In-situ liquid-cell TEM study of radial flow-guided motion of octahedral Au nanoparticles and nanoparticle clusters

摘要

The dynamic behavior of octahedral gold nanoparticles (NPs) and nanoparticle clusters (NPCs) in aqueous solution is studied by in-situ liquid-cell transmission electron microscopy (TEM).The octahedral Au NPs/NPCs show preferential orientations in the liquid cell,due to the interaction with the SiNx window.The Au NPs show long-range reversible hopping and three-dimensional (3D) rotational motions in the liquid environment.At the same time,the Au NPCs and NPs perform slow stick-slip and stick-roll motions,respectively,with a centripetal trend.The centripetal motions were explained by a liquid evaporation-induced radial flow model,in which the NPCs/NPs trajectories are controlled by Stokes forces and surface friction by the silicon nitride window.The calculated radius-dependent force (Fc) on the NPCs/NPs shows a semi-linear correlation with the distance r between the NPCs/NPs and the center of mass,accompanied with stochastic fluctuations,in agreement with the model predictions.This work thus demonstrates the effectiveness of in situ liquid-cell TEM for the in-depth understanding of complicated liquid flow and force interactions in nanomaterials.