The Experts below are selected from a list of 400365 Experts worldwide ranked by ideXlab platform
Jun Kawai - One of the best experts on this subject based on the ideXlab platform.
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Quantitative Chemical State Analysis of Supported Vanadium Oxide Catalysts by High Resolution Vanadium Kα Spectroscopy
Analytical chemistry, 2011Co-Authors: Takashi Yamamoto, Fumitaka Nanbu, Tsunehiro Tanaka, Jun KawaiAbstract:Oxidation States of vanadium species on Al2O3, SiO2, and TiO2 were quantitatively analyzed by least-squares fitting of V Kα spectra recorded with a two-crystal X-ray fluorescence spectrometer. Uncertainties of analytical results by the normalization procedure, and coefficient of validation and the reduction behavior of vanadium species by X-ray irradiation were discussed. The V5+/V4+/V3+ ratios on Al2O3, SiO2, and TiO2 calcined at 773 K in air were determined to be ca. 6/3/1, 3/6/1, and 5/4/1, respectively. The possible Chemical States of vanadium species on supports were proposed.
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Sulfur Chemical State analysis of diesel emissions of vehicles using X-ray absorption
Spectrochimica Acta Part B: Atomic Spectroscopy, 2006Co-Authors: Satoshi Matsumoto, Yoshinori Kitajima, Yoichi Tanaka, Hideshi Ishii, Teruo Tanabe, Jun KawaiAbstract:Abstract Soft X-ray absorption spectra of sulfur K edge were measured for diesel exhaust particles from three different vehicles. The X-ray spectra were measured using a synchrotron radiation beamline. The spectra were measured by surface sensitive total electron yield method and bulk sensitive X-ray fluorescence yield method. One vehicle concentrated the S 2− on the surface of the emission particles; the others did not concentrate S 2− . This type of Chemical State analysis method is useful for the process analysis such as diesel emissions.
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Depth selective Chemical State analysis of Pb and S in fly ash in municipal solid waste incinerators using X-ray absorption spectroscopy
Spectrochimica Acta Part B: Atomic Spectroscopy, 2003Co-Authors: Jun Kawai, Yoshinori Kitajima, Susumu Tohno, Orlando E. Raola, Masaki TakaokaAbstract:Abstract Soft X-ray absorption spectra of sulfur K edge and lead M4,5 edges were measured for fly ash samples collected from two types of municipal solid waste incinerators. The X-ray spectra were measured using a synchrotron radiation beam line. The spectra were measured by surface sensitive total electron yield method and bulk sensitive X-ray fluorescence yield method. The instruments to measure the X-ray absorption spectra were an electric current amplifier and a proportional counter. The spectra recorded with these two yield methods were different for one incinerator sample and same for the other incinerator sample. This observation was supported from the X-ray fluorescence quantitative elemental analysis of Pb. One type of incinerator concentrated the lead on the surface of the fly ash particles. The other did not concentrate lead. This type of depth selective Chemical State analysis method is useful for the process analysis such as an incinerator.
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High resolution soft X-ray absorption spectroscopy for the Chemical State analysis of Mn
Spectrochimica Acta Part B: Atomic Spectroscopy, 2000Co-Authors: Jun Kawai, Yoshinobu Mizutani, Tetsuro Sugimura, Makoto Sai, Tohru Higuchi, Yoshihisa Harada, Yoichi Ishiwata, Akiko Fukushima, Masami Fujisawa, M. WatanabeAbstract:Abstract Mn L 2,3 X-ray absorption spectra of various manganese compounds were measured using a synchrotron radiation facility. Very high-resolution spectra were obtained. Sharp lines, which were not found before, were observed, and reproducibility was checked using a different beam line in the synchrotron radiation facility. Difference in spectral line shape was observed as the difference of quantum yield method. An unknown sample was measured and the specimen was concluded to be a mixture of two different oxidation States of Mn. The effects on the change of spectral profiles are discussed.
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Chemical State Analysis of Grain Boundaries in ZnO Varistors by Auger Electron Spectroscopy
Journal of Solid State Chemistry, 1993Co-Authors: Tanaka Shigeru, Jun Kawai, Chiyoshi Akita, Naoki Ohashi, Hajime Haneda, Junzo TanakaAbstract:The Chemical State of grain boundaries in Bi[sub 2]O[sub 3]-doped ZnO ceramics was investigated by Auger electron spectroscopy. The additive Bi was segregated into grain boundaries 2 to 3 nm thick, where oxygen deficiency occurred. Auger transitions KL[sub 2,3]L[sub 2,3] for oxygen at the grain boundaries were composed of three peaks whose relative intensities varied with the amount of the segregated Bi. Results calculated using a molecular orbital method suggested that the metal-oxygen bonding State in the grain boundary changed with increased amounts of Bi. The change of the bonding character was considered to be related to the formation of an interfacial State at the grain boundary causing nonlinear current-voltage characteristics. 16 refs., 9 figs.
David G Castner - One of the best experts on this subject based on the ideXlab platform.
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fluorescence xps and tof sims surface Chemical State image analysis of dna microarrays
Journal of the American Chemical Society, 2007Co-Authors: Chi Ying Lee, Gregory M Harbers, David W Grainger, Lara J Gamble, David G CastnerAbstract:Performance improvements in DNA-modified surfaces required for microarray and biosensor applications rely on improved capabilities to accurately characterize the chemistry and structure of immobilized DNA molecules on micropatterned surfaces. Recent innovations in imaging X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) now permit more detailed studies of micropatterned surfaces. We have exploited the complementary information provided by imaging XPS and imaging TOF-SIMS to detail the Chemical composition, spatial distribution, and hybridization efficiency of amine-terminated single-stranded DNA (ssDNA) bound to commercial polyacrylamide-based, amine-reactive microarray slides, immobilized in both macrospot and microarray diagnostic formats. Combinations of XPS imaging and small spot analysis were used to identify micropatterned DNA spots within printed DNA arrays on slide surfaces and quantify DNA elements within individual microarray spots for determination of probe immobilization and hybridization efficiencies. This represents the first report of imaging XPS of DNA immobilization and hybridization efficiencies for arrays fabricated on commercial microarray slides. Imaging TOF-SIMS provided distinct analytical data on the lateral distribution of DNA within single array microspots before and after target hybridization. Principal component analysis (PCA) applied to TOF-SIMS imaging datasets demonstrated that the combination of these two techniques provides information not readily observable in TOF-SIMS images alone, particularly in identifying species associated with array spot nonuniformities (e.g., "halo" or "donut" effects often observed in fluorescence images). Chemically specific spot images were compared to conventional fluorescence scanned images in microarrays to provide new information on spot-to-spot DNA variations that affect current diagnostic reliability, assay variance, and sensitivity.
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fluorescence xps and tof sims surface Chemical State image analysis of dna microarrays
Journal of the American Chemical Society, 2007Co-Authors: Gregory M Harbers, David W Grainger, Lara J Gamble, David G CastnerAbstract:Performance improvements in DNA-modified surfaces required for microarray and biosensor applications rely on improved capabilities to accurately characterize the chemistry and structure of immobilized DNA molecules on micropatterned surfaces. Recent innovations in imaging X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) now permit more detailed studies of micropatterned surfaces. We have exploited the complementary information provided by imaging XPS and imaging TOF-SIMS to detail the Chemical composition, spatial distribution, and hybridization efficiency of amine-terminated single-stranded DNA (ssDNA) bound to commercial polyacrylamide-based, amine-reactive microarray slides, immobilized in both macrospot and microarray diagnostic formats. Combinations of XPS imaging and small spot analysis were used to identify micropatterned DNA spots within printed DNA arrays on slide surfaces and quantify DNA elements within individual microarray spots for determin...
Beatriz Roldan Cuenya - One of the best experts on this subject based on the ideXlab platform.
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dynamic changes in the structure Chemical State and catalytic selectivity of cu nanocubes during co2 electroreduction size and support effects
Angewandte Chemie, 2018Co-Authors: Philipp Grosse, Beatriz Roldan Cuenya, Dunfeng Gao, Fabian Scholten, Ilya Sinev, Hemma MistryAbstract:In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, Chemical State, and reactivity of size- and shape-controlled ligand-free Cu nanocubes during CO2 electroreduction (CO2 RR). Dynamic changes in the morphology and composition of Cu cubes supported on carbon were monitored under potential control through electroChemical atomic force microscopy, X-ray absorption fine-structure spectroscopy and X-ray photoelectron spectroscopy. Under reaction conditions, the roughening of the nanocube surface, disappearance of the (100) facets, formation of pores, loss of Cu and reduction of CuOx species observed were found to lead to a suppression of the selectivity for multi-carbon products (i.e. C2 H4 and ethanol) versus CH4 . A comparison with Cu cubes supported on Cu foils revealed an enhanced morphological stability and persistence of CuI species under CO2 RR in the former samples. Both factors are held responsible for the higher C2 /C1 product ratio observed for the Cu cubes/Cu as compared to Cu cubes/C. Our findings highlight the importance of the structure of the active nanocatalyst but also its interaction with the underlying substrate in CO2 RR selectivity.
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dynamic changes in the structure Chemical State and catalytic selectivity of cu nanocubes during co2 electroreduction size and support effects
viXra, 2018Co-Authors: Philipp Grosse, Beatriz Roldan Cuenya, Dunfeng Gao, Fabian Scholten, Ilya Sinev, Hemma MistryAbstract:In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, Chemical State, and reactivity of size- and shape-controlled ligand-free Cu nanocubes (Cu-cubes) during CO2 electroreduction (CO2RR). Dynamic changes in the morphology and composition of Cu-cubes supported on carbon were monitored under potential control via electroChemical atomic force microscopy, X-ray absorption fine-structure spectroscopy and X-ray photoelectron spectroscopy. Under reaction conditions, the roughening of the nanocube surface, disappearance of the (100) facets, formation of pores, loss of Cu and reduction of CuOx species observed were found to lead to a suppression of the selectivity for multi-carbon products (i.e. C2H4 and ethanol) versus CH4. A comparison with Cu-cubes supported on Cu foils revealed an enhanced morphological stability and persistence of Cu(I) species under CO2RR. Both factors are held responsible for the higher C2/C1 product ratio observed for the Cu cubes/Cu as compared to Cu cubes/C. Our findings highlight the importance of the structure of the active nanocatalyst but also its interaction with the underlying substrate in CO2RR selectivity.
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long range segregation phenomena in shape selected bimetallic nanoparticles Chemical State effects
ACS Nano, 2013Co-Authors: Mahdi Ahmadi, Farzad Behafarid, Chunhua Cui, Peter Strasser, Beatriz Roldan CuenyaAbstract:A study of the morphological and Chemical stability of shape-selected octahedral Pt0.5Ni0.5 nanoparticles (NPs) supported on highly oriented pyrolytic graphite (HOPG) is presented. Ex situ atomic force microscopy (AFM) and in situ X-ray photoelectron spectroscopy (XPS) measurements were used to monitor the mobility of Pt0.5Ni0.5 NPs and to study long-range atomic segregation and alloy formation phenomena under vacuum, H2, and O2 environments. The Chemical State of the NPs was found to play a pivotal role in their surface composition after different thermal treatments. In particular, for these ex situ synthesized NPs, Ni segregation to the NP surface was observed in all environments as long as PtOx species were present. In the presence of oxygen, an enhanced Ni surface segregation was observed at all temperatures. In contrast, in hydrogen and vacuum, the Ni outward segregation occurs only at low temperature (<200-270 °C), while PtOx species are still present. At higher temperatures, the reduction of the Pt oxide species results in Pt diffusion toward the NP surface and the formation of a Ni-Pt alloy. A consistent correlation between the NP surface composition and its electrocatalytic CO oxidation activity was established.
Gregory M Harbers - One of the best experts on this subject based on the ideXlab platform.
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fluorescence xps and tof sims surface Chemical State image analysis of dna microarrays
Journal of the American Chemical Society, 2007Co-Authors: Chi Ying Lee, Gregory M Harbers, David W Grainger, Lara J Gamble, David G CastnerAbstract:Performance improvements in DNA-modified surfaces required for microarray and biosensor applications rely on improved capabilities to accurately characterize the chemistry and structure of immobilized DNA molecules on micropatterned surfaces. Recent innovations in imaging X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) now permit more detailed studies of micropatterned surfaces. We have exploited the complementary information provided by imaging XPS and imaging TOF-SIMS to detail the Chemical composition, spatial distribution, and hybridization efficiency of amine-terminated single-stranded DNA (ssDNA) bound to commercial polyacrylamide-based, amine-reactive microarray slides, immobilized in both macrospot and microarray diagnostic formats. Combinations of XPS imaging and small spot analysis were used to identify micropatterned DNA spots within printed DNA arrays on slide surfaces and quantify DNA elements within individual microarray spots for determination of probe immobilization and hybridization efficiencies. This represents the first report of imaging XPS of DNA immobilization and hybridization efficiencies for arrays fabricated on commercial microarray slides. Imaging TOF-SIMS provided distinct analytical data on the lateral distribution of DNA within single array microspots before and after target hybridization. Principal component analysis (PCA) applied to TOF-SIMS imaging datasets demonstrated that the combination of these two techniques provides information not readily observable in TOF-SIMS images alone, particularly in identifying species associated with array spot nonuniformities (e.g., "halo" or "donut" effects often observed in fluorescence images). Chemically specific spot images were compared to conventional fluorescence scanned images in microarrays to provide new information on spot-to-spot DNA variations that affect current diagnostic reliability, assay variance, and sensitivity.
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fluorescence xps and tof sims surface Chemical State image analysis of dna microarrays
Journal of the American Chemical Society, 2007Co-Authors: Gregory M Harbers, David W Grainger, Lara J Gamble, David G CastnerAbstract:Performance improvements in DNA-modified surfaces required for microarray and biosensor applications rely on improved capabilities to accurately characterize the chemistry and structure of immobilized DNA molecules on micropatterned surfaces. Recent innovations in imaging X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) now permit more detailed studies of micropatterned surfaces. We have exploited the complementary information provided by imaging XPS and imaging TOF-SIMS to detail the Chemical composition, spatial distribution, and hybridization efficiency of amine-terminated single-stranded DNA (ssDNA) bound to commercial polyacrylamide-based, amine-reactive microarray slides, immobilized in both macrospot and microarray diagnostic formats. Combinations of XPS imaging and small spot analysis were used to identify micropatterned DNA spots within printed DNA arrays on slide surfaces and quantify DNA elements within individual microarray spots for determin...
Lara J Gamble - One of the best experts on this subject based on the ideXlab platform.
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fluorescence xps and tof sims surface Chemical State image analysis of dna microarrays
Journal of the American Chemical Society, 2007Co-Authors: Chi Ying Lee, Gregory M Harbers, David W Grainger, Lara J Gamble, David G CastnerAbstract:Performance improvements in DNA-modified surfaces required for microarray and biosensor applications rely on improved capabilities to accurately characterize the chemistry and structure of immobilized DNA molecules on micropatterned surfaces. Recent innovations in imaging X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) now permit more detailed studies of micropatterned surfaces. We have exploited the complementary information provided by imaging XPS and imaging TOF-SIMS to detail the Chemical composition, spatial distribution, and hybridization efficiency of amine-terminated single-stranded DNA (ssDNA) bound to commercial polyacrylamide-based, amine-reactive microarray slides, immobilized in both macrospot and microarray diagnostic formats. Combinations of XPS imaging and small spot analysis were used to identify micropatterned DNA spots within printed DNA arrays on slide surfaces and quantify DNA elements within individual microarray spots for determination of probe immobilization and hybridization efficiencies. This represents the first report of imaging XPS of DNA immobilization and hybridization efficiencies for arrays fabricated on commercial microarray slides. Imaging TOF-SIMS provided distinct analytical data on the lateral distribution of DNA within single array microspots before and after target hybridization. Principal component analysis (PCA) applied to TOF-SIMS imaging datasets demonstrated that the combination of these two techniques provides information not readily observable in TOF-SIMS images alone, particularly in identifying species associated with array spot nonuniformities (e.g., "halo" or "donut" effects often observed in fluorescence images). Chemically specific spot images were compared to conventional fluorescence scanned images in microarrays to provide new information on spot-to-spot DNA variations that affect current diagnostic reliability, assay variance, and sensitivity.
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fluorescence xps and tof sims surface Chemical State image analysis of dna microarrays
Journal of the American Chemical Society, 2007Co-Authors: Gregory M Harbers, David W Grainger, Lara J Gamble, David G CastnerAbstract:Performance improvements in DNA-modified surfaces required for microarray and biosensor applications rely on improved capabilities to accurately characterize the chemistry and structure of immobilized DNA molecules on micropatterned surfaces. Recent innovations in imaging X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) now permit more detailed studies of micropatterned surfaces. We have exploited the complementary information provided by imaging XPS and imaging TOF-SIMS to detail the Chemical composition, spatial distribution, and hybridization efficiency of amine-terminated single-stranded DNA (ssDNA) bound to commercial polyacrylamide-based, amine-reactive microarray slides, immobilized in both macrospot and microarray diagnostic formats. Combinations of XPS imaging and small spot analysis were used to identify micropatterned DNA spots within printed DNA arrays on slide surfaces and quantify DNA elements within individual microarray spots for determin...