Papers by Author: Hideo Watanabe

Abstract: Layered clay has been of great interest because of their nano-sized layer structure and hence intercalation and ion-exchange capacity to be used as a host material of composite with polymers and/or metals. In this study, smectite as a silicate-layered clay was easily exfoliated and dispersed into purified water, and was deposited onto a cupper plate for which dc voltage ranging from + 1.0 V to + 6.0 V was applied with respect to a counter platinum plate electrode. The cupper plate was pre-treated by chemical and chemical mechanical polishing (CP and CMP) prior to the electrophoretic deposition (EPD). The surface roughness of the substrate as well as the smectite film formed was characterized by an atomic force microscope (AFM). The thickness of smectite layer was estimated using an X-ray fluorescence (XRF) analysis as well as a scanning electron microscope (SEM) observation. The layer thickness can be described as a function of operational parameters such as applied voltage and operating time. Smooth smectite film with thickness ranging from 100 nm to 10 μm has been successfully fabricated onto the CMP cupper plate by the EPD method in this study.

Abstract: Nobel metal particles with nanometer size have attracted keen interest because of, for example, their high catalytic activity to be applied for industrial applications. In this study, nano-sized gold particles were deposited onto a graphite carbon plate by two approaches: 1) electrophoresis of colloidal gold nanoparticles, 2) electrolysis of chlorauric acid. For former case, commercially-available gold nanoparticle and anionic mercapto ligand-stabilized gold nanoparticles, synthesized by citric acid reduction of chlorauric acid, were used. Size and morphology of the gold particles deposited were characterized by scanning electron microscopy. Electrolytic deposition resulted in larger gold particles around tens to hundreds nm in size. Electrophoretic deposition accomplished particle sizes smaller than 15 nm, which basically reflected the size of colloidal gold particles used.