Breakdown of the correlation between oxidation states and core electron binding energies at the sub-nanoscale

Federico Loi, Monica Pozzo, Luca Sbuelz, Luca Bignardi, Paolo Lacovig, Ezequiel Tosi, Silvano Lizzit, Aras Kartouzian, Ulrich Heiz, Rosanna Larciprete, Dario Alf è, Alessandro Baraldi

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


X-ray photoelectron spectroscopy is a powerful analytical tool to fingerprint the atomic oxidation state. However, the well-established trend that is found for bulk, ultra-thin films and surface oxides, which is usually characterized by an incremental binding energy shift upon increasing oxidation state, may not apply at the sub-nanoscale where reduced dimensionality and quantum size effects play a relevant role. Here we investigate through a combined experimental and theoretical approach the oxidation of size-selected Ag7 and Ag11 clusters supported on graphene, revealing an anomalous Ag 3d5/2 core level shift trend upon increasing O coverage. We show that the negative core level shift trend typical of Ag reverts back in the case of the highest Ag(III) oxidation state, an effect that is due to the peculiar electronic structure of Ag nano-oxides. Our results highlight the great care needed to extend at the zero-dimensional scale the knowledge acquired for the spectral interpretation of 3D and 2D materials.

Original languageEnglish
Article number156755
JournalApplied Surface Science
StatePublished - 15 May 2023
Externally publishedYes


  • Ag Oxide
  • Core-level Photoelectron Spectroscopy
  • DFT
  • Size-selected Clusters
  • Sub-nm Clusters
  • XPS


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