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-containing porous hydrogel via freeze-crosslinking for efficiency and salt-robust dye DecolorizationSugita, Tsuyoshi; Ueda, Yuki; Nakabe, Rintaro; Mori, Masanobu*; Nankawa, Takuya; Sekine, Yurina
Journal of Photochemistry and Photobiology A; Chemistry, 473, p.116773_1 - 116773_9, 2026/04
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)We developed a WO-embedded hydrogel (WFG) by freeze-cross-linking that retained high activity even in the presence of coexisting salts. Confocal laser scanning microscope revealed interconnected channels < 200 
m. ensuring good water permeability, and contrast-matching small-angle neutron scattering showed that the secondary particle size of embedded WO (~300 nm) matched that in aqueous suspension. Under visible-light irradiation, WFG decolorized indigo carmine (INC) 1.5-fold increase in rate than suspended WO and 3.7-fold increase in rate than a WO-coated glass plate. Coexisting salts (NaNO, NaCl, Na
SO
, NaHPO) altered the decolorization efficiency; NaNO and NaSO enhanced, whereas Cl
and HPO suppressed the reaction, indicating that ionic strength and anion-species affect contact efficiency and charge transfer.
Beni, Yusuke*; Sekine, Yurina; Nankawa, Takuya; Takahara, Yuta*; Ikeda-Fukazawa, Tomoko*
Bulletin of the Chemical Society of Japan, 99(2), p.uoag017_1 - uoag017_9, 2026/02
To investigate the effects of pore size on the water structure in polysaccharide hydrogels, differential scanning calorimetry was applied to freeze cross-linked carboxymethyl cellulose nanofiber (CMCF) and agarose hydrogels. Water was classified into bound, free, and two types of intermediate water. The melting point of 1st intermediate water, associated with hydrogen bonding to bound water, showed similar water-content dependence in both hydrogels, indicating minimal pore-size effects. In contrast, the relative amount of 2nd intermediate water differed significantly between CMCF and agarose hydrogels and depended on the specific surface area of pore walls. These results demonstrate that 2nd intermediate water plays a key role in determining hydrogel physicochemical properties.
and Pb adsorptionNankawa, Takuya; Sugita, Asako; Fukakusa, Chihoko*; Yamada, Teppei*; Sekine, Yurina
Separation and Purification Technology, 378(3), p.134780_1 - 134780_9, 2025/12
Times Cited Count：4 Percentile：74.65(Engineering, Chemical)We report a sustainable and chemical free strategy to fabricate sponge like chitosan hydrogels via freeze induced physical crosslinking using mild alkaline solutions, without toxic crosslinkers or synthetic additives. The resulting freeze crosslinked biomass-based chitosan sponge hydrogels exhibited interconnected macropores, high water permeability, excellent compressibility, and mechanical recoverability. These features enabled outstanding adsorption of hazardous heavy metals, achieving far better maximum capacities for Cu and Pb markedly surpassing conventional hydrogels. Notably, Cu adsorption induced visible color changes and enhanced mechanical strength, attributed to metal induced secondary crosslinking between amino and hydroxyl groups and adsorbed ions. Cu adsorption also led to a measurable increase in the Youngs modulus of the hydrogels, likely due to coordination with chitosan functional groups.
Sekine, Yurina; Honda, Michiyo*; Sugita, Asako; Nankawa, Takuya; Sakanaka, Rimi*; Fukazawa, Tomoko*; Ariga, Katsuhiko*
ACS Applied Materials & Interfaces, 17(37), p.52768 - 52778, 2025/09
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology) capture and release at high pressures on a unique large-pore mesoporous carbonSzab
, L.*; Inoue, Mizuki*; Sekine, Yurina; Motokawa, Ryuhei; Matsumoto, Yusuke*; Nge, T. T.*; Ismail, E.*; Ichinose, Izumi*; Yamada, Tatsuhiko*
ChemSusChem, 18(10), p.e202402034_1 - e202402034_13, 2025/05
Times Cited Count：0 Percentile：0.00(Chemistry, Multidisciplinary)Here, we developed a large-pore mesoporous carbon with pore sizes centered around 20-30 nm using a templated technical lignin. During the soft-templating process, unique cylindrical supramolecular assemblies form from the copolymer template, distinct from other systems reported thus far. This peculiar nanostructuring takes place due to the presence of polyethylene glycol (PEG) segments on both the Pluronic template and the PEG- grafted lignin derivative (glycol lignin). A large increase in CO uptake occurs on the resulting large-pore mesoporous carbon at 270 K close to the saturation pressure, owing to capillary condensation.
Cho, S. H.*; Cho, S. W.*; Lv, Z.*; Sekine, Yurina; Liu, S.*; Zhou, M.*; Nuxoll, R. F.*; Kanatzidis, E. E.*; Ghaffari, R.*; Kim, D.*; et al.
Lab on a Chip, 25(7), p.1647 - 1655, 2025/04
Times Cited Count：10 Percentile：98.18(Biochemical Research Methods)Amino acids are essential for protein synthesis and metabolic processes in support of homeostatic balance and healthy body functions. This study quantitatively investigates eccrine sweat as a significant channel for loss of amino acids during exercise, to improve an understanding of amino acid turnover and to provide feedback to users on the need for supplement intake. The measurement platform consists of a soft, skin-interfaced microfluidic system for real-time analysis of amino acid content in eccrine sweat. This system relies on integrated fluorometric assays and smartphone-based imaging techniques for quantitative analysis.
Sekine, Yurina
Geruka, Zonenzai No Tsukaikata To Atarashii Geru No Katsuyo Jirei, p.270 - 275, 2025/01
no abstracts in English
Sugiyama, Hitoshi*; Kato, Kenichi*; Sekine, Naoko*; Sekine, Yurina; Watanabe, Tomoaki*; Fukazawa, Tomoko*
Chemical Physics Letters, 856, p.141655_1 - 141655_8, 2024/12
Times Cited Count：17 Percentile：96.14(Chemistry, Physical)To investigate the effects of polymer hydrophilicity on structures of water in hydrogels, differential scanning calorimetry and X-ray diffraction measurements were performed. The results show that the amount of intermediate water in polyacrylamide (PAA) hydrogel is about 12% smaller than that in poly-
-dimethylacrylamide (PDMAA) hydrogel. Furthermore, it was found that the bound water in PAA hydrogel primarily exists around the surface of the polymer bundles, whereas that in PDMAA hydrogel acts as a crosslinker factor for dehydration and water absorption in hydrogels.
Takahara, Yuta*; Beni, Yusuke*; Sekine, Yurina; Nankawa, Takuya; Fukazawa, Tomoko*
ACS Omega (Internet), 9(45), p.45554 - 45563, 2024/11
Times Cited Count：9 Percentile：68.68(Chemistry, Multidisciplinary)no abstracts in English
Nankawa, Takuya; Sekine, Yurina; Yamada, Teppei*
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 23(2), p.50 - 63, 2024/06
Selective separation of radioactive ions is essential for reducing or cleaning radioactive wastes. Among the radioisotopes to be removed, 
Sr poses a major threat to human health and the environment. However, removal of Sr from environmental wastewater is still challenging due to the difficulty of separating Sr from Ca. Here, we developed a series of isostructural lanthanide oxalate frameworks (LOFs) comprising oxalate and eight kinds of lanthanide (Ln) ions, i.e., from Samarium (Sm) to Thulium (Tm) for application to selective removal of Sr from wastewater using its tuned porous structure. The LOFs had ion exchangeable anionic pores, in which the size of the pores changed in a stepwise manner depending on the host Ln species. When Tb was the host Ln of the LOF, the LOF showed extremely high Sr selectivity and was able to distinguish the subtle difference in ionic radius (0.2 
) between Sr and Ca. The Sr selectivity was higher than that of conventional adsorbents. The pore size tuning of the LOFs by selecting the constituent Ln species yielded a highly ion-selective adsorbent material. This novel strategy will be useful in developing custom porous materials that are easy to prepare and applicable across various fields.
Kumada, Takayuki; Nakagawa, Hiroshi; Miura, Daisuke; Sekine, Yurina; Motokawa, Ryuhei; Hiroi, Kosuke; Inamura, Yasuhiro; Oku, Takayuki; Oishi, Kazuki*; Morikawa, Toshiaki*; et al.
Hamon, 34(2), p.50 - 53, 2024/05
Spin-contrast-variation (SCV) small-angle neutron scattering (SANS) enabled us to determine structure of nano-ice crystals that were generated in rapidly frozen sugar solution. In the frozen glucose solution, we found that the nano-ice crystals formed a planar structure with a radius larger than several tens of nanometers and a thickness of 2-3 nm, which was close to the critical nucleation size of ice crystals in supercooled water. This result suggests that the glucose molecules were preferentially bound to a specific face of nano-ice crystals, and then blocked the crystal growth perpendicular to that face.
Sekine, Yurina; Nankawa, Takuya; Sugita, Tsuyoshi; Nagakawa, Yoshiyasu*; Shibayama, Yuki; Motokawa, Ryuhei; Ikeda-Fukazawa, Tomoko*
Nanoscale, 16(19), p.9400 - 9405, 2024/05
Times Cited Count：5 Percentile：56.05(Chemistry, Multidisciplinary)A tough carboxymethyl cellulose nanofiber (CMF)/ zirconium (Zr) hydrogel was obtained by freeze cross-linking method. The hydrogel was prepared by adding HCl solution containing Zr to frozen CMF and thawing it. The hydrogel showed high adsorptivity for fluoride. This simple gelation method provides useful insight for developing hydrogel-metal complexes.
Sekine, Yurina; Nankawa, Takuya; Hiroi, Kosuke; Oba, Yojiro*; Nagakawa, Yoshiyasu*; Sugita, Tsuyoshi; Shibayama, Yuki; Ikeda-Fukazawa, Tomoko*
Carbohydrate Polymers, 327, p.121538_1 - 121538_11, 2024/03
Times Cited Count：20 Percentile：91.36(Chemistry, Applied)We describe non-toxic, tough nanocellulose (NC) hydrogels formed from chemically unmodified NC by cellulose crystalline transformation and subsequent freeze cross-linking reaction. Using low-concentration NaOH and freezing together induced the crystalline transformation of NC from cellulose I to II via freeze concentration. After the crystalline transformation, cross-linking between the NC and CA in the freeze concentration layer (FCL) provided a strong NC network structure, forming NC hydrogels with high mechanical strength. The freeze-cross-linked NC hydrogel easily retained powder adsorbents in its inner space by mixing the NC-NaOH sol and the powder, and the hydrogel showed high removal efficiency for heavy metals. The results highlight the versatility of chemically unmodified celluloses in developing functional materials, suggest possible practical applications.
Nankawa, Takuya; Sekine, Yurina; Matsumura, Daiju; Hiroi, Kosuke; Takata, Shinichi; Kamiya, Yoshimi*; Honda, Takayuki*
Langmuir, 40(11), p.5725 - 5730, 2024/03
Times Cited Count：2 Percentile：21.30(Chemistry, Multidisciplinary)The chemical reaction between Fe and lacquer has been used to create the black color lacquer since ancient times. Here, the chemical state of Fe ions in black lacquer was investigated by using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Fourier transform-infrared (FT-IR) spectroscopy. Fe(II) or Fe(III) was added to the lacquer paste to prepare black lacquer films by air drying, heating, or UV irradiation. The XANES spectral features of all the film samples were similar, meaning that the Fe ions in the samples existed in the trivalent state regardless of the oxidation state of the initially added Fe. The corresponding Fourier transforms of the EXAFS spectra around the Fe K-edge were used to investigate Fe sites in the lacquer films. The spectra of all the film samples were similar shapes, but the peak intensities decreased in the order air dried 
heated UV irradiated films. This result indicates that heating and UV irradiation made the coordination structure of Fe in the lacquer non-uniform, and that heating caused the greatest non-uniformity. The complementary use of XANES, XAFS, and FT-IR spectroscopy is highly effective for non-destructive analysis of black lacquer in precious cultural artifacts.
Sekine, Yurina
Cellulose Communications, 30(4), p.203 - 208, 2023/12
In this paper, we introduce the fabrication and properties of carboxymethyl cellulose nanofiber (CMCF) hydrogels with high compression recoverability, macroporosity, and nontoxic properties by utilizing the phase separation phenomenon of ice crystals and solutes that occurs during freezing of aqueous solutions. The features of the developed freeze cross-linked CMCF hydrogel include that it can be made from harmless raw materials with simple procedure, high water content, and biodegradability. By taking advantage of these properties, this hydrogel synthesis technique can contribute to expanding the use of cellulose derivatives as environmental purifiers, functional materials, etc.
Kumada, Takayuki; Motokawa, Ryuhei; Oba, Yojiro; Nakagawa, Hiroshi; Sekine, Yurina; Micheau, C.; Ueda, Yuki; Sugita, Tsuyoshi; Birumachi, Atsushi; Sasaki, Miki; et al.
Journal of Applied Crystallography, 56(6), p.1776 - 1783, 2023/12
Times Cited Count：28 Percentile：98.42(Chemistry, Multidisciplinary)The combination of the existing position-sensitive photomultiplier and the 
He main detector with focusing devices, and the newly installed front detectors in SANS-J at JRR-3 covers small-angle neutron scattering signals in the range of the magnitude of the scattering vector Q from 0.002 to 6 nm-1 gaplessly with three standard device layouts. The installation of the front detector and a graphical user interface system largely improved the usability of SANS-J.
Sekine, Yurina; Nankawa, Takuya
Bulletin of the Chemical Society of Japan, 96(10), p.1150 - 1155, 2023/10
Times Cited Count：9 Percentile：21.52(Chemistry, Multidisciplinary)The phase separation of ice crystals and solutes and bound water that occurs during freezing can be used as a reaction field to control a hierarchical structure of hydrogels. Here, we present a study of carboxymethyl cellulose nanofiber (CMCF) hydrogels formed using the solid-quasi liquid phase separation. CMCF hydrogels were formed simply by adding citric acid to frozen CMCF and thawing the mixture. It was found that rearrangement of CMCF structures via hydrogen bonding proceeds in the freeze concentration layer before the ice crystals melt. Under freeze concentration, CMCF and bound water are confined at high concentrations. The crosslinking reaction in such a unique space contributed to the formation of CMCF hydrogel with high mechanical strength. We discuss the gelation behavior and properties of freeze crosslinked CMCF hydrogels and their applications.
Yang, D. S.*; Wu, Y.*; Kanatzidis, E. E.*; Avila, R.*; Zhou, M.*; Bai, Y.*; Chen, S.*; Sekine, Yurina; Kim, J.*; Deng, Y.*; et al.
Materials Horizons, 10(11), p.4992 - 5003, 2023/09
Times Cited Count：25 Percentile：85.02(Chemistry, Multidisciplinary)This paper presents a set of findings that enhances the performance of these systems through the use of microfluidic networks, integrated valves and microscale optical cuvettes formed by three-dimensional printing in hard/soft hybrid materials systems, for accurate spectroscopic and fluorometric assays. Field studies demonstrate the capability of these microcuvette systems to evaluate the concentrations of copper, chloride, and glucose in sweat, along with the sweat pH, with laboratory grade accuracy and sensitivity.
Sekine, Yurina
Fuain Kemikaru, 52(8), p.25 - 32, 2023/08
By using the freezing phenomenon, we discovered that a hydrogel with high compressive strength can be formed using only harmless materials, mainly carboxymethyl cellulose nanofibers. The key is the phase separation of ice crystals and solutes that occurs when aqueous solutions freeze. This paper describes the formation mechanism of the freeze crosslinked hydrogel and its properties.
