Yashima Yuga, Yamazaki Tomoya, Kimura Yuki
Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-ku, Sapporo 060-0819, Japan.
ACS Omega. 2024 Sep 12;9(38):39914-39924. doi: 10.1021/acsomega.4c05477. eCollection 2024 Sep 24.
In situ liquid-cell transmission microscopy has attracted much attention as a method for the direct observations of the dynamics of soft matter. A graphene liquid cell (GLC) has previously been investigated as an alternative to a conventional SiN liquid cell. Although GLCs are capable of scavenging radicals and providing high spatial resolutions, their production is fundamentally stochastic, and a significant compositional change in liquids encapsulated in GLCs has recently been pointed out. We found that graphene-based liquid cells were formed in nano- to micrometer sizes with high reproducibility when the concentration of the encapsulated aqueous salt solution was high. In contrast, when we revisited conventional fabrication methods, water-encapsulated GLC was formed with low yield, and any electron diffraction spots from ice were not confirmed by a cooling experiment. The reason for this was the presence of intrinsic defects in the graphene, the presence of which we confirmed by the etch-pit method. The shrinkage of a water-encapsulated cell and a decrease in the bubble area in an aqueous (NH)SO solution cell suggested that volatile water molecules and gas molecules can leak from the cells during the fabrication and observation processes. Further revision of the conditions for the formation of liquid cells and a reduction in the number of intrinsic graphene defects are expected to lead to the provision of graphene-based liquid cells capable of encapsulating dilute aqueous solutions or pure water.
原位液池透射显微镜作为一种直接观察软物质动力学的方法备受关注。石墨烯液池（GLC）此前已被研究作为传统氮化硅液池的替代方案。尽管GLC能够清除自由基并提供高空间分辨率，但其制备从根本上来说是随机的，并且最近有人指出，封装在GLC中的液体存在显著的成分变化。我们发现，当封装的盐水溶液浓度较高时，基于石墨烯的液池能够以高重现性形成纳米到微米尺寸。相比之下，当我们重新审视传统制备方法时，水封装的GLC产率较低，并且冷却实验未证实来自冰的任何电子衍射斑点。原因是石墨烯中存在固有缺陷，我们通过蚀坑法证实了其存在。水封装液池的收缩以及硫酸铵水溶液液池中气泡面积的减小表明，挥发性水分子和气体分子在制备和观察过程中可能会从液池中泄漏。进一步改进液池形成条件并减少石墨烯固有缺陷的数量，有望提供能够封装稀水溶液或纯水的基于石墨烯的液池。
