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Current Affiliation Organization 【 display / non-display 】

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Research Areas 【 display / non-display 】

Published Papers 【 display / non-display 】

Published Papers 【 display / non-display 】

• Anion-exchange-controlled chiroptical properties in viologen-linked glutamide nanofibrillar assembly for electroresponsive chiroptical switches

  Yutaka Kuwahara, Mio Ito, Kaho Nishimura, Daiki Aome, Taito Nakamura, Makoto Takafuji, Hirotaka Ihara, Naoya Ryu, Tomoyasu Mani

  The Journal of Physical Chemistry B ( American Chemical Society (ACS) )  130 ( 30 ) 7634 - 7645   2026.07 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Abstract Supramolecular assemblies of dicationic 4,4′-bipyridinium (viologen: V2+) moieties modifying glutamide (G) derivatives, i.e., GV2+, are promising candidates for nanomaterials enabling redox-induced electroresponsive chiroptical switching in the visible region (ECSv), with potential applications in next-generation chiroptical management technologies. In this study, we investigated the dependence of the chiroptical properties of GV-X assemblies on the counteranion X– using ultraviolet–visible (UV–vis) absorption and circular dichroism (CD) spectroscopy to enhance their versatility. Density functional theory (DFT) and time-dependent (TD) DFT calculations reveal that the chiroptical properties of GV2+ interacting with I–, Br–, or Cl– ions (GV-I, GV-Br, and GV-Cl) depend on the charge-transfer interactions of V2+ and X–, determined by the electron-donating strength of X–. The counterion-exchanged GV-X assemblies, synthesized from as-prepared GV-PF6 salts in acetonitrile solution or prepared by excess addition of salts including targeted X– ions, showed composition-dependent chiroptical properties. Notably, the GV-Br assembly with a nanofibrillar structure exhibited ECSv, characterized by color and chiroptical signal changes without sign inversion, differing from those with sign inversion of the previous GV-BrI assembly. The ability to modulate chiroptical properties through anion-exchange and charge-transfer interactions provides a pathway for designing custom materials with specific optical properties for targeted applications.

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• Evaluation of the anticancer activity of medicinal plants predominantly accumulating ellagic acid compounds

  Domantas Armonavičius, Audrius Maruška, Baltramiejus Jakštys, Mantas Stankevičius, Tomas Drevinskas, Kristina Bimbiraitė-Survilienė, Modesta Čaplikaitė, Hirotaka Ihara, Makoto Takafuji, Elżbieta Skrzydlewska, Ona Ragažinskienė, Yutaka Kuwahara, Shoji Nagaoka, Vilma Kaškonienė, Saulius Šatkauskas, Arvydas Kanopka

  Antioxidants   14 ( 11 ) 1339-1 - 1339-30   2025.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Impact of silica nanoparticles on mechanical properties and self-healing performance of PVA hydrogels

  Moustapha Mohamed Mahamoud, Yutaka Kuwahara, Hirotaka Ihara, Makoto Takafuji

  Polymers ( MDPI AG )  17 ( 21 ) 2883-1 - 2883-12   2025.10 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Hydrogels are three-dimensional polymeric networks capable of retaining large amounts of water. Polyvinyl alcohol (PVA)-based hydrogels exhibit autonomous self-healing through reversible physical interactions within the hydrogel matrix, including hydrogen bonding, crystallite formation, and dynamic crosslinking. However, their long self-healing times and low strength limit practical application. Herein, we propose an effective strategy to simultaneously achieve excellent self-repairing and high mechanical strength. The tensile strength of uncut PVA hydrogel was 1.21 MPa; after cutting and rejoining for 12 h at room temperature (RT), it recovered 94% of the original uncut strength. To accelerate self-healing, hydrogels were treated at 40, 50, and 60 °C for 20, 40, and 60 min. Under optimal conditions (60 °C for 60 min), 96% recovery was achieved. Mechanical properties were further improved by silica (Si) nanoparticles of various sizes (~12, ~85, and ~200 nm). Si-loaded hydrogels, particularly ~12 nm, demonstrated increased mechanical properties, reaching a tensile strength of 1.45 MPa and a self-healing recovery of 95% of the uncut hydrogel strength. Ultra-small (~12 nm) Si nanoparticles enhanced the overall mechanical properties by acting as an efficient nucleating agent and did not hinder the existing self-healing mechanism. The developed strategy will pave the way for novel techniques in hydrogel research and will advance applications such as soft robotics and wound dressing.

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• A spectroscopy solution for contactless conductivity detection in capillary electrophoresis

  Tomas Drevinskas, Audrius Maruška, Hirotaka Ihara, Makoto Takafuji, Linas Jonušauskas, Domantas Armonavičius, Mantas Stankevičius, Kristina Bimbiraitė-Survilienė, Elzbieta Skrzydlewska, Ona Ragažinskienė, Yutaka Kuwahara, Shoji Nagaoka, Vilma Kaškonienė, Loreta Kubilienė

  Micromachines ( MDPI AG )  15 ( 12 ) 1430-1 - 1430-11   2024.11 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  This paper introduces a novel contactless single-chip detector that utilizes impedance-to-digital conversion technology to measure impedance in the microfluidic channel or capillary format analytical device. The detector is designed to operate similarly to capacitively coupled contactless conductivity detectors for capillary electrophoresis or chromatography but with the added capability of performing frequency sweeps up to 200 kHz. At each recorded data point, impedance and phase-shift data can be extracted, which can be used to generate impedance versus frequency plots, or phase-shift versus frequency plots. Real and imaginary parts can also be calculated from the data, allowing for the generation of Nyquist diagrams. This detector represents the first of its kind in the contactless conductivity class to provide spectrum-type data, as demonstrated in capillary electrophoresis experiments.

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• Enhancement of mechanical properties of benign polyvinyl alcohol/agar hydrogel by crosslinking tannic acid and applying multiple freeze/thaw cycles

  Moustapha Mohamed Mahamoud, Tadesse Mekonnin Ketema, Yutaka Kuwahara, Makoto Takafuji

  Gels ( MDPI AG )  10 ( 8 ) 527-1 - 527-14   2024.08 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Hydrogels composed of natural and synthetic polymers have considerable potential for use in diverse areas such as biomedical applications and water purification. This is primarily because of their biocompatibility, biodegradability, and low toxicity. The widespread usage of composite hydrogels is hindered by a lack of simultaneous properties, such as high strength and low swelling rate. Herein, we report the preparation of novel hydrogels composed of polyvinyl alcohol (PVA)–intercalated agar polymer networks physically crosslinked with tannic acid. The hydrogel was subjected to multiple freeze/thaw (F/T) cycles (1, 3, and 5), and it was found to exhibit the highest strength after 5 F/T cycles. After 1 F/T cycle, the tensile strength of the composite hydrogel reached 1.56 MPa with a 1.0 wt% crosslinker, whereas after 5 F/T cycles, it increased to 3.77 MPa with a reduced amount (0.75 wt%) of the crosslinker. In addition, the swelling ability decreased upon increasing the crosslinker content and number of F/T cycles. Furthermore, the hydrogel demonstrated excellent water retention and a strong ability to adhere to different substrates. We have successfully implemented an innovative approach to improve the mechanical properties of PVA-based hydrogels by combining the use of tannic acid as a cross-linking agent and multiple F/T cycles. The developed hydrogels are expected to facilitate new developments in hydrogel technology, thus impacting diverse fields such as biomedical (wound dressing and artificial cartilage).

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Books 【 display / non-display 】

Books 【 display / non-display 】

• New Designs of Supramolecular Gels ―Development & Application―

  ( Part: Allotment Writing )

  2023.07

• Molecular Technology: Synthesis Innovation

  Hirotaka Ihara, Makoto Takafuji, Yutaka Kuwahara, Yutaka Okazaki, Naoya Ryu, Takashi Sagawa, Reiko Oda ( Part: Allotment Writing ,  Vol.4, Chapter 11 Supramolecular Web and Application for Chiroptical Functionalization of Polymer )

  Wiley  2019.04

• New frontiers in photochromism and photomechanical materials

  ( Part: Allotment Writing )

  2011.11

Presentations 【 display / non-display 】

Presentations 【 display / non-display 】

• Chirality enhancement in polymer films for CPL generation and its application to microalgae cultivation

  Noriko Okita, Asahi Okada, Misaki Asano, Riku Tamayose, Sora Nagahama, Jia Chen, Qiu Hongdeng, Yutaka Kuwahara, Makoto Takafuji, Hirotaka Ihara

  20th Asian Chemical Congress (20ACC)  2025.06  -  2025.06 

• Chiroptical polymer system functionalized with glutamide-based chiral molecular gel

  Yutaka Kuwahara, Makoto Takafuji, Takashi Sagawa, Noriko Okita, Hongdeng Qiu, Hirotaka Ihara

  14th International Gel Symposium (Gel Symposium 2024)  2024.11  -  2024.11 

• Chirality control of supramolecular assemblies from metal-ion coordinated catechol-bonded glutamide lipid via the complexation with non-chiral guest ligands

  Makoto Takafuji, Ryuya Hirata, Nanami Hano, Mayuko Sakai, Koichiro Takezono, Naoya Ryu, Yutaka Kuwahara, Reiko Oda, Hirotaka Ihara

  The 3rd Materials Research Meeting (MRM)/ The 24th IUMRS-International Conference in Asia (IUMRS-ICA) (MRM2023/IUMRS-ICA2023)  2023.12  -  2023.12 

• Circularly polarized luminescent polymer system fabricated with glutamide-derived supramolecular gel

  Yutaka Kuwahara, Nananmi Hano, Mio Ito, Masahiro Matsunaga, Aiki Kamo, Nao Nagatomo, Makoto Takafuji, Noriko Okita, Hirotaka Ihara

  The 1st KOSEN Research International Symposium (KRIS)  2023.03  -  2023.03 

• Chiroptical supramolecular gel induced by cationic glutamide derivatives and their binary systems

  Yutaka Kuwahara, Mio Ito, Yuki Fujimoto, Tatsumi Iwamoto, Hirotaka Ihara, Makoto Takafuji, Naoya Ryu, Tomoyasu Mani

  POLYSOLVAT-14, 14th International IUPAC conference on Polymer-solvent Complexes and Intercalates and 1st conference on Next-Generation of (Macro)-Molecular Self-Assembled Systems  2022.09  -  2022.09 

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Industrial Property 【 display / non-display 】

Industrial Property 【 display / non-display 】

• 黒色粒子及び黒色粒子の製造方法

  Industrial Property No 特願2017-518168  (2017.02.17)

  Patent No 特許第6941837号  (2021.09.09)

  孫 仁徳, 野里 省二, 中壽賀 章, 伊原 博隆, 高藤 誠, 桑原 穣, 村上 晶子

  J-GLOBAL

Grant-in-Aid for Scientific Research 【 display / non-display 】

Grant-in-Aid for Scientific Research 【 display / non-display 】

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2024.04  -  2027.03 

  Direct: 3,600,000 (YEN)  Overheads: 1,080,000 (YEN)  Total: 4,680,000 (YEN)

• Fabrication of functionally graded organic-inorganic nanocomposites for high refractive index

  Challenging research (sprout)

  Project Year: 2020.07  -  2024.03 

  Direct: 5,000,000 (YEN)  Overheads: 1,500,000 (YEN)  Total: 6,500,000 (YEN)

• Grant-in-Aid for Scientific Research(C)

  Project Year: 2020.04  -  2024.03 

  Direct: 3,300,000 (YEN)  Overheads: 990,000 (YEN)  Total: 4,290,000 (YEN)

• Development of nano-catalyst based on chirally-assembling of reaction center and enhancement of its catalytic ability

  Grant-in-Aid for Scientific Research(C)

  Project Year: 2017.04  -  2020.03 

  Investigator(s): Kuwahara Yutaka 

  Direct: 3,600,000 (YEN)  Overheads: 1,080,000 (YEN)  Total: 4,680,000 (YEN)

  　View Summary

  Functional extension of lightweight and flexible organic materials is a promising approach toward a novel advanced material for various applications. We focus on metal complexes (MCs) as functional moieties, demonstrate fabrication of nano-fibrillar organic/inorganic-hybrid materials of MC and self-assembling molecular tool, and have aimed to enhance their functions via orientation of MCs induced by the self-assembling tool. Glutamide (G) derivatives obtained from a glutamic acid has been employed as a self-assembling molecular tool. We confirmed that the MC/G systems comprising MCs and G derivatives formed nano-sized fibrillar assembly in various solvents after temperature treatments as results of spectroscopies and microscopies. The results also indicated that the MC on MC/G systems aligned with chirality in various solutions. The effect of assembling on the functional properties like emission and catalytic abilities has been discussed for the nano-fibrillar materials.

• Assemblies of catalytic groups induced by self-assembling molecular tools and control of their catalytic ability via external stimuli(Fostering Joint International Research)

  Fund for the Promotion of Joint International Research (Fostering Joint International Research)

  Project Year: 2017  -  2019 

  Investigator(s): Kuwahara Yutaka 

  Direct: 9,200,000 (YEN)  Overheads: 2,760,000 (YEN)  Total: 11,960,000 (YEN)

  　View Summary

  We investigated fabrication of supramolecular nano-catalyst systems for CO2 reduction composed with self-assemblies of metal complexes (MCs) as catalytic groups organized by glutamide (G) self-assembling molecular tools obtained from the glutamic acid. In those systems, we also introduced external stimuli responsive (SR) groups to the G systems to control intermolecular interaction of the catalytic groups and/or thermal stability of the supramolecular assemblies. The introduction of SR has aimed to enhance the catalytic ability via orientation control of the catalytic MCs. We confirmed that MC/G and SR/G hybrid systems formed nano-sized fibrillar assemblies in various solvents as results of spectroscopies and microscopies. The results also indicated that the MC and SR moieties orientated with chirality in each hybrid system. The aggregation effect on optical and catalytic properties in the nano-catalyst systems has been discussed.

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