Pristine and oxidised Ag-nanoparticles on free-standing graphene as explored by X-ray photoelectron and Auger spectroscopy

•Nanofocusing photoelectron spectroscopy using zone-plate X-ray optics.•Exploration of Ag-nanoparticles (2–20 nm) on free-standing graphene via X-ray photoelectron and Auger spectroscopy.•Formation of a thin passivating oxide layer upon oxidation of Ag-nanoparticles.•Size-dependent morphology change (3D→2D) of Ag-nanoparticles.•Final state Coulomb shift upon photoionization of oxidized Ag-nanoparticles.