S. Yagi

Robust Binding between Carbon Nitride Nanosheets and a Binuclear Ruthenium(II) Complex Enabling Durable, Selective CO2 Reduction under Visible Light in Aqueous Solution

Carbon nitride nanosheets (NS-C3 N4 ) were found to undergo robust binding with a binuclear ruthenium(II) complex (RuRu) even in basic aqueous solution. A hybrid material consisting of NS-C3 N4 (further modified with nanoparticulate Ag) and RuRu promoted the photocatalytic reduction of CO2 to formate in aqueous media, in conjunction with high selectivity (approximately 98u2009%) and a good turnover number (>2000 with respect to the loaded Ru complex). These represent the highest values yet reported for a powder-based photocatalytic system during CO2 reduction under visible light in an aqueous environment. We also assessed the desorption of RuRu from the Ag/C3 N4 surface, a factor that can contribute to a loss of activity. It was determined that desorption is not induced by salt additives, pH changes, or photoirradiation, which partly explains the high photocatalytic performance of this material.

Design and performance of a soft X-ray double crystal monochromator at HSRC

Abstract A new soft X-ray beamline has been constructed at the Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University. This beamline has a unique mechanism of an exchange system for a monochromator crystal. A double crystal monochromator of a Golovchenko-type is equipped with a crystal bank. The beamline delivers photons with energies from 800 to 5000xa0eV. Users can obtain the effective X-ray absorption fine structure spectra for Si, P, S, Cl, Ar and K K-edge on this beamline.

Generation of gaseous sulfur-containing compounds in tumour tissue and suppression of gas diffusion as an antitumour treatment

Background and aims The mechanisms of cancer cell growth and metastasis are still not entirely understood, especially from the viewpoint of chemical reactions in tumours. Glycolytic metabolism is markedly accelerated in cancer cells, causing the accumulation of glucose (a reducing sugar) and methionine (an amino acid), which can non-enzymatically react and form carcinogenic substances. There is speculation that this reaction produces gaseous sulfur-containing compounds in tumour tissue. The aims of this study were to clarify the products in tumour and to investigate their effect on tumour proliferation. Methods Products formed in the reaction between glucose and methionine or its metabolites were analysed in vitro using gas chromatography. Flatus samples from patients with colon cancer and exhaled air samples from patients with lung cancer were analysed using near-edge x-ray fine adsorption structure spectroscopy and compared with those from healthy individuals. The tumour proliferation rates of mice into which HT29 human colon cancer cells had been implanted were compared with those of mice in which the cancer cells were surrounded by sodium hyaluronate gel to prevent diffusion of gaseous material into the healthy cells. Results Gaseous sulfur-containing compounds such as methanethiol and hydrogen sulfide were produced when glucose was allowed to react with methionine or its metabolites homocysteine or cysteine. Near-edge x-ray fine adsorption structure spectroscopy showed that the concentrations of sulfur-containing compounds in the samples of flatus from patients with colon cancer and in the samples of exhaled air from patients with lung cancer were significantly higher than in those from healthy individuals. Animal experiments showed that preventing the diffusion of sulfur-containing compounds had a pronounced antitumour effect. Conclusions Gaseous sulfur-containing compounds are the main products in tumours and preventing the diffusion of these compounds reduces the tumour proliferation rate, which suggests the possibility of a new approach to cancer treatment.

Structural study on (CH3)2S/Cu(100) by near edge x-ray absorption fine structure and x-ray photoelectron spectroscopy

We have investigated the (CH3)2S/Cu(100) system using polarization dependent S K-edge near edge x-ray absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS) for both S 1s and C 1s electrons. From the XPS results, the (CH3)2S molecule is found to adsorb through the sulfur atom on the Cu(100) surface. There is a little polarization dependence in the S K-edge NEXAFS spectra for submonolayer phase. The orientation angle of the molecular plane is estimated to be 33° from the surface.

High-resolution photoelectron spectroscopy of Heusler-type Fe2VAl alloy

The electronic structure of Heusler-type Fe(2)VAl has been studied by high-resolution photoelectron spectroscopy with the excitation photon energy hnu ranging from 21.2 eV (the He I laboratory light source) to 904 eV (the soft X-ray synchrotron light source) for clean surfaces prepared by scraping or fracturing polycrystalline and single crystalline specimens. Photoelectron spectra recorded for the fractured surfaces show a 10 eV-wide valence band with fine structures and a clear decrease in the intensity towards the Fermi level E(F), while a high intensity at E(F) and no fine structures are observed for the scraped surface. Comparison with the theoretical density of states (DOS) indicates that the vacuum ultraviolet photoelectron spectra emphasize the transition-metal 3d bands but the soft X-ray photoelectron spectra agree remarkably well with the DOS including the fine structures and the pseudogap at E(F). The present results suggest that the electronic structure of Fe(2)VAl is highly sensitive to possible strain and defects induced by scraping. Bulk electronic structures of Fe(2)VAl are discussed in relation to the reported fascinating transport properties.

Molecular adsorption of (CH3)2S on Ni(100) studied by S K-edge NEXAFS and XPS

We report the investigation of the adsorption behavior of sulfur-containing (CH 3 ) 2 S molecule on Ag(1I 1) surface. Submonolayer and multilayer adsorption phases under UHV and liquid N 2 temperature conditions were studied by means of polarization dependent Sulfur-K near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) techniques. The (CH 3 ) 2 S molecule for submonolayer phase adsorbs molecularly on Ag(111) surface at 86 K. The sulfur and two methyl groups of the (CH 3 ) 2 S molecule have some interaction with surface Ag atoms. The orientation angle of two S-C bonds is estimated to be 23 ± 5° from the surface.

Electronic Structure of Pd‐ and Zr‐based Bulk Metallic Glasses Studied by Use of Hard X‐ray Photoelectron Spectroscopy

The hard x‐ray photoelectron spectroscopy has been applied to the investigation of the electronic structures and the chemical states of the constituent atoms of the binary Zr‐TM (TM = Ni and Cu) and ternary Zr‐TM‐Al metallic glasses and a Pd42.5Ni7.5Cu30P20 bulk metallic glass. The Zr 2p and Al 1s spectra as well as the O 1s line show that the Zr‐based glasses are covered with a thick oxide surface layer, while the core level spectra other than the P 1s and 2s levels in Pd42.5Ni7.5CU30P20 reveal almost no oxide components, indicating that the oxide layer is essentially negligible. The bulk valence‐band electronic structures of the Zr‐based glasses can be successfully estimated by measuring the detection angle dependence of the valence‐band and Zr 2p core level spectra. In Zr‐Cu, the Cu 3d band is shifted toward the high binding energy with the Cu concentration increased, which is consistent with the chemical shifts of the bulk Zr and Cu 2p levels observed in this study. These core level shifts indicate an...

XAFS Measurement System for Nano, Bio and Catalytic Materials in Soft X‐ray Energy Region

In soft X‐ray energy region, there are really many absorption edges for the constituents of the useful materials. We have reported the powerful XAFS measurement system at soft X‐ray energy beamline on small or compact storage ring HiSOR and also recent NEXAFS spectra data about nano, bio and catalytic materials. The XAFS measurement system has a Be window, which can separate the ultra‐high vacuum (UHV) and the atmospheric pressure condition. Moreover the XAFS spectra can obtain by yielding a fluorescent X‐ray emitted from the samples.

Structural study of C5H5N on Si(111)-(7×7)

Abstract The adsorption structure of the C 5 H 5 N molecule on the Si(111)-(7×7) surface has been studied by low-temperature scanning tunneling microscopy (STM). Two adsorption states are observed: one appears chemisorbed and the other is physisorbed. The C 5 H 5 N molecule adsorbs above a dimer row on the surface between the two halves of the unit cell.

IN SITU XPS STUDY OF Pd NANOPARTICLE FABRICATED BY GAS EVAPORATION METHOD

The Pd nanoparticles were fabricated by the gas evaporation method without any capping molecules. It is found that the average diameter of the nanoparticles are 1.7 nm with standard deviation of 0.8 nm by AFM observations. The chemical states of the nanoparticles were measured by the in situ XPS. The XPS results indicate that the chemical states of the nanoparticles become almost the same as the bulk Pd. The chemical states of the air-exposed Pd nanoparticles were also observed by the ex situ XPS and NEXAFS methods. Both ex situ XPS and NEXAFS measurements indicate that the nanoparticles were naturally oxidized under an atmospheric environment. Considering from the behavior of Pd 3d XPS and the diameter of nanoparticles, it is suggested that the depth of oxidized Pd layer is less than 1.4 monolayer from the nanoparticles surface.