Radiolysis‐Driven Evolution of Gold Nanostructures – Model Verification by Scale Bridging In Situ Liquid‐Phase Transmission Electron Microscopy and X‐Ray Diffraction

Abstract

Utilizing ionizing radiation for in situ studies in liquid media enables unique insights into nanostructure formation dynamics. As radiolysis interferes with observations, kinetic simulations are employed to understand and exploit beam‐liquid interactions. By introducing an intuitive tool to simulate arbitrary kinetic models for radiation chemistry, it is demonstrated that these models provide a holistic understanding of reaction mechanisms. This is shown for irradiated HAuCl4 solutions allowing for quantitative prediction and tailoring of redox processes in liquid‐phase transmission electron microscopy (LP‐TEM). Moreover, it is demonstrated that kinetic modeling of radiation chemistry is applicable to investigations utilizing X‐rays such as X‐ray diffraction (XRD). This emphasizes that beam‐sample interactions must be considered during XRD in liquid media and shows that reaction kinetics do not provide a threshold dose rate for gold nucleation relevant to LP‐TEM and XRD. Furthermore, it is unveiled that oxidative etching of gold nanoparticles depends on both, precursor concentration, and dose rate. This dependency is exploited to probe the electron beam‐induced shift in Gibbs free energy landscape by analyzing critical radii of gold nanoparticles.

Revealing Controlled Etching Behaviors of Gold Nanobipyramids by Carbon Film Liquid Cell Transmission Electron Microscopy

“…Therefore, the accumulation of [AuCl 4 ] − ions would change the oxidizing environment around the Au NBPs and ultimately affect the etching behavior. According to previous reports, the calculated concentration of the oxidizing species is closely related to the electron energy and dose rate 34,35. The electron beam dose rate was 280 e − •Å −2 •s −1 in our experiment.…”

“…However, the three-dimensional (3D) morphology of the metal nanoparticle catalyst affects its catalytic properties. The surface atoms have different reactivity on facets, edges, and corners. − The etching process may occur in edges or corners or both. Previously, the etching of metal nanoparticles was studied mainly relying on ex situ characterization under reaction environments. , We expect that in situ monitoring of the nanoparticle oxidation etching process can be achieved, which will allow us to understand the mechanism in more accuracy and detail …”

Nonclassical Nucleation and Growth of Pd Nanocrystals from Aqueous Solution Studied by In Situ Liquid Transmission Electron Microscopy

“…This indirect reduction of the encapsulated Pd precursor by the electron beam thus triggers the formation of Pd nanoparticles once the Pd concentration exceeds the solubility limit. We should keep in consideration that the radiochemistry in the solution might be affected by the local change in temperature induced by electron-beam heating. − Despite the fact that we cannot measure the temperature inside the graphene-based nanoreactors, we conclude that the temperature increase in these liquid pockets is moderate and that it is the radiochemistry of the electron beam that governs the observed reaction because the aqueous solvent remains liquid and does not form gaseous pockets. Moreover, the graphene windows and the small volume warrant that possible heat can be dissipated quickly, particularly when considering the scanning mode of imaging, which does not stationarily illuminate the entire field of view as this is the case in the broad beam transmission electron microscopy (TEM) mode.…”

Electric Field-Induced Water Condensation Visualized by Vapor-Phase Transmission Electron Microscopy

“…In these experiments, the liquid or gas can be held at atmospheric pressure and the temperature controlled between room temperature and the normal boiling point of water. For instance, prior work has utilized liquid-phase TEM to investigate nanoscale droplet transport dynamics on a flat solid surface, wetting of water films on nanostructured surfaces, and the behavior of nanoscale bubbles in water. − TEM beam electrons have energies ranging from 100 to 300 keV, which ionize in the sample and cause omnipresent electron beam effects such as heating, electric charging, and radiolysis. ,− While these electron beam–sample interactions have been thoroughly explored for liquid-phase nanoparticle synthesis and organic samples, , their impact on aerosol-phase phenomena remains unknown. Cataloging and quantifying how the electron beam impacts aerosol-phase phenomena (condensation, evaporation, and nucleation) and the associated physical parameters (humidity, diffusivity, and temperature) during in situ TEM is critical to delineating these phenomena from the aerosol phenomena of interest.…”