Oxidative etching can be a powerful approach to modify the morphology of nanoscale materials for various applications. Unveiling of the etching mechanisms and morphological evolution during etching is critical. Using the liquid cell transmission electron microscopy, we investigate the etching behavior of gold nanorods under different electron beam dose rates: case I, 3.5×10⁹ Gy s⁻¹; case II, 1.5×10¹⁰ Gy s⁻¹; case III, 4.5×10¹⁰ Gy s⁻¹. The Au nanorod develops facets at the tips (case I) or adopts a transit ellipsoid shape and eventually dissolves (case II), depending on the dose rate. The rapid etching under an even higher dose rate (case III) may lead to the formation of Au³⁺ ion-rich intermediates around the nanorod, which further accelerates the lateral etching and unexpectedly increases the aspect ratio of the nanorod. Our quantitative analysis shows that the critical size of the nanorod, below which the etching rate increases significantly with the reduction of nanorod size, may vary subject to the degree that the system is away from equilibrium. These results provide significant insights into the oxidative etching mechanisms and shed light on the rational design and synthesis of nanostructures.

氧化蚀刻可以是一种强大的方法，可以针对各种应用修改纳米级材料的形态。揭示蚀刻机制和蚀刻过程中的形态演变至关重要。使用液体细胞透射电子显微镜，我们研究了金纳米棒在不同电子束剂量率下的腐蚀行为：情况I，3.5×10 ⁹ Gy s ^-1；情况II，1.5×10 ¹⁰ Gy s ^-1 ; 情况III，4.5×10 ¹⁰ Gy s ^-1。金纳米棒在尖端处形成刻面（情况I）或采用过渡椭球形状，并最终溶解（情况II），具体取决于剂量率。在更高剂量率下的快速蚀刻（案例III）可能导致金的形成围绕纳米棒的³⁺富离子中间体，这进一步加速了横向蚀刻，并出乎意料地增加了纳米棒的长宽比。我们的定量分析表明，纳米棒的临界尺寸会随着系统偏离平衡的程度而变化，在临界尺寸以下，蚀刻速率会随着纳米棒尺寸的减小而显着增加。这些结果提供了对氧化蚀刻机理的重要见解，并为合理设计和合成纳米结构提供了启示。