Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

Platinum nanocatalysts play critical roles in CO oxidation, an important catalytic conversion process. As the catalyst size decreases, the influence of the support material on catalysis increases which can alter the chemical states of Pt atoms in contact with the support. Herein, we demonstrate that under-coordinated Pt atoms at the edges of the first cluster layer are rendered cationic by direct contact with the Al2O3 support, which affects the overall CO oxidation activity. The ratio of neutral to cationic Pt atoms in the Pt nanocluster is strongly correlated with the CO oxidation activity, but no correlation exists with the total surface area of surface-exposed Pt atoms. The low oxygen affinity of cationic Pt atoms explains this counterintuitive result. Using this relationship and our modified bond-additivity method, which only requires the catalyst-support bond energy as input, we successfully predict the CO oxidation activities of various sized Pt clusters on TiO2.

DOI： 10.1038/s41467-020-15850-4

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer New York LLC  

The measurement procedure of oxophilicity and electrocatalytic activity for oxygen reduction reaction (ORR) on size-selected Au clusters was developed and applied. Mass-selected Au9 clusters were deposited on a glassy carbon substrate under ultrahigh vacuum (UHV) conditions, and the model electrode was transferred to an electrochemical cell with the rotating disk electrode (RDE) configuration. Cyclic voltammetry exhibited a significantly lower oxide-reduction peak potential of the Au clusters than that of bulk Au in the first cycle, thus confirming the exceptionally higher oxophilicities for the former. After performing cyclic voltammetry with an upper limit potential of 1.8 V versus a reversible hydrogen electrode, the ORR activity of the Au clusters was lower than that of bulk Au and bulk Pt. This result was partially ascribed to aggregations of Au clusters during the potential cycles. [Figure not available: see fulltext.].

DOI： 10.1007/s12678-018-0464-4

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Institute of Physics Inc.  

Supported Pt catalysts and ceria are well known for their application in automotive exhaust catalysts. Size-selected Pt clusters supported on a CeO2(111) surface exhibit distinct physical and chemical properties. We investigated the morphology of the size-selected Ptn (n = 5-13) clusters on a CeO2(111) surface using scanning tunneling microscopy at room temperature. Ptn clusters prefer a two-dimensional morphology for n = 5 and a three-dimensional (3D) morphology for n ≥ 6. We further observed the preference for a 3D tri-layer structure when n ≥ 10. For each cluster size, we quantitatively estimated the relative fraction of the clusters for each type of morphology. Size-dependent morphology of the Ptn clusters on the CeO2(111) surface was attributed to the Pt-Pt interaction in the cluster and the Pt-O interaction between the cluster and CeO2(111) surface. The results obtained herein provide a clear understanding of the size-dependent morphology of the Ptn clusters on a CeO2(111) surface.

DOI： 10.1063/1.5017906

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A bimetallic catalyst of Au and Ni significantly increased the catalytic activity of the NO-CO reaction in comparison to monometallic Au and Ni catalysts. Unraveling the roles of Au and Ni atoms in the each of the NO-CO reaction steps occurring on the Au-Ni catalyst surface is crucial to reveal the origin of the increased activity. For this purpose, a well-defined Au/Ni(111) model catalyst was prepared, on which CO and NO adsorption, their coadsorption, NO dissociation, CO2 formation, and N-2 formation were investigated using infrared reflection absorption spectroscopy, temperature-programmed desorption/reaction, and density functional theory calculations. In the reaction process, the catalyst surface would be dominantly covered by N and O atoms, which would be removed from the surface by N-2 formation and CO2 formation. O atoms preferentially occupy the Ni hollow sites by segregating N atoms to the adsorption sites made up of Au and Ni atoms. Thus, only the N-2 formation step was affected by the Au atoms. The activation energy for the N-2 formation step, which was assigned as a rate-limiting step, was significantly lowered by the Au atoms, and this effect will contribute to the decrease of the activation energy of the overall NO-CO reaction. These results suggest that, by utilizing the adsorption site preferences among the coadsorbates on the bimetallic surface, the activation energy of a rate-limiting step would be significantly decreased; this could be useful in the development of advanced NOx reduction catalysts.

DOI： 10.1021/acscatal.6b02714

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：A V S AMER INST PHYSICS  

A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstrated by a successful PTRF-XAFS study of Pt-4 clusters deposited on a TiO2(110) surface. (C) 2015 American Vacuum Society.

DOI： 10.1116/1.4936344

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL INST MATERIALS SCIENCE  

Catalysis of atomically precise clusters supported on a substrate is reviewed in relation to the type of reactions. The catalytic activity of supported clusters has generally been discussed in terms of electronic structure. Several lines of evidence have indicated that the electronic structure of clusters and the geometry of clusters on a support, including the accompanying clustersupport interaction, are strongly correlated with catalytic activity. The electronic states of small clusters would be easily affected by cluster-support interactions. Several studies have suggested that it is possible to tune the electronic structure through atomic control of the cluster size. It is promising to tune not only the number of cluster atoms, but also the hybridization between the electronic states of the adsorbed reactant molecules and clusters in order to realize a quantumcontrolled catalyst.

DOI： 10.1088/1468-6996/15/6/063501

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The adsorption states of size-selected Pt-n clusters (7 <= n <= 20) soft-landed on an Al2O3/NiAl(110) substrate were investigated using scanning tunneling microscopy, infrared reflection absorption spectroscopy, and temperature programmed desorption. Pt-n clusters lay flat on the surface with a planar structure (n <= 18), and three-dimensional two-layer clusters start to appear at n >= 19. By considering the Pt-Pt and Pt-oxide bonds in the cluster, the morphological transition could be reasonably explained. Using CO probe molecules, the chemical states of the Pt atoms inside the clusters were investigated. Two ontop CO species were observed inside the clusters, and were assigned as adsorbed CO on neutral and slightly cationic Pt atoms. Despite the first layer Pt atoms, the Pt-n clusters are composed of two kinds of Pt atoms. The observed size dependence of the Pt atoms inside the clusters may contribute to the size-dependent chemical reactivity of Pt-n clusters on the Al2O3 surface.

DOI： 10.1039/c4cp01767f

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Scanning tunneling microscope observations show a geometrical transition from a planar structure to a 3D structure at n = 8. This geometrical transition resulted in a significant decrease in the activation energy of the CO oxidation reaction. The upper-layer Pt atoms of the 3D cluster structure that starts to form at n = 8 are low-coordinated Pt atoms, and they may play an important role in the CO oxidation reaction.

DOI： 10.1039/c1cy00204j

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A numerical model for lean NOx catalytic reaction in consideration of hydrocarbon adsorption and desorption process, which is capable of predicting the performance of diesel lean NOx catalyst using diesel fuel as a supplemental reductant, has been developed. This model is based on our simplified kinetics for the adsorption and desorption of hydrocarbons, for the oxidation of hydrocarbons, and for the reduction of NOx by hydrocarbons including the desorbed one. The adsorption of diesel exhaust hydrocarbons was expressed by the Freundlich-type isotherm that has the adsorption equilibrium constant of exponential temperature dependence. The behavior of HC and NOx reactions and HC adsorption and desorption in diesel exhaust has been simulated successfully. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0926-3373(00)00282-4

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

DOI： 10.1006/jcat.1993.1287

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The alveoli, critical sites for gas exchange in the lungs, comprise alveolar epithelial cells and pulmonary capillary endothelial cells. Traditional experimental models rely on porous polyethylene terephthalate or polycarbonate membranes, which restrict direct cell-to-cell contact. To address this limitation, we developed AlveoMPU, a new foam-based mortar-like polyurethane-formed alveolar model that facilitates direct cell–cell interactions. AlveoMPU features a unique anisotropic mortar-shaped configuration with larger pores at the top and smaller pores at the bottom, allowing the alveolar epithelial cells to gradually extend toward the bottom. The underside of the film is remarkably thin, enabling seeded pulmonary microvascular endothelial cells to interact with alveolar epithelial cells. Using AlveoMPU, it is possible to construct a bilayer structure mimicking the alveoli, potentially serving as a model that accurately simulates the actual alveoli. This innovative model can be utilized as a drug-screening tool for measuring transepithelial electrical resistance, assessing substance permeability, observing cytokine secretion during inflammation, and evaluating drug efficacy and pharmacokinetics.

DOI： 10.3390/polym16111486

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：AIP publishing  

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1063/5.0132957

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

Identifying the catalytically active sites and determining the reaction pathways on metal-oxide-supported few-atom clusters are of great importance for realizing mass-efficient heterogeneous catalysts. However, thermodynamics-based kinetic analyses, which are usually employed to elucidate such reaction mechanisms, can lead to contradictory conclusions even for simple catalytic systems such as CO oxidation. For CO oxidation on TiO2, a typical reducible oxide, the reaction is considered to proceed using the lattice O in the oxide. However, using isotopically labeled (CO)-C-13 and O-18(2), we herein show that only similar to 20% of the total CO2 is produced with the lattice O from TiO2; instead, most of the obtained CO2 is produced by O atoms from the introduced O-2 gas adsorbed on Pt atoms in the size-specific Pt clusters deposited on TiO2. We also show that both the introduced O-2 and lattice O react with CO adsorbed on hexa-coordinated Pt atoms at the edge of the Pt nanoclusters, suggesting that an edge structure that maximizes the coordination number of the edge Pt atoms could exhibit an improved catalytic activity.

DOI： 10.1021/acscatal.1c03948

Authorship：Last author   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Vanadium dioxide (VO2), which exhibits a metal-insulator phase transition at 70 °C, is known to alter its physical properties according to its surface morphology and fabrication process. The systematic investigation of a new fabrication method could not only clarify the origin of its phase transition but also advance progress in applications employing VO2 nanostructures. Here, we demonstrate the drastic enhancement of both the surface morphology and hysteresis of VO2 nanostructures composed of nanoparticles, by applying a sputtering deposition fabrication process, followed by lamp annealing. We investigated different growth conditions for VO2, especially using metallic precursor oxidation under a controlled pressure and temperature, and found that each growth condition led to different morphologies, nanoparticle sizes, and phase transition properties (hysteresis width). Despite a slight increase in particle diameter with annealing time and O2 pressure, the particle aggregation was found to substantially decrease. The temperature width of the hysteresis loop obtained by infrared light reflection measurements increased as the aggregation of VO2 nanoparticles decreased. During the cooling procedure, the transition of slightly aggregated VO2 nanoparticles was revealed to be a two-step process, with the lower transition temperature decreasing with an increase in particle isolation. Our results have the potential to elucidate the hysteresis-inducing mechanisms in VO2 and to aid the materialization of novel devices such as passive thermal control and thermal memory devices.

DOI： 10.1063/5.0047985

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/B978-0-12-409547-2.12983-X

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/B978-0-12-409547-2.12995-6

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Catalytic CO oxidation is unveiled on size-selected Pt-10 clusters deposited on two very different ultrathin (approximate to 0.5-0.7 nm thick) alumina films: (i) a highly ordered alumina obtained under ultra-high vacuum (UHV) by oxidation of the NiAl(110) surface and (ii) amorphous alumina obtained by atomic layer deposition (ALD) on a silicon chip that is a close model of real-world supports. Notably, when exposed to realistic reaction conditions, the Pt-10/UHV-alumina system undergoes a morphological transition in both the clusters and the substrate, and becomes closely akin to Pt-10/ALD-alumina, thus reconciling UHV-type surface-science and real-world experiments. The Pt-10 clusters, thoroughly characterized via combined experimental techniques and theoretical analysis, exhibit among the highest CO oxidation activity per Pt atom reported for CO oxidation catalysts, due to the interplay of ultra-small size and support effects. A coherent interdisciplinary picture then emerges for this catalytic system.

DOI： 10.1039/c6ta10989f

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

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Relaxation dynamics of hot metal clusters on oxide surfaces play a crucial role in a variety of physical and chemical processes. However, their transient mobility has not been investigated as much as other systems such as atoms and molecules on metal surfaces due to experimental difficulties. To study the role of the transient mobility of dusters on the oxide surface, we investigated the initial adsorption process of size-selected Pt clusters on a thin Al2O3 film. Soft-landing the size-selected clusters while suppressing the thermal migration resulted in the transient migration controlling the initial adsorption states as an isolated and aggregated duster, as revealed using scanning tunneling microscopy. We demonstrate that transient migration significantly contributes to the initial cluster adsorption process; the cross section for aggregation is seven times larger than the expected value from geometrical considerations, indicating that metal clusters are highly mobile during a energy dissipation process on the oxide surface.

DOI： 10.1021/acs.jpclett.6b02362

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：A V S AMER INST PHYSICS  

Size-selected clusters can be deposited on the surface using size-selected cluster ion beams. However, because of the cross-sectional intensity distribution of the ion beam, it is difficult to define the coverage of the deposited clusters. The aggregation probability of the cluster depends on coverage, whereas cluster size on the surface depends on the position, despite the size-selected clusters are deposited. It is crucial, therefore, to deposit clusters uniformly on the surface. In this study, size-selected clusters were deposited uniformly on surfaces by scanning the cluster ions in the form of Lissajous pattern. Two sets of deflector electrodes set in orthogonal directions were placed in front of the sample surface. Triangular waves were applied to the electrodes with an irrational frequency ratio to ensure that the ion trajectory filled the sample surface. The advantages of this method are simplicity and low cost of setup compared with raster scanning method. The authors further investigated CO adsorption on size-selected Pt-n(n = 7, 15, 20) clusters uniformly deposited on the Al2O3/NiAl(110) surface and demonstrated the importance of uniform deposition. (C) 2016 American Vacuum Society.

DOI： 10.1116/1.4944051

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Surface Science Society of Japan  

Platinum nano clusters, which are attractive material for highly activated catalysis, are usually evaluated by scanning tunneling microscopy (STM). Here we challenge to evaluate the structure of Pt nano clusters by reflection high-energy electron diffraction (RHEED) for the first time. The nano cluster models are made of n = 7 and n = 15 Pt atoms, which are deposited on TiO2 (110) substrate. The former has two dimensional (planer) and the latter three dimensional (two layer's) shapes. They are rotated around their [111] axes of Pt crystal, whose axes are also inclined from the substrate surface normal because of the atomically rough substrate surface. The RHEED patterns have been calculated by kinematic diffraction theory. From the calculated patterns for the two types of the clusters (n = 7 and 15), it is found that there is characteristic difference in the radial intensity distributions. The difference is attributed to existence or absence of the higher order reflections which arise from two layers of Pt(111).

DOI： 10.1380/ejssnt.2015.125

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Reduction of CeO2(111)/Ru(0001) surface by atomic hydrogen was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). We observed the formation of oxygen vacancy trimers and hydroxyl trimers on the stoichiometric CeO2(111) surface when it was exposed to atomic hydrogen at room temperature. The reaction of an impinging hydrogen atom with a surface oxygen atom yields a hydroxyl species, which diffuse on the surface until stabilized by the formation of OH trimers. The hydrogen atoms were located at atop sites of the oxygen atoms in the topmost surface layer. A reaction between the hopping hydrogen atom and the hydroxyl species yields a water molecule, which is desorbed from the surface leaving an oxygen defect. The oxygen vacancies were also observed as a trimer of vacancies. XPS measurements showed an increase of a reduced Ce and hydroxyl species with an amount of exposed hydrogen atoms. The former was estimated by measuring the ratio of Ce3+/Ce4+ in the Ce 3d components. Our study shows the formation of hydroxyl trimer species in atomic scale upon atomic hydrogen exposure to CeO2(111) surface which could offer new catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.susc.2014.05.008

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We formed an epitaxial film of CeO2(111) by sublimating Ce atoms on Ru(0001) surface kept at elevated temperature in an oxygen ambient. X-ray photoemission spectroscopy measurement revealed a decrease of Ce4+/Ce3+ ratio in a small temperature window of the growth temperature between 1070 and 1096 K, which corresponds to the reduction of the CeO2(111). Scanning tunneling microscope image showed that a film with a wide terrace and a sharp step edge was obtained when the film was grown at the temperatures close to the reduction temperature, and the terrace width observed on the sample grown at 1060 K was more than twice of that grown at 1040 K. On the surface grown above the reduction temperature, the surface with a wide terrace and a sharp step was confirmed, but small dots were also seen in the terrace part, which are considerably Ce atoms adsorbed at the oxygen vacancies on the reduced surface. This experiment demonstrated that it is required to use the substrate temperature close to the reduction temperature to obtain CeO2(111) with wide terrace width and sharp step edges. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

DOI： 10.1063/1.4849595

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Co-adsorption states and thermal stability of NO + CO on Ni(111) were investigated using infrared reflection absorption spectroscopy and temperature programed desorption. The mechanism for the displacement of CO by NO was clarified. Co-adsorbed NO induced hollow-to-ontop site-conversion of CO; NO molecules occupied hollow sites. Ontop and two hollow CO species were observed in the co-adsorbed phase. The ontop and lower frequency hollow CO were assigned to CO neighboring hollow NO; higher frequency hollow CO were assigned to CO forming those domain. The hollow-to-ontop site-conversion of CO occurred due to local interactions between CO and NO, which destabilized the CO by 0.5 eV. This destabilization afforded facile displacement of CO by NO at 300 K. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.susc.2013.03.001

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Adsorption states of size-selected Pt7 clusters soft-landed on an Al2O3/NiAl(1 1 0) were investigated using scanning tunneling microscopy and spectroscopy at 300 K. Pt-7 clusters lay flat on the surface with a planar structure and were preferentially adsorbed on domain boundaries (DBs) of the Al2O3 film. Because the clusters are thermally immobile, adsorption to DBs is controlled by transient mobility on the surface. The mean lateral displacement by transient migration is estimated to be similar to 8 nm. Distinct conductivity resonances through unoccupied states of the Pt7 clusters were observed near 2 V. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2013.05.033

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Low-temperature (25 K) adsorption states and the site conversion of adsorbed CO between the ontop and the hollow sites on Ni(111) were studied by means of temperature programmed desorption and infrared reflection absorption spectroscopy. The activation energy and pre-exponential factor of desorption were estimated to be 1.2 eV and 2.6x10(13) s(-1), respectively, in the limit of zero coverage. At low coverage, CO molecules preferentially adsorbed at the hollow sites below 100 K. With increasing temperature, the ontop sites were also occupied. Using a van't Hoff plot, the enthalpy and the entropy differences between the hollow and ontop CO were estimated to be 36 meV and 0.043 meV K-1, respectively, and the vibrational entropy difference was estimated to be 0.085 meV K-1. The positive entropy difference was the result of the low-energy frustrated translational mode of the ontop CO, which was estimated to be 4.6 +/- 03 meV. With the harmonic approximation, the upper limit of the activation energy of site hopping from ontop sites to hollow sites was estimated to be 61 meV. In addition, it was suggested that the activation energy of hollow-to-hollow site hopping via a bridge site was less than 37 meV. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.susc.2012.07.026

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：A V S AMER INST PHYSICS  

In order to examine cluster size dependence, mass-selected platinum clusters, Pt-n (n=2-5, 7, 8, 10, 15), were deposited on TiO2(110) surfaces at room temperature under soft landing conditions, and their core levels were investigated by x-ray photoelectron spectroscopy. Pt core-level shifts with cluster size are observed. The binding energies of Pt 4f(7/2) decrease steeply with increasing cluster size up to n=7 for Pt-n and decrease gradually for n >= 8. This inflection point (n=8) agrees well with the cluster size at a geometric transition (planar-to-three-dimensional) seen with scanning tunneling microscopy (STM) [N. Isomura, X. Wu, and Y. Watanabe, J. Chem. Phys. 131, 164707 (2009)]. It was found that the core-level shifts of mass-selected Pt clusters deposited on TiO2 are closely correlated with cluster geometries determined directly by atomic-resolution STM imaging. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3467033]

DOI： 10.1116/1.3467033

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Size-selected Pt-n (n=4, 7-10, 15) clusters were deposited on TiO2(110)-(1 x 1) surfaces and imaged at atomic resolution using an ultrahigh-vacuum scanning tunneling microscope with a carbon nanotube tip. Clusters smaller than Pt-7 lay flat on the surface with a planar structure and a planar-to-three-dimensional transition occurred at n=8 for Pt-n clusters on TiO2. However, both Pt-8 and Pt-9 had two types of geometric structures. The geometric structures depend strongly on the number of atoms in the deposited cluster possibly because of the differences in binding energies in different-sized clusters and different degrees of interaction with the surface. We obtained atomic-resolution images of size-selected clusters on surfaces for the first time, enabling the identification of atomic alignments in the clusters on the surface. (C) 2009 American Institute of Physics. [doi:10.1063/1.3251786]

DOI： 10.1063/1.3251786

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：A V S AMER INST PHYSICS  

A new experimental setup to study catalytic and electronic properties of size-selected clusters on metal oxide substrates from the viewpoint of cluster-support interaction and to formulate a method for the development of heterogeneous catalysts such as automotive exhaust catalysts has been developed. The apparatus consists of a size-selected cluster source, a photoemission spectrometer, a scanning tunneling microscope (STM), and a high-pressure reaction cell. The high-pressure reaction cell measurements provided information on catalytic properties in conditions close to practical use. The authors investigated size-selected platinum clusters deposited on a TiO(2)(110) surface using a reaction cell and STM. Catalytic activity measurements showed that the catalytic activities have a cluster-size dependency.

DOI： 10.1116/1.3179160

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Absolute cross sections for NO chemisorption, NO decomposition, and cluster dissociation in the collision of a nitrogen monoxide molecule, NO, with cluster ions Co-n(+) and ConH+ (n = 2-5) were measured as a function of the cluster size, n, in a beam-gas geometry in a tandem mass spectrometer. Size dependency of the cross sections and the change of the cross sections by introduction of H to Co-n(+) (effect of H-introduction) are explained by a statistical model based on the RRK theory, with the aid of the energetics obtained by a DFT calculation. It was found that the reactions are governed by the energetics rather than dynamics. For instance, Co-3(+) does not react appreciably with NO because the reactions are endothermic, while Co3H+ does because the reaction becomes exothermic by the H-introduction.

DOI： 10.1021/jp063273a

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A new method that optimizes a control map of hydrocarbon (HC) addition to diesel exhaust gas for HC type Selective Catalytic Reduction DeNO(x) catalyst system has been developed. This method comprises a numerical model and a new optimization technique. The numerical model is capable of predicting performance of HC DeNO(x) with diesel fuel as a supplemental reductant. The control map of HC addition was optimized with the evolutionary programming based on the evolution of living things. As a result, NOx conversion with the optimized control map was found to be greater by 21% than that with the conventional control on Japanese 10-15 mode. (C) 2003 Society of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0389-4304(02)00249-7

Publishing type：Research paper (scientific journal)  

DOI： 10.4271/2002-01-0954

Publishing type：Research paper (scientific journal)  

DOI： 10.4271/2002-01-0953

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Possible future developments of new automobile catalysts undoubtedly utilize transient phenomena at the change of gas composition under the cooperative functions of the catalytic components: noble metal particles, supports and third additives including 'migration' of adsorbed species and their temporal 'storage'. To explore highly cooperative he ts of the catalytic components, a new tool to detect transient products from artificially designed small area samples in the ms range was developed, which is more robust and tolerant for dynamic changes of vacuum conditions than the conventional UHV surface science tools. (C) 1997 Elsevier Science B.V.

DOI： 10.1016/S0169-4332(97)00315-2

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Catalytic properties of simultaneously obliquely sputter-deposited platinum-metal oxide thin films were studied. We attempted to study the effect of combination of the metal oxide with platinum on the NO-CO reaction by minimizing differences in the particle size and the dispersion of platinum in the samples. Simultaneously obliquely sputter-deposited Pt-metal oxide thin film systems gave comparable particle sizes and dispersion of platinum in different combinations of several metal oxides with platinum. The catalytic property of platinum was changed by the choice of metal oxide. We found this simultaneous oblique sputter deposition to be an excellent technique for obtaining a model catalyst suitable for exploring the synergistic catalytic reaction and the role of promoters at the interfaces of different materials, which facilitates the survey of industrial catalysts.

DOI： 10.1016/0040-6090(94)06279-X

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

Thermally induced structural modification of a nm-order multilayer of Mo/Si was investigated by spectral reflectance of soft X-rays from laser-produced plasma. Dependence of reflectivity of the nm-order multilayers on the incidence angle of soft X-rays indicated that some structural changes start to occur at 300-degrees-C and that the nm-order multilayer structures shrink at 500-degrees-C because of the formation of Mo-silicide. These results were found to be consistent with the cross-sectional transmission electron microscope observations. It is clearly shown that measurement of spectral reflectance of soft X-rays from laser plasma is a powerful method for analyzing nm-order structural modifications of multilayers.

DOI： 10.1143/JJAP.32.2078

Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN J APPLIED PHYSICS  

We propose a new experimental arrangement to measure spectral reflectance of multilayer coatings in the soft X-ray region in a single laser shot, where laser-produced plasma is used as a light source. Reflectivity measurement of a Mo/Si multilayer having a 2d spacing of 24 nm is presented.

DOI： 10.1143/JJAP.31.L203

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

Thin films were formed by simultaneous depositions from two AF-sputter sources which were mounted so that the incident angles of the sputtered particles were +70° and -70° from the substrate normal. A microstructure of ZnTe/SiO<SUB>2</SUB> thin film were examined by TEM. The ZnTe/SiO<SUB>2</SUB> thin film was an anisotropic nm-scale composite whose microstructure was similar to that of the film computer-generated with the simulated deposition conditions. A Cu/SiO<SUB>2</SUB> thin film was also inferred to have an anisotrop ic microstructure through the observation of the polarization of the...

DOI： 10.2497/jjspm.38.345

Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press ({CUP})  

DOI： 10.1557/proc-206-423

Language：Japanese   Publisher：The Japan Society of Vacuum and Surface Science  

Language：English   Publisher：ELSEVIER SCIENCE BV  

A new method that optimizes a control map of hydrocarbon (HC) addition to diesel exhaust gas for HC type Selective Catalytic Reduction DeNO(x) catalyst system has been developed. This method comprises a numerical model and a new optimization technique. The numerical model is capable of predicting performance of HC DeNO(x) with diesel fuel as a supplemental reductant. The control map of HC addition was optimized with the evolutionary programming based on the evolution of living things. As a result, NOx conversion with the optimized control map was found to be greater by 21% than that with the conventional control on Japanese 10-15 mode. (C) 2003 Society of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0389-4304(02)00249-7

Language：English   Publisher：豊田中央研究所  

Language：Japanese   Publisher：豊田中央研究所  

Language：Japanese   Publisher：Japan Society of Powder and Powder Metallurgy  

Thin films were formed by simultaneous depositions from two AF-sputter sources which were mounted so that the incident angles of the sputtered particles were +70° and -70° from the substrate normal. A microstructure of ZnTe/SiO₂ thin film were examined by TEM. The ZnTe/SiO₂ thin film was an anisotropic nm-scale composite whose microstructure was similar to that of the film computer-generated with the simulated deposition conditions. A Cu/SiO₂ thin film was also inferred to have an anisotrop ic microstructure through the observation of the polarization of the transmitted light. Simultaneous oblique depositions from two sources will be a promising method to generate unique sans composites.

DOI： 10.2497/jjspm.38.345

Other Link： https://jlc.jst.go.jp/DN/JALC/00008562395?from=CiNii

Language：Japanese   Presentation type：Oral presentation (invited, special)