Atoms swimming in liquid encapsulated by graphene. Image: The University of Manchester.
Atoms swimming in liquid encapsulated by graphene. Image: The University of Manchester.

Graphene scientists at the University of Manchester in the UK have created a novel ‘nano-petri dish’ using two-dimensional (2D) materials to create a new method for observing how atoms move in liquid.

The team, led by researchers based at the National Graphene Institute (NGI), used stacks of 2D materials like graphene to trap liquid in order to further understand how the presence of liquid changes the behavior of the solid.

The team were able to capture images of single atoms ‘swimming’ in liquid for the first time. These findings, reported in a paper in Nature, could have widespread impact on the future development of green technologies such as hydrogen production.

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 behaviour of batteries and fuel cells for generating clean electricity, as well as determining the efficiency of clean water generation and underpinning many biological processes.

“Given the widespread industrial and scientific importance of such behaviour 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 Sarah Haigh, one of the lead researchers. “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 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 behaviour is studied in vacuum instead of using our liquid cells,” explained first author Nick Clark.

Roman Gorbachev at NGI has pioneered the stacking of 2D materials for electronics, but in this study his group used those same techniques to develop a ‘double graphene liquid cell’. A 2D layer of molybdenum disulphide was fully suspended in liquid and encapsulated by graphene windows. This novel design allowed the researchers to produce precisely controlled liquid layers, which, in turn, allowed them to capture unprecedented videos showing single atoms ’swimming’ around surrounded by liquid.

By analyzing how the atoms moved in the videos and comparing this to theoretical insights provided by colleagues at Cambridge University in the UK, the researchers were able to understand the effect of the liquid on atomic behaviour. They found that the liquid sped-up the motion of the atoms and also changed their preferred resting sites with respect to the underlying solid.

The team 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,” said Clark.

This story is adapted from material from the University of Manchester, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.