Language：Japanese   Publisher：Surface and Interface Analysis  

Carbon-binding state of humin (HM, a non-conductive insoluble organo-mineral humic substance) was successfully characterized for the first time by synchrotron-radiation–based X-ray photoelectron spectroscopy (XPS). Four sample preparation techniques—HM on double-sided carbon tape, indium sheet, copper mesh, and in pellet formed from the mixture of HM and copper powder (Cu) at different mixing ratios (1:1, 1:2, and 1:6 v/v)—were compared. The results show that HM samples prepared using the first three methods had significant charge buildup, which made the interpretation of the XPS spectra impossible because of the shifts in the binding energy of C 1s XPS spectra. Pellets of HM:Cu mixture enhanced the electrical conductivity and reduced charge buildup on the sample surface. Pellets prepared with HM:Cu ratio of 1:1 (v/v) provided the minimum charge buildup and high sensitivity with difference in C 1s spectra regardless of the observing position. The C 1s spectra, estimated by the subtraction of the carbon contamination in Cu, showed the resolution of CC (284.0 eV), CC/CH (285.1 eV), CO (286.3 eV), CO (287.3 eV), and OCO (288.3 eV) and three additional peaks of CF (289.3 eV), CF2 (290.2 eV), and CF3 (291.4 eV). Soft X-ray absorption spectroscopic (XAS) analysis further proved the existence of fluoride (F 1s) in HM structure. The detection of fluorinated carbon in HM showed a great advancement of XPS compared with other conventional analyses. X-ray with the incident angle of 0° provided the smallest (nearly negligible) energy shift in the C 1s spectra of HM and did not damage the surface of the sample.

DOI： 10.1002/sia.6574

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Language：Japanese   Publisher：Surface and Interface Analysis  

In this study, gold nanoparticles (AuNPs) prepared in a 5 mM CsCl aqueous solution using the solution-plasma method are characterized via transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy with synchrotron radiation (SR-XPS). The particle diameter is measured over the process time via TEM. During the solution-plasma process, small particles of 2.1 to 2.2-nm diameter are generated in the CsCl aqueous solution; these particles then enlarge via Ostwald ripening over time until they reach an equilibrium size of ~13 nm after 36 days. In addition, the surface chemical states of the AuNPs are characterized at different depths via SR-XPS. The SR-XPS measurements obtained using incident X-ray energy (hν) of 945.0 eV revealed that Cs─Au, Cl─Au, and Cs─Cl─Au bonds are present 1.2 nm below the surface. The measurements obtained at an incident X-ray energy of 2515.0 eV showed that Cs─Cl─Au bonding is also present 2.5 nm below the surface, indicating that Cs and Cl strongly interact with Au. The TEM and SR-XPS measurements revealed that 2 processes occur cyclically during the growth process via Ostwald ripening: (i) the Cs and Cl in the aqueous solution adsorb on the AuNP surface and (ii) Au atoms subsequently bond to the AuNPs surface.

DOI： 10.1002/sia.6555

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Language：Japanese   Publisher：Surface and Interface Analysis  

Au nanorods with a low toxicity are important in medical field. The nanorods are generally fabricated by using cetyltrimethylammonium bromide (CTAB), which has a high toxicity. We have attempted the fabrication of Au nanorods without CTAB reagent. In this study, Au nanoparticles as growth seeds of the nanorods have been fabricated by using Au rods and NaCl aqueous solution. Subsequently, Au3+ ions of HAuCl4 have been reduced in the mixing solution, which includes the Au nanoparticles and the NaCl aqueous solution, by means of the solution plasma between W rods. The amount of Au3+ ion has been directly monitored during the solution plasma process by using in-situ UV–Vis-NIR. The fabricated solution possesses the Au nanoparticles of shapes of rod, sphere, triangle plate and hexagonal plate, respectively. The Au nanorods may be fabricated by both aggregating the reduced Au3+ ion at the surfaces of the Au nanoparticles as the growth seeds and controlling the growth orientation of the Au nanorods by the adsorption of Cl− ions on Au{100} facets. To control the narrow dispersion relation between the short and the long axes lengths of the Au nanorods, the addition of HAuCl4 aqueous solution in small volume steps is a key point. Copyright © 2016 John Wiley & Sons, Ltd.

DOI： 10.1002/sia.6096

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Scopus

Publisher：e-Journal of Surface Science and Nanotechnology  

Mg nanoparticles covered with the Pd nanoparticles (Pd/Mg NPs) have been fabricated by the gas evaporation method using He gas. The coaxial formation of the Mg and Pd NPs enables to fabricate the Pd/Mg NPs. The surfaces of the Pd and Mg NPs are quite clean because only pure He gas has been used during the fabrication of the NPs. The surface and interface chemical states of the Pd/Mg NPs have been investigated by X-ray photoelectron spectroscopy (XPS) without the exposure to the air. The XPS investigation has revealed that the formation of the interfacial alloy state between the Mg and Pd NPs. The Pd/Mg NPs can absorb the hydrogen at the room temperature by the hydrogenation of the most of the Mg atoms inside the Pd/Mg NPs.

DOI： 10.1380/ejssnt.2016.150

Scopus

Language：Japanese   Publisher：Journal of Physics: Conference Series  

Ga2O3 loaded Al2O3 samples (Ga2O3/Al2O3) were prepared to change coordination structures around Ga atoms. Ga K-edge XANES spectra of the Ga2O3/Al2O3 samples showed two peaks assigned to Ga atoms having tetrahedral coordination structure (Ga(t)) and octahedral one (Ga(o)). Curve-fitting analysis of XANES spectra was carried out with a set of pseudo- Voight and arctangent functions, and the fractions of Ga(t) and Ga(o) were quantitatively estimated from the ratio of the peak areas. EXAFS curve-fitting analysis also evaluated the fractions of Ga(t) and Ga(o) and they were in good agreement with those obtained by XANES analysis. It was revealed that the fraction of Ga(t) increased with the decrease in the loading amount of Ga2O3 due to the interaction of Ga species with Al2O3. The fractions of Ga(t) and Ga(o) might relate to the photocatalytic activity for CO2 reduction with H2O over the Ga2O3/Al2O3 samples.

DOI： 10.1088/1742-6596/712/1/012056

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Language：Japanese   Publisher：Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms  

A nitrogen doped TiO2 as a visible-light response photocatalyst was prepared by N+ implantation technique. N+-implanted TiO2 samples promoted the photocatalytic activity for degradation of methylene blue under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1 ≤ x ≤ 2) species. In the valence band XPS spectrum of the high activity sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substitutional nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts.

DOI： 10.1016/j.nimb.2015.04.010

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Language：Japanese   Publisher：Applied Surface Science  

Gold nanoparticles are prepared in various concentrations of NaCl solutions by solution plasma sputtering. The absorption spectra of these solutions during and after the plasma process are measured by in situ ultraviolet-visible (UV-vis) spectroscopy to estimate the particle diameters and concentrations of gold. The distributions of particle diameters are obtained by transmission electron microscope (TEM) observations. These experiments indicate the gold nanoparticles with about 2.2 nm are directly formed by plasma phase and the diameters are increasing over time. These increases of particle diameters are caused by Ostwald ripening of gold nanoparticles in NaCl solution. We estimate the equilibrium diameter at which the gold nanoparticles are not solved in NaCl solution using in situ UV-vis spectroscopy. These diameters are about 5, 7 and 10 nm in 3, 5 and 10 mM NaCl solution, respectively. We make it possible to control the diameter of gold nanoparticles prepared by solution plasma sputtering in NaCl solution.

DOI： 10.1016/j.apsusc.2015.04.139

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Publisher：International Journal of Hydrogen Energy  

We have fabricated the materials composed of the Mg and the Ni nanoparticles and clarified the hydrogen storage property by using TEM, XPS and QCM. The Mg and the Ni nanoparticles have been fabricated by gas evaporation method and been mixed. The diameters of the Mg and the Ni nanoparticles have been estimated as 20.0 ± 8.4 and 4.7 ± 2.0 nm, respectively. And the Mg and the Ni nanoparticles as prepared sample possess almost clean surface. This sample can absorb the hydrogen under atmospheric pressure at 30 °C before completely oxidized. However, the hydrogen storage ability of this sample has been lost by the adsorption of residual gases even under vacuum condition in several hours after the end of fabrication. Due to the Mg oxide shell on the surface of the Mg nanoparticles is formed by the residual gases, the hydrogenation of the Mg nanoparticles are hindered.

DOI： 10.1016/j.ijhydene.2015.05.031

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DOI： 10.1016/j.ijhydene.2015.04.087

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Publisher：e-Journal of Surface Science and Nanotechnology  

The hydrogen absorption behavior of the Pd NPs has been investigated by the noble techniques. The Pd NPs with the clean surface have been fabricated by the gas evaporation method. The P-C isotherm of the hydrogen absorption of the Pd NPs has been obtained using the QCM without the exposure to the air. The P-C isotherms have shown the clear size dependent absorption behavior for the Pd NPs. Further absorption and desorption cycles decrease the solubility of H significantly in the Pd NPs.

DOI： 10.1380/ejssnt.2015.343

Scopus

Publisher：Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals  

We introduce the spectroscopic investigation of the nano-composite materials consisted of Mg and Pd. Mg is most promising material for the application of the hydrogen storage because of the high gravimetric hydrogen storage capacity up to 7.6 mass%. In spite of the advantage of the hydrogen storage capacity, the practical use of Mg has not been established due to the slow hydro-/dehydrogenation reactions and the high temperature required to store and release the hydrogen. Nano-sized Mg such as Mg nanoparticle is expected to store the hydrogen rapidly because of the high specific surface area of the nanoparticle. Moreover, addition of Pd decreases the temperature for the hydrogen storage of Mg because of the catalytic effect for the dissociation reaction of hydrogen molecules. We have fabricated the nanoparticles composed of the both Mg and Pd by the gas evaporation method using He gas. These nanoparticles can store the hydrogen at the room temperature. After the storage of the hydrogen, the release of the hydrogen has not been observed up to 100°C. The analyses of the X-ray absorption fine structure (XAFS) have revealed that the irreversible change of the chemical state during the hydrogen storage causes the inactivation of the surface of nanoparticles and inhibits the dehydrogenation reaction of the MgH2.

DOI： 10.2320/jinstmet.JC201409

Scopus

Language：Japanese   Publisher：IOP Conference Series: Materials Science and Engineering  

Vulcanized rubber materials are useful in our surroundings. However, detail structure and reaction are not revealed even in present. Since squalene molecule possesses some same properties compared with natural rubber, we have prepared the samples of vulcanized squalene at 140 ° C for several hours. To understand the vulcanization reaction,sulfur K-edge NEXAFS measurements have been carried out for the vulcanized squalene under liquid phase with He-path system and fluorescence detection mode. Moreover, we have tried curve fitting analysis of NEXAFS spectra. The results indicate that the squalene has been vulcanized by the S8 molecule at 140 ° C and the S8 molecule length is shortened from 8 to 5-6 after the vulcanization reaction.

DOI： 10.1088/1757-899X/76/1/012004

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Language：Japanese   Publisher：IOP Conference Series: Materials Science and Engineering  

The gold nanoparticles (Au NPs) colloidal solution and the phosphatidylcholine (PC) liposome aqueous solution are fabricated by the solution plasma method and the extrusion procedure, respectively. When the Au NPs colloidal solution and the PC liposome aqueous solution are mixed, considering the TEM image, we think that the Au NPs firstly are covered with the PC molecules, which do not contribute to form the PC liposome, and subsequently the Au NPs covered with the PC adsorb on the PC liposome surface. We propose that the PC molecule adsorbs on the Au sheet surface at the methyl group of N-CH3 and the oxygen atoms of P-O, P=O, C-O and C=O bonds, because each peak intensity of N, O and P K-edges NEXAFS spectra for the PC/Au sheet is reduced in comparison with that for the PC multilayer. Furthermore, the Au NPs covered with PC seem to be aggregated each other through the hydrophobic groups of PC on Au NPs.

DOI： 10.1088/1757-899X/76/1/012001

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Language：Japanese   Publisher：Surface and Interface Analysis  

We have fabricated the Ni nanoparticles with a clean surface by the gas evaporation method and clarified the hydrogen storage property by using atomic forcemicroscope (AFM), X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance(QCM)measurements. The diameter has been estimated as 4.0 ± 1.5nm by AFM observation. The Ni nanoparticles possess a clean surface, because the surface chemical state has been confirmed asmainlymetallic state by XPS. The hydrogen storage property has been investigated by QCM fromthe vacuum to the atmospheric pressure of the hydrogen at 300 K. The plateau pressure of the Ni nanoparticles and amaximum hydrogen storage capacity are about 7 Torr and H/Ni = 0.56, respectively. And the hydrogen release from the Ni nanoparticles has not been observed by QCM. The hydrogen adsorption/desorption reaction have also been observed as the plateau like pressure by QCM. These results indicate that (i) the plateau pressure of Ni is decreased by the nanosizing of the material, (ii) the large specific surface area of the Ni nanoparticlesmakes it possible to observe the adsorption/desorption reaction and (iii) the Ni hydride is stable under the vacuum condition. The chemical shift of Ni 2p3/2 has not been observed in the XPS spectrum between before and after exposure to the hydrogen. This result implies that there is no strong chemical bonding between Ni and hydrogen or the hydrogen in the lateral surface has been released.

DOI： 10.1002/sia.5566

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Publisher：e-Journal of Surface Science and Nanotechnology  

We have prepared silver-loaded gallium oxide (Ag/Ga2O 3) photocatalysts by the solution plasma method (SPM) and impregnation method (imp), and investigate the effects of the chemical states and the size of the Ag nanoparticles on their photocatalytic activities. The photocatalytic reduction of CO2 with water proceeds over all the Ag/Ga2O3 photocatalysts to produce CO, however the CO production rates decrease during photocatalytic reaction. Measurements of UV-VIS diffuse reflectance spectra, XANES spectra and TEM images reveal the followings: the Ag oxide nanoparticles in the as-prepared Ag/Ga 2O3 (imp) samples exist and their size distribution is wide from 5 to 10 nm. They become a lot of metallic nanoparticles by UV light-irradiation, and become larger particles with the size of ca. 20 nm during the photocatalytic reaction. On the other hand, the Ag nanoparticles in the as-prepared Ag/Ga2O3 (SPM) samples are metallic with the size of less than 10 nm. The size does not change under UV light irradiation, while become larger particles during the photocatalytic reaction as similar to the case of the Ag/Ga2O3 (imp) samples. Such small metallic Ag nanoparticles with the size of 5-10 nm are suitable for CO production. However, they aggregate during the reaction for 5 h to degrade the photocatalytic activity. © 2014 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2014.263

Scopus

Publisher：20th World Hydrogen Energy Conference, WHEC 2014  

The hydrogen storage property of the nanoparticles composed of the Mg and Pd atoms (Mg-Pd NPs) has been investigated by QCM technique without the exposure to the air. We have also studied the chemical state of the Mg-Pd NPs by XPS and XAFS. The Mg-Pd NPs can store the hydrogen under the room temperature and 1 atm of H2 gas. However, the release of the hydrogen has not been observed. XAFS study has revealed that the irreversible change of the Mg-Pd NPs has caused the inhibition of the release of hydrogen.

Scopus

Publisher：20th World Hydrogen Energy Conference, WHEC 2014  

We have fabricated the materials composed of the Mg and the Ni nanoparticles and clarified the hydrogen storage property by using TEM, XPS and QCM. The Mg and the Ni nanoparticles have been fabricated by the gas evaporation method and been mixed. The diameters of the Mg and the Ni nanoparticles have been estimated as 20.0±8.4 and 4.7±2.0 nm, respectively. The XPS results show that the Mg and the Ni nanoparticles as prepared sample possess almost clean surface. However, this materials has not been hydrogenated under hydrogen atmospheric pressure at 303 K. The QCM results indicate that the hydrogen storage ability of this materials has been lost by the adsorption of residual gases even under vacuum condition in several hours after the end of fabrication. The XPS results after hydrogen exposure show that due to the Mg oxide shell on the surface of the Mg nanoparticles is formed by the residual gases, the hydrogenation of the Mg nanoparticles are hindered.

Scopus

Publisher：20th World Hydrogen Energy Conference, WHEC 2014  

The hydrogen storage property of the binary nanoparticles composed of Mg and Pd has been investigated by QCM technique without the exposure to the air. The two types of nanoparticles have been fabricated by the gas evaporation method with 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 each Mg and Pd nanoparticles (Mg NPs-Pd NPs). We have also studied the chemical state of the nanoparticles by XPS and XAFS. Both the Mg-Pd NPs and the Mg NPs-Pd NPs can store the hydrogen under the room temperature and 1 atm of H2 gas. However, the releases of the hydrogen have not been observed about the both samples. XAFS study has revealed that the irreversible change of the Mg-Pd NPs has caused the inhibition of the release of hydrogen. On the other hand, it seems that the Mg NPs-Pd NPs cannot release the hydrogen due to the stability of the MgH2 or the low hydrogen diffusion property inside of the MgH2.

Scopus

Language：Japanese   Publisher：Applied Surface Science  

We have studied on the hydrogen storage materials based on Mg-Ni alloy and fabricated the sample constructed with the Pd thin layer (TL) on Mg 6 Ni alloy substrate. The adsorption behavior of the dimethyl disulfide (DMS) molecules on the sample has been measured to reveal the sulfur poisoning of the Pd TL/Mg 6 Ni by means of XPS and Sulfur K-edge NEXAFS techniques. The chemisorbed DMS, methanethiolate (MT) and atomic S have been observed on the surface. Especially, it is clear that some atomic S has been oxidized by air and detected the adsorbate of the SO 32- and SO 42- species. During exposure to the atmosphere, most of the adsorbed DMS and MT adsorbates desorb from the Pd TL surface. We thus conclude the Pd TL might be able to prevent the hydrogen storage materials from the sulfur poisoning. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2012.05.098

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Language：Japanese   Publisher：Applied Surface Science  

We have revealed the enlargement mechanism of Pd nanoparticles (NPs) on SiO 2 /Si by the AFM observation and the XPS measurement, when the Pd NPs react with the l-cysteine under water environment. Furthermore, the adsorbates on the Pd NPs/SiO 2 /Si have been confirmed by the XPS measurement. The Pd NPs with clean surface are fabricated and deposited on the SiO 2 /Si substrate by the gas evaporation method. In that aspect, the Pd NPs possess an interaction with the SiO 2 /Si surface. When the Pd NPs/SiO 2 /Si is reacted into the l-cysteine aqueous solution, the adsorbates originated from the l-cysteine exist on the Pd NPs surface. On the contrary, the l-cysteine hardly adsorb on the SiO 2 /Si. The enlargement of the Pd NPs is stimulated by the contributions of the H 2 O and/or the l-cysteine molecules because the Pd NPs can be more easily migrated on the SiO 2 /Si surface due to those contributions. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2012.05.123

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Publisher：e-Journal of Surface Science and Nanotechnology  

We have investigated the L-cysteine adsorption reaction on the Au nanoparticles (NPs) prepared by means of the solution plasma method. The particle size of the Au NPs is estimated to be 2.4±1.0 nm as prepared. When the L-cysteine adds into the Au NPs colloidal solution, the solution color is quickly changed from red to dark blue. It is found that the adsorbates of L-cysteine thiolate, cystine and atomic sulfur exist on the Au NPs surface by sulfur K-edge NEXAFS. In addition, the Au NPs aggregate each other by the hydrogen bonding at carboxyl groups and produce the black colored precipitate. In this paper, we have revealed the adsorption behavior of the L-cysteine on the Au NPs by AFM, UV-vis, ζ-potential measurement and NEXAFS techniques. © 2013 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2013.18

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Language：Japanese   Publisher：Journal of Physics: Conference Series  

The air oxidation reaction of Mg nanoparticle thin film has been investigated by Mg K-edge NEXAFS technique. It is revealed that MgO is formed on the Mg nanoparticle surfaces at the early stage of the air oxidation for Mg nanoparticle thin film. The simulation of NEXAFS spectrum using standard spectra indicates the existence of complex magnesium carbonates (x(MgCO 3).yMg(OH2).z(H2O)) in addition to MgO at the early stage of the air oxidation.

DOI： 10.1088/1742-6596/417/1/012065

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Language：Japanese   Publisher：Applied Surface Science  

We focus on the biocompatibility of Pd nanoparticles (NPs) from the point of microscopic view. Thus, as the basic research for the biocompatibility, we have investigated the adsorbates on the Pd NPs surface and the aggregation mechanism for the Pd NPs on Si substrate after dipping into l-cysteine aqueous solution by means of NEXAFS measurement and AFM observation. The Pd NPs have been fabricated and deposited on the Si wafer by the gas evaporation method. Judging from the results of NEXAFS measurement, it is clear that the l-cysteine thiolate and atomic S exist on the Pd NPs surface. The results of AFM observation show that the Pd NPs aggregate. It is thought that the aggregation of the Pd NPs occurs by both the migration of the Pd NPs on Si wafer and the cross-linked reaction. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2012.04.123

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Language：Japanese   Publisher：Applied Surface Science  

We have focused on the biocompatibility of the Ag nanoparticles. In this paper, we have fabricated the Ag nanoparticles by means of the solution plasma method. Since this method does not need to use the surfactant molecule, such as the water soluble polymer, the fabricated nanoparticle might possess the clean surface. The average diameter of the Ag nanoparticles is estimated to be 5.0 ± 1.1 nm. NEXAFS spectra show l-cysteine thiolate adsorbs on the Ag nanoparticle surface and l-cystine is synthesized. Though this reaction behavior is similar to the result of Rh(PVP, polyvinylpyrrolidone) system, in our previous study, the reaction speed for the Ag nanoparticle is much faster than that for the Rh(PVP) nanoparticle. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2012.06.107

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Publisher：e-Journal of Surface Science and Nanotechnology  

The cobalt and cobalt nitride nanoparticles (NPs) have been fabricated by gas evaporation method under helium or nitrogen gases environment. These chemical states and compositions have been investigated by in-situ XPS and those distributions have been estimated by AFM. It is found that both cobalt and cobalt nitride NPs are slightly oxidized by the residual gas in the chamber. The cobalt nitride NPs fabricated under nitrogen gas are including the nitrogen atoms at 4.7% and the nitrogen atoms have the chemical bonding with the cobalt atoms. © 2012 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2012.351

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Publisher：NANOCON 2012 - Conference Proceedings, 4th International Conference  

We have revealed the radiation damage for the cys/Au NPs/Ni sample by the X-ray irradiation at the energy regions of N and O K-edges NEXAFS. The Au NPs colloidal solution is fabricated by the solution plasma method, and the adsorption reaction between the Au NPs and L-cysteine is promoted under water environment. About the cys/Au NPs/Ni sample after the X-ray irradiation, the radiation damages appear at N and O K-edges NEXAFS, S2p XPS and N1s XPS spectra. It is found that the L-cysteine adsorbates desorb from the Au NPs surface. This desorption occurs by means of the electron bombardment of secondary electrons excited from the Au NPs surface.

Scopus

Publisher：NANOCON 2012 - Conference Proceedings, 4th International Conference  

The chemical state around the Mg and Pd atoms in the Mg-Pd nanoparticles has been investigated by the Mg K- and Pd L3-edges NEXAFS techniques under in-situ condition. The Mg-Pd nanoparticles possess metallic Mg and Pd states and the surface of the Mg-Pd nanoparticles is partly oxidized. Moreover, both the Mg K- and Pd L3-edges NEXAFS spectra show that the Mg-Pd alloy phases are formed in the Mg-Pd nanoparticles. The variation of the chemical states around the Pd atom after the cycles of the exposure to the H2 gas has been also investigated by the Pd L3-edge NEXAFS technique. The Mg-Pd alloy phases dissociate by the cycles of hydrogenation and dehydrogenation.

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1380/ejssnt.2011.315

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Publisher：e-Journal of Surface Science and Nanotechnology  

The adsorption reaction of L-cysteine on Pd thin layer surface constructed by nano-dots under water envi- ronment has been investigated by S K-edge NEXAFS with He-path system under atmospheric pressure. It is revealed that L-cysteine physisorbs on Pd/Al2O3/NiAl(111) substrate surface through the thiol group and the carboxyl one, and chemisorbed L-cysteine exists on the surface as L-cysteine thiolate. Before and after dipping the Pd/Al 2O3/NiAl(111) substrate into L-cysteine aqueous solution, the surface morphology is observed using AFM. The morphology of the Pd/Al 2O3/NiAl(111) substrate is composed of many nano-dots before dipping. After dipping, the nano-dots are enlarged. ©2011.289] 2011 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2011.289

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1380/ejssnt.2011.438

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1380/ejssnt.2010.246

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Publisher：e-Journal of Surface Science and Nanotechnology  

We have studied the adsorption reaction of dimethyl sulfide (DMS) on the Rh-polyvinylpyrrolidone (Rh(PVP)) nanoparticles by using AFM, XPS and NEXAFS techniques. The AFM images show the morphology of the Rh(PVP) nanoparticles depends on the amount of them. The XPS results indicate that the dissociation reaction of DMS into atomic S does not depend upon the existence of the Rh(PVP) nanoparticles. The NEXAFS results show that there is a strong chemical bonding between Rh(PVP) nanoparticle and atomic S. © 2010 The Surface Science Society of Japan.

DOI： 10.1380/ejssnt.2010.233

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：IEEJ Transactions on Electronics, Information and Systems  

The Mg nanoparticles have been fabricated by the gas evaporation method under the several He gas pressures. We have estimated the size of Mg nanoparticles by atomic force microscopy (AFM) observation and have studied the chemical state of Mg nanoparticles exposed to atmosphere by near-edge X-ray absorption fine structure (NEXAFS) technique. The average diameters of Mg nanoparticles fabricated under 3, 5 and 10 kPa of He are 3.6, 8.0 and 5.0 nm, respectively. It is found that the degree of atmospheric oxidation of Mg nanopaticles depends on the size of nanoparticles. © 2010 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejeiss.130.1746

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Publisher：IEEJ Transactions on Electronics, Information and Systems  

We have studied the adsorption reaction of dimethyl sulfide (DMS: (CH 3)2S) on the surface of Rh(PVP) nanoparticles by using AFM, XPS and NEXAFS techniques. The AFM images show the degree of dispersion of the Rh(PVP) nanoparticles depends on the amount of them. The in-situ XPS results indicate that the dissociation reaction of DMS into atomic S does not depend upon the existence of the Rh(PVP) nanoparticles. The NEXAFS results show that there is a strong chemical bonding between Rh(PVP) nanoparticle and atomic S. The ex-situ XPS results show the atomic S adsorbed on the Rh(PVP) nanoparticles partially desorb by exposing to the air. © 2010 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejeiss.130.1751

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Publisher：NANOCON 2010 - 2nd International Conference, Conference Proceedings  

We have revealed the radiation damage for the cys/Au NPs/Ni sample by the X-ray irradiation at the energy regions of N and O K-edges NEXAFS. The Au NPs colloidal solution is fabricated by the solution plasma method, and the adsorption reaction between the Au NPs and L-cysteine is promoted under water environment. About the cys/Au NPs/Ni sample after the X-ray irradiation, the radiation damages appear at N and O K-edges NEXAFS, S2p XPS and N1s XPS spectra. It is found that the L-cysteine adsorbates desorb from the Au NPs surface. This desorption occurs by means of the electron bombardment of secondary electrons excited from the Au NPs surface.

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

Silver nanoparticles (Ag NPs) were synthesized by a solution plasma method (SPM) in an aqueous solution of ammonia. Optical emission spectra of the plasma revealed that Ag NPs are fabricated with the sputtering of Ag rods as electrode by the produced energetic plasma particles such as H, OH and O radicals. In-situ optical absorption measurements of the solution during the discharge directly presented the concerted formation and aggregation processes of the Ag NPs, which controlled the size of Ag NPs. The synthesized Ag NPs were loaded on gallium oxide (Ga2O3) photocatalyst, and the photocatalytic activities of the obtained Ag loaded Ga2O3 (Ag/Ga2O3) samples were evaluated. Although the photocatalytic reaction proceeded over all the samples to produce CO, the CO production rates decreased with the reaction time. Measurements of DR UV–vis spectra and TEM images revealed that a part of the Ag NPs migrated and aggregated on the photocatalyst surface to become larger particles during the photocatalytic reaction, which would be related to the decrease of the photocatalytic activity. It was also found that the photoirradiation treatment on the prepared Ag/Ga2O3 sample before the use for the photocatalytic reaction improves the photocatalytic performance.

DOI： 10.1016/j.cattod.2017.08.047

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Surface Science Society of Japan  

Rhodium nanoparticles were deposited by the evaporation method on a silicon wafer. The process used He gas in a Rh evaporation chamber that was connected to the load-lock chamber of BL6N1 at Aichi Synchrotron Radiation Center (Aichi SR). NO gas was introduced into the evaporation chamber, and the deposited Rh nanoparticles were exposed to NO with and without an ambient atmosphere to study the effect of O2 on the electronic properties of the Rh nanoparticles and the behavior of NO molecules using synchrotron-radiation X-ray photoelectron spectroscopy (SR-XPS). The diameter of the Rh nanoparticles was estimated by transmission electron microscopy to be 2.7±0.6 nm. The XPS analysis indicates that the deposited Rh nanoparticles before NO exposure were in the metallic state. After exposure to NO, a part of the outermost surface of the Rh nanoparticles changed into Rh oxide, and NO molecules, atomic N and O species, and NO2 were detected. On the other hand, after exposure to NO in ambient air, the surface of the Rh nanoparticles was preferentially oxidized. In addition, a few NO molecules were adsorbed on the surface of Rh, and a small amount of the adsorbed NO that reacted with the surface oxygen turned into NO2.

DOI： 10.1380/ejssnt.2018.36

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Surface Science Society of Japan  

Rh nanoparticles have been fabricated by the evaporation method using the He gas in the Rh evaporation chamber, connected with the pre-evacuation chamber of BL6N1 at Aichi Synchrotron Radiation Center (Aichi SR). The electronic and geometric properties of the Rh nanoparticles have been verified without atmosphere exposure (in situ XPS) and after atmosphere exposure (ex situ XPS) using SR-XPS and TEM. The size of Rh nanoparticles is estimated 1.8±0.5 nm in diameter and deposited on a substrate. Judging from the result of the in situ XPS analysis with photon energy of 2.0 keV and 3.5 keV, the surface of the deposited Rh nanoparticles without atmosphere exposure is the metallic state. On the other side, the outermost surface changes into Rh oxide after atmosphere exposure even in a short time. For a long time atmosphere exposure moreover, the Rh oxide increases in the depth direction, and the deep area is in the higher oxidation state.

DOI： 10.1380/ejssnt.2017.50

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

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 nanopardcles 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 H-2 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. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2015.04.087

Web of Science

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/jinstmet.JC201409

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The nanoparticles composed of Mg and Pd atoms (Mg-Pd NPs) have been fabricated by the gas evaporation method, and the variation of the chemical state during hydro-/dehydrogenations has been investigated by X-ray photoelectron spectroscopy (XPS) and in-situ X-ray absorption fine structure (XAFS) analyses. Both XPS and XAFS spectra have indicated that the Mg-Pd NPs contain the chemical state of the metallic Pd and Mg-Pd alloy phases. The Mg-Pd alloy phase has been identified as MgPd and Mg6Pd by the Pd K-edge EXAFS analysis. The hydrogen release of the Mg-Pd NPs has not been observed after first hydrogenation due to the migration of Mg toward the surface of the Mg-Pd NPs during the hydrogen storage. This irreversible migration has led the inhibition of the hydrogen diffusion into the surface from the inside of the Mg-Pd NPs. Copyright (c) 2014 John Wiley & Sons, Ltd.

DOI： 10.1002/sia.5647

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1384/jsa.17.319

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン開催