Scientists have observed atoms that remain motionless within liquid metals at high temperatures, influencing how materials solidify. Using advanced microscopy, researchers from the University of Nottingham and the University of Ulm captured this phenomenon in molten metal nanoparticles. The finding reveals a new hybrid state of matter with potential implications for catalysis and materials engineering.
In a study published on December 9, 2025, in ACS Nano, researchers utilized transmission electron microscopy to observe the solidification of molten metal nano-droplets, such as those made from platinum, gold, and palladium. The experiments involved heating nanoparticles deposited on graphene, which served as a thin support to facilitate melting. Surprisingly, while most atoms moved rapidly, some remained fixed in place, anchored to point defects in the graphene even at extreme temperatures.
Professor Andrei Khlobystov of the University of Nottingham, who led the team, explained, "When we consider matter, we typically think of three states: gas, liquid, and solid. While the behavior of atoms in gases and solids is easier to understand and describe, liquids remain more mysterious." Dr. Christopher Leist, who conducted the microscopy at Ulm's SALVE instrument, noted that focusing the electron beam created additional defects, allowing control over the number of stationary atoms.
These pinned atoms disrupt crystal growth during solidification. When few are present, crystals form normally. However, a high density of stationary atoms can form rings, creating "atomic corrals" that trap the liquid in a supercooled state. For platinum, this corralled liquid persists at temperatures as low as 350 degrees Celsius—over 1,000 degrees below its typical freezing point—before forming an unstable amorphous solid.
Professor Ute Kaiser highlighted the dual nature of electrons in the observations: "Our experiments have surprised us as we directly observe the wave-particle duality of electrons in the electron beam." This marks the first corralling of atoms, previously seen only with photons and electrons.
Dr. Jesum Alves Fernandes emphasized applications: "The discovery of a new hybrid state of metal is significant. Since platinum on carbon is one of the most widely used catalysts globally, finding a confined liquid state with non-classical phase behavior could change our understanding of how catalysts work."
Funded by the EPSRC's Metal Atoms on Surfaces and Interfaces (MASI) program, the work suggests potential for designing efficient catalysts and new materials combining liquid and solid properties.
