XAFS Analysis Research Articles

Abstract 3337: Titanium peroxide nanoparticles enhance antitumor efficacy through reactive oxygen species in pancreatic cancer radiation therapy

Abstract Purpose: Pancreatic cancer is a highly lethal disease and notoriously resistant to many types of cytotoxic chemotherapy and radiotherapy. A novel strategy should be explored for these radioresistant tumors. We originally synthesized a titanium peroxide nanoparticle (TiOxNP) which had a distinct ability to produce reactive oxygen species (ROS) upon X-ray irradiation (IR). Here, the characterization and efficacy of TiOxNP as radiosensitizer for pancreatic cancer therapy were investigated. Methods: TiOxNPs were synthesized from anatase titanium oxide nanoparticles (TiO2NPs) by H2O2 processing and coated by polyacrylic acid. The ability of TiOxNPs to enhance ROS generation upon X-ray irradiation (IR) was tested by using 3′-(p-Aminophenyl) fluorescein and several antioxidants. A xenograft mouse model using the human pancreatic cancer cell line MIAPaCa-2 was used to evaluate the cytotoxic effects of a combination of TiOxNPs and IR in vivo. MIAPaCa-2 cells were injected subcutaneously into the hind legs of immunodeficient BALB/c mice. Seven days after injection, the tumor was treated with a TiOxNP suspension injected directly into the tumor and application of 5 Gy of IR. Tumor size and health of the mice were monitored for 43 days after the treatment. Induction of apoptosis was evaluated by immunohistochemistry using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling staining. We also characterized TiOxNPs by ESR and XAFS analyses. Results: ROS generation was enhanced dramatically by TiOxNPs in a concentration- and radiation dose- dependent manner compared to enhancement by TiO2NPs. At the highest concentration of TiOxNPs, ROS generation upon an irradiation dose of 30 Gy was enhanced by a factor of more than 10. Also, ROS generated by TiOxNPs upon IR were scavenged by vitamin C or glutathione. Growth inhibition of the tumor in the group receiving both TiOxNP and IR was significantly greater than single treatment subgroups (P < 0.05). The number of apoptotic cells was also significantly higher in the combination group (P < 0.05). Histologically, large pools of TiOxNPs around tumor cells and small amounts inside the tumor cells were observed. No mice died within a 43-day observation period or showed any apparent body weight loss. In the ESR spectra, some signals were observed for TiOxNPs. The spectral shapes of Ti K-edge X-ray absorption near edge structure, spectra were the same among the mineral anatase, TiO2NPs and TiOxNPs. Conclusions: TiOxNPs induced remarkable ROS production upon IR. They were safe and effective in a xenograft mouse model using engrafted human pancreatic cancer cells. Further studies would be necessary to elucidate a mechanism of radical generation and long-term toxicity, however our study shows that TiOxNPs are promising radiosensitizers for application in pancreatic cancer therapy. Citation Format: Masao Nakayama, Ryohei Sasaki, Toru Mukohara, Chiaki Ogino, Kenta Morita, Mitsuo Umetsu, Satoshi Ohara, Kazuyoshi Sato, Chiya Numako, Seiichi Takami, Akihiko Kondo. Titanium peroxide nanoparticles enhance antitumor efficacy through reactive oxygen species in pancreatic cancer radiation therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3337. doi:10.1158/1538-7445.AM2015-3337

Exploiting the dynamic Sn diffusion from deformation of FTO to boost the photocurrent performance of hematite photoanodes

Herein, we report on exploiting effective Sn diffusion from the underlying FTO (F:SnO2) substrate during post-growth annealing treatment to boost the photocurrent performance of α-Fe2O3 photoanodes. Conventionally, hematite photoanodes are activated at high temperature (800°C>T>650°C) after initial low temperature annealing. The purpose of such activation is to utilize the diffusion of Sn ions leached from FTO deformation for improving the electronic conductivity and hence the photocurrent response of hematite photoanodes. However, the pre-formed oxide layer (in the first annealing) on the surface of FTO creates obstacle for diffusion of Sn ions during FTO deformation. To overcome this difficulty and to exploit Sn diffusion, we employed a direct single-step annealing of as-grown iron-coated FTO electrodes at 800°C for short duration followed by quenching in air. Such activation greatly improved the water oxidation photocurrent response of hematite by 37% on account of increased Sn diffusion which was confirmed from X-ray photoelectron spectroscopy. Moreover, the onset of photocurrent is shifted cathodically meaning that the water oxidation reaction proceeds at lower applied bias. Higher Sn content increased the electron donor concentration and hence improved the charge transfer kinetics of hematite as studied from EIS and Mott–Schottky measurements. Interestingly, despite higher Sn diffusion, the loss of FTO conductivity was minimal and the structural ordering was highest in one-step-activated hematite compared to conventionally activated hematite photoanodes as studied from XAFS analysis.

Hydrogen storage of binary nanoparticles composed of Mg and Pd

The hydrogen storage property of the binary nanoparticles composed of Mg and Pd has been investigated by the QCM technique without the exposure to the air. The two types of nanoparticles have been fabricated by the gas evaporation method with the He gas. The one is the nanoparticles composed of the both Mg and Pd atoms (Mg–Pd NPs) and the other one is the composite of the Mg and Pd nanoparticles (Mg NPs-Pd NPs). Both the Mg–Pd NPs and the Mg NPs-Pd NPs can absorb the hydrogen under the room temperature and 1 atm of H2 gas. However, the desorptions of the hydrogen have not been observed about the both samples. We have also studied the chemical state of the NPs by XPS and XAFS. The XAFS analyses have revealed that the MgH2 in the NPs can not be dehydrogenated at the room temperature even if the catalytic effect of the Pd.

Stability of Copper Nitride Nanoparticles under High Humidity and in Solutions with Different Acidity

Abstract Stability of copper nitride nanoparticles under high humidity and in acidic and alkaline solutions was investigated. The copper nitride was exposed to the humid condition (RH 85%, 358 K) for three weeks, which resulted in decomposition to copper oxide as revealed by XRD and XAFS analyses. However, the copper nitride nanoparticles were stable in acidic and alkaline solutions even for 11 days. We established conservation conditions for the copper nitride nanoparticles.

XAFS Analysis in Air and Reducing Atmosphere of (La, Sr)(Ti, Fe)O3-δ Ceramics for SOFC

XAFS Analysis in Air and Reducing Atmosphere of (La, Sr)(Ti, Fe)O_3-δ Ceramics for SOFC

Average, Local and Electronic Structures of LiMn2-XAlxO4(x=0, 0.2) in Charge-Discharge Process by Neutron and Synchrotron X-ray

INTRODUCTION As Li ion battery cathode materials, stratified formation materials such as LiCoO2 in which the Co are used mainly now. The Co-free spinel compound LiMn2O4 has been studied as Li-ion battery cathode materials. Simple composition and low cost of Mn is preferable for the battery material. However, there are the problems such as elution of the Mn with the cycle and the Jahn-Teller distortion by the Mn3+.1,2) Characteristic remarkable deterioration in this way occurs for a cycle. As solution to this problem, characteristic improvement by the substitution of the metallic element (Al, Co, Cr, Li, Mg, Ni, Ti, Zn) was reported.3) It is intended to examine a crystal structure change during charge and discharge process of the Al substituted spinel using the average and local structure analysis with ex-situ method. The average structures were calculated by Rietveld analysis and electron density by Maximum Entropy Method (MEM) using the neutron and synchrotron X-ray diffractions. In addition, we examined the local structure by XAFS and the PDF analysis using synchrotron X-ray total scattering. EXPERIMENTAL LiMn2-xAlxO4 (x=0, 0.2) were synthesized by the solid-phase method. The samples were determined for the valence state of Mn by potentiometric titration, and also characterized by XRD and ICP measurements. Charge-discharge test was performed using the HS cell (3.5 ~ 4.3V vs Li/Li+, the negative electrode: Li metal, separator: polypropylene, electrolyte: 1M LiPF6/EC:DMC (1:2)). Measured sample was obtained by the electrode after two cycles of charge and discharge process. These samples were measured at 4.04V, 4.15V, 4.3V in the charge process, and 4.12V, 4.02V, 3.5V in the discharge process. These samples were performed by neutron diffraction (BL20, BL09, J-PARC) and synchrotron X-ray diffraction (BL02B2, SPring-8). We attempted to Rietveld analysis, PDF and XAFS analysis using the measured data, and examined the electronic structure and the distortion during the charge discharge process. RESULTS AND DISCUSSION At first we performed the Rietveld analysis using the neutron diffractions about each sample of Al substituted material at charge process after 2 cycles. As a result, the occupancy of Li at 8a site changed with charge discharge process, and the occupancy of Li at 16d site was constant. Thus it was thought that only the Li at 8asite participates in electrochemical insertion and extraction. In addition, distortion parameter λ in the distance calculated from each analysis showed few changes. As for the Al substituted spinel, it was suggested that the host structure was stable in 2nd cycles during charge discharge process. We performed Rietveld analysis by the synchrotron X-ray diffraction measurement and calculated electron density in MEM and demanded a line profile of M(Mn,Al)-O. The line profile of charge discharge process of LiMn1.8Al0.2O4showed Fig. 1. It was demonstrated that the M(Mn, Al)-O bond of the Al substituted sample was more stable than unsubstituted one in charge discharge process. We examined XANES and EXAFS. The EXAFS spectrum of LiMn2O4 and LiMn1.8Al0.2O4were shown Fig. 2. From EXAFS spectrum, the relaxation of the Jahn-Teller distortion of the Mn was suggested, because peak intensity at charge state increased. Furthermore, we examined the PDF by synchrotron X-ray total scattering. In unsubstituted sample at discharge, the decrease in peak was confirmed in comparison with before charge. It was thought that this decrease was attributed to the elution of Mn. This study reported in detail on that day. It was performed by help of NEDO (RISING) and shows thanks to the members concerned. References 1) H. Mao, J.N. Reimers, Q. Zhong and U. von Sacken, Electrochem, Soc., Prec., 94-28, 245 (1994).2) M.M. Thackeray, A. De Kock, M.H. Rossouw, D. Liles, R. Bittihn and D. Hoge, J. Electrochem. Soc., 139, 2, 363 (1992).3) Y. Idemoto, K. Horiko, Y. Ito, N. Koura, and K. Ui, Electrochemistry, 72, 755 (2004).

Analysis of Crystal and Electronic Structure of Reduced Layered Material 0.5Li2MnO3-0.5LiMn5/12Ni5/12Co1/6O2 during Electrochemical Cycling

INTRODUCTION The solid solution materials of Li2MnO3-Li(Mn,Ni,Co)O2 show high electric discharge capacity. However, detachment of oxygen, hydrogen, carbon dioxide causes irreversible capacity at initial charge and discharge1). It was reported that oxygen in particular induced the irreversible behavior and extracted from the structure, which causes irreversible capacity and degradation of cycle performance2). However, the change of the crystal structure during electrochemical cycling of the sample which a quantity of oxygen decreased has been not clarified. In restraint of the oxygen detachment by the reduction heat-treatment was tried to solve this problem and examined properties of matter, a crystal, electronic structure, battery properties. In this work, it was intended to clarify the influence that reduction heat-treatment gave to a crystal and electronic structure during electrochemical cycling about 0.5Li2MnO3-0.5LiMn5/12Ni5/12Co1/6O2 (Li1.2Mn0.5667Ni0.1667Co0.0667O2). EXPERIMENTAL The 0.5Li2MnO3-0.5LiMn5/12Ni5/12Co1/6O2 was prepared by the coprecipitation method. The reduced sample material was obtained by heat treatment under vacuum atmosphere (800℃, 10-4Pa, 4h). The provided samples were identified by powder X-ray diffraction and measured for the valence of the transition metals by potential difference titration and for the chemical composition by ICP-OES. The cathode used by electrochemical measurement performed blend kneading on fire in active material : AB : KS-6 : PVdF (80 : 5 : 5 : 10 wt. ratio) in NMP. The slurry was then casted onto Al foil of current collector and dried at 100℃. The electrode was pressed with a pressure of 40MPa. The cells were assembled by using lithium foil as the counter electrode and a polypropylene film as the separator. The electrolytes were 1 M LiPF6 dissolved ethyl carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1/2. The electrochemical cycles were performed with the current density of 20 mA/g and the voltage range of 2.5-4.8 V vs. Li+/Li. After having dismantled it, the electrode in the cell was picked up (active material of ca. 10 mg) and was measured by synchrotron X-ray diffraction (BL02B2, BL04B2, Spring-8) and by neutron diffraction (iMATERIA, J-PARC). A provided diffraction patterns were analysed by the Rietveld method and were examined in the average structure. The XAFS analysis was also carried out to real the local structure. Based on Pair Distribution Function method (PDF), the local structures were also analyzed using powder X-ray total scattering. RESULTS AND DISCUSSION From powder X-ray diffractions, it was found that a product can be attributed to a single phase of the layered structure with space group of C2/m. The ratio of peaks in the diffraction pattern changed after reduction heat-treatment. As a result of ICP-OES, composition of lithium for the transition metal decreased from 1.165(5) to 1.093(4) after reduction heat treatment. The coulombic efficiency of the initial cycle was improved 73% to 77% by reduction heat-treatment By The synchrotron X-ray diffration, the lattice constants of the reduced sample increased from untreated one. The neutron diffraction of the electrode after initial charge-discharge process was measured to clarify the structural change during the first Li extraction/insertion process. Mn-ordering increased after the reductive heat treatment while oxygen amounts and the cation-mixing decreased. In the local structural information of the EXAFS for reduced sample also showed the increase of Mn- and Ni-ordering (Fig. 1). It was suggested that the diffrence of the both samples, a local change was seen in structure after an electric discharge by Pair Distribution Function method (Fig. 2). Reference 1) P. Lanza, H. Sommera, M.-S. Dobrickb, P. Nováka, Electrochimica Acta, 93, 117 (2013).2) Y. Idemoto, T. Kashima and N. Kitamura, Electrochemistry, 80, 791 (2012).

Unique structural characteristics of tin hydroxide nanoparticles-embedded montmorillonite (Sn-Mont) demonstrating efficient acid catalysis for various organic reactions

Tin hydroxide nanoparticles-embedded montmorillonite (Sn-Mont) was prepared by the simple treatment of sodium ion-exchanged montmorillonite (Na-Mont) with aqueous SnCl4, the physical and chemical properties of which were investigated by N2 adsorption, XRD, TG, TEM, 119Sn-MAS-NMR, and XAFS analyses. It was revealed that Sn-Mont was composed of Sn(OH)4-based nanoparticles (nano-Sn(OH)4) of less than 3nm in diameter surrounded by delaminated montmorillonite aluminosilicate unit layers. The arrangement of each aluminosilicate unit layer in the Sn-Mont is not laminated like that of the parent Na-Mont, but almost completely disordered to make a porous structure with a high surface area and a large pore volume that embraces the tin hydroxide-based nanoparticles. The intrinsic solid acid catalysis of Sn-Mont was used for the cyanotrimethylsilylation of benzophenone with cyanotrimethylsilane in an excellent yield, which was ascribed to the smooth reactant/product transfers in the micro/meso pores as well as the acidic property of the nano-Sn(OH)4 enwrapped by the delaminated aluminosilicate unit layers.

The coloring of geopolymers by the addition of copper compounds

The development of a new coloring technique is desirable to increase the commercial value of geopolymers. Selected copper compounds, i.e. Cu(OH)2, CuO, Cu2O, CuCO3∙Cu(OH)2∙H2O, CuCl2∙2H2O and CuSO4∙5H2O, were added to the initial reactants in order to color the geopolymers in the same manner as naturally occurring minerals. When Cu(OH)2, CuO and Cu2O were used, these compounds remained in the geopolymer matrix following hardening of the material. On the contrary, CuCO3∙Cu(OH)2∙H2O, CuCl2∙2H2O and CuSO4∙5H2O were not detected in the final products. XAFS analyses were performed to investigate the local structure of copper in the geopolymers produced. The results showed that the copper spectra of geopolymers incorporating Cu(OH)2, CuO and Cu2O correspond to those of pure Cu(OH)2, CuO and Cu2O, respectively. However, when CuCO3∙Cu(OH)2∙H2O, CuCl2∙2H2O and CuSO4∙5H2O were added, the copper generated spectra similar to that of the mineral chrysocolla ((Cu, Al)2H2Si2O5(OH)4∙nH2O) than the respective copper compounds.

XAFS study on Ca local structure in natural glasses and tektite

The local structures of tektite and natural glasses were studied by Ca K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in order to provide quantitative data on bonding distances and coordination numbers. The pre-edge peak intensities of tektites are 10.7-11.7%, and those of peudotachylite, Kirauea volcanic glass, impactite, pitchstone and perlite are 6.7–10.9%. The main peak shoulder intensities of tektites are 68.3–70.7%, and other natural glasses are 63.0–63.9%. XAFS analysis indicated all tektites possess 7-coordinated Ca, but natural glasses possess 6-, 7- and 8- coordinated Ca. This study indicated that different petrogenesis of natural glasses gives different local structures of calcium.

Volatilization characteristics of boron compounds during coal combustion

Boron behavior during coal combustion was studied experimentally and theoretically. Seven types of coal with different boron concentrations were pyrolyzed or burned, using an electrically heated drop tube furnace. In order to understand the effect of coal type on the boron component of ash, chemical equilibrium calculations were made to determine which boron compounds contributed to forming the boron compounds found in the ash particles. Additionally, XAFS analyses were also carried out to evaluate the results obtained by the chemical equilibrium calculations. Some boron compounds in coal were volatilized, and others remained in the molten coal ash after combustion. Both the chemical equilibrium calculations of the boron compounds under the combustion condition and the boron analysis of the ash particles by the XAFS suggested that the boron compound contained in the ash was mainly B2O3. The boron compounds were concentrated in the molten slag during combustion. The enrichment of boron into the ash as particles was related to the amount of slag formed. The index, (Base/Acid ratio)×(Ash content), correlates well with the volatilization fraction of boron even in the actual power plants.

Structure of selenium incorporated in pyrite and mackinawite as determined by XAFS analyses

Selenium has a toxic potential leading to diseases by ingestion and a radiotoxic potential as 79Se radionuclide if discharged from a high-level nuclear waste repository in deep geological formations into the biosphere. Selenium is often associated with sulfides, such as pyrite, the most important near-surface iron sulfide and constituent of host rocks and bentonite backfills considered for radioactive waste disposal. This study was aimed at investigating the incorporation of Se2− and Se4+ into pyrite and mackinawite to determine the relevance of iron sulfides to Se retention and the type of structural bonding. The syntheses of pyrite and mackinawite occurred via direct precipitation in batches and also produced coatings on natural pyrite in mixed-flow reactor experiments (MFR) under anoxic conditions at Se concentrations in the solutions of up to 10−3mol/L. Mineralogical analyses by SEM and XRD reveal the formation of pyrite and mackinawite phases. The average Se2− uptake in pyrite in batch experiments amounts to 98.6%. In MFR syntheses, it reaches 99.5%, both suggesting a high potential for retention. XAFS results indicate a substitution of sulfur by selenide during instantaneous precipitation in highly supersaturated solutions only. In selenide-doted mackinawite S2− was substituted by Se2−, resulting in a mackinawite-type compound. S− is substituted by Se− in selenide-doted pyrite, yielding a FeSSe compound as a slightly distorted pyrite structure. Under slighter supersaturated conditions, XAFS results indicate an incorporation of Se2− and Se4+ predominantly as Se0. This study shows that a substitution of S by Se in iron sulfides is probable only for highly supersaturated solutions under acidic and anoxic conditions. Under closer equilibrium conditions, Se0 is expected to be the most stable species.

Characterization and dynamic behavior of precious metals in automotive exhaust gas purification catalysts

Both the behaviors of sintering and reactivation of Pt and Rh on various metal oxide supports were investigated by TEM, CO pulse chemisorption and XAFS analysis. The results suggest that phenomenon of reversible sintering and re-dispersion to reduced, active metallic sites is related to the electron density of O atoms in support and to the crystal structure of support. As a result of in situ XAFS and in situ TEM analysis, Pt reversible sintering and re-dispersion phenomenon was observed on CeO2 based metal oxide. The Pt re-dispersion process proceeds by the repetition of (1) migration of Pt oxide from the surface of large Pt particles, (2) adsorption of Pt oxide on the surface of CeO 2 based metal oxide by strong Pt–O–Ce interaction and (3) reduction Pt oxide and Pt–O–Ce bond. To achieve a good balance between activity and the sintering suppression, CeO 2 based metal oxide is selected as Pt support, and ZrO 2 is used as Rh support. The blended catalyst of Pt on ceria based oxide and Rh on ZrO 2 has higher activity after aging.

Depth-Resolved XAFS Analysis of SrTiO<sub>3</sub> Thin Film

Depth-Resolved XAFS Analysis of SrTiO<sub>3</sub> Thin Film

Structure and infrared radiation property of Co1−x Zn x Fe2O4 ferrites by XAFS analysis

Co1−xZnxFe2O4 ferrites were prepared by solid state reaction. The microstructure and performance were studied by X-ray diffraction, X-ray absorption fine-structure analysis and IRE-2 infrared radiant test. It is found that infrared radiance show a nonlinear change with x, exhibiting the infrared radiance of this material improved and the average radiance in the 8–14 µm waveband reached 0.91. The Co3+ and Zn2+ ions are found to occupy both tetrahedral and octahedral sites, and correspondingly, the fraction of Fe3+ ions in B-site decreases nonlinearly in ferrites. The lattice parameters are found to concern with Zn2+, and the activation energy deduces from crystal strain and crystal vibrate increases with content Zn2+. The redistribution of the Co3+ and Zn2+ ions between tetrahedral and octahedral sites is related to the providing a selective tetrahedral and octahedral sites infrared radiance of Co1−xZnxFe2O4 ceramics with increasing x.

Fluorescence XAFS study of local structures in high-k gate dielectrics HfSiON/SiON/Si annealed at various nitrogen gas partial pressure

Geometric structures for HfSiON/SiON/Si films annealed at various N2 gas partial pressures were investigated using fluorescence XAFS measurement at Hf LIII- and LI-edge. The XAFS analysis has revealed that the local structures around the Hf atoms strongly depend on the N2 gas partial pressure. For the sample annealed at the N2 gas partial pressure of 10 Torr HfN and HfSiON coexist, and for the samples annealed at the N2 gas partial pressure above 100 Torr Hf atoms form HfSiON only. These results indicate that the formation of HfN for HfSiON/SiON/Si films can be suppressed by annealing at proper partial pressure of N2 gas.

XAFS studies on a modified Al-Si hypoeutectic alloy

To understand the role of Sr in doped aluminium-silicon alloys, we have conducted for the first time, Sr- K edge XAFS measurements on Al-3%Si-0.04%Sr. Aluminium-Silicon alloys are widely used in automobile and aerospace applications. Modification of these alloys with addition of trace levels of Sr (200–400 ppm) results in changing the morphology of Si eutectic from "plate" like structure to "fibrous" structure. Several theories have been proposed to understand the mechanism of modification of eutectic phases with Sr addition in these alloys, but there is no conclusive evidence in support of these theories. From our XAFS analysis, we suggest Sr-Si bonds and Sr-Sr correlations may be responsible for the morphological transformation observed in the alloy.

A XAFS study on the mechanism of isotopic fractionation of molybdenum during its adsorption on ferromanganese oxides

Due to its potential as a paleoredox proxy, there have been many studies on Mo isotopic fractionation during adsorption onto ferromanganese oxides in seawater. However, the mechanisms of both adsorption and isotopic fractionation are still under debate due to the lack of structural information on the adsorbed species. In this study, XAFS analyses were performed to reveal the mechanism, based on structural information at the molecular level, of Mo isotopic fractionation during adsorption onto ferromanganese oxides. Molybdenum L3-edge XANES and K-edge EXAFS revealed that Mo species adsorbed on the surface of ferrihydrite was a tetrahedrally coordinated outer-sphere complex, while that on δ-MnO2 was an octahedrally coordinated inner-sphere complex. Additionally, it was also revealed that δ-MnO2 was the dominant host phase of Mo in the hydrogenetic ferromanganese nodules from the comparison of their XAFS spectra. Previous studies reported that lighter isotopes of Mo were preferentially incorporated into ferromanganese oxides from seawater. This fractionation can be explained based on the structural difference between tetrahedral MoO42- (=a major species in seawater) and the octahedral species adsorbed on the Mn oxide phase in ferromanganese nodules. In contrast, little change in Mo local structures during its adsorption onto ferrihydrite also suggested the little or no fractionation of Mo isotopes in the presence of Fe hydroxides without Mn oxides. These facts imply that the Mo isotopic composition in ancient marine sediments can distinguish redox boundaries of Fe2+/Fe(OH)3 and of the more oxic Mn2+/MnO2.

Effect of Potential on Sulfur-Poisoning of Pt/C Catalyst

The Pt/C catalyst of polymer electrolyte membrane fuel cell (PEMFC) was poisoned by 5 ppm of hydrogen sulfide for 5 hours at potentials of 0V, 0.3V, 0.6V and 0.9V vs. RHE, and the catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) analysis. Only diffraction peaks of Pt, carbon and ionomer were observed in all samples, and the crystallite size of Pt was about the same after poisoning. In the XPS and XAFS analyses, accumulation of sulfur species on Pt/C catalyst and oxidation of Pt were observed in the samples poisoned at 0.3V and 0.6V.

Synthesis and characterization of lanthanide-incorporated FSM-16 type mesoporous silica

Noble FSM-16 type mesoporous silicas incorporating lanthanides (Ln = La, Ce, Pr) have been successfully synthesized by a modified sheet folding process of kanemite–CTAB system. For comparison, Ln-loaded FSM-16 was prepared by a simple impregnation method. The local structure of Ln species and pore structure were investigated by XRD, diffuse reflectance UV absorption, XAFS and N 2 adsorption measurement. The impregnation causes the deposition of Ln species on the pore walls and thus decreases the pore size and pore volume. By contrast, Ln-incorporated FSM-16 exhibited mesoporosity comparable to the pristine FSM-16. XAFS analysis indicated that Ln species showed tetrahedral coordination and the Ln–O atomic distance was smaller than that of bulk oxide such as La 2O 3, CeO 2 and Pr 2O 3. The pore structure of Ln–FSM-16 and local structure of lanthanide were thermostable up to 800 °C.