Physicists Capture Images of Single Atoms ‘Swimming’ in Liquid

Using a transmission electron microscope and a double graphene liquid cell, physicists at the UK’s National Graphene Institute have monitored the dynamics of atoms in an aqueous salt solution. Their findings could have widespread impact on the future development of green technologies such as hydrogen production.

Clark et al. show that a double graphene liquid cell makes it possible to monitor with atomic resolution the dynamics of platinum adatoms on the monolayer in an aqueous salt solution. Image credit: Clark et al., doi: 10.1038/s41586-022-05130-0.

When a solid surface is in contact with a liquid, both substances change their configuration in response to the proximity of the other.

Such atomic scale interactions at solid-liquid interfaces govern the behavior of batteries and fuel cells for clean electricity generation, as well as determining the efficiency of clean water generation and underpinning many biological processes.

“Given the widespread industrial and scientific importance of such behavior it is truly surprising how much we still have to learn about the fundamentals of how atoms behave on surfaces in contact with liquids,” said Professor Sarah Haigh, senior author of a paper published in the journal Nature.

“One of the reasons information is missing is the absence of techniques able to yield experimental data for solid-liquid interfaces.”

Transmission electron microscopy (TEM) is one of only a few techniques that allows individual atoms to be seen and analyzed.

However, the TEM instrument requires a high vacuum environment, and the structure of materials changes in a vacuum.

“In our work, we show that misleading information is provided if the atomic behavior is studied in vacuum instead of using our liquid cells,” said Dr. Nick Clark, first author on the study.

For their study, the authors developed a double graphene liquid cell, comprised of a central molybdenum disulfide monolayer separated by hexagonal boron nitride spacers from the two enclosing graphene windows.

This design allowed the team to provide precisely controlled liquid layers, enabling the first videos to be captured showing the single atoms ‘swimming’ around surrounded by liquid.

By analyzing how the atoms moved in the videos and comparing to theoretical insights, the researchers were able to understand the effect of the liquid on atomic behavior.

The liquid was found to speed up the motion of the atoms and also change their preferred resting sites with respect to the underlying solid.

The researchers studied a material that is promising for green hydrogen production, but the experimental technology they have developed can be used for many different applications.

“This is a milestone achievement and it is only the beginning — we are already looking to use this technique to support development of materials for sustainable chemical processing, needed to achieve the world’s net zero ambitions,” Dr. Clark said.

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N. Clark et al. Tracking single adatoms in liquid in a Transmission Electron Microscope. Nature, published online July 27, 2022; doi: 10.1038/s41586-022-05130-0

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