For the first time, the movement of single atoms through liquid has been captured on video.
Scientists trapped and observed platinum atoms'swimming' along a surface under different pressures by combining two-dimensional materials.
The results will assist us in understanding how liquid alters the behavior of a solid with which it is in contact, which in turn could lead to the development of new substances and materials.
"It's surprising how little we still need to learn about the fundamentals of how atoms behave on surfaces in contact with liquids," said materials scientist Sarah Haigh of the University of Manchester in the United Kingdom.
"One of the main reasons for which information is lacking is the absence of methods capable of producing experimental data for solid-liquid interfaces."
The behaviors of both materials are modified where they meet, whether it be the transport of materials inside our own bodies or the ignition of chemicals inside batteries.
Researchers agree that it is extremely difficult to see the world on the atomic scale. TEM, which involves the use of a beam of electrons to create an image, is one of the few techniques available.
Even so, obtaining reliable data on the behavior of atoms this way has been difficult. Previous work in graphene liquid cells has been promising, but has yielded inconsistent results. TEM typically requires a high vacuum environment to run. This is a concern since many materials do not behave the same way under different pressure conditions.
Fortunately, a technique called TEM has been created to operate in both liquid and gaseous environments, which was employed by the group for their research.
The next step was to construct a special set of microscope "slides" to contain the hydrogen. Graphene is the ideal material for these experiments because it is two-dimensional, strong, inert, and impermeable. The team also created a double graphene liquid cell capable of using existing TEM technology.
The cells were filled with a precisely-controlled salt water solution containing platinum atoms, which the team observed moving around on a solid surface of molybdenum disulfide.
The photographs revealed some fascinating insights. For example, the atoms moved faster in liquid than outside of it, and chose different places on the solid surface to rest.
The results inside and outside of a vacuum chamber were also different, implying that fluctuations in the environment's pressure can influence how atoms behave. In addition, the results of experiments conducted in vacuum chambers will not necessarily be comparable in the real world.
"In our research, we demonstrate that misleading information is obtained when the atomic behavior is studied in vacuum rather than using our liquid cells," said materials engineer Nick Clark of the University of Manchester.
"This is a milestone, and it is only the start we're already looking to use this technique to support the development of materials for sustainable chemical processing, required to meet the world's net zero goals."
Both their methods and the conclusions they obtained have much larger implications, according to the researchers.
The article has been published in Nature.