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Journal Articles

Application of diffusive gradients in thin films (DGT) for the dynamic speciation of radioactive cesium in Fukushima Prefecture, Japan

Tanaka, Takuro*; Fukuoka, Masafumi*; Toda, Kanako*; Nakanishi, Takahiro; Terashima, Motoki; Fujiwara, Kenso; Niwano, Yuma*; Kato, Hiroaki*; Kobayashi, Natsuko*; Tanoi, Keitaro*; et al.

ACS ES&T Water (Internet), 4(8), p.3579 - 3586, 2024/08

https://doi.org/10.1021/acsestwater.4c00453

Journal Articles

Development of an iron(II) complex exhibiting thermal- and photoinduced double proton-transfer-coupled spin transition in a short hydrogen bond

Nakanishi, Takumi*; Hori, Yuta*; Shigeta, Yasuteru*; Sato, Hiroyasu*; Kiyanagi, Ryoji; Munakata, Koji*; Ohara, Takashi; Okazawa, Atsushi*; Shimada, Rintaro*; Sakamoto, Akira*; et al.

Journal of the American Chemical Society, 145(35), p.19177 - 19181, 2023/08

https://doi.org/10.1021/jacs.3c06323
 Times Cited Count：2 Percentile：33.15(Chemistry, Multidisciplinary)

Journal Articles

Observation of proton-transfer-coupled spin transition by single-crystal neutron-diffraction measurement

Nakanishi, Takumi*; Hori, Yuta*; Shigeta, Yasuteru*; Sato, Hiroyasu*; Wu, S.-Q.*; Kiyanagi, Ryoji; Munakata, Koji*; Ohara, Takashi; Sato, Osamu*

Physical Chemistry Chemical Physics, 25(17), p.12394 - 12400, 2023/05

https://doi.org/10.1039/D3CP00527E
 Times Cited Count：2 Percentile：39.35(Chemistry, Physical)

Journal Articles

Dispersive XAFS Study on the Laser-Induced Reduction of a Rh$$^{3+}$$ ion complex; Presence of a Rh$$^{+}$$ Intermediate in Direct Photoreduction

Saeki, Morihisa*; Matsumura, Daiju; Nakanishi, Ryuzo*; Yomogida, Takumi; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

Journal of Physical Chemistry C, 126(12), p.5607 - 5616, 2022/03

https://doi.org/10.1021/acs.jpcc.1c10160
 Times Cited Count：2 Percentile：16.27(Chemistry, Physical)

The reaction mechanism of the direct photoreduction of a Rh$$^{3+}$$ ion complex to a Rh$$^{0}$$ species induced by pulsed ultraviolet laser irradiation was studied using dispersive X-ray absorption fine structure (DXAFS) spectroscopy. The time-resolved X-ray absorption near edge structure (XANES) showed the absence of isosbestic points and suggested that more than two Rh$$^{n+}$$ species contribute toward the direct photoreduction of Rh$$^{3+}$$. Analysis of the time-resolved XANES data by singular value deposition showed that the direct photoreduction involves three Rh$$^{n+}$$ species. Multivariate curve resolution by alternating least-squares analysis (MCR-ALS) of the time-resolved XANES data gave pure spectra and concentration profiles of the three Rh$$^{n+}$$ species. The Rh$$^{n+}$$ species were assigned to Rh$$^{3+}$$, Rh$$^{+}$$, and Rh$$^{0}$$ species based on the features of the pure XANES spectra. The concentration profiles suggested that the direct photoreduction proceeds in the order of Rh$$^{3+}$$ $$rightarrow$$ Rh$$^{+}$$ $$rightarrow$$ Rh$$^{0}$$. A reaction mechanism, which was proposed involving photoreductions of Rh$$^{3+}$$ and Rh$$^{+}$$, photoinduced autocatalytic reductions of Rh$$^{3+}$$ and Rh$$^{+}$$, and photooxidation of Rh$$^{+}$$, well reproduced the concentration profiles of three Rh$$^{n+}$$ species.

Journal Articles

Application of an augmentation method to MCR-ALS analysis for XAFS and Raman data matrices in the structural change of isopolymolybdates

Saeki, Morihisa*; Yomogida, Takumi; Matsumura, Daiju; Saito, Takumi*; Nakanishi, Ryuzo*; Tsuji, Takuya; Oba, Hironori*

Analytical Sciences, 36(11), p.1371 - 1378, 2020/11

https://doi.org/10.2116/analsci.20P147
 Times Cited Count：4 Percentile：18.15(Chemistry, Analytical)

We measured X-ray absorption fine structure (XAFS) and Raman spectra of isopolymolybdates(VI) in HNO$$_{3}$$ solution (0.15- 4.0 M), which change their geometries depending on acid concentration, and performed simultaneous resolution of the XAFS and Raman data using a multivariate curve resolution by alternating least-squares (MCR-ALS) analysis. In iterative ALS optimization, initial data matrices were prepared by two different methods. The MCR-ALS result of single XAFS data matrix shows large dependence on the preparation method of the initial data matrices. The MCR-ALS result of an augmented matrix of Raman and XAFS data has little dependence on the initial data matrices. It indicates that the augmentation method effectively improves the rotation ambiguities in the MCR-ALS analysis of the XAFS data. Based on the model fitting of the pure EXAFS oscillations, we revealed the change of [Mo$$_{36}$$O$$_{112}$$(H$$_{2}$$O)$$_{16}$$]$$^{2+}$$ $$rightarrow $$ [Mo$$_{2}$$O$$_{5}$$(H$$_{2}$$O)$$_{6}$$]$$^{2+}$$ $$rightarrow $$ [HMoO$$_{3}$$(H$$_{2}$$O)$$_{3}$$]$$^{+}$$ in the highly concentrated HNO$$_{3}$$ solution.

Journal Articles

Temporal changes in radiocesium deposition on the Fukushima floodplain

Nakanishi, Takahiro; Sato, Seiji; Matsumoto, Takumi*

Radiation Protection Dosimetry, 184(3-4), p.311 - 314, 2019/10

https://doi.org/10.1093/rpd/ncz086
 Times Cited Count：8 Percentile：61.40(Environmental Sciences)

There has been significant concern about an increase of exposure dose in living sphere due to the accumulation of radiocesium discharged from contaminated mountainous forest in Fukushima. In this study, we investigated the history of radiocesium deposition on some floodplains in Fukushima. Radiocesium concentrations of river suspended particles and air dose rates at floodplains were also observed continuously. In many situations, annual sediment accumulation at floodplains was only several kg m$$^{-2}$$ and its radiocesium concentration was gradually decreasing in line with that of suspended particle. Simultaneously, air dose rates on floodplains were decreasing with time. In 2015 with heavy flood discharge, several hundred kg m$$^{-2}$$ of sediment accumulation and sharply decrease of air dose rate was observed at rivers without reservoir. Conversely, radiocesium accumulation at floodplain was significant reduced due to deposition on upstream reservoir.

Oral presentation

None

Kai, Itsuki*; Nakanishi, Yuki*; Taniguchi, Naoki; Dobashi, Ryuta*; Hirohata, Yohei*; Haruna, Takumi*

no journal, , 

no abstracts in English

Oral presentation

In situ time-resolved XAFS studies on photo-induced particle formation in an aqueous/ethanol solution of PdCl$$_{4}$$$$^{2-}$$ using ns pulsed UV laser; Dependence of chemical kinetics on laser pulse energy

Saeki, Morihisa*; Yomogida, Takumi; Matsumura, Daiju; Nakanishi, Ryuzo*; Taguchi, Tomitsugu*; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

no journal, , 

In the absence of a photoactivator, the laser-induced particle formation in an H$$_{2}$$O/ EtOH solution of PdCl$$_{4}$$$$^{2-}$$ was performed by three kinds of irradiation condition using fourth harmonics of the pulsed UV laser (266 nm). In the irradiation, pulsed laser energy was arranged to 5, 10 and 25 mJ, where average laser power is kept to 250 mW. The reaction kinetics of the laser-induced particle formation was observed using dispersive XAFS measurement. About half of Pd ions were reduced with 5 mJ pulsed laser irradiation. In contrast, all Pd ions were reduced with 25 mJ pulsed laser irradiation. The result elucidates that the laser photon contributes to the generation of Pd metals by the multi-photon process.

Oral presentation

DXAFS study on laser-induced photoreduction mechanism of Rh$$^{III}$$ ion complexes; Extraction of intermediates information by multivariate spectral analysis

Saeki, Morihisa*; Matsumura, Daiju; Nakanishi, Ryuzo*; Yomogida, Takumi; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

no journal, , 

The precious metal (PM) ions complexed with negative ions and water molecules in solution has a charge transfer absorption band in the UV region. When alcohol is added to such a PM$$^{n+}$$ complex solution and irradiated with an ultraviolet laser, the PM$$^{n+}$$ complex is electronically excited and reacts with the alcohol to be reduced to the neutral atom PM$$^{0}$$. The reduced PM$$^{0}$$ spontaneously aggregates in the solution to form fine particles. This process is called Laser-Induced Particle Formation (LIPF), and is used for the formation of precious metal nanoparticles and the recovery of precious metals from factory effluents. We have investigated the LIPF reaction mechanism of Rh$$^{3+}$$ ion complexes by in situ energy-dispersive X-ray absorption fine structure spectroscopy(XAFS). As a result of analyzing the obtained XAFS spectra, we found that Rh species with three oxidation numbers are involved in the Rh$$^{3+}$$reduction reaction, which proceeds from Rh$$^{3+}$$ to Rh$$^{int}$$ (intermediate) to Rh$$^{0}$$.

Oral presentation

In Situ Time-Resolved XAFS Studies on Laser-Induced Particle Formation of Platinum Groups Metal Ions in a H$$_{2}$$O / EtOH Solution

Saeki, Morihisa*; Matsumura, Daiju; Yomogida, Takumi; Taguchi, Tomitsugu*; Tsuji, Takuya; Saito, Hiroyuki*; Nakanishi, Ryuzo*; Oba, Hironori*

no journal, , 

When nanosecond pulsed UV laser is irradiated into a H$$_{2}$$O / EtOH solution of platinum group metal (PGM) ions, PGM particles with sub-micron size are formed. We investigated laser induced particle formation of Pd$$^{2+}$$ in the H$$_{2}$$O / EtOH solution by in situ time-resolved XAFS spectroscopy and showed dependence of the reaction rate of laser-induced particle formation on the laser fluence. The dependence on the laser fluence elucidated that the photons contribute not only to the reduction of the Pd$$^{2+}$$, but also to the autocatalytic growth of the Pd particles.

Oral presentation

Evaluation of labile Cs-137 in Fukushima rivers by diffusive gradients in thin films (DGT, 2; Examination in river basins

Tanaka, Takuro*; Saito, Takumi*; Toda, Kanako*; Fujiwara, Kenso; Terashima, Motoki; Nakanishi, Takahiro; Kobayashi, Natsuko*; Tanoi, Keitaro*

no journal, , 

Cs-137 dispersed by the Fukushima Daiichi Nuclear Power Plant accident deposited in Fukushima area, that are not decontaminated in mountainous areas, may migrate through river water to animals and plants. Most of Cs-137 in river are fixed in clay minerals, but there are some Cs that can be easily desorbed, named as labile components. It has been suggested that labile components affect the bioavailability of Cs-137. In this study, the labile Cs-137 was sampled in situ from upstream to downstream in several rivers of Fukushima using a passive sampler called diffusive gradients in thin films (DGT). Sampling was conducted at a different season in addition to the previous studies.

Oral presentation

Dispersive XAFS study on the laser-induced reduction of a Rh$$^{3+}$$ ion complex in a H$$_{2}$$O/EtOH solution

Saeki, Morihisa*; Matsumura, Daiju; Nakanishi, Ryuzo*; Yomogida, Takumi; Tsuji, Takuya; Saito, Hiroyuki*; Oba, Hironori*

no journal, , 

The reaction mechanism of the direct photo-reduction of a Rh$$^{3+}$$ ion complex to a Rh$$^{0}$$ species was studied using dispersive X-ray absorption fine structure spectroscopy. The time-resolved X-ray absorption near edge structure (XANES) showed the absence of isosbestic points. It suggested that more than two Rhn+ species contribute toward the reaction. We applied singular value deposition to the time-resolved XANES data and showed the contribution of three Rh$$^{n+}$$ species to the direct photoreduction. Next, in order to extract spectral information on the Rh$$^{n+}$$ intermediate, we analyzed the time-resolved XANES data using multivariate curve resolution analysis, which gives pure spectra and concentration profile of the Rh$$^{n+}$$ species. Finally, based on feature of the pure spectrum, we assigned the Rh$$^{n+}$$ intermediate to the Rh$$^{n+}$$ species.

Oral presentation

Evaluation of labile $$^{137}$$Cs in Fukushima rivers by diffusive gradients in thin films (DGT), 3; Relations between geochemical parameters

Tanaka, Takuro*; Saito, Takumi*; Toda, Kanako*; Fujiwara, Kenso; Terashima, Motoki; Nakanishi, Takahiro; Kobayashi, Natsuko*; Tanoi, Keitaro*; Kato, Hiroaki*

no journal, , 

$$^{137}$$Cs dispersed by the Fukushima Daiichi Nuclear Power Plant accident deposited in Fukushima area, that are not decontaminated in mountainous areas, may migrate through river water to animals and plants. Most of $$^{137}$$Cs in river are fixed in clay minerals, but there are some Cs that can be easily desorbed, named as labile components. It has been suggested that labile components affect the bioavailability of $$^{137}$$Cs. In this study, the labile $$^{137}$$Cs was sampled in situ from upstream to downstream in several rivers of Fukushima using a passive sampler called diffusive gradients in thin films (DGT). The desorption behavior of the labile component and factors affecting it will be discussed by examining the relationship with particulate $$^{137}$$Cs and geochemical parameters in river water.

Oral presentation

Advanced examination technique for river erosion in inland area; A Case study of the Kii Peninsula, Japan

Nakanishi, Toshimichi; Komatsu, Tetsuya; Ogata, Manabu; Hosoya, Takashi*; Kaga, Takumi*

no journal, , 

no abstracts in English

Oral presentation

Speciation of isopolymolybdate(VI) in a highly concentrated HNO$$_{3}$$ solution by Raman and EXAFS spectroscopies

Saeki, Morihisa*; Yomogida, Takumi; Matsumura, Daiju; Saito, Takumi*; Nakanishi, Ryuzo*; Tsuji, Takuya; Okamoto, Yoshihiro; Oba, Hironori*

no journal, , 

Speciation of isopolymolybdates in a highly concentrated HNO$$_{3}$$ solution was investigated by Raman spectroscopy and Mo K-edge extended X-ray absorption fine structure (EXAFS). A series of Raman spectra and EXAFS oscillations were analyzed using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS). The MCR-ALS analysis gives us the fraction profile in change of [Mo$$_{36}$$O$$_{112}$$(H$$_{2}$$O)$$_{16}$$]$$^{8-}$$$$rightarrow$$[Mo$$_{2}$$O$$_{5}$$]$$^{2+}$$$$rightarrow$$[MoO$$_{2}$$]$$^{2+}$$ with the increase of the HNO$$_{3}$$ concentration.

Oral presentation

Trend of $$^{137}$$Cs concentration in river water following the Fukushima nuclear accident in FY 2015-2017

Nakanishi, Takahiro; Katayose, Yuji*; Osotsuka, Koji*; Haginoya, Takumi*; Matsumoto, Takumi*

no journal, , 

A large amount of radiocesium emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was deposited in terrestrial areas. It is therefore important to determine the quantity of radiocesium transported from these areas by hydrological processes to predict the future contamination status and propose effective countermeasures to reduce exposure. In this paper, we report the trend of the radiocesium concentration in 2 rivers nearby FDNPP and discuss the environmental factors on behavior of radiocesium.

16 (Records 1-16 displayed on this page)
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