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Journal Articles

Effects of hydrophilic groups of polymer on change in hydrogen-bonding structure of water in hydrogels during dehydration

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:1 Percentile:0.00(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-$$N,N$$-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.

Journal Articles

None

Sekine, Yurina

Kagaku To Kogyo, 77(12), p.865 - 868, 2024/12

no abstracts in English

Journal Articles

Structural changes of water in carboxymethyl cellulose nanofiber hydrogels during vapor swelling and drying

Takahara, Yuta*; Beni, Yusuke*; Sekine, Yurina; Nankawa, Takuya; Fukazawa, Tomoko*

ACS Omega (Internet), 9(45), p.45554 - 45563, 2024/11

 Times Cited Count:0 Percentile:0.00(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Subangstrom tuning of pore size for selective separation of radioactive strontium over environmental calcium by lanthanide-oxalate frameworks

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, $$^{90}$$Sr poses a major threat to human health and the environment. However, removal of $$^{90}$$Sr from environmental wastewater is still challenging due to the difficulty of separating $$^{90}$$Sr$$^{2+}$$ from Ca$$^{2+}$$. 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 $$^{90}$$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$$^{2+}$$ selectivity and was able to distinguish the subtle difference in ionic radius (0.2 ${AA}$) between Sr$$^{2+}$$ and Ca$$^{2+}$$. The Sr$$^{2+}$$ 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.

Journal Articles

Nanometer-thick crystalline ice plates in rapidly-frozen glucose solution observed by spin-contrast-variation small-angle neutron scattering

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.

Journal Articles

Freeze-crosslinking approach for preparing carboxymethyl cellulose nanofiber/zirconium hydrogels as fluoride adsorbents

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:2 Percentile:62.87(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.

Journal Articles

Nanocellulose hydrogels formed via crystalline transformation from cellulose I to II and subsequent freeze cross-linking reaction

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:7 Percentile:78.97(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.

Journal Articles

Effects of Fe ions, ultraviolet irradiation, and heating on microscopic structures of black lacquer films

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:0 Percentile:0.00(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.

Journal Articles

Development of tough cellulose hydrogels using freeze-concentrated layers

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.

Journal Articles

Upgrade of the small-angle neutron scattering diffractometer SANS-J at JRR-3

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:11 Percentile:96.87(Chemistry, Multidisciplinary)

The combination of the existing position-sensitive photomultiplier and the $$^{3}$$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.

Journal Articles

Freeze-concentrated layers as a unique field for the formation of hydrogels

Sekine, Yurina; Nankawa, Takuya

Bulletin of the Chemical Society of Japan, 96(10), p.1150 - 1155, 2023/10

 Times Cited Count:4 Percentile:24.80(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.

Journal Articles

3D-printed epidermal sweat microfluidic systems with integrated microcuvettes for precise spectroscopic and fluorometric biochemical assays

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:10 Percentile:82.64(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.

Journal Articles

Novel hydrogel properties by microstructural control of carboxymethyl cellulose nanofibers using freezing

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.

Journal Articles

Polarized neutrons observed nanometer-thick crystalline ice plates in frozen glucose solution

Kumada, Takayuki; Nakagawa, Hiroshi; Miura, Daisuke; Sekine, Yurina; Motokawa, Ryuhei; Hiroi, Kosuke; Inamura, Yasuhiro; Oku, Takayuki; Oishi, Kazuki*; Morikawa, Toshiaki*; et al.

Journal of Physical Chemistry Letters (Internet), 14(34), p.7638 - 7643, 2023/08

 Times Cited Count:0 Percentile:0.00(Chemistry, Physical)

The structure of nano-ice crystals in rapidly frozen glucose solution was elucidated by using spin-contrast-variation small-angle neutron scattering, which distinguishes the nano-ice crystal signal from the frozen amorphous solution signal by the polarization-dependent neutron scattering. The analysis revealed that the nano-ice crystals form a planar structure with a diameter exceeding tens of nanometers and a thickness of 1 nm, which is close to the critical nucleation size. This result suggests that the glucose molecules are preferentially bound to a specific face of nano-ice crystals, and then block the crystal growth perpendicular to that face.

Journal Articles

Fractionation of hydrogen isotopes in a hydrogel during dehydration

Watanabe, Teppei*; Sekine, Yurina; Ikeda-Fukazawa, Tomoko*

Macromolecules, 56(16), p.6217 - 6221, 2023/08

 Times Cited Count:3 Percentile:40.98(Polymer Science)

To investigate the ability of hydrogels to separate hydrogen isotopes in water, we analyzed the Raman spectra of poly-N,N-dimethylacrylamide (PDMAA) hydrogels containing deuterated water during dehydration. The results show a significant fractionation of hydrogen isotopes during dehydration. The D molar ratio of the hydrogel increases from 0.056 to $$sim$$0.2 during dehydration from 90.5 wt% to 5 wt% in water content. Deuterated water preferentially forms hydrogen bonds with hydrophilic groups of the polymer in hydrogels because of the difference in strengths of hydrogen bonds between protium and deuterium. As a result, normal water preferentially evaporates in the initial stage of dehydration, leaving deuterated water in the drying hydrogel. The results suggest that hydrogels are an efficient material for isotope fractionation with evaporation.

Journal Articles

Soft, environmentally degradable microfluidic devices for measurement of sweat rate and total sweat loss and for colorimetric analysis of sweat biomarkers

Liu, S.*; Yang, D. S.*; Wang, S.*; Luan, H.*; Sekine, Yurina; Model, J. B.*; Aranyosi, A. J.*; Ghaffari, R.*; Rogers, J. A.*

EcoMat (Internet), 5(1), p.e12270_1 - e12270_18, 2023/01

 Times Cited Count:35 Percentile:93.88(Chemistry, Physical)

Advanced capabilities in noninvasive, in situ monitoring of sweat serve as the basis for obtaining real-time insights into human physiological state, health, and performance. Although recently reported microfluidic systems support powerful functions, most are designed as single-use disposables. Here, we introduce materials and molding techniques that bypass these concerns through biodegradable microfluidic systems with a full range of features. The key components fully degrade through the enzymatic action of microorganisms in natural soil environments. Detailed characterization of the device reveal a set of essential performance parameters that are comparable to, or even better than, those of non-degradable counterparts. Human subject studies illustrate the ability of these devices to acquire accurate measurements of sweat loss, sweat rate, pH, and chloride concentration.

Journal Articles

Microscopic structural changes during the freeze cross-linking reaction in carboxymethyl cellulose nanofiber hydrogels

Miura, Daisuke*; Sekine, Yurina; Nankawa, Takuya; Sugita, Tsuyoshi; Oba, Yojiro; Hiroi, Kosuke; Ozawa, Tatsuhiko

Carbohydrate Polymer Technologies and Applications (Internet), 4, p.100251_1 - 100251_9, 2022/12

The reaction mechanism of carboxymethyl cellulose nanofiber (CMCF) hydrogel formed by freeze-crosslinking was investigated. We succeeded in observing the hierarchical structural changes during the freeze-crosslinking reaction. Freeze-crosslinked CMCF hydrogels exhibited a characteristic hierarchical alignment structure from the angstrom to micrometer scale that differed from normal cross-linked CMCF hydrogels produced by a conventional method without freezing. It was shown that the characteristic hierarchical structure contributes the excellent mechanical properties of freeze-crosslinked CMCF hydrogels.

Journal Articles

Ion-selective adsorption of lead by a two-dimensional terbium oxalate framework

Nankawa, Takuya; Sekine, Yurina; Yamada, Teppei*

Bulletin of the Chemical Society of Japan, 95(5), p.825 - 829, 2022/05

 Times Cited Count:4 Percentile:33.96(Chemistry, Multidisciplinary)

Advances in hazardous metal ion removal are essential for wastewater clean-up to tackle the global water shortage crisis. Here, we report a Pb-selective adsorbent using a Tb oxalate framework (TOF) synthesized by a one-pot hydrothermal method. The TOF has a two-dimensional sheet structure, in which the interlayer space functions as an ion exchangeable site. Sorption tests using a mixed-ion solution containing Pb$$^{2+}$$, Cd$$^{2+}$$, Mn$$^{2+}$$, Co$$^{2+}$$, Ni$$^{2+}$$, Cu$$^{2+}$$, Na$$^{+}$$, K$$^{+}$$, Mg$$^{2+}$$, and Ca$$^{2+}$$ showed that the TOF has high selectivity for Pb$$^{2+}$$ among other metal ions. The saturated adsorption capacity of the TOF for Pb$$^{2+}$$ was 276 mg g$$^{-1}$$, which is higher than that of conventional adsorbents. Furthermore, the TOF exhibited reversible Pb$$^{2+}$$ adsorption/desorption and could be used for at least three cycles. The results showed that TOF has excellent potential as an adsorbent for removing Pb$$^{2+}$$, and because of its reusability, it is also a promising material for wastewater clean-up.

Journal Articles

Development of spin-contrast-variation neutron powder diffractometry for extracting the structure factor of hydrogen atoms

Miura, Daisuke*; Kumada, Takayuki; Sekine, Yurina; Oku, Takayuki; Takata, Shinichi; Hiroi, Kosuke; Iwata, Takahiro*

J-PARC 22-02; J-PARC MLF Annual Report 2021, p.6 - 7, 2022/03

We carried out spin contrast variation neutron powder diffractometry of glutamic acid crystal. The diffraction peak intensities varied as a function of proton polarization. We extracted the structure factor of hydrogen atoms from the variation of peak intensities.

Journal Articles

Eco-friendly cellulose nanofiber hydrogels prepared via freeze crosslinking and their applications

Sekine, Yurina

Kensetsu Kikai Seko, 74(2), p.94 - 97, 2022/02

This research has revealed that a high strength hydrogel can be prepared by adding an aqueous solution of citric acid to a frozen carboxymethyl cellulose nanofiber (CMCF) and then thawing the sol. The reaction between the freeze-concentrated CMCF and CA created a rigid porous structure, which resembled the ice crystal structure. The cellulose hydrogel material obtained through this technique exhibited sufficient strength along with a high level of moldability that allows it to be molded into different three-dimensional shapes. In addition, the material has the potential to be used as an adsorbent to remove hazardous substances.

97 (Records 1-20 displayed on this page)