanostructures with desired functions. However, it remains difficult to controllably investigate the reactions of semiconductor nanocrystals with LCTEM, because of the highly reactive environment formed by radiolysis of liquid. Here, we harness the radiolysis processes and report the single-particle etching trajectories of prototypical semiconductor nanomaterials with well-defined crystalline facets. Lead selenide nanocubes represent an isotropic structure that retains the cubic shape during etching via a layer-by-layer mechanism. The anisotropic arrow-shaped cadmium selenide nanorods have polar facets terminated by either cadmium or selenium atoms, and the transformation trajectory is driven by etching the selenium-terminated facets. LCTEM trajectories reveal how nanoscale shape transformations of semiconductors are governed by the reactivity of specific facets in liquid environments.

中文翻译：

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单个半导体纳米晶体的刻面选择性蚀刻轨迹

半导体纳米晶体的尺寸和形状决定了它们的光学和电子特性。液体细胞透射电子显微镜 (LCTEM) 是一种新兴工具，可以直接可视化纳米级化学转化，从而为具有所需功能的纳米结构的精确合成提供信息。然而，由于液体辐射分解形成的高反应性环境，难以可控地研究半导体纳米晶体与 LCTEM 的反应。在这里，我们利用辐射分解过程并报告具有明确晶面的原型半导体纳米材料的单粒子蚀刻轨迹。硒化铅纳米立方体代表一种各向同性结构，在蚀刻过程中通过逐层机制保持立方体形状。各向异性箭头形硒化镉纳米棒具有由镉或硒原子终止的极性面，并且通过蚀刻以硒终止的面来驱动转变轨迹。LCTEM 轨迹揭示了半导体的纳米级形状转变如何受液体环境中特定面的反应性控制。