The significance of bromide in the Brust–Schiffrin synthesis of thiol protected gold nanoparticles

The mechanism of the two-phase Brust–Schiffrin synthesis of alkane thiol protected metal nanoparticles is known to be highly sensitive to the precursor species and reactant conditions. In this work X-ray absorption spectroscopy is used in conjunction with liquid/liquid electrochemistry to highlight the significance of Br⁻ in the reaction mechanism. The species [AuBr₄]⁻ is shown to be a preferable precursor in the Brust–Schiffrin method as it is more resistant to the formation of Au(I) thiolate species than [AuCl₄]⁻. Previous literature has demonstrated that avoidance of the Au(I) thiolate is critical to achieving a good yield of nanoparticles, as [Au(I)X₂]⁻ species are more readily reduced by NaBH₄. We propose that the observed behavior of [AuBr₄]⁻ species described herein explains the discrepancies in reported behavior present in the literature to date. This new mechanistic understanding should enable nanoparticle synthesis with a higher yield and reduce particle size polydispersity

Gold nanoparticles : tailored preparation and assembly in 2- and 3-dimensions

The synthesis, characterization, and assembly of thiol-stabilized gold nanoparticles in 2- and 3-dimensions are the focus of this thesis.Assemblies of gold nanoparticles in 2-dimensions were prepared by the reduction of gold(I)-thiolate thin films on carbon and silicon surfaces. These films were reduced by direct exposure to an electron beam. The electron beam-induced growth of gold nanoparticles was observed in-situ in a transmission electron microscope. Electron beam lithography of the gold(I)-thiolate films allowed for the fabrication of sub-50 nm arrays of small gold nanoparticles (from 2 to 6 nm in diameter). Variation in the electron dose allowed for a variation in nanoparticle surface coverage.Novel polymer-stabilized gold nanoparticles with high grafting densities were prepared for their 3D dispersion in polymer matrices. The resulting polymer nanocomposites were characterized by transmission electron microscopy, UV-visible spectroscopy, and small angle X-ray scattering. The homogeneous blending of the nanoparticles in polymer matrices was a function of the polymeric ligand molecular weight, as well as the polymeric ligand grafting density on the gold core. The truncated octahedral shape of the gold core seems to favor the wetting of the polymer ligand brush by the polymer matrix. This in turn seems to favor the dispersion of the gold nanoparticles in the polymer matrices.Finally, small thiol-capped gold nanoparticles were prepared by the chemical reduction of gold(I)-thiolate complexes in solution. The sizes of the resulting nanoparticles were compared to those prepared by conventional methods

Le diabète (diététique et sport)

AIX-MARSEILLE2-BU Pharmacie (130552105) / SudocSudocFranceF