Microscopy and Microanalysis | 2019
Electron-Beam-Induced Nucleation in an Antisolvent
Abstract
The crystallization from a solution is an important process in many systems, such as the creation of nanomaterials, the crystallization of proteins for molecular structure analysis, the production of minerals from living organisms, etc. In order to understand its physical picture, in situ observation using a variety of microscopies is a powerful method for visualizing such process directly. However, the understanding of early stages of crystallization, especially appearance of crystal nuclei (nucleation) and subsequent crystal growth under sub-micrometer scale, is still limited because of limitation of techniques to observe these rapid, unexpected and small-scale phenomena in real time. Liquid cell transmission electron microscopy (LC-TEM) is a promising method for observing the early stages of crystallization directly because the spatial resolution of this method is in nanometer scale [1]. In fact, several groups succeeded in observing the nucleation of calcium carbonate [2] and protein [3] crystals using LC-TEM, and these observations suggest that the pathways of the nucleation are multiple, and the nucleation of some crystalline phases are multistep. However, behind the mechanisms in the selectivity of the pathways and steps of nucleation are still incompletely understood. One of the reasons of this problem is great difficulty of capturing a moment of a nucleation event because the observable area of this method is small (< 100 μm2) and the event is typically very rare in the tiny volume within the area. In order to observe nucleation events efficiently, a supersaturation of a sample solution should be increased with observing the solution. To make the situation, we focus on using the anti-solvent crystallization technique, which crystallize a solute to add a solvent with extremely low solubility of the solute (antisolvent), to LC-TEM. Here we report our attempts to observe the nucleation of salt crystals using their anti-solvent by LC-TEM.