Takao A. Yamamoto

Radiolysis of aqueous phenol solutions with nanoparticles. 1. Phenol degradation and TOC removal in solutions containing TiO2 induced by UV, γ-ray and electron beams

Aqueous phenol solutions containing TiO(2) nanoparticles were irradiated with ultraviolet (UV), gamma-ray and electron beams. Organic compounds were fully removed by each type of radiation in the presence of the particles. The absorbed energy of the ionizing radiation (gamma-ray and electron beams) needed for removal was much lower than that of UV photocatalysis. Phenol was decomposed by the ionizing radiation in the absence of the nanoparticles and the addition of TiO(2) had no significant effect on phenol decomposition rate. Instead, total organic carbon (TOC) removal using the ionizing radiation was accelerated drastically by TiO(2). It is suggested that TiO(2) particles affect the intermediate compounds produced through the decomposition of phenol. The amount of removed TOC per absorbed energy were compared in the absence and the presence of TiO(2) nanoparticles. Radiolysis with the nanoparticles showed consistently high rate and high efficiency of TOC removal.

Direct cell entry of gold/iron-oxide magnetic nanoparticles in adenovirus mediated gene delivery

Gold/iron-oxide MAgnetic Nanoparticles (GoldMAN) imparts useful magnetic properties to various biomolecules. Gold nanoparticles immobilized on the surface of magnetic nanoparticles allow for the conjugation of biomolecules via an Au-S bond. Here, we present a practical application by utilizing GoldMAN and a magnetic field to induce intracellular transduction. This method has great potential for application of the adenovirus gene delivery vector (Ad), widely used for in vitro/in vivo gene transfer, to Ad-resistant cells. We demonstrated that Ad was easily immobilized on GoldMAN and the Ad/GoldMAN complex was introduced into the cell by the magnetic field, which increased gene expression over 1000 times that of Ad alone. The GoldMAN penetrated the plasma membrane directly, independent of the cell-surface virus receptors and endocytosis pathway. This mechanism will contribute to improve the gene expression efficiency of Ad. This technology is a useful tool for extending Ad tropism and enhancing transduction efficiency. GoldMAN also makes possible the effective use of various biomolecules within the cell because of its interesting cell-entry mechanism.

Crystal and magnetic structures and their temperature dependence of Co2Z-type hexaferrite (Ba,Sr)3Co2Fe24O41 by high-temperature neutron diffraction

We have prepared nonoriented and magnetically oriented specimens of Co2Z-type Ba ferrite Ba3Co2Fe24O41 (Ba3Z) and those with Sr2+ substitution for Ba2+, i.e., Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5Z) and Sr3Co2Fe24O41 (Sr3Z) with the conventional solid-state reaction method. Permeability measurements of nonoriented specimens have shown that this substitution improves the frequency characteristic of permeability, though the permeability in Sr3Z significantly decreases. X-ray diffraction (XRD) and magnetization measurements of magnetically oriented specimens have shown that the magnetic moments of iron and cobalt ions in Ba3Z and Ba1.5Sr1.5Z lie in the c plane, but that those in Sr3Z deviate from the c plane. We have studied the substitution effect of Sr2+ for Ba2+ on the crystal structures and the effective sizes and directions of magnetic moments and their temperature dependences with high-temperature neutron diffraction technique. This substitution induces the change in the distribution of cobalt ions and mome...

Magnetocaloric effect of mononitride containing gadolinium and dysprosium GdxDy1−xN

The binary rare-earth mononitride, GdxDy1−xN, was synthesized by carbothermic reduction performed in a nitrogen gas stream. A continuous solid solution with the NaCl structure was observed through the whole composition range, and the Curie temperature was found to vary from 61 to 21 K as x changes from 1 to 0. The magnetocaloric effect was evaluated as a function of x by calculating the magnetic entropy changes ΔS from the magnetization data sets measured at various temperatures and applied fields. The ΔS values of GdxDy1−xN expressed in terms of J K−1 m−3 were comparable to those of intermetallic compounds of rare earth and transition metals previously reported. GdxDy1−xN is a promising magnetic refrigerant for hydrogen liquefying system because rare earth nitrides would not react with hydrogen.

Detection of Charged Particles Emitted by Electrolytically Induced Cold Nuclear Fusion

We have tried to obtain evidence for electrolytically induced cold nuclear fusion by detecting charged particles associated with the nuclear reaction. Charged particles were detected by a conventional silicon surface barrier detector attached close to the thin foil cathode which formed the bottom of an electrolysis cell. The efficiency and signal-to-noise ratio of this system are higher than those of neutron detection systems, which made it easy to determine whether the fusion occurred or not. The energy spectrum measured with the electrolysis of D2O suggested that the nuclear reaction took place in palladium cathode.

Simple PEG conjugation of SPIO via an Au-S bond improves its tumor targeting potency as a novel MR tumor imaging agent.

Gold/iron oxide magnetic nanoparticles are hybrid nanoparticles containing a core of magnetic iron oxide and surface colloidal gold, which allows for various biomaterials to be immobilized on the surface of the iron oxide nanoparticles via colloidal gold. Here, we developed a novel magnetic resonance (MR) imaging agent to broaden the MR tumor-imaging spectrum of superparamagnetic iron oxide nanoparticles (SPIO), e.g., Feridex(), a clinical MR imaging agent for diagnosing liver cancer. Au/Feridex was synthesized by electron beam irradiation, and thiol-modified poly(ethylene glycol) (PEG-SH) was easily conjugated to its surface via an Au-S bond without the need for any chemical reactions. PEG conjugation of Au/Feridex enhanced its accumulation in Meth-A tumor tissue and decreased its accumulation in normal liver tissue. In addition, MRI using PEG-Au/Feridex, in contrast to MRI using unmodified Au/Feridex and Feridex, detected B16BL6 and Meth-A tumor tissues in vivo. This finding indicates that PEG-Au/Feridex is useful for diagnosing various types of tumors. In addition, because the synthesis of PEG-Au/Feridex is simple and high yields are easily produced, PEG-modified SPIO for tumor diagnosis can be prepared on an industrial scale with low cost.

Enhancement of Hydrogen Evolution Yield from Water Dispersing Nanoparticles Irradiated with Gamma-Ray

Hydrogen gas evolution from water dispersing nanoparticles induced by 60Co γ-ray irradiation was studied. Nanoparticles of TiO2 and Al2O3 with average sizes of 7–33 nm supplied from several suppliers were examined. It was indicated that reactions enhancing the hydrogen evolution proceed on particles surface. It was implied that the yield depends on size of agglomerated particle regardless of their primary particle size and chemical species. Reactions that enhance the hydrogen yields were discussed, and radiolysis process was concluded dominant in the total enhancement mechanism.

Carbon-supported AuPd bimetallic nanoparticles synthesized by high-energy electron beam irradiation for direct formic acid fuel cell

Nanoparticle catalysts of carbon-supported Pd (Pd/C) and carbon-supported AuPd (AuPd/C) for the direct formic acid fuel cell (DFAFC) anode were synthesized by the reduction of precursor ions in an aqueous solution irradiated with a high-energy electron beam. We obtained three kinds of nanoparticle catalysts: (1) Pd/C, (2) AuPd/C of the core–shell structure, and (3) AuPd/C of the alloy structure. The structures of AuPd nanoparticles were controlled by the addition of citric acid as a chelate agent, and sodium hydroxide as a pH controller. The structures of nanoparticle catalysts were characterized using transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, the techniques of X-ray diffraction and X-ray absorption fine structure. The catalytic activity of the formic acid oxidation was evaluated using linear sweep voltammetry. The oxidation current value of AuPd/C was higher than that of Pd/C. This indicated that the addition of Au to Pd/C improved the oxidation activity of the DFAFC anode. In addition, the AuPd/C of the alloy structure had higher oxidation activity than the AuPd/C of the core–shell structure. The control of the AuPd mixing state was effective in enhancing the formic acid oxidation activity.

Synthesis of gold/magnetic iron oxide composite nanoparticles for biomedical applications with good dispersibility

Composite nanoparticles consisting of gold and magnetic iron oxide were synthesized in an aqueous solution system by sonochemical and radiochemical processes. Small Au nanoparticles were immobilized on the surface of the iron oxide nanoparticles. Removal of the excess polymers in the solution leads to the good dispersibility of the composite nanoparticles. The composite nanoparticles are expected as a type of nanocarrier for biomedical applications.Composite nanoparticles consisting of gold and magnetic iron oxide were synthesized in an aqueous solution system by sonochemical and radiochemical processes. Small Au nanoparticles were immobilized on the surface of the iron oxide nanoparticles. Removal of the excess polymers in the solution leads to the good dispersibility of the composite nanoparticles. The composite nanoparticles are expected as a type of nanocarrier for biomedical applications.

Interfacial mixed-crystal layer in CdSCdTe heterostructure elucidated by electroreflectance spectroscopy

Abstract Electroreflectance (ER) spectroscopy has been carried out on the CdS CdTe thin-film solar cells to reveal the CdS CdTe interfacial properties, which is believed to play a crucial role in determining the photovoltaic performances. The ER feature at around 1.46 eV is to be ascribed as due to the mixed-crystal CdTe0.95S0.05 layer unintentionally formed at the CdS CdTe interface during CdTe deposition on CdS. Comparing the ER spectrum with the quantum efficiency (QE) response of the solar cell, the indication is that the n-p junction locates itself in the mixed-crystal layer, because no pronounced response due to the CdTe layer is observed in the ER spectrum whereas it is observed in the QE spectrum.