Highly Oxidized Gold Nanoparticles: In Situ Synthesis, Electronic Properties, and Reaction Probability Toward CO Oxidation

Highly oxidized gold nanoparticles prepared by RF-discharge under an oxygen atmosphere were studied by X-ray photoelectron spectroscopy and transmission electron microscopy depending on the particle size. A surface-like gold oxide was found in the case of small nanoparticles (1–2 nm) obtained at the first steps of deposition. With an increase of the particle size up to 5 nm, a bulklike gold oxide was formed. The O 1s spectra exhibited an oxygen peak at binding energy E_b = 529.4 eV for the surface-like oxide and E_b = 530.7 eV for the bulklike gold-oxide. The reaction probability of oxidized gold nanoparticles was examined in the reaction of CO oxidation at room temperature. The surface-like gold oxide interacted with CO with a high reaction probability of approximately 0.005, while CO interaction with the bulklike oxide was characterized by an induction period with lower reaction probability (0.001). The mechanisms of the interaction of oxidized gold nanoparticles with CO depending on its size are discussed.