title: Ultrafast photosynthetic reduction of elemental sulfur by Au nanoparticle-loaded TiO2.
abstract: Nanometer-sized gold particles with varying mean size from 3.2 to 12.2 nm were loaded on the surfaces of TiO2 particles in a highly dispersed state with the loading amount maintained constant (0.46 +/- 0.02 mass %) using the deposition-precipitation method. Light irradiation (lambda(ex) > 300 nm) to a deaerated ethanol TiO2 particle suspension containing elemental sulfur (S8) led to the energetically uphill reduction of S8 to H2S. It has been found that this reaction is dramatically enhanced with such a low level of Au loading on TiO2 and that the zero-order rate constant of reaction increases with decreasing mean size of Au nanoparticles (d). The effects of reaction parameters (substrate concentration, light intensity, temperature) on the rate of reaction were studied to infer the essential reaction mechanism. Further, a kinetic analysis has led to a conclusion that the increase in the rate of reaction with decreasing d results from the improvement of the charge separation efficiency.
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Kiyonaga
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mitsui
authors.forename: Motofumi
authors.initials: M
authors.lastname: Torikoshi
authors.forename: Manabu
authors.initials: M
authors.lastname: Takekawa
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Soejima
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tada