Hierarchical aggregation in a complex fluid; The Role of isomeric interconversion

Massey, D.*; Williams, C. D.*; Mu, J.*; Masters, A. J.*; Motokawa, Ryuhei; Aoyagi, Noboru; Ueda, Yuki; Antonio, M. R.*

Journal of Physical Chemistry B, 127(9), p.2052 - 2065, 2023/03

https://doi.org/10.1021/acs.jpcb.2c07527

Uranium (VI) sorption on illite under varying carbonate concentrations; Batch experiments, modeling, and cryogenic time-resolved laser fluorescence spectroscopy study

Mei, H.; Aoyagi, Noboru; Saito, Takumi*; Kozai, Naofumi; Sugiura, Yuki; Tachi, Yukio

Applied Geochemistry, 136, p.105178_1 - 105178_8, 2022/01

https://doi.org/10.1016/j.apgeochem.2021.105178

Spectroscopic studies of Mssbauer, infrared, and laser-induced luminescence for classifying rare-earth minerals enriched in iron-rich deposits

Aoyagi, Noboru; Nguyen, T. T.*; Kumagai, Yuta; Nguyen, T. V.*; Nakada, Masami; Segawa, Yukari; Nguyen, H. T.*; Le, B. T.*

ACS Omega (Internet), 5(13), p.7096 - 7105, 2020/04

https://doi.org/10.1021/acsomega.9b03247

Flow-electrode CDI removes the uncharged Ca-UO-CO ternary complex from brackish potable groundwater; Complex dissociation, transport, and sorption

Ma, J.*; Zhang, Y.*; Collins, R. N.*; Tsarev, S.*; Aoyagi, Noboru; Kinsela, A. S.*; Jones, A. M.*; Waite, T. D.*

Environmental Science & Technology, 53(5), p.2739 - 2747, 2019/03

https://doi.org/10.1021/acs.est.8b07157

Europium binding to humic substances extracted from deep underground sedimentary groundwater studied by time-resolved laser fluorescence spectroscopy

Saito, Takumi*; Aoyagi, Noboru; Terashima, Motoki

Journal of Nuclear Science and Technology, 54(4), p.444 - 451, 2017/04

https://doi.org/10.1080/00223131.2016.1274688

Humic substances (HSs) are ubiquitous in various environments including deep underground and play an important role in the speciation and mobility of radionuclides. The binding of Eu, a chemical homologue of trivalent actinide ions, to HSs isolated from sedimentary groundwater at -250 m below the surface was studied by time-resolved laser fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) as a function of pH and salt concentration. PARAFAC modeling reveals the presence of multiple factors that corresponds to different Eu species. These factors resemble those observed for Eu binding to HSs from surface environments; however, detailed comparison shows that there are some particularities in Eu binding to the deep groundwater HSs. The distribution coefficients () of Eu binding to the HSs calculated from the PARAFAC modeling exhibits a rather strong salt effect. At 0.01 M NaClO the values are relatively large and comparable to those to the surface HSs; they are decreaed at 0.1 M NaClO by more than an order of the magnitude. The values are larger for humic acid fraction of the deep underground HSs than fulvic acid over the entire range of pH and salt concentration investigated in this study.

Role of TfN anions in the ionic liquid-water distribution of europium(III) chelates

Okamura, Hiroyuki; Aoyagi, Noboru; Shimojo, Kojiro; Naganawa, Hirochika; Imura, Hisanori*

RSC Advances (Internet), 7(13), p.7610 - 7618, 2017/01

https://doi.org/10.1039/C6RA27208H

The role of bis(trifluoromethanesulfonyl)imide (TfN) anions in the ionic liquid-water distribution systems of the Eu(III) chelates with 2-thenoyltrifluoroacetone (Htta) was investigated by the liquid-liquid distribution and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The effect of the ionic liquids on the distribution constant of Eu(tta) was evaluated by the regular solution theory. The distribution constant of Eu(tta) in 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cmim][TfN]) was increased dramatically by the solvation effects of Eu(tta) in [Cmim][TfN]. TRLFS for [Eu(tta)(HO)] synthesized revealed that the Eu(tta) chelate was almost completely dehydrated in a series of [Cmim][TfN]. The Eu(tta) chelate exists as di- or tri-hydrates in 1-ethyl-3-methylimidazolium perchlorate ([Cmim][ClO]) containing 20 M water, whereas mono-hydrated chelate was formed in [Cmim][TfN, ClO] in the presence of 0.50 M TfN and 20 M water. These results show that the coordinated water molecules of [Eu(tta)(HO)] were replaced by the TfN anions. In fact, an anionic adduct, [Eu(tta)(TfN)], was observed by electrospray ionization mass spectrometry in the presence of [Cmim][TfN].

Physicochemical and ion-binding properties of highly aliphatic humic substances extracted from deep sedimentary groundwater

Saito, Takumi; Terashima, Motoki; Aoyagi, Noboru; Nagao, Seiya*; Fujitake, Nobuhide*; Onuki, Toshihiko

Environmental Science; Processes & Impacts, 17(8), p.1386 - 1395, 2015/08

https://doi.org/10.1039/C5EM00176E

The deep groundwater HSs were different from surface HSs, having high aliphaticities, sulfur contents, and small molecular sizes. The amounts of their acidic functional groups were comparable to or slightly larger than those of surface HSs; however, the magnitude of Cu binding to the deep groundwater HSs was smaller. The NICA-Donnan model attributed this to the binding of Cu to chemically homogeneous carboxylic-type sites via mono-dentate coordination at relatively low pH. The binding mode tended to shift to multi-dentate coordination with carboxylic-type and probably more heterogeneous alcoholic hydroxide-type groups at higher pH. This study shows the particularity of the deep groundwater HSs in terms of their physicochemical and ion-binding properties, compared with surface HSs.

Photophysical property of -bis(thiocyanato)aurate(I) complexes in ionic liquids

Aoyagi, Noboru; Shinha, Yusuke*; Ikeda, Atsushi*; Haga, Yoshinori; Shimojo, Kojiro; Brooks, N. R.*; Izuoka, Akira*; Naganawa, Hirochika; Kimura, Takaumi; Binnemans, K.*

Crystal Growth & Design, 15(3), p.1422 - 1429, 2015/03

https://doi.org/10.1021/cg501792m

The photochemistry of a gold(I) thiocyanate complex has been investigated to determine the coordination structure in both the solid and liquid states. The coordination geometries of the supramolecular complex and the concomitant exciplex have mainly been analyzed by crystallographic analysis and X-ray absorption spectroscopy. The Au-S bond distance and Au-Au separation of the compound in the ground state and in the phosphorescent excited state were compared. Upon irradiation with UV light, the excimeric interactions were enhanced, resulting in a contraction of the Au-Au aurophilic distance. A broad luminescence spectrum was observed for the one-dimensional chain suprastructure. The time-resolved luminescence spectra indicated the entity of several oligomeric species in the crude liquid without neutral solvent molecules. In addition, EXAFS spectroscopy exhibited a slight change in the nearest Au-S distance due to the photo-switched transformation. The deformation of the (Au-Au)* exciplexes was not apparently promoted in the liquid state with the asymmetrical imidazoium cations having a non-local charge distribution in the present observation. This is plausibly due to a flexible molecular structure and a property in the liquid state. In conclusion, the photo-excited nature of the pseudo-one dimensional complexes is emerged in controlling bond distances among the supramolecular networks.

Time-resolved laser-induced fluorescence spectroscopy combined with parallel factor analysis; A Robust speciation technique for UO

Saito, Takumi; Aoyagi, Noboru; Kimura, Takaumi

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1129 - 1132, 2015/02

https://doi.org/10.1007/s10967-014-3465-7

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) is a powerful speciation technique for fluorescent metal ions and can be further improved by combining with multi-mode factor analysis such as parallel factor analysis (PARAFAC). This study demonstrates the applicability of TRLFS combined with PARAFAC for the speciation of uranyl (UO) in the presence of silicic acid (Si(OH)). A series of TRLFS data with varied Si(OH) concentration was processed by PARAFAC, resulting in three factors corresponding to free UO, UOSiO(OH), and UOOH. The stability constant of UOSiO(OH) was further optimized, based on the intensity profiles of the factors.

Stabilization of uranium hexafluoride by hydrolysis method for decommissioning of safeguard laboratory facility

Inagawa, Jun; Hotoku, Shinobu; Oda, Tetsuzo; Aoyagi, Noboru; Magara, Masaaki

JAEA-Technology 2014-007, 48 Pages, 2014/03

JAEA-Technology-2014-007.pdf:5.76MB

In safeguard laboratory (SGL) facility of Nuclear Science Research Institute of JAEA, uranium hexafluoride (UF) of enriched uranium of various enrichment was used for research and development of a spectrometric method for the determination of the enrichment of uranium in April 1983 through March 1993. After completion of this R&D, the UF has been stored in SGL facility. It was decided that the UF is carried to out of the facility, because the SGL facility will be decommissioning until March 2015. To transport and store in safety after transportation, it is necessary that the UF should be converted to stable chemical form. Hydrolysis of UF to uranyl fluoride (UOF) and evaporation to solid state were selected for the stabilization method. The equipment for hydrolysis and evaporation was installed in the SGL facility. Stabilization was operated in this equipment, and all of the UF in the SGL facility was converted to UOF solid state in October 2012 through August 2013. In this report, results of examination and operation for stabilization of UF were reported.