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

Reaction Monitoring of Gold Oxides Prepared by an Oxygen-dc Glow Discharge from Gold Films in Various Aqueous Solutions by a Surface Plasmon Resonance-based Optical Waveguide Sensing System and X-ray Photoelectron Spectroscopy

“…Gold oxides can also be preserved for long periods in hydrocarbons (hexane, octane, and dodecane). 32 The results above indicate that gold oxide remains stable in these solvents and that these solvents are thus suitable for studying the oxide reactivity in the solutions.…”

“…The gold oxide layers on 50-nm-thick gold films were prepared by vacuum deposition of gold (>99.99%, Tanaka Kikinzoku Kogyo, Tokyo, Japan) on cleaved mica substrates (dimensions: 9 mm × 18 mm × 0.1 mm; Nisshin EM, Tokyo, Japan) followed by an oxygen-dc glow discharge at room temperature under high vacuum (<6.7×10 −4 Pa) conditions. 31,32 A calibrated thickness monitor (XTM/2, Leybold Inficon, East Syracuse, NY, USA) was used to measure both the deposition rate and the gold film thickness. An oxygen-dc glow discharge (10 Pa, 5 mA, 10 min) from a high-purity oxygen (>99.999%, Japan Fine Products, Kawasaki, Japan) flow in a vacuum evaporator that was equipped with a negatively-biased (to approximately 400 V) aluminum electrode was then used to oxidize the gold films.…”

“…Components I and II have both been assigned to hydroxyl groups and are stable up to 500°C, but differ only in the vertical position. 31,32 The angular dependence of the XPS spectra of the gold oxides indicated that the oxygen species of components I and II are present in this order from the top surface of the gold oxide (component III).…”

“…Gold oxide layers with thicknesses of less than 1 nm were prepared by an oxygen-dc glow discharge over various periods (0.5-10 min) from gold films at room temperature and were characterized by XPS in our previous papers. 31,32 A schematic representation of the formation and decomposition of a gold oxide layer with a thickness of approximately 0.6 nm prepared by an oxygen-dc glow discharge (10 Pa, 5 mA, 10 min) from a gold film is shown in Fig. 1.…”

“…The gold oxide can be preserved in the oxidized state for 84 d in anhydrous dodecane. 32 This simple method for preservation of a gold oxide immersed in a hydrocarbon with low water content will be helpful for practical use in future applications. Since a hydrophobic gold film surface can be changed into a hydrophilic surface by forming a gold oxide layer on it, the gold oxide layer formation by an oxygen-dc glow discharge from a gold film is promising as a new hydrophilization technology for the gold surface.…”