Scientists capture images of atoms 'swimming' in liquid

Graphene scientists from The University of Manchester have created a new ‘nano-petri dish’ using a two-dimensional (2D) material to create a new method of observing how atoms move in a liquid.

Published in the journal Nature, a team led by researchers based at the National Graphene Institute (NGI) used stacks of 2D materials such as graphene to trap liquids to better understand how the presence of liquids changes the behavior of solids.

The team was able to capture images of a single atom ‘swimming’ in a liquid for the first time. These findings could have far-reaching implications for the future development of green technologies such as hydrogen production.

When a solid surface comes into contact with a liquid, the two substances change their configuration in response to the proximity of the other. Such atomic-scale interactions at the solid-liquid interface regulate the behavior of batteries and fuel cells for clean electricity generation, as well as determine the efficiency of clean water generation and support many biological processes.

One of the lead researchers, Professor Sarah Haigh, commented: “Given the widespread industrial and scientific importance of such behavior, it is surprising how much we still have to learn about the basics of how atoms behave on surfaces in contact with liquids. One of the reasons information is missing is the absence of a technique that can generate experimental data for solid-liquid interfaces.”

Transmission electron microscopy (TEM) is one of the few techniques that allows individual atoms to be viewed and analyzed. However, the TEM instrument requires a high vacuum environment, and the structure of the material changes in a vacuum. First author, Dr Nick Clark explained: “In our work, we show that misleading information is provided if atomic behavior is studied in a vacuum rather than using our liquid cell.”

Professor Roman Gorbachev has pioneered the stacking of 2D materials for electronics but here his group has used the same technique to develop a ‘double graphene liquid cell’. The 2D molybdenum disulfide layer is completely suspended in the liquid and encapsulated by the graphene window. This new design allows them to provide a precisely controlled layer of liquid, allowing unprecedented video to be captured showing single atoms ‘swimming’ surrounded by liquid.

By analyzing how atoms move in the video and comparing it with theoretical insights provided by colleagues at Cambridge University, the researchers were able to understand the effects of fluids on atomic behavior. The liquid was found to accelerate the motion of atoms and also change the preferred resting place with respect to the underlying solid.

The team studied a promising material for green hydrogen production but the experimental technology they had developed could be used for many different applications.

Dr Nick Clark said: “This is an important achievement and it is just the beginning – we are already looking at ways to use this technique to support the development of materials for sustainable chemical processing, which are needed to achieve the world’s net zero ambitions.”

Reference:

1. Nick Clark, Daniel J. Kelly, Mingwei Zhou, Yi-Chao Zou, Chang Woo Myung, David G. Hopkinson, Christoph Schran, Angelos Michaelides, Roman Gorbachev, Sarah J. Haigh. Tracing single adatoms in liquids in a Transmission Electron Microscope. Nature, 2022; DOI: 10.1038/s41586-022-05130-0

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