Publications by authors named "Takashi Narushima"

By decreasing the water content in an NH4F and glycerol-water electrolyte, the transition from single-wall to double-wall TiO2 nanotube arrays was successfully achieved using an anodization method. The double-wall TiO2 nanotube structures exhibited better photocatalytic activity than the typical single-wall structures. After modification with platinum nanoparticles, the photocatalytic activity of both the single- and double-wall TiO2 nanotubes was improved further.

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With the continuous progress in nanomaterial development for biomedicine, the potential cytotoxicity of nanoparticles is drawing more attention and concern for clinical applications. The purpose of this study was to evaluate biological responses of new water-dispersible silver nanoparticles (Ag-NPs) stabilized by Ag-C σ-bonds in cultured murine macrophages (RAW264.7) and osteoblast-like cells (MC3T3-E1) using cell viability and morphological analyses.

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Nanometals are currently receiving considerable attention for industrial and biomedical applications, but their potentially hazardous and toxic effects have not been extensively studied. This study evaluated the biological responses of novel water-dispersible gold (Au-NPs) and silver nanoparticles (Ag-NPs) stabilized by Au-C or Ag-C σ-bonds in cultured macrophages (RAW264.7), via analysis of the cell viability, the integrity of the plasma membrane, and the inflammatory and morphological properties.

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Many nanoporous metals have been applied for catalysis and show active properties. In this study, nanoporous platinum was successfully prepared from a Cu-Pt (50/50 w/w) alloy plate by electrochemical dealloying. In order to reveal their detailed structures in nanometer order, TEM observation of the surface area of the alloy plate was performed by using focused ion beam (FIB) for sample preparation.

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Copper/gelatin composite particles with controlled sizes were prepared at room temperature from cupric sulfate pentahydrate in the presence of gelatin as a protective reagent by using hydrazine monohydrate as a reducing agent. The formed particles with the size between 190-940 nm were secondary aggregated particles which were composed of smaller nanosized particles ("particle-in-particle"), the presence of which was established by XRD patterns and a cross-sectional TEM image. The sintering behavior of these copper/gelatin composite particles was demonstrated by in-situ heating TEM under a high vacuum (approximately 10(-5) Pa) and separately with the oxygen partial pressure controlled at the 10(-4) Pa level.

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Choline-type ionic liquids (CILs), which have a molecular structure resembling that of the vitamin-like active substance choline, have high water solubility, high osmotic pressure, and high cell membrane permeability. Their physical properties make them a very useful pretreatment agent for scanning electron microscopy (SEM) observation of hydrous samples because they can replace water in the samples, causing them to retain their shapes. SEM images of pollen without dissolution of cell membranes, damage, or deformation were obtained by a simple visualization process using CILs.

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We have successfully prepared Kompeito-like platinum particles by hydrogen reduction of Pt4+ in the presence of sodium polyacrylate. We performed in situ TEM observation of these platinum particles at high temperatures. At 300 degrees C, a thin carbon layer due to polyacrylate formed on the particle surface.

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The temperature distribution on a centre-holed thin foil of molybdenum, used as a sample and heated using a sample-heating holder for electron microscopy, was measured using an infrared thermal camera. The temperature on the heated foil area located near the heating stage of the heating holder is almost equal to the temperature on the heating stage. However, during the measurement of the temperature at the edge of the hole of the foil located farthest from the heating stage, a drop in temperature should be taken into consideration; however, so far, no method has been developed to locally measure the temperature distribution on the heated sample.

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Surfactant-free, single-nano-sized copper nanoparticles (Cu NPs) (size: about 2 nm) were prepared by the DMF reduction method. The Cu NPs showed high catalytic activity (with a turnover number (TON) of up to 2.2 × 10(4)) in Ullmann-type cross-coupling of aryl halides with phenols under ligand-free conditions.

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We report the synthesis of 2 nm copper nanocrystals (Cu NCs) via a microwave-assisted polyol method without using additional protective and reducing agents. The Cu NCs are oxidation resistant and exhibit photoluminescence and highly stable properties in a colloidal dispersion.

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