Plasmonic cyclohexane-sensing by sputter-deposited Au nanoparticle array on SiO

Kawaguchi, Kazuhiro*; Yamamoto, Shunya; Yoshikawa, Masahito; Takahiro, Katsumi*

Thin Solid Films, 562, p.648 - 652, 2014/07

https://doi.org/10.1016/j.tsf.2014.04.092

Liquid organic-hydrides such as cyclohexane which can release-absorbing hydrogen in reversible have been proposed approvable carriers to store and transport hydrogen. However, organic-hydrides are known as highly flammable in air. To realize practical use of this hydrogen production process, the monitoring of leakage of organic-hydride gas is strongly required. In the present work, we have examined the plasmonic sensing ability of Au nanoparticle (NP) arrays for dilute cyclohexane. Au NP arrays were prepared on SiO by a sputter deposition technique. The change in an extinction spectrum of Au NP arrays before and after exposure of cyclohexane vapor enabled us to detect it. The Au NP array prepared with 4.4 10 Au atoms/cm deposited at 300C was and demonstrated a high sensitivity for cyclohexane at RT. The experimentally detectable concentration of cyclohexane was as low as 0.5 vol%, much lower than its explosion limit (1.3 vol%).

Flow electrolysis of U, Np and Pu ions utilizing electrocatalysis at a column electrode with platinized glassy carbon fiber working electrode

Kitatsuji, Yoshihiro; Kimura, Takaumi; Kihara, Sorin*

Electrochimica Acta, 74, p.215 - 221, 2012/07

https://doi.org/10.1016/j.electacta.2012.04.055

Redox reactions of U, Np and Pu ions of various oxidation states were investigated by flow electrolysis at a column electrode (CE) equipped with a platinized glassy carbon (GC) fiber working electrode (Pt/GC-WE), and compared with those observed at the CE with an ordinary activated GC fiber working electrode (GC-WE). Since the overpotential for the reduction of NpO and PuO were decreased when Pt/GC-WE was employed, the one-electron reduction of NpO to Np followed by that of Np to Np and the one-step three-electron reduction of PuO to Pu proceeded at the CE with Pt/GC-WE, different from the reduction processes of NpO and PuO at the CE with GC-WE. A rapid and precise method for the preparation of U, Np and Pu ion of a desired oxidation state was proposed by taking advantage of the unique characteristics of the CE with Pt/GC-WE.

Standard Gibbs free energies for transfer of actinyl ions at the aqueous/organic solution interface

Kitatsuji, Yoshihiro; Okugaki, Tomohiko*; Kasuno, Megumi*; Kubota, Hiroki*; Maeda, Koji*; Kimura, Takaumi; Yoshida, Zenko; Kihara, Sorin*

Journal of Chemical Thermodynamics, 43(6), p.844 - 851, 2011/06

https://doi.org/10.1016/j.jct.2010.12.023

Standard Gibbs energies for transfer (G) of actinyl ions (AnO; z = 2 or 1; An: U, Np or Pu) between an aqueous solution and an organic solution were determined based on distribution method combined with voltammetry for ion transfer at the interface of two immiscible electrolyte solutions. The organic solutions examined were nitrobenzene, 1,2-dichloroethane, benzonitrile, acetophenone and 2-nitrophenyl octyl ether. Irrespective of the type of organic solutions, G of UO, NpO and PuO were nearly equal to each other and slightly larger than that of Mg. The G of NpO was extraordinary large compared with those of ordinary monovalent cations. The dependence of G of AnO on the type of organic solutions was similar to that of H or Mg. The G of An and An were also discussed briefly.

Application of X-ray photoelectron spectroscopy to characterization of Au nanoparticles formed by ion implantation into SiO

Takahiro, Katsumi*; Oizumi, Shinnosuke*; Morimoto, Keiichi*; Kawatsura, Kiyoshi*; Isshiki, Toshiyuki*; Nishio, Koji*; Nagata, Shinji*; Yamamoto, Shunya; Narumi, Kazumasa; Naramoto, Hiroshi*

Applied Surface Science, 256(4), p.1061 - 1064, 2009/11

https://doi.org/10.1016/j.apsusc.2009.05.104

Development of high performance electrochemical solvent extraction method

Okugaki, Tomohiko*; Kitatsuji, Yoshihiro; Kasuno, Megumi*; Yoshizumi, Asuka*; Kubota, Hiroki*; Shibafuji, Yayoi*; Maeda, Koji*; Yoshida, Zenko; Kihara, Sorin*

Journal of Electroanalytical Chemistry, 629(1-2), p.50 - 56, 2009/04

A high performance electrochemical solvent extraction method was developed based on the quantitative transfer of ions from an aqueous, W, to an organic solution, O. It was realized by applying a potential difference between W and O. The cell was composed of a porous Teflon tube immersed with O, a Ag wire inserted into the tube, a Pt wire placed outside the tube. When W containing ions was forced to flow through the narrow gap between the tube and Ag wire, and potential was applied, a very rapid quantitative ion transfer was attained. When O containing extractant, more than 99% of U(VI) in W was extracted during the residence (e.g., 40 s) in the cell. The fundamental feature of the extraction system was investigated, taking into account the application of the system to the extraction of actinide, lanthanide, Sr or Cs ions. The use of a column electrode system connected before the extraction system was examined in order to adjust the oxidation state of the element to that desired.

Electrochemical evaluation of the distribution of a metal ion at the aqueousorganic solution interface in chelate extraction

Uehara, Akihiro*; Kasuno, Megumi*; Okugaki, Tomohiko*; Kitatsuji, Yoshihiro; Shirai, Osamu*; Yoshida, Zenko; Kihara, Sorin*

Journal of Electroanalytical Chemistry, 604(2), p.115 - 124, 2007/06

The distribution ratio of a metal ion between an aqueous solution and an organic solution in solvent extraction with a chelating agent was evaluated by using physicochemical constants determined electrochemically such as standard Gibbs energies for transfers of the ions, the overall complex formation constants and the acid dissociation constants of the chelating agent. The distribution ratio thus evaluated agreed well with those determined by the distribution experiment.

Core level and valence band photoemission spectra of Au clusters embedded in carbon

Takahiro, Katsumi*; Oizumi, Shinnosuke*; Terai, Atsushi*; Kawatsura, Kiyoshi*; Tsuchiya, Bun*; Nagata, Shinji*; Yamamoto, Shunya; Naramoto, Hiroshi; Narumi, Kazumasa; Sasase, Masato*

Journal of Applied Physics, 100(8), p.084325_1 - 084325_6, 2006/10

https://doi.org/10.1063/1.2359688

X-ray photoelectron spectroscopy (XPS) has been applied for size estimation of Au clusters formed by ion implantation into glassy carbon. The 4f and 5d XPS spectra reveal the presence of the cluster 0.7-2.5nm in diameter, depending on the Au concentration. The elationship between XPS 4f-binding energy shift and 5d splitting is determined for the Au clusters embedded in the carbon and found to be significantly different from the previous data for the ones supported on a carbon substrate. We suppose that this difference results from the effect of the environment around a cluster on Coulomb charging during photoemission at the final state.

Amorphization of carbon materials studied by X-ray photoelectron spectroscopy

Takahiro, Katsumi*; Terai, Atsushi*; Oizumi, Shinnosuke*; Kawatsura, Kiyoshi*; Yamamoto, Shunya; Naramoto, Hiroshi

Nuclear Instruments and Methods in Physics Research B, 242(1-2), p.445 - 447, 2006/01

https://doi.org/10.1016/j.nimb.2005.09.009

X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy have been applied to investigate amorphization processes by ion irradiation for various carbon materials, including highly oriented pyrolytic graphite (HOPG), isotropic graphite, glassy carbon (GC) and C crystalline film. It is found that the asymmetry of the XPS C 1s line increases as the irradiation dose increases. The origin of the asymmetry appeared on the C 1s line is discussed. It is concluded that the asymmetry of the C 1s line is not correlated with the increase in the size of a graphitic layer, but is related with the structural disorders, such as a bond angle disorder.

Rapid and quantitative electrolytic preparation and speciation of neptunium ions of various oxidation states using multi-step column electrodes

Aoyagi, Hisao*; Kitatsuji, Yoshihiro; Yoshida, Zenko; Kihara, Sorin*

Analytica Chimica Acta, 538(1-2), p.283 - 289, 2005/05

https://doi.org/10.1016/j.aca.2005.02.035

Redox behavior of Np(III), (IV), (V) and (VI) ions in aqueous perchloric, nitric and sulphuric acid solutions was elucidated by using column electrodes connected in series in a flow system. Using a glassy carbon fiber working electrode as the column electrode was found to be very useful for the investigation of current-potential relations of not only reversible redox processes such as Np(VI)/(V) or Np(IV)/(III) but also irreversible processes such as Np(V)/(IV) or Np(V)/(III), the latter not observed by conventional voltammetry which uses a glassy carbon or platinum electrode. Quantitative electrolysis could be executed even if the redox process was completely irreversible by the use of the column electrodes. By taking advantage of column electrode electrolysis, a novel method was developed for the rapid preparation of a neptunium species of a desired oxidation state, including unstable species. The multi-step column electrode system was demonstrated to be useful for the coulometric determination and speciation of Np(IV), (V) and (VI) in aqueous HNO solution as an example.

A New electrochemical method to study the distribution of weak acid at the aqueousorganic solution interface

Uehara, Akihiro*; Yoshida, Zenko; Yoshida, Yumi*; Kitatsuji, Yoshihiro; Kasuno, Megumi*; Maeda, Koji*; Kihara, Sorin*

Journal of Electroanalytical Chemistry, 563(2), p.257 - 267, 2004/03

no abstracts in English