Characterization and preservation of gold oxides prepared by an oxygen-dc glow discharge from gold films and studied by X-ray photoelectron spectroscopy

Gold oxides with thicknesses of less than 1 nm that were prepared by an oxygen-dc glow discharge over various periods (0.5–10 min) from gold films at room temperature were characterized by X-ray photoelectron spectroscopy (XPS), and a preservation method was developed for these oxides. The O 1s spectra show three oxygen species comprising components I, II, and III in the gold oxides. Components I and II are both stable and assigned to hydroxyl groups. The angular dependence of the XPS spectra of the gold oxides indicates that the oxygen species of components I and II are present in this order from the top surface of the gold oxide (component III). The gold oxides decompose after 36 h at room temperature and decompose immediately at temperatures exceeding 121 °C in a dark atmosphere. These gold oxides also decompose under ultraviolet (UV) light irradiation (254, 302, and 365 nm) at room temperature and decompose more rapidly in water vapor at the shorter wavelengths. These findings indicate that the gold oxide decomposition is accelerated via a reaction with excited water molecules produced by UV light absorption. The gold oxide decomposes after 6 h in water but decomposes more slowly in hydrocarbons (hexane, octane, and dodecane) at room temperature in a dark atmosphere. The gold oxide can be preserved in the oxidized state for 84 days in anhydrous dodecane. This simple preservation method of a gold oxide immersed in a hydrocarbon with low water content will be helpful for practical use in future applications.