Yamazaki Tomoya, Kimura Yuki
Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo060-0819, Japan.
Microsc Microanal. 2021 Mar 22:1-7. doi: 10.1017/S1431927621000179.
In situ liquid cell transmission electron microscopy (LC-TEM) is an innovative method for studying the processes involved in the formation of crystals in liquids. However, it is difficult to capture early stages of crystallization because of the small field of view and the unfavorable changes in sample composition resulting from electron-beam radiolysis. Nevertheless, if the radiolysis required to induce the crystallization of a sample could be controlled in LC-TEM, this would be advantageous for observing the crystallization process. Here, we examined this possibility by using a mixture of sodium chlorate (NaClO3) and acetone in the LC-TEM. The electron beam induced the formation of dendritic crystals in a saturated acetone solution of NaClO3; moreover, these crystals consisted of sodium chloride (NaCl), rather than NaClO3, suggesting that chloride ions (Cl−), which were not present in the initial solution, were generated by radiolysis of chlorate ions ${\rm \lpar ClO}_3^- \rpar$. As a result, the solution then supersaturated with NaCl because its solubility in acetone is much lower than that of NaClO3. The combination of radiolysis and a solvent in which a solute is much less soluble is potentially useful for establishing crystallization conditions for materials that are difficult to crystallize directly in LC-TEM experiments.
原位液体池透射电子显微镜（LC-TEM）是一种研究液体中晶体形成过程的创新方法。然而，由于视野小以及电子束辐解导致样品成分发生不利变化，难以捕捉结晶的早期阶段。尽管如此，如果能在LC-TEM中控制诱导样品结晶所需的辐解，这将有利于观察结晶过程。在此，我们通过在LC-TEM中使用氯酸钠（NaClO3）和丙酮的混合物来研究这种可能性。电子束在NaClO3的饱和丙酮溶液中诱导形成树枝状晶体；此外，这些晶体由氯化钠（NaCl）组成，而非NaClO3，这表明初始溶液中不存在的氯离子（Cl−）是由氯酸根离子（ClO3−）的辐解产生的。结果，溶液随后因NaCl在丙酮中的溶解度远低于NaClO3而对NaCl过饱和。辐解与溶质在其中溶解度低得多的溶剂相结合，可能有助于为在LC-TEM实验中难以直接结晶的材料建立结晶条件。
