Oxidation at the sub-nanoscale: oxygen adsorption on graphene-supported size-selected Ag clusters

Abstract

The evolution of the aggregation of condensed matter from single atoms to three-dimensional structures represents an important topic in nanoscience, since it contains essential information to achieve tailor-made growth of...

The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters

“… nanoclusters with n = 11, 12, 13, 15 and 20 were deposited on graphene/Ru(0001), where they are electrically neutralized. Graphene/Ru(0001) is a very stable and highly corrugated 2D material which was already adopted for the growth and deposition of atomic clusters 42 , 43 . The morphology of this template reduces the cluster mobility as they tend to remain confined in the valley regions of the moiré lattice 44 .…”

“…On the contrary, we show that the oxidation process of Fe nanoclusters leads to a stable Fe(II) oxide compound, as confirmed by negligible Fe 2p 3/2 spectral changes upon further oxygen exposure. It is important to stress out that the oxidation method that we employed providing atomic oxygen at very low temperatures is extremely efficient, as it was proved for the case of Pt(111) 67 and for the oxidation of size selected Ag clusters where atoms in the clusters reached an oxidation state 3+ 43 . Conversely, the hindering towards a 3+ oxidation state in iron may be closely related to size of the unit cells of iron oxide compounds that include Fe(III) ions and higher density of oxygen atoms.…”

“…Nanoclusters oxidation was obtained employing a photodissociation approach at T = 20 K. At this temperature, it is possible to achieve a high degree of oxidation inducing the O 2 dissociation by soft x-rays irradiation as schematically described in Fig. 1 43,[67][68][69] . After being exposed to molecular oxygen (Fig.…”