Liquid‐Phase Transmission Electron Microscopy for Studying Colloidal Inorganic Nanoparticles

Abstract

For the past few decades, nanoparticles of various sizes, shapes, and compositions have been synthesized and utilized in many different applications. However, due to a lack of analytical tools that can characterize structural changes at the nanoscale level, many of their growth and transformation processes are not yet well understood. The recently developed technique of liquid-phase transmission electron microscopy (TEM) has gained much attention as a new tool to directly observe chemical reactions that occur in solution. Due to its high spatial and temporal resolution, this technique is widely employed to reveal fundamental mechanisms of nanoparticle growth and transformation. Here, the technical developments for liquid-phase TEM together with their application to the study of solution-phase nanoparticle chemistry are summarized. Two types of liquid cells that can be used in the high-vacuum conditions required by TEM are discussed, followed by recent in situ TEM studies of chemical reactions of colloidal nanoparticles. New findings on the growth mechanism, transformation, and motion of nanoparticles are subsequently discussed in detail.

The Mixed-Electrode Concept for Understanding Growth and Aggregation Behavior of Metal Nanoparticles in Colloidal Solution

“…While the Lamer model seems to be valid in several cases [27,28], it is unable to explain all observations. Probably, the model is not applicable for the formation of all colloidal metal nanoparticles by chemical reduction of metal ions or complex compounds in liquid phase.…”

Investigating Dynamic Processes of Nanomaterials Using in Situ Liquid Phase TEM Technologies: 2014-2019

“…3 In 2018, Kim et al have summarized the application of liquid phase TEM in the studying of colloidal inorganic nanoparticles in the aspect of the growth mechanism, transformation and motion of those nanoparticles. 40 Most recently, in 2019, Shi et al have described the formation of nanocrystal electrocatalysts studied by liquid phase TEM. 6 It shows that liquid cell TEM promises great potential for promoting the science of nanoparticles synthesis.…”

In Situ Techniques for Probing Kinetics and Mechanism of Hollowing Nanostructures through Direct Chemical Transformations

“…It becomes extremely challenging to in situ probe the hollowing process of colloidal nanoparticles in volatile liquids, which easily vaporize under the low pressure of EM operation to damage the microscopes. Benefiting from the significant advance in microfabrication and materials engineering, miniaturized cells have been successfully fabricated to place liquid dispersions of colloidal nanoparticles in TEM chambers for in situ study . A typical in situ TEM liquid cell is constructed with two electron‐transparent Si 3 N 4 films of < 100 nm in thickness, which are separated to provide a thin space (usually < 200 nm) to host the desired colloidal nanoparticle dispersions.…”