Spatiotemporal Visualization of Nanoscale Rotational Dynamics by Movie-Mode Transmission Electron Microscopy.

Abstract

Nanoscale rotational dynamics has recently gathered significant interest in many fields, including ultrasensitive sensing and precision manipulation, but presents challenges for observation techniques. Here, we employ movie-mode transmission electron microscopy to investigate the rotational dynamics of laser-excited nanotriangles, achieving multiframe imaging with nanosecond and nanometer resolution. A motion reconstruction methodology was developed to facilitate accurate spatiotemporal trajectory tracking. The observed rotation dynamics of nanotriangles exhibit an obvious axis dependence, characterized by stable rotation around the first principal axis and inherent instability with respect to the second axis. This rotational stability bifurcation resulting from angular momentum redistribution aligns impeccably with the tennis racket effect, marking the first confirmation of classical rigid-body rotational theory at the nanosecond-nanometer scale. Furthermore, through the theoretical analysis of laser-induced rotation, we quantitatively assessed the adhesion state between the nanotriangle and substrate, offering an effective approach for evaluating interfacial properties. This study confirms the tennis racket effect at the nanosecond-nanometer scale and enhances the understanding of nanoscale rotational dynamics.