Showing papers by "Toshiharu Teranishi published in 2005"

Large-scale synthesis of thiolated Au25 clusters via ligand exchange reactions of phosphine-stabilized Au11 clusters

Abstract: Phosphine-stabilized Au11 clusters in chloroform were reacted with glutathione (GSH) in water under a nitrogen atmosphere. The resulting Au:SG clusters exhibit an optical absorption spectrum similar to that of Au25(SG)18, which was isolated as one of the major products from chemically prepared Au:SG clusters (Negishi, Y. et al. J. Am. Chem. Soc. 2005, 127, 5261). Rigorous characterization by optical spectroscopy, electrospray ionization mass spectrometry, and polyacrylamide gel electrophoresis confirms that the Au25(SG)18 clusters were selectively obtained on the sub-100 mg scale by ligand exchange reaction under aerobic conditions. The ligand exchange strategy offers a practical and convenient method of synthesizing thiolated Au25 clusters on a large scale.

Tunneling resistance of double-barrier tunneling structures with an alkanethiol-protected au nanoparticle

Abstract: Coulomb staircases in double-barrier tunneling junctions consisting of a scanning-probe--vacuum-gap--alkanethiol-protected Au nanoparticle/Au (111) electrode have been measured as a function of the set point current of scanning tunneling spectroscopy. The tunneling resistances of the scanning probe-Au core of a nanoparticle $({R}_{1})$ and the Au core-Au (111) electrode $({R}_{2})$ are evaluated by fitting a theoretical Coulomb staircase into the experimental tunneling current-voltage characteristics measured by scanning tunneling spectroscopy. When a vacuum gap exists between the scanning probe and alkanethiol Au nanoparticles, ${R}_{1}$ is inversely proportional to the set point current. On the contrary, in the case of ${R}_{1}l{R}_{2}$, the top of the tip of the scanning probe tends to penetrate the octanethiol-protecting molecule of an Au nanoparticle. ${R}_{2}$ is found to be independent of the set point current, and ${R}_{2}$ of octanethiol- and hexanethiol-protected Au nanoparticles are evaluated as $7.6\phantom{\rule{0.3em}{0ex}}\mathrm{G}\ensuremath{\Omega}\ifmmode\pm\else\textpm\fi{}10%$ and $460\phantom{\rule{0.3em}{0ex}}\mathrm{M}\ensuremath{\Omega}\ifmmode\pm\else\textpm\fi{}10%$, respectively.

Size-tuning and Optical Properties of High-quality CdSe Nanoparticles Synthesized from Cadmium Stearate

Abstract: High-quality CdSe nanoparticles were synthesized with a hot-injection method from cadmium stearate and selenium powder in the size range of 2.0 ± 0.2 to 8.6 ± 2.3 nm, corresponding to blue to red e...

Synthesis of Stably Water-Soluble Gold Nanoparticles Protected by Porphyrin-Thiol Derivative

Abstract: Meso-tetraphenylporphyrin derivative having four thioacetyl groups was synthesized using Lindsay's method. Monodisperse small gold (Au) nanoparticles passivated by the synthesized ligand were prepared by a liquid phase synthesis. The nanoparticles were extremely stable and can be homogeneously dispersed in basic aqueous solution. [DOI: 10.1380/ejssnt.2005.30]

Analysis of supported zirconocenes by x-ray emission and absorption techniques

Abstract: Metal contents in supported zirconocene catalysts were comparatively determined by x-ray fluorescence spectroscopy and Rutherford backscattering spectrometry. A series of supported zirconocenes was prepared by grafting sequentially Cp2ZrCl2 (Cp = cyclopentadienyl) and (nBuCp)2ZrCl2 on to silica. The addition order and molar ratio of the two catalysts were varied. The grafted metal content was shown to be coherent between the two techniques and was between 0.37 and 0.53 wt% Zr/SiO2. The steric effect played by the ligand influences the final zirconocene grafted content. No influence of the grafting order was observed. Nevertheless, catalyst systems in which (nBuCp)2ZrCl2 was either immobilized in the first place or at a higher molar ratio were shown to be more active in ethylene polymerization. Extended x-ray absorption fine structure analysis in the Zr-edge showed that systems bearing Cp2ZrCl2 and (nBuCp)2ZrCl2 in a 1:3 molar ratio afforded a more disoriented system. According to electron probe microanalysis, the metal distribution in the catalyst particle was more uniform than that resulting from the immobilization of solely (nBuCp)2ZrCl2 on silica. Copyright © 2004 John Wiley & Sons, Ltd.