Oxidation of size-selected clusters on graphene

Federico Loi, Physics Department, University of Trieste, Trieste, Italy

Thursday, February 2, 15:00h J. Heyrovský Institute, Seminar Room 108

Abstract

Understanding the interaction of supported metallic size-selected clusters with oxygen and their oxidation process in conditions where the mass selection is not compromised is experimentally challenging. In this talk, I will discuss how we investigated this aspect for Agn, Ptn and Fen clusters supported on epitaxial graphene combining x-ray synchrotron spectroscopy and ab initio DFT calculations. I will focus on the strategy we adopted to oxidize the clusters at T = 20 K and compare their electronic and geometric evolution with respect to their bulk counterparts. DFT calculations revealed that oxidized Agn clusters show distinct bulk-features that resemble the hybrid AgO phase, although the behavior of the d-band and of the core level binding energies is remarkably different at the sub-nanoscale. In the case of Pt, the stronger interaction with the substrate leads to a layered structure where the topmost atoms of the clusters reach a higher oxidation state than those at the cluster/graphene interface. Finally, Fen clusters show different 2p core level binding energies that can be linked to the electron density of state at the Fermi level and predict a higher reactivity for non-magic numbers. Their oxidation leads to homogeneous configurations where all the Fe atoms are in the oxidation state 2+, similarly to the FeO bulk oxide.

Federico Loi is a PhD student at the University of Trieste. He obtained his Bachelor degree in physics and Master degree in Condensed Matter Physics at the same University, and now he is enrolled in the third year of his PhD in Nanotechnology doing his research in the Nanoscale Materials Lab at the Elettra synchrotron facility in Trieste, Italy.