title: The effect of UV irradiation on the reduction of Au(III) ions adsorbed on manganese dioxide.
abstract: The effect of UV (ultraviolet) irradiation on the adsorption of Au(III) ions on manganese dioxide and their reduction to Au(0) (gold with 0 valence state) was investigated using XPS (X-ray photoelectron spectroscopy) and 197Au Mössbauer spectroscopy. The UV irradiation accelerated the adsorption and the reduction. From the fact that the proportion of Au(0) estimated from Au 4f XPS spectra for surface analysis was significantly smaller than that from 197Au Mössbauer spectra for bulk analysis, we deduced that Au(0) was interpenetrated to the inside of manganese dioxide (into deeper places than about 30 A) where XPS is impossible to detect. The content of surface hydroxyl groups on manganese dioxide also increased due to the UV irradiation. The relationship between the charge in the content of hydroxyl groups and the interpenetration of Au(0) is discussed.
authors.affiliation: Department of Chemistry, Faculty of Science, Kyushu University, Chuo-ku, Fukuoka 810-8560, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Ohashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ezoe
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okaue
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Shuji
authors.initials: S
authors.lastname: Matsuo
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kurisaki
authors.forename: Akane
authors.initials: A
authors.lastname: Miyazaki
authors.forename: Hisanobu
authors.initials: H
authors.lastname: Wakita
authors.forename: Takushi
authors.initials: T
authors.lastname: Yokoyama