Abstract
Recent advances in graphene liquid cells for in situ transmission electron microscopy (TEM) have opened many opportunities for the study of materials transformations and chemical reactions in liquids with high spatial resolution. However, the behavior of thin liquids encapsulated in a graphene liquid cell has not been fully understood. Here, we report real time TEM imaging of the nanoscale dynamic behavior of liquids in graphene nanocapillaries. Our observations reveal that the interfaces between liquid and gas bubble can fluctuate, leading to the generation of liquid nanodroplets near the interfaces. Liquid nanodroplets often show irregular shape with dynamic changes of their configuration under the electron beam. We consider that the dynamic motion of liquid-gas interfaces might be introduced by the electrostatic energy from transiently charged interfaces. We find that improving the wettability of graphene liquid cells by ultraviolet-ozone treatment can significantly modify the dynamic motion of the encapsulated liquids. Our study provides valuable information of the interactions between liquid and graphene under the electron beam, and it also offers key insights on the nanoscale fluid dynamics in confined spaces.
Highlights
Liquid cell transmission electron microscopy (TEM) enables the direct observation of dynamic phenomena in liquids, including electrochemical reactions, crystal growth, and the activity of biological materials in their native environment
We characterize the aqueous solution encapsulated in graphene liquid cells using TEM operated at 200 kV
We have studied the dynamic behavior of aqueous liquid encapsulated between two graphene nanosheets using in situ TEM
Summary
Liquid cell transmission electron microscopy (TEM) enables the direct observation of dynamic phenomena in liquids, including electrochemical reactions, crystal growth, and the activity of biological materials in their native environment. Dynamic Behavior of Nanoscale Liquids in Graphene Liquid Cells Revealed by In Situ Studied dynamic behavior of nanoscale liquids in graphene liquid cells using in situ TEM. Imaged liquid nanodroplet formation resulting from dynamic motion of liquid-gas interfaces.
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