Investigating Charge-Induced Transformations of Metal Nanoparticles in a Radically-Inert Liquid: A Liquid-Cell TEM Study

Abstract

We present a novel in situ liquid-cell transmission electron microscopy (TEM) approach to study the behavior of metal nanoparticles under high-energy electron irradiation. By utilizing a radically-inert liquid environment, we aim to minimize radiolysis effects and explore the influence of charge-induced transformations. We observed complex dynamics in nanoparticle behavior, including morphological changes and transitions between amorphous and crystalline states. These transformations are attributed to the delicate interplay between charge accumulation on the nanoparticles and enhanced radiolysis, suggesting a significant role for charge-assisted processes in nanoparticle evolution. Our findings provide valuable insights into the fundamental mechanisms driving nanoparticle behavior at the nanoscale and demonstrate the potential of liquid-cell TEM for studying complex physicochemical processes in controlled environments.

Keywords: Au nanoparticle; liquid-phase transmission electron microscopy; phase transition.

Figure 1

(a) Schematics of an electrically insulated liquid cell configuration with electrodes. (b) The potential between the working electrode and reference electrode was measured during electron illumination of the environmental cell.

Figure 2

Morphological evolution of Au nanoparticles dispersed in acetonitrile under varying electron doses. (a) At a moderate electron dose rate of 9.2 × 10³ e⁻/Ų·s, typically used during liquid phase electron microscopy (LPEM), the nanoparticle exhibits slight surface deformation and viscous behavior. (b) At a high electron dose rate of 1.3 × 10⁵ e⁻/Ų·s, comparable to high-resolution TEM conditions for solid phases, the nanoparticle undergoes significant deformation, displaying behavior characteristic of solid-liquid phase transformation. Scale bar is 10 nm.

Figure 3

The postmortem crystallinity mapping of the particle revealed a combination of crystalline FCC Au and amorphous Au within a single particle. Regions 1, 2, and 5 show a well-ordered face-centered cubic (FCC) structure, while regions 3 and 4 exhibit amorphous phases.