Tetsu Yonezawa 교수

Three types of polymer-protected bimetallic clusters of noble-metals, prepared by simultaneous alcohol reduction, have been totally shown to have special ‘core-shell’ structures, on the basis of X-ray diffraction and quantitative X-ray photoelectron spectroscopic measurements. In situ UV–VIS spectral changes during the formation of clusters indicated that the redox potentials of metal ions can control the order of the reduction and that redox reactions between two kinds of metal elements occur d

Size control of gold nanoparticles by tuning molecular cross section of stabilizer molecules is reported. A newly synthesized four-chained disulfide ligand was used as the stabilizer of gold nanoparticles, and the nanoparticles were prepared by NaBH4 reduction of gold ions. By the use of this stabilizer, smaller and monodispersed gold nanoparticles were obtained, when compared to those prapred by using conventional monoalkanethiols. The present design of stabilizer molecules can be used to syste

Mesoscopic honeycomb structures (see Figure) and regular, hexagonally packed monolayers are produced when fluorocarbon-stabilized silver particles are cast onto solid substrates from flurocarbon solution. The structures formed are shown to depend on the concentration of the solution and the humidity of the atmosphere.

Nanocomposite films of gold nanoparticles and TiO2 gel have been successfully prepared by combination of a surface sol−gel technique and layer-by-layer assembly. Thanks to surface hydroxyl groups of gold nanoperticles, gold particles were deposited as close-packed monolayers on TiO2 gel layers. The resulting nanocomposite contained ca. 50 wt % of gold. Multilayer films were successfully prepared by alternate assembly of TiO2 gel and gold nanoparticles.

Abstract Metastable cationic gold nanoparticles were newly developed by the use of thiocholine bromide (TCB) as stabilizer. The gold nanoparticles electrostatically bound to DNA molecules and then underwent self-fusion into the wire-like structures. The use of TCB as a labile ligand was essential to achieve non-electrochemical plating of the non-conductive molecules.

One-pot direct synthesis of cationic palladium nanoparticles that are stabilized by newly synthesized quaternary ammonium alkylisocyanides is reported. Reduction of PdCl42- by hydrazine in the presence of cationic isocyanides gave a stable aqueous dispersion of cationic palladium nanoparticles. The particle size depended on the alkyl chain lengths of the stabilizer molecules.

Reduction of AgNO3 by sodium borohydride in the presence of quaternary ammnoium disulfide gave a stable aqueous dispersion of silver nanoballs. The obtained Ag nanoballs showed a strong plasmon absorption peak, indicating that they consisted of metal Ag, although the counteranion of the stabilizer was Br-. They are obtainable in a powder form by reprecipitation and can be kept without any change under air. Redispersibility of the obtained powder into water was high, and even in slightly acidic c

An overview of recent literature on the micro- and nano-encapsulation of metallic phase-change materials (PCMs) is presented in this review to facilitate an understanding of the basic knowledge, selection criteria, and classification of commonly used PCMs for thermal energy storage (TES). Metals and alloys with high thermal conductivity can be used as PCMs for rapid heat storage in compact systems owing to their high volumetric TES density. The emerging application of metal PCMs in different fie

Abstract A de novo synthesis of gold‐nanoparticle‐embedded, nitrogen‐doped nanoporous carbon nanoparticles (Au@NC) was investigated in this work. Chloroauroic acid was encapsulated inside zeolitic imidazolate framework‐8 (ZIF‐8) nanoparticles during the synthesis and later reduced into gold nanoparticles. The as‐synthesized gold‐nanoparticle‐embedded ZIF‐8 (Au@ZIF‐8) was then carbonized into Au@NC to enhance the stability of the nanoporous support. The results show that Au@NC exhibits a porous s

A novel low cost sintering process of copper fine particles to a copper conductive layer with Cu²⁺-alkanolamine metallacycle complexes at as low as 100 °C without reductive gas flow.

Well size-controlled copper fine particles (diameter: 100-300 nm) were used as the inner electrode material of multilayered ceramic capacitors (MLCCs). The particles were dispersed in terpineol to form a printing paste with 50 wt% copper particles. The MLCC precursor modules prepared by the layer-by-layer printing of copper and BaTiO(3) particles were cosintered. Detailed observation of the particles, paste, and MLCCs before and after sintering was carried out by electron microscopy. The sinteri