The Pulse Electron Study of Three-Dimensional Atomic Resolution Dynamics in Metal-Peapod

Abstract

Currently, the use of aberration-corrected Transmission Electron Microscopy (TEM) has been effective in analyzing the nanostructures of materials, but two major bottlenecks hinder the development of this technique. Firstly, TEM typically provides only two-dimensional projection images. Secondly, to achieve atomic-level resolution, a high electron dose rate is required. However, at such dose rates, the electron beam generated by TEM can cause irradiation damage to the structure of the material, particularly in electron beam-sensitive (soft) materials such as proteins, organic materials, and nanoparticles. In principle, the use of cryo-electron microscopy can reduce sample irradiation damage but at the cost of losing dynamical information about the material and may cause deformation at low temperature. Recent studies have shown that by keeping the energy of the electron beam below the critical voltage and controlling the electron dose rate within a certain threshold, material damage can be significantly reduced or even entirely avoided.

Metal-peapod, a kind of material that encapsulates metal atoms within fullerene@SWCNT (Single-Walled Carbon Nanotube), is regarded as an excellent nanoscale reaction chamber, facilitating a better analysis of single-atom dynamics. In this thesis, we introduce a method using low-dose pulsed electron beams to obtain the focal series images of metal-peapod and reconstruct their three-dimensional structures. This method allows the extraction of three-dimensional structural information of metal-peapod from holographic images obtained from only one observation direction, enhancing the spatial three-dimensional resolution to the single-atom scale. Furthermore, by capturing the focal series images at different time intervals using the ultra-fast camera, we obtained time-resolved exit waves, recording the dynamic changes in the structure of metal-peapod under different times and dose rates. This approach further promotes the study of three-dimensional atomic resolution dynamics of metal-peapod.

By combining advanced techniques such as low-dose pulsed electron holography and atomic model reconstruction, we successfully obtained time-resolved three-dimensional structures of metal-peapods. We analyzed the interaction mechanisms and dynamic behaviours of metal atoms, fullerenes, and carbon nanotubes within the metal-peapods under the influence of the electron beam which provided valuable insights for the study of nanostructures and dynamics in the field of materials science.

This thesis not only reveals the impact of electron beams on material structures but also provides a novel method for analyzing the three-dimensional structures of soft materials at the nanoscale.