title: Electrochemical Insight into the Brust-Schiffrin Synthesis of Au Nanoparticles.
abstract: The mechanism of the Brust-Schiffrin gold nanoparticle synthesis has been investigated through the use of ion transfer voltammetry at the water/1,2-dichloroethane (DCE) solution interface, combined with X-ray absorption fine structure (XAFS) of the reaction between [AuCl4](-) and thiol (RSH) in homogeneous toluene (TL) solution. Ion transfer calculations indicate the formation of [AuCl2](-) at RSH/Au ratios from 0.2-2 with a time-dependent variation observed over several days. At RSH/Au ratios above 2 and after time periods greater than 24 h, the formation of Au(I)SR is also observed. The relative concentrations of reaction products observed at the liquid/liquid interface are in excellent agreement with those observed by XAFS for the corresponding reaction in a single homogeneous phase. BH4(-) ion transfer reactions between water and DCE indicate that the reduction of [AuCl4](-) or [AuCl2](-) to Au nanoparticles by BH4(-) proceeds in the bulk organic phase. On the other hand, BH4(-) was unable to reduce the insoluble [Au(I)SR]n species to Au nanoparticles. The number and size of the nanoparticles formed was dependent on the concentration ratio of RSH/Au, as well as the experimental duration because of the competing formation of the [Au(I)SR]n precipitate. Higher concentrations of nanoparticles, with diameters of 1.0-1.5 nm, were formed at RSH/Au ratios from 1 to 2.
authors.affiliation: Division of Nuclear Engineering Science, Research Reactor Institute, Kyoto University , Asashironishi, Kumatori, Osaka 590-0494, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Uehara
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Booth
authors.forename: Sin Yuen
authors.initials: SY
authors.lastname: Chang
authors.affiliation: School of Chemical and Process Engineering, Faculty of Engineering, University of Leeds , Leeds LS2 9JT, United Kingdom.
authors.forename: Sven L M
authors.initials: SL
authors.lastname: Schroeder
authors.affiliation: Department of Materials Chemistry, Faculty of Science and Technology, Ryukoku University , Otsu, Shiga 520-2194, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Imai
authors.forename: Teruo
authors.initials: T
authors.lastname: Hashimoto
authors.affiliation: Diamond Light Source Ltd , Didcot, Oxfordshire OX11 0DE, United Kingdom.
authors.forename: J Frederick W
authors.initials: JF
authors.lastname: Mosselmans
authors.forename: Robert A W
authors.initials: RA
authors.lastname: Dryfe