Naoki Toshima

Barium titanate stabilized by γ-cyclodextrin nanoparticles were prepared by using a microwave reactor equipped with ultrasonic nozzle mixing at 240°C in a tetraethylene glycol solution of barium ethoxide and titanium ethoxide in the presence of γ-cyclodextrin. Particles in γ-cyclodextrin-stabilized BaTiO₃ nanoparticles had an average diameter of 2.1 nm and mainly distributed within the range of about 1 to 4 nm. The γ-cyclodextrin-stabilized BaTiO₃ nanoparticles were mixed with 4-cyano-4′-pentylbiphenyl at room temperature resulting in a liquid crystal sol of 4-cyano-4′-pentylbiphenyl. The response time of liquid crystal devices in the presence of γ-cyclodextrin-stabilized BaTiO₃ nanoparticles was faster than that in the absence.

We successfully synthesized Au–Pt bimetallic core–shell nanoparticles by simultaneous reduction covered with a perfluorinated sulfonic acid ionomer (PFSA) in an aqueous solution. The core–shell structure was confirmed by energy-dispersive X-ray spectrometry line analysis. Electrocatalytic activity of the Au–Pt nanoparticles for oxygen reduction reaction was higher than those of PFSA-covered Pt nanoparticles and a conventional carbon-supported Pt catalyst.

Summary: Polymer‐capped metal nanoparticles can be recognized as a kind of macromolecule‐metal nanoparticle complexes. Here the preparations of the capped bimetallic and trimetallic nanoparticles, in which each particle contains two and three elements of metal, respectively, are presented. They may have a random alloy, a core/shell, or other kinds of structure depending on the preparation method and the combination of elements. The core/shell structure is advantageous to electronically control the activity of metal catalysts. The triple core/shell structured trimetallic nanoparticles were found to have higher catalytic activity than the corresponding monometallic and bimetallic nanoparticles in three cases. Capped metal nanoparticles were also used as a dopant to liquid crystals. Liquid crystal displays, fabricated by metal nanoparticle‐doped liquid crystals, showed faster response than those without dopants. Bimetalization could increase the long‐term stability in the doped liquid crystal displays. Thus, metal nanoparticles can improve the electronic display system, which occupies an important position in information technology. In addition, SmCo₅ nanomagnets were successfully prepared by a chemical method, possibly providing a new building block for information technology. The prepared SmCo₅ nanoparticles have a coercivity of 1500 Oe at room temperature. The bimetallic nanoparticles may open a new field in super‐high‐density magnetic memories.