Identification and Detailed Characterization of Metal Oxide Powders as a Fundamental Chemical Product

Here we propose a method for identification and detailed characterization of metal-oxide powders with patterns of energy-resolved density of electron traps (ERDT) and conduction-band bottom (CBB) position, as a fingerprint, measured by newly developed reversed double-beam photoacoustic spectroscopy (RDB-PAS).     Keywords: Electron Traps, Photoacoustic Spectroscopy, Metal-oxide Powders, Degree of Coincidenc

ゼブラフィッシュにおける植物性ステロール代謝機構に関する研究

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 潮 秀樹, 東京大学教授 金子 豊二, 東京大学教授 松永 茂樹, 東京大学教授 浅川 修一, 東京大学准教授 木下 滋晴University of Tokyo(東京大学

Preparation of concentrated multilayer graphene dispersions and TiO2-graphene composites for enhanced hydrogen production

Photocatalytic hydrogen (H2) production is an attractive hydrogen production technology. It is initiated by charge-separation in titanium (IV) dioxide (TiO2) upon photoexcitation. Electrons reduce water to generate H2 while holes oxidize hydroxide to generate hydroxyl radicals. TiO2 is widely used because it is inexpensive, chemically stable, nontoxic, and environmentally friendly. The activity of TiO2 is limited, but adding a supporting noble metal nanoparticle such as platinum greatly enhances it. Due to resource risks and cost issues, we consider using graphene as an alternative to noble metal nanoparticles. Herein we report a new method to prepare a concentrated multilayer graphene solution and hydrogen production from an aqueous methanol solution. When we used graphene with different sheet sizes or improved the aggregation of TiO2 (TIO-9), the H2 evolution rate is 1.6 times higher than that of pristine TIO-9. The contact state and the dispersed state of graphene and TiO2 play important roles in improving the activity

Kinetic analysis supporting multielectron reduction of oxygen in bismuth tungstate-photocatalyzed oxidation of organic compounds

Light-intensity dependence of the rate of carbon-dioxide liberation in the photocatalytic decomposition of acetic acid by bismuth tungstate particles suspended in an aqueous solution under aerobic conditions was measured by monochromatic photoirradiation using a monochromator (lower intensity < 20 mW) and high-intensity UV-LED (higher intensity < 300 mW). The light-intensity dependence of both flake ball-shaped micrometer-sized particles (FB-BWO) and wet ball-milled nanometer-sized particles (ML-BWO) seemed to be bimodal, i.e., first and 0.5th orders in the lower and higher intensity ranges, respectively. Approximately 1.5th and second-order light-intensity dependences were also observed for ML-BWO at the lowest intensity range and for FB at the highest intensity range, respectively. The light-intensity dependences could be reproduced by a kinetic model that was derived on the basis of the assumption of oxygen reduction via two-electron (and possibly four-electron at the highest intensity region) transfer and a radical chain mechanism with peroxy radicals as chain carriers. The calculated threshold intensity between the first and 0.5th-order light-intensity dependences for FB-BWO was appreciably lower than that of ML-BWO, suggesting that the higher FB-BWO activity is attributable to the larger effective particle size for accumulation of two (or four) electrons

Changes in Intestinal Gene Expression of Zebrafish (Danio rerio) Related to Sterol Uptake and Excretion upon β-Sitosterol Administration

Replacement of fishmeal with plant ingredients will introduce not only plant oil and protein but also phytosterol to the fish diet. Mammals strictly restrict the uptake of phytosterol at intestinal epithelial cells by regulating the gene expressions of sterol uptake and excretion proteins; however, phytosterol is found in the fish muscle and other organs. In order to assess the ability of phytosterol uptake by the intestinal epithelial cells of fish, no-sterol diet, cholesterol-, and β-sitosterol-containing diet was separately administered to zebrafish, and the relative mRNA expressions related to sterol uptake and excretion were evaluated. Gene expression of Niemann-Pick C1-like protein 1 in the sitosterol-fed group was significantly higher than that of the cholesterol-fed group (p &lt; 0.05). The expression of apolipoprotein A-I gene was also higher in the sitosterol-fed group than that in the no-sterol and cholesterol-fed groups. The expressions of ATP-binding cassette, sub-family G, member 5 and 8, were significantly higher in the sitosterol-fed group, compared to the no-sterol group. Regarding the gene expression of ATP-binding cassette sub-family A, member 1, the sitosterol-fed group showed higher expression level compared to the other groups (p &lt; 0.01). These results suggest that fish should be tolerant to phytosterols in contrast to mammals

A fingerprint of metal-oxide powders: energy-resolved distribution of electron traps

Here we propose a method for the identification of metal-oxide powders with the energy-resolved distribution of electron traps and conduction-band bottom position reflecting a surface structure and a bulk structure, respectively, as a fingerprint, based on the degree of coincidence for a given pair of samples, measured using newly developed reversed double-beam photoacoustic spectroscopy

Reversed double-beam photoacoustic spectroscopy of metal-oxide powders for estimation of their energy-resolved distribution of electron traps and electronic-band structure

A novel instrumental methodology, reversed double-beam photoacoustic spectroscopy (RDB-PAS), was developed for measuring the energy-resolved distribution of electron traps (ERDT) of metal-oxide powders. In the RDB-PAS measurement, electrons in the valence band of a powder sample are directly excited to electron traps (ETs) and accumulated in the ETs from the deeper (anodic) side to the shallower (cathodic) side by wavelength-scanned continuous light, and the increase in photoabsorption of electron-filled ETs is measured by modulated light at a fixed wavelength by PAS. It was shown that ERDT/CBB (conduction-band bottom) patterns measured by RDB-PAS can be used for not only identification and detailed characterization of a wide range of metal-oxide powder samples but also estimation of difference in apparent valence-band top (VBT) position. (c) 2018 Elsevier Ltd. All rights reserved

Multielectron reduction of molecular oxygen in photocatalytic decomposition of organic compounds by bismuth tungstate particles without cocatalyst loading

A photocatalytic reaction mechanism that involves multielectron reduction of molecular oxygen (O-2), as a key step, in photocatalytic decomposition of acetic acid by pristine bismuth tungstate (Bi2WO6; BWO) particles is proposed on the basis of results of studies on (i) comparison of photocatalytic activity trends of BWO, tungsten (VI) oxide and titanium(IV) oxide photocatalyst powders with or without platinum deposits in three photocatalytic reaction systems (oxidative decomposition of acetic acid in aerobic aqueous suspensions, methanol dehydrogenation in deaerated aqueous suspensions and O-2 liberation from deaerated silver salt solutions) and (ii) effects of morphology and structural properties of BWO particles on photocatalytic activities