Analytical Sciences

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

Morihide HIGO,* Kazuma ONO,* Kazutoshi YAMAGUCHI,* Masaru MITSUSHIO,* Toshifumi YOSHIDOME,* and Sadafumi NAKATAKE**

*Department of Chemistry, Biotechnology, and Chemical Engineering, Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
**Kagoshima University Innovation Center, 1-21-40 Korimoto, Kagoshima 890-0065, Japan

The chemical properties of thin (∼0.6 nm) gold oxide layers prepared by an oxygen-dc glow discharge from gold films at room temperature in various solvents and solutions were studied using a surface plasmon resonance (SPR)-based optical waveguide sensing system and X-ray photoelectron spectroscopy (XPS). New insights into the stability and reactivity of gold oxides under these conditions were obtained. The O 1s XPS spectra show three oxygen species, comprising components I, II, and III in the gold oxides, and components I and II are present in this order from the top surface of the oxide (component III). The gold oxide is stable in various solvents (water, methanol, ethanol, acetone, acetonitrile, diethyl ether, chloroform, hydrocarbons) for 10 – 30 min at room temperature. The gold oxide decomposes in aqueous 10⁻² M solutions of acetaldehyde, hydrochloric acid, and sodium hydroxide during these periods. Gold oxide decomposition in these solutions was monitored by SPR and the decomposition rates were obtained. Decomposition of the gold oxides was confirmed and their surfaces were characterized after decomposition by XPS.

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