Direct Observations of the Rotation and Translation of Anisotropic Nanoparticles Adsorbed at a Liquid–Solid Interface

We can learn about the interactions between nanoparticles (NPs) in solution and solid surfaces by tracking how they move. Here, we use liquid cell transmission electron microscopy (TEM) to follow directly the translation and rotation of Au nanobipyramids (NBPs) and nanorods (NRs) adsorbed onto a SiNx surface at a rate of 300 frames per second. This study is motivated by the enduring need for a detailed description of NP motion on this common surface in liquid cell TEM. We will show that NPs move intermittently on the time scales of milliseconds. First, they rotate in two ways: (1) rotation around the center of mass and (2) pivoted rotation at the tips. These rotations also lead to different modes of translation. A NP can move through small displacements in the direction roughly parallel to its body axis (shuffling) or with larger steps via multiple tip-pivoted rotations. Analysis of the trajectories indicates that both displacements and rotation angles follow heavy-tailed power law distributions, implying...