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Journal Articles

Live-cell imaging study of mitochondrial morphology in mammalian cells exposed to X-rays

Noguchi, Miho; Kanari, Yukiko; Yokoya, Akinari; Narita, Ayumi; Fujii, Kentaro

Radiation Protection Dosimetry, 166(1-4), p.101 - 103, 2015/09

 Times Cited Count:0 Percentile:100(Environmental Sciences)

Journal Articles

Visualisation of cell cycle modifications by X-ray irradiation of single HeLa cells using fluorescent ubiquitination-based cell cycle indicators

Kaminaga, Kiichi; Noguchi, Miho; Narita, Ayumi; Sakamoto, Yuka; Kanari, Yukiko; Yokoya, Akinari

Radiation Protection Dosimetry, 166(1-4), p.91 - 94, 2015/09

 Times Cited Count:5 Percentile:45.16(Environmental Sciences)

Journal Articles

Real-time observation of irradiated HeLa-cell modified by fluorescent ubiquitination-based cell-cycle indicator using synchrotron X-ray microbeam

Narita, Ayumi; Kaminaga, Kiichi; Yokoya, Akinari; Noguchi, Miho; Kobayashi, Katsumi*; Usami, Noriko*; Fujii, Kentaro

Radiation Protection Dosimetry, 166(1-4), p.192 - 196, 2015/09

 Times Cited Count:2 Percentile:73.66(Environmental Sciences)

For the knowledge about irradiation effects of mammalian cells depending on the cell cycle, most of them had been analyzed by statistical approches. Our purpose is to establish the method for real-time observation of irradiated cells under a microscope. Fluorescent ubiquitination-based cell cycle indicator (FUCCI) human cancer (HeLa) cells (red indicates G1; green, S/G2) were exposed to a synchrotron X-ray microbeam. Cells in either G1 or S/G2 were selectively irradiated according to cell color observed in the same microscopic field in a culture dish. Time-lapse micrographs of the irradiated cells were acquired for 24 h after irradiation. The cell cycle was strongly arrested by irradiation at S/G2 and never progressed to G1. In contrast, cells irradiated at G1 progress to S/G2 with a similar time course as non-irradiated control cells. These results show single FUCCI cell exposure and live cell imaging are powerful methods for studying radiation effects on the cell cycle.

Journal Articles

Bond cleavages of adenosine 5'-triphosphate induced by monochromatic soft X-rays

Fujii, Kentaro; Narita, Ayumi; Yokoya, Akinari

Journal of Physics; Conference Series, 502(1), p.012034_1 - 012034_4, 2014/04

In order to clarify the unoccupied electronic structure exposed to soft X-rays, we measured XANES spectrum of adenosine 5'-triphosphate (ATP) before and after irradiation. Experiments were performed at soft X-ray beamline BL23SU in SPring-8. We observed the spectral changes of the resonant peak near nitrogen and oxygen K-ionization thresholds by an irradiation with 560 eV photons which is above oxygen ionization potential. Irradiated samples were also analyzed by electrochemistry and mass spectrometry. Decomposition patterns of ATP exposed to soft X-ray will be discussed from these results.

Journal Articles

DNA damage by soft X-ray exposure at oxygen K-edge

Sugaya, Yuki; Narita, Ayumi; Fujii, Kentaro; Yokoya, Akinari

Journal of Physics; Conference Series, 502(1), p.012040_1 - 012040_4, 2014/04

 Times Cited Count:0 Percentile:100

Journal Articles

Immobilization of alkyl chain molecules on oxide surface using phosphonic acid as an anchor

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Yaita, Tsuyoshi

e-Journal of Surface Science and Nanotechnology (Internet), 10, p.367 - 373, 2012/07

To apply organic thin films as new devices, it is important to immobilize organic molecules on oxide surfaces. In this study, we investigated the formation of organic self-assembled monolayer on the oxide surface. Decyl phosphonic acid (DPA) molecules were used as the adsorbed molecule on the surface. The DPA film was prepared by immersing the sapphire substrate in DPA ethanol solution. The sample was measured by XPS using synchrotron soft X-ray. For the P 1s XPS spectra of the DPA powder and the DPA film on the sapphire surface, a single peak was observed and the binding energies of the two samples were almost the same. And we measured the sample by the total reflection (TR) XPS, which is highly surface sensitive method. Compared with the normal XPS, the intensity of the C 1s peak in TR-XPS was enhanced. As a result, it was elucidated that the phosphonic acid of the DPA molecule was located at the lower side, while the alkyl chain was located at the upper side on the surface.

Journal Articles

Structure determination of self-assembled monolayer on oxide surface by soft-X-ray standing wave

Baba, Yuji; Narita, Ayumi; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Entani, Shiro; Sakai, Seiji

e-Journal of Surface Science and Nanotechnology (Internet), 10, p.69 - 73, 2012/04

We report on the first results for the geometrical determination of adsorbed atoms on an oxide by a soft-X-ray sanding wave method. The samples investigated were alkyl phosphonic acid (C10) adsorbed on a sapphire surface, which is one of the candidate systems for organic self-assembled monolayer (SAM) on oxides. The surface was irradiated by synchrotron soft X-rays from the surface normal. The intensity of photoelectrons was plotted as a function of the photon energy. We observed clear profiles of the photoelectron intensity due to the standing wave from the substrate. Compared with the simulation using the crystal parameters, it was found that the phosphorus atoms are located at 0.11 nm from the surface, while the constant height was not observed for carbon atoms. The results are in consistent with the results by XPS and NEXAFS; the molecules form SAM on the sapphire surface with phosphonic acids and alkyl chains are located at the upper side.

Journal Articles

Anchoring of alkyl chain molecules on oxide surface using silicon alkoxide

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Yaita, Tsuyoshi

Applied Surface Science, 258(6), p.2034 - 2037, 2012/01

 Times Cited Count:4 Percentile:76.61(Chemistry, Physical)

In order to apply the organic thin films to electric and optical devices, the immobilization of organic molecules on inorganic substrate is essential. Considering optical devices, it is important to immobilize organic molecules on oxide surfaces, because many of oxides have insulating and transparent properties. In this study, we have investigated the chemical states of the interface between organic molecules with silicon alkoxide and sapphire surfaces by X-ray photoelectron spectroscopy and near edge absorption fine structure (NEXAFS). Octadecyl-triethoxy-silane (ODTS) molecules which are terminated by silicon alkoxide were adsorbed on sapphire surfaces. On the basis of the Si 1s XPS spectra for monolayer, it is supposed that the chemical bond between silicon alkoxide and the surface is formed. For Si K-edge NEXAFS spectra, the polarization dependence was observed, which suggests that the Si-O bond in ODTS was located perpendicular to the surface.

Journal Articles

Structure determination of self-assembled monolayer on oxide surface by soft-X-ray standing wave

Baba, Yuji; Narita, Ayumi; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Entani, Shiro; Sakai, Seiji

Photon Factory Activity Report 2011, Part B, P. 201, 2012/00

no abstracts in English

Journal Articles

Immobilization of alkyl chain molecules with phosphonic acid on oxide surface

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Yaita, Tsuyoshi

Photon Factory Activity Report 2011, Part B, P. 94, 2012/00

Immobilization of organic molecules on oxide surface has been investigated using phosphonic acid as an anchor. The molecule investigated was decyl-phosphonic acid (DPA). The DPA film was formed by immersing the sapphire substrate in DPA ethanol solution. The results for X-ray photoelectron spectra (XPS) showed that the alkyl chain of the DPA molecules is located at the upper side, while the phosphonic acid is the lower side on the surface. The XPS and near-edge X-ray absorption fine structure (NEXAFS) results indicated that the DPA film became homogeneous monolayer by heating at 250$$^{circ}$$C. It is concluded that the phosphonic acid is an excellent anchor that immobilizes the organic molecules on an oxide surface.

Journal Articles

Self-ordering of silicon polymer thin film grown on indium tin oxide surface investigated by X-ray absorption spectroscopy

Mannan, M. A.*; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Hirao, Norie; Narita, Ayumi; Nagano, Masamitsu*; Noguchi, Hideyuki*

Journal of Electron Spectroscopy and Related Phenomena, 181(2-3), p.242 - 248, 2010/08

 Times Cited Count:5 Percentile:64.96(Spectroscopy)

The ordering and molecular orientation of polydimethylsilane (PDMS) films grown on indium tin oxide (ITO) surface has been assigned. The orientation of the samples as well as that of the annealed sample was studied by Si K-edge near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy using linearly polarized synchrotron radiation. The Si K-edge NEXAFS spectra for the thick film have at least four resonance peaks of which two peaks are found to be strongly polarization dependent. On the basis of the polarization dependences of the peak intensities, it is revealed that the backbones of the PDMS films are perpendicularly oriented on the ITO surface. The angle between surface and the Si-Si bonds for multilayered film calculated from the helical structure of PDMS molecule was found to be 41.5 $$^{circ}$$ which was almost coincided with the experimentally obtained angle of 40 $$^{circ}$$. It was concluded that PDMS molecules are highly self-ordered on ITO surface.

Journal Articles

Orientation of Si phthalocyanine investigated by X-ray absorption spectroscopy and molecular orbital calculation

Sekiguchi, Tetsuhiro; Baba, Yuji; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie; Narita, Ayumi; Deng, J.*

Surface and Interface Analysis, 42(6-7), p.863 - 868, 2010/06

 Times Cited Count:1 Percentile:97.84(Chemistry, Physical)

Metal phthalocyanines (Pc) have attracted growing attention due to potential application as organic semiconductors or light emitters. Recently it has been pointed out that orientation of Pc molecules is one of key properties that improve the career mobility. We studied orientation property of Si-phthalocyanine thin films using synchrotron radiation. We report on following topics: (1) Orientation analysis using polarized X-rays, (2) Effect of metal substrates and annealing on orientation, (3) Analysis aided by molecular orbital method, and (4) New method to observe chemical-bond directions in nanometer scale using combined techniques of polarized X-ray absorption fine structure (XAFS) spectroscopy and photoelectron emission microscopy (PEEM).

Journal Articles

Real-time observation on surface diffusion and molecular orientations for phthalocyanine thin films at nanometer spacial resolution

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie; Narita, Ayumi; Deng, J.

Surface Science, 603(16), p.2612 - 2618, 2009/08

 Times Cited Count:5 Percentile:71.6(Chemistry, Physical)

The morphology, electronic structure and ordering for micropatterns of silicon phthalocyanine thin films on gold have been investigated at nanometer scale by photoelectron emission microscopy (PEEM) excited by polarized soft X-rays from synchrotron light source. The incident angle dependences of the X-ray absorption fine structure (XANES) spectra at the silicon K-edge revealed that the molecules of 5-layered films are lying nearly flat on the surface. Clear image of the micropattern was observed by PEEM at room temperature, while the surface diffusion was observed upon heating. On the basis of the photon-energy dependences of the brightnesses in the PEEM images, it was found that the molecules diffusing to the fresh gold surface rather stand-up at 240$$^{circ}$$C. The observed changes in the molecular orientations at nanometer domains are discussed on the basis of the strengths of the molecular-molecular and molecular-surface interactions.

Journal Articles

Formation of C$$_{rm n}$$H$$_{rm x}$$ (n$$geq$$2) molecules from adsorbed methane by low-energy ion irradiation

Narita, Ayumi; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie; Yaita, Tsuyoshi

Hyomen Kagaku, 29(8), p.489 - 494, 2008/08

The formation of molecular ions and neutral molecules from adsorbed CH$$_{4}$$, CD$$_{4}$$ and N$$_{2}$$ following 1 keV He$$^{+}$$ ion irradiation has been investigated. The thickness of the adsorbed layer was precisely controlled. For mono-layered methane, only monomer ions (CH$$_{rm x}$$$$^{+}$$) were desorbed, while a large number of heavy ions (C$$_{rm n}$$H$$_{rm x}$$$$^{+}$$) up to n = 20 as well as heavy neutral molecules (C$$_{rm n}$$H$$_{rm x}$$) were desorbed from multi-layered film. Among the desorbed ions and neutral molecules, molecules with C-C covalent bonds such as acetylene and ethylene were found. The results indicate that chemical bonds are newly formed by ion irradiation. Based on the results for thickness dependences of the mass spectra and calculation of He$$^{+}$$ energy loss process from TRIM-Code, it was elucidated that the monomer ions are desorbed from the top surface layer through single electron excitation. On the other hand, the cluster ions are formed mainly in the inside of the layers along the nuclear track due to phonon excitation, which is produced by nuclear collision between incident He$$^{+}$$ ions and adsorbed molecules.

Journal Articles

Chemical-state-selective observations on Si-SiO$$_{rm x}$$ at nanometer scale by photoelectron emission microscopy combined with synchrotron radiation

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori; Hirao, Norie*; Deng, J.; Narita, Ayumi

Journal of Physics; Conference Series, 100, p.012015_1 - 012015_4, 2008/00

 Times Cited Count:1 Percentile:44.72

Chemical-state-selective mapping of micro-patterns for silicon compounds has been demonstrated using photoelectron emission microscopy excited by soft X-rays from synchrotron light source. The samples investigated were micro-patterns of silicon oxides, silicon nitrides, and organic silicon compounds. By scanning the X-ray energy around the Si $$K$$-edge, we succeeded in observing the sub-micron images depending on the valence states. When we annealed the sample, the lateral diffusion was observed from 700 degree Celsius. During the annealing, however, no intermediate valence states were observed at the Si-SiO$$_{2}$$ interfaces. It was elucidated that the diffusion of oxygen induced the sudden changes of the Si valence states from Si$$^{0}$$ to Si$$^{4+}$$ without any intermediate valence states. The results for the chemical-state-selective mappings and lateral diffusions are also presented for organic silicon compounds.

Oral presentation

Formation of cluster ions from adsorbed molecules at extremely low temperature by ion irradiation

Narita, Ayumi*; Baba, Yuji; Honda, Mitsunori; Hirao, Norie*; Yaita, Tsuyoshi

no journal, , 

no abstracts in English

Oral presentation

Desorption of cluster ions from adsorbed molecules under cryojenic condition by ion irradiation

Narita, Ayumi*; Honda, Mitsunori; Hirao, Norie*; Baba, Yuji; Yaita, Tsuyoshi

no journal, , 

no abstracts in English

Oral presentation

Metal-Molecular interface bonda state of amino acid on gold surface

Honda, Mitsunori; Baba, Yuji; Hirao, Norie*; Narita, Ayumi*; Sekiguchi, Tetsuhiro

no journal, , 

no abstracts in English

Oral presentation

Metal-molecular interface of sulfur-containing amino acid and molecules on gold surface

Honda, Mitsunori; Baba, Yuji; Hirao, Norie*; Narita, Ayumi; Sekiguchi, Tetsuhiro

no journal, , 

no abstracts in English

Oral presentation

Metal-molecular bond state of sulfur containing amino acid and compound on gold surface

Honda, Mitsunori; Baba, Yuji; Hirao, Norie*; Narita, Ayumi; Sekiguchi, Tetsuhiro; Shimoyama, Iwao

no journal, , 

no abstracts in English

112 (Records 1-20 displayed on this page)