University of Manchester Graphene researchers have developed a new “nano-petri dish” using two-dimensional (2D) materials to develop a new technique for observing how atoms move in a liquid.

Atoms floating in liquid thanks to graphene. Image credit: The University of Manchester

The team, led by scientists from the National Graphene Institute (NGI), used stacks of 2D materials, such as graphene, to trap a liquid to really understand how the existence of a liquid changes the behavior of a solid. Their findings were published in the journal Nano letters.

For the first time, the team was able to photograph an atom “floating” in a liquid. The results could have a significant effect on how green technologies such as hydrogen production develop in the coming years.

When a liquid and a solid are in close proximity to each other, both substances adapt to the presence of the other. These atomic-scale interactions at solid-liquid interfaces control the behavior of fuel cells and batteries used to generate clean energy, as well as the efficiency of systems used to produce clean water and many biological activities.

Given the widespread industrial and scientific importance of such behavior, it is truly surprising how much we still need to learn about the fundamentals of how atoms behave on surfaces in contact with liquids. One of the reasons for the lack of information is the lack of techniques that can provide experimental data for solid-liquid interfaces.

Sarah Hay, Principal Investigator and Professor, National Graphene Institute

One of the few methods that allows the observation and analysis of individual atoms is transmission electron microscopy (TEM). The structure of the materials is set up in a vacuum, and the TEM apparatus needs a high vacuum set up.

In our work, we show that misleading information is provided if atomic behavior is studied in vacuum instead of using our liquid cells.

Dr. Nick Clark, first author of the study, National Graphene Institute

Professor Roman Gorbachev of NGI developed the stacking of 2D materials for electronics; thus, his team has developed a “double graphene liquid cell” using the same methods.

The graphene windows wrap a 2D layer of molybdenum disulfide that is fully suspended in the liquid. They were able to create perfectly regulated liquid layers thanks to their innovative design, which allowed them to record the first movies of individual atoms “floating” in a liquid.

The scientists were able to understand how the liquid affected the behavior of the atoms by studying the movements of the atoms in the videos and comparing their findings with theoretical explanations proposed by colleagues at the University of Cambridge. It was found that the liquid both accelerates the mobility of the atoms and changes their preferred resting places with respect to the underlying solid.

The researchers investigated a material that holds promise for green hydrogen production, but the experimental system they created has a wide range of potential applications.

This is an important achievement and is just the beginning – we are already looking to use this technique to help develop materials for the sustainable chemical processing needed to achieve the world’s net zero ambitions.

Dr. Nick Clark, first author of the study, National Graphene Institute

Journal reference:

Kelly, DJ, and others. (2022) Elemental mapping with nanometer resolution in graphene-based liquid TEM cells. Nano letters.


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