Researchers from the University of Manchester, Diamond Light Source, Cardiff University and University of Sheffield have developed a graphene‑based “nano‑aquarium” platform that, for the first time, captures atomic‑resolution videos of individual gold atoms at solid-liquid interfaces in a wide range of non‑aqueous solvents.
By combining this liquid‑phase electron microscopy design with deep‑learning analysis, the team tracked the locations of more than 106 graphite‑supported gold adatoms, dimers, and larger clusters across five industrially relevant solvents, establishing a statistically robust link between solvent environment, drying kinetics and catalytic performance.
At the heart of the work is a set of nanoscale liquid cells formed by sealing tiny pockets of test liquids between ultra‑thin graphene windows just a few atoms thick. Each “nano‑aquarium” confines only about 100 attolitres of liquid - a volume roughly a billion times smaller than a raindrop - yet the graphene is mechanically strong enough to sustain transmission electron microscopy (TEM) high vacuum while remaining almost completely transparent to the electron beam. This design overcomes the long‑standing incompatibility between TEM’s vacuum requirements and liquid samples, enabling atomic‑scale imaging of processes that were previously inaccessible in realistic solvent environments.
A key fabrication innovation was to seal the graphene liquid cells while they were fully submerged in the target liquid using a thin ceramic cantilever to manipulate the graphene crystals. Earlier approaches suffered from significant evaporation during sealing, which led to large and uncontrolled changes in solvent composition and solute concentration. Here, immersed encapsulation provides precise control over the cell contents, ensuring that each experiment probes a well‑defined solvent and solute mixture and allowing fair, quantitative comparisons between different liquids.
Using an advanced TEM at the national ePSIC facility, the researchers recorded videos of gold atoms at the graphene - liquid interface for five industrial solvents, covering a broad range of polarity, boiling point and surface tension. These videos directly resolve both the gold atoms and the underlying graphene lattice, enabling the team not only to see where individual atoms move but also to quantify how their motion is guided by the atomic structure of the support. The data reveal atoms hopping between specific adsorption sites, pairing into dimers and trimers, and then aggregating into larger nanoparticles, with the detailed dynamics highly sensitive to the surrounding solvent.
To move beyond qualitative observations, the team implemented an AI‑enabled automated analysis pipeline capable of tracking the trajectories of more than a million individual gold atoms, dimers, trimers and clusters across all five liquids. This scale of analysis represents a step change from most atomic‑resolution imaging studies, which typically base conclusions on datasets of only tens or hundreds of atoms. Here, the large population enables extraction of statistically meaningful distributions of adatom coordination, cluster sizes, and spatial correlations, underpinning a quantitative picture of how solvent properties and the graphite lattice together shape interfacial atomic behavior.
The experiments demonstrate that the initial atomic dispersion of gold at the solid–liquid interface is primarily governed by solvent polarity, while the final catalyst structure is jointly controlled by solvent choice and drying kinetics. Fast drying at low temperature was found to be essential for locking in highly dispersed, catalytically active configurations before atoms can migrate and coarsen into larger particles. In particular, acetone - a common solvent combining low polarity with low boiling point and low surface tension - favored the retention of individually separated gold atoms during both the liquid phase and subsequent drying, whereas higher‑boiling liquids such as cyclohexanone and water tended to promote the growth of larger gold particles.
These structural trends were independently verified through catalytic testing performed at the Cardiff Catalysis Institute, confirming that samples with higher fractions of isolated gold atoms exhibit superior performance in relevant reactions. The results highlight the dual role of the liquid: in solution, solvent polarity controls the dispersion and mobility of gold species, while during drying, properties such as boiling point and surface tension govern how quickly and uniformly the structure is frozen in. By directly connecting solvent‑dependent interfacial dynamics to measurable catalytic activity, the work provides a mechanistic framework for rationally designing impregnation and drying protocols for single‑atom catalysts.
Beyond heterogeneous catalysis, the new platform opens a general route to studying atomic‑scale processes at solid–liquid interfaces in technologically important but previously inaccessible environments. Because the graphene liquid cells are compatible with a wide range of non‑aqueous organic solvents, the same approach can now be applied to systems relevant to fuel cells, batteries, membranes, molecular separations and precious‑metal recovery from waste streams. Instead of relying solely on ensemble‑averaged measurements that can mask nanoscale complexity, researchers can now directly watch individual atoms in liquid, understand how they interact with both the solvent and the solid substrate, and then leverage that knowledge to engineer better materials and devices.
