From clusters to atoms: spontaneous fragmentation of metal nanoclusters on magnetite
Size-selected clusters can lose their identity upon soft landing, as strong interactions with magnetite drive their spontaneous fragmentation.
G. Coltrioli, D. Perco et al.,
J. Am. Chem. Soc. 148, 41612 (2026)
|
Below 1 nm, the properties of matter are exquisitely sensitive to the exact number and arrangement of atoms. This has made size-selected clusters particularly attractive as model systems for understanding how catalytic and functional properties emerge between the atomic and bulk limits. However, this approach implicitly assumes that a cluster reaching a surface preserves, at least to some extent, the atomic identity that was so carefully selected before deposition. Our work shows that this assumption can fail completely.
We investigate the deposition of extremely small, mass-selected early-transition-metal clusters onto a well-defined magnetite surface, Fe₃O₄(001). Because the clusters are selected in the gas phase according to their exact mass, the number of metal atoms reaching the surface is precisely known. Their evolution after soft landing is followed by combining high-resolution photoelectron spectroscopy with scanning probe microscopy and first-principles calculations. Rather unexpectedly, the deposited clusters do not necessarily remain intact.
For specific cluster sizes and compositions, the interaction with magnetite is sufficiently strong to induc spontaneous fragmentation already at room temperature. The surface therefore does much more than simply immobilize the incoming clusters: it actively reshapes them and can ultimately destroy their original structure. The driving force originates from the strong interaction between the early transition-metal atoms and the oxygen atoms of the oxide surface.
Formation of new metal–oxygen bonds can compensate, or even overcompensate, the energetic cost required to break the metal–metal bonds within the cluster. As a consequence, fragmentation becomes energetically favorable without requiring high-temperature activation.
The process produces highly dispersed surface species and, under appropriate conditions, even isolated metal atoms derived directly from the fragmentation of the deposited clusters.
The relevant nanoscale object is no longer necessarily the cluster that was produced and mass-selected before deposition, but rather the structure resulting from the competition between intracluster cohesion and cluster–surface interaction. |
The calculations reveal how this interaction modifies both the geometry and electronic structure of the incoming clusters and identifies the energetic pathway leading from an intact cluster to dispersed surface species. The experiments provide direct spectroscopic evidence that the chemical environment of the deposited atoms changes profoundly upon interaction with the oxide. Together, experiment and theory therefore establish a microscopic picture in which cluster fragmentation is an intrinsic consequence of the energetics of the supported system rather than an accidental effect of deposition. The result also has important implications for single-atom catalysis. Isolated atoms on oxide surfaces are commonly prepared by depositing individual atoms or by exploiting specific trapping sites that prevent their aggregation. Our results demonstrate a conceptually different pathway: single atoms can emerge spontaneously from larger, precisely defined clusters through support-induced fragmentation. This suggests that the formation of atomically dispersed species may in some cases be governed by processes occurring immediately upon cluster–support contact. More generally, our findings emphasize that the properties of supported nanoclusters cannot be understood by considering the free cluster and the substrate as two essentially independent components. At the sub-nanometric scale, the interaction with the support can become comparable to, or stronger than, the forces holding the cluster itself together. The surface can therefore determine not only where a cluster binds and what its electronic structure becomes, but even whether the cluster continues to exist as a cluster at all. This provides a broader perspective for designing supported nanomaterials: controlling cluster size before deposition is only the first step; understanding whether that size and structure survive contact with the support is equally fundamental. Retrieve article Room-Temperature Adsorption on Magnetite Induces Spontaneous Fragmentation of Early Transition-Metal Size-Selected Nanoclusters Gabriele Coltrioli, Deborah Perco, Luca Sementa, Marco Bianchi, Ancrea Berti, Mikhail Bandurist, Paolo Lacovig, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Alessandro Fortunelli, and Alessandro Baraldi |
|
