Takio Noguchi

Layer-by-layer thin film-coated electrodes for electrocatalytic determination of ascorbic acid

Multilayer thin films composed of poly(allylamine hydrochloride) (PAH) and carboxymethyl cellulose (CMC) have been prepared on the surface of a gold (Au) disk electrode by a layer-by-layer deposition of PAH and CMC and ferricyanide ions ([Fe(CN)(6)](3-)) were confined in the film. [Fe(CN)(6)](3-) ions can be successfully confined in the films from weakly acidic or neutral [Fe(CN)(6)](3-) solutions, while, in basic solution, [Fe(CN)(6)](3-) ion was not confined. The [Fe(CN)(6)](3-) ion-confined Au electrode showed clear redox peaks in the cyclic voltammogram around 0.35V versus Ag/AgCl. The amounts of [Fe(CN)(6)](3-) ions confined in the films depended on the thickness of the films or the number of layers in the LbL films. The [Fe(CN)(6)](3-) ion-confined Au electrode was used for electrocatalytic determination of ascorbic acid in the concentration range of 1-50mM.

Green solvent for green materials: a supercritical hydrothermal method and shape-controlled synthesis of Cr-doped CeO2 nanoparticles.

This paper describes a supercritical hydrothermal synthesis method as a green solvent process, along with products based on this method that can be used as green materials that contribute to solving environmental problems. The first part of this paper summarizes the basics of this method, including the mechanism of the reactions, specific features of the supercritical state for nanoparticle synthesis, the continuous flow-type reactor and applications; this provides a better understanding of the suitability of this method to synthesize green materials. The second part of the paper describes the method used to synthesize Cr-doped CeO2 nanoparticles, which show an extremely high oxygen storage capacity, suggesting their high potential as an environmental catalyst. Transmission electron microscopy and scanning electron microscope images showed octahedral Cr-doped CeO2 nanoparticles with sizes of 15–30 nm and cubic Cr-doped CeO2 nanoparticles with sizes of 5–8 nm. Octahedral Cr-doped CeO2 nanoparticles exposing (111) facets and cubic Cr-doped CeO2 nanoparticles exposing (100) facets were determined by high-resolution transmission electron microscopy and selected area electron diffraction. The X-ray diffraction peaks shifted to a high angle because the radius of the Cr ion is smaller than that of the Ce ion.

X-ray detection capabilities of plastic scintillators incorporated with hafnium oxide nanoparticles surface-modified with phenyl propionic acid

We synthesized plastic scintillators incorporated with HfO2 nanoparticles as detectors for X-ray synchrotron radiation. Nanoparticles with sizes of less than 10 nm were synthesized with the subcritical hydrothermal method. The detection efficiency of high-energy X-ray photons improved by up to 3.3 times because of the addition of the nanoparticles. Nanosecond time resolution was successfully achieved for all the scintillators. These results indicate that this method is applicable for the preparation of plastic scintillators to detect X-ray synchrotron radiation.