Early Detection of Nucleation Events From Solution in LC-TEM by Machine Learning.

Hiroyasu Katsuno,Ichigaku Takigawa,Tomoya Yamazaki,Yuki Kimura

doi:10.3389/fchem.2022.818230

Hiroyasu Katsuno, Ichigaku Takigawa + Show 2 more

Open Access

https://doi.org/10.3389/fchem.2022.818230

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Abstract

To support the detection, recording, and analysis of nucleation events during in situ observations, we developed an early detection system for nucleation events observed using a liquid-cell transmission electron microscope. Detectability was achieved using the machine learning equivalent of detection by humans watching a video numerous times. The detection system was applied to the nucleation of sodium chloride crystals from a saturated acetone solution of sodium chlorate. Nanoparticles with a radius of more greater than 150 nm were detected in a viewing area of 12 μm × 12 μm by the detection system. The analysis of the change in the size of the growing particles as a function of time suggested that the crystal phase of the particles with a radius smaller than 400 nm differed from that of the crystals larger than 400 nm. Moreover, the use of machine learning enabled the detection of numerous nanometer sized nuclei. The nucleation rate estimated from the machine-learning-based detection was of the same order as that estimated from the detection using manual procedures.

Highlights

The nucleation of crystals is the first stage of crystallization and the origin of all materials
We proposed a method for the early detection of nucleation phenomena using TEM observations in conjunction with the machine learning
We inferred from the high growth rate, the circular shape, small interfacial energy that the observed unknown phase was an amorphous or dense-liquid phase of NaCl

Summary

Introduction

The nucleation of crystals is the first stage of crystallization and the origin of all materials. Because materials have a wide range of applications, including metals, chemical compounds, and biological materials, numerous studies of the crystallization of materials have been conducted over the past 50 years. The general understanding of crystallization is summarized in the classical nucleation theory (Markov, 2003). In the classical nucleation theory, only the exchange of single growth units is considered and there is only one nucleation pathway. The simple classical nucleation theory provides important basic concepts, such as a critical nucleus, and observable physical quantities, such as the nucleation rate. The validity of the nucleation theory on an atomic scale has been studied through the two-dimensional epitaxial growth of metals and semiconductors using a combination of molecular beam epitaxy and scanning probe microscopy (Michely and Krug, 2004)

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