Controlled oxidative etching of gold nanorods revealed through in-situ liquid cell electron microscopy金纳米棒可控刻蚀机制的原位液体环境透射电子显微学研究

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.