Japanese researchers succeed in shooting the moment when a crystal is completed for the first time in the world

On January 22, 2021, a group of Professor Eiichi Nakamura of the University of Tokyo announced that he had succeeded in shooting the moment when a crystal, which had been difficult until now, was completed.

How can crystals be made? I saw that moment! --Graduate School of Science, Faculty of Science, University of Tokyo
https://www.su-tokyo.ac.jp/ja/press/2021/7211/

Capturing the Moment of Emergence of Crystal Nucleus from Disorder | Journal of the American Chemical Society
https://pubs.acs.org/doi/10.1021/jacs.0c12100

Crystallization, in which solid crystals are formed from a uniform solution , has become an indispensable technology in various fields such as pharmaceuticals and materials. However, while the structure such as the atomic arrangement in the crystal has been clarified so far, it is difficult to analyze nucleation, which is the earliest process of the crystallization phenomenon, by conventional experimental methods, and theoretical research by simulation etc. Although research has been carried out in, no definitive results have been obtained. This time, Professor Nakamura's group will observe using a special electron microscope called ' atomic resolution transmission electron microscope ' that can distinguish and observe each atom, and capture the moment of crystallization and the growth process in the image. Was successful.

Professor Nakamura's group photographed how the NaCl inside the CNT crystallizes under vacuum by encapsulating an aqueous solution of sodium chloride (NaCl) in conical carbon nanotubes (CNTs) and removing water by drying. It is said that this imaging was achieved by the special shape of the cone inducing the nucleation of NaCl at the tip of the CNT, and the nanometer-sized space inside the CNT suppressing molecular diffusion. The following is a movie shot, and you can see that 1 nanometer- sized NaCl crystal nuclei are repeatedly generated at the tip of CNT.

9 times repeated NaCl crystallization slow motion video-YouTube


In addition, this study also revealed that the pre-crystallization molecular assembly fluidly changes its structure, switching between a disordered structure and a crystal-like ordered structure, and the nucleation process. The research group states that it suggests that not only the size of the molecular assembly but also its structural dynamics play an important role in.

The time required for nucleation is reproducible, from 2 seconds to 10 seconds each time. 'By designing an appropriate space, it is possible to precisely control the nucleation process, which has been considered difficult to control, at the atomic level. It shows that it is expected to develop as a crystal size and crystal polymorph control method. ' 'It is expected to be applied to innovative molecular technologies such as designing and developing new materials with desired shapes and properties based on observations at the molecular level,' he concludes.