A preparation method for silver-oxide containing nanoparticles is described. The suggested approach allows varying the oxidation degree from monoxide to an oxygen-rich state resembling superoxide The method is based on magnetron reactive sputtering and vapour aggregation, and utilizes silver-oxygen interaction in the vapour phase - prior to the nanoparticle aggregation from the vapour. Synchrotron-based photoelectron spectroscopy - a local probing method with high chemical sensitivity - allows 'on-the-fly' analysis of the composition and oxidation degree in nanoparticles, before any deposition of the particles. Preparation and properties of oxygen-rich nanoparticles are discussed in connection to the catalytic processing of economically important hydrocarbons. (C) 2014 Elsevier B.V. All rights reserved.