Single atoms swim inside the liquid cell of a graphene sandwich

Amazing stuff!

"... a new approach that enables them to track the motion of single atoms on a surface when that surface is surrounded by liquid. They showed that the atoms behave very differently under these circumstances than they do in vacuum. ... .

In their experiments, the ... researchers sandwiched their sample – in this case, atomically-thin sheets of molybdenum disulphide – between two sheets of boron nitride (BN) in a TEM. They then used lithography to etch holes in specific regions of the BN so that the sample could be suspended in the areas where the holes overlapped. Finally, they added two graphene layers above and below the BN and used these to trap a liquid in the holes. The resulting structure, in which the sample is suspended between two layers of liquid, is just 70 nm thick ...

Thanks to this so-called double graphene liquid cell, the researchers were able to acquire videos of the single atoms “swimming” while surrounded by liquid. ..."

From the abstract:

"Single atoms or ions on surfaces affect processes from nucleation to electrochemical reactions and heterogeneous catalysis. Transmission electron microscopy (TEM) is a leading approach for visualizing single atoms on a variety of substrates. It conventionally requires high vacuum conditions, but has been developed for in situ imaging in liquid and gaseous environments with a combined spatial and temporal resolution that is unmatched by any other method —notwithstanding concerns about electron beam effects on samples. ... Graphene liquid cells, on the other hand, have enabled atomic resolution imaging of metal nanoparticles in liquids. Here we show that a double graphene liquid cell, comprised of a central molybdenum disulphide monolayer separated by hexagonal boron nitride spacers from the two enclosing graphene windows, makes it possible to monitor with atomic resolution the dynamics of platinum adatoms on the monolayer in an aqueous salt solution. By imaging over 70,000 single adatom adsorption sites, we compare the site preference and dynamic motion of the adatoms in both a fully hydrated and vacuum state. We find a modified adsorption site distribution and higher diffusivities for the adatoms in liquid phase compared to those in vacuum. ..."

Single atoms swim inside a graphene sandwich – Physics World

Tracking single atoms in liquid in a Transmission Electron Microscope (no public access)