Scientists reveal the first images of atoms “swimming” in liquid

The movement of individual atoms through the liquid was first captured by the camera.

Using a sandwich of materials so thin that they are actually two-dimensional, the scientists trapped and observed platinum atoms “swimming” along a surface under varying pressures.

The results will help us better understand how the presence of liquid alters the behavior of a solid it is in contact with – which, in turn, has implications that it could in the development of new substances and materials.

“Given the widespread industrial and scientific importance of such behavior, it is truly amazing how much we still have to learn about the fundamentals of how atoms behave on surfaces in contact with liquids,” explained materials scientist Sarah Haigh of the University of Manchester in United Kingdom .

“One of the reasons why information is lacking is the absence of techniques capable of producing experimental data for solid-liquid interfaces.”

When a solid and a liquid are in contact with each other, the behaviors of both materials change where they meet. These interactions are important for understanding a wide range of processes and applications, such as the transport of materials within our bodies or the movement of ions within batteries.

As the researchers note, it is extremely difficult to see the world on an atomic scale. Transmission electron microscopy (TEM), which uses an electron beam to generate an image, is one of the few techniques available.

Even so, obtaining reliable data on the behavior of atoms in this way was complicated. Previous work on graphene liquid cells has been promising, but has yielded inconsistent results. Additionally, TEM typically requires a high vacuum environment to function. This is a problem as many materials do not behave the same under different pressure conditions.

Thankfully, a form of TEM was developed to operate in liquid and gaseous environments, which is what the team employed for their research.

The next step was to create a special set of microscope “slides” to hold the atoms. Graphene is the ideal material for these experiments, because it is two-dimensional, strong, inert and waterproof. Building on previous work, the team developed a dual graphene liquid cell capable of working with existing TEM technology.

This cell was filled with a precisely controlled saltwater solution containing platinum atoms, which the team observed moving on a solid molybdenum disulfide surface.

The images revealed some fascinating insights. For example, atoms move faster in the liquid than outside it and choose different places on the solid surface to rest.

Furthermore, the results inside and outside a vacuum chamber were different, suggesting that changes in ambient pressure can affect the behavior of atoms. Furthermore, the results of experiments obtained in vacuum chambers will not necessarily be indicative of such behavior in the real world.

“In our work we show that misleading information is given if atomic behavior is studied in a vacuum instead of using our liquid cells,” said materials engineer Nick Clark of the University of Manchester.

“This is an important milestone and it is only the beginning: we are already trying to use this technique to support the development of materials for sustainable chemical processing, necessary to achieve the net zero ambitions of the world.”

The material the team studied is relevant to green hydrogen production, but both their techniques and their results have much broader implications, the researchers said.

The document was published in Nature.

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