For the first time, a group from the University of Tokyo and the National Institute of Advanced Industrial Science and Technology has succeeded in continuously photographing and analyzing the process of crystal nucleus formation from disordered molecular aggregates.
Conventionally, with regard to crystals, while static structures such as atomic arrangements in crystals have been clarified, it has been difficult to observe the dynamic process of "crystallization" in detail at the atomic level.In particular, nucleation, which is the earliest process of the crystallization phenomenon, is extremely difficult to analyze by conventional experimental methods due to its probabilistic behavior and minute time / space scale.
Through the development of a technology called "atomic resolution single molecule real-time electron microscope (SMART-EM) imaging method", this group has been engaged in research to record the movement of individual small molecules and molecular aggregates by video recording. rice field.In line with this technology, carbon nanotubes (CNTs) are used as nanoflasks to spatially control crystallization, and direct observation of crystallization phenomena at the atomic level has been achieved.
In the experiment, an aqueous solution of sodium chloride (NaCl) was encapsulated in a conical CNT, and then water was removed by drying. The conical shape induced self-assembly and nucleation of NaCl molecules at the tip of the CNT, and nanometers inside the CNT. The size-restricted space suppressed molecular diffusion, and NaCl crystal nuclei of about 1 nanometer were repeatedly formed with good reproducibility.It is a result showing that the nucleation process can be controlled at the atomic level by designing an appropriate space.
In addition, for the first time in this study, the molecular assembly before the formation of crystal nuclei, whose properties have not been clarified so far, moves back and forth between ordered and disordered structures similar to crystals. It also turned out to have sex.
This achievement, which found new findings by reviewing the crystallization process from a microscopic perspective, will lead to innovative technologies such as designing and developing new materials with desired shapes and properties based on observations at the molecular level. It is expected.
Paper information:[Journal of the American Chemical Society] Capturing the Moment of Emergence of Crystal Nucleus from Disorder
