Spontaneous Reshaping and Splitting of AgCl Nanocrystals under Electron Beam Illumination

Abstract

AgCl is photosensitive and thus often used as micromotors. However, the dynamics of individual AgCl nanoparticle motion in liquids upon illumination remains elusive. Here, using liquid cell transmission electron microscope (TEM), AgCl nanocrystals reshaping and splitting spontaneously in an aqueous solution under electron beam illumination are observed. It is found that the AgCl nanocrystals are negatively charged in the liquid environment, where the charge induces a repulsive Coulomb force that reshapes and stretches those nanocrystals. Upon extensive stretching, the AgCl nanocrystal splits into small nanocrystals and each nanocrystal retracts back into cuboid shapes due to the cohesive surface. This analysis shows that each nanocrystal maintains a single crystal rocksalt structure during splitting. The splitting of AgCl nanocrystals is analogous to the electrified liquid droplets or other reported the Coulomb fission phenomenon, but with distinctive structural properties. Revealing of the dynamic behavior of AgCl nanocrystals opens the opportunity to explore their potential applications as actuators for nanodevices.

Observable Two-Step Nucleation Mechanism in Solid-State Formation of Tungsten Carbide

“…In addition, high-energy electron beams are frequently argued to exert complex effects towards specific samples upon intense illumination. − Accordingly, in addition to rational experimental operations to avoid high-dose exposure of our interested areas to electron beam (see Methods), we assessed the impact of the electron beam by comparing different areas across the sample during the annealing experiment. It is found, however, a negligible electron beam effect on the whole process throughout nucleation stages of tungsten carbide.…”

Liquid cell transmission electron microscopy and its applications

“…For example, Zecěvićet al [108] showed that under STEM, the narrowly focused electron beam probe can elongate silica nanoparticles. Tian et al [109] showed that the electron beam can split AgCl nanocrystals, which reassemble when illumination terminates. As we will discuss later, often the electron beam effect is something that the experimentalist wants to avoid, with beam-induced damage changing the behaviour of the sample in adverse ways.…”

2019 Awards of the Materials Research Society

“…By developing and applying in situ liquid phase transmission electron microscopy, her group studies the nucleation, growth, and transformations of nanoscale materials and solid–liquid interfaces. Zheng published a Communication in Angewandte Chemie on tailoring transition‐metal hydroxides and oxides by photon‐induced reactions and a Full Paper in Small on the behavior of AgCl nanocrystals under electron beam illumination …”