Isobe, Tetsuhiko

写真a

Affiliation

Faculty of Science and Technology, Department of Applied Chemistry (Yagami)

Position

Professor

Related Websites

External Links

Profile Summary 【 Display / hide

  • 私たちの研究室では、ユニークな液相合成法を活用して0次元や2次元の形態を有するナノ蛍光体材料を開発しています。たとえば、ディスプレイの広色域化を可能にするペロブスカイト量子ドット、太陽電池応用を指向した近紫外線を赤色や近赤外線に波長変換するナノシート、低毒性・環境親和性を有するカーボンドット、近紫外線照射で可視光を発する銀イオン交換ゼオライトナノ粒子などを研究しています。

Career 【 Display / hide

  • 1989.04
    -
    1995.03

    Keio University, Assistant

  • 1993.09
    -
    1994.08

    Vanderbilt University (USA), Visiting scholar

  • 1995.04
    -
    1999.03

    Keio University, Assistant Professor

  • 1999.04
    -
    2007.03

    Keio University, Associate Professor

  • 1999.09
    -
    2000.08

    École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI)(France), Visiting scholar

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Academic Background 【 Display / hide

  • 1986.03

    Keio University, Faculty of Science and Engineering, 応用化学科

    University, Graduated

  • 1988.03

    Keio University, Graduate School, Division of Science and Engineeri, 応用化学専攻

    Graduate School, Completed, Master's course

  • 1991.03

    Keio University, Graduate School, Division of Science and Engineeri, 応用化学専攻

    Graduate School, Withdrawal after completion of doctoral course requirements, Doctoral course

Academic Degrees 【 Display / hide

  • 博士(工学), Keio University, Coursework, 1992.02

 

Research Areas 【 Display / hide

  • Nanotechnology/Materials / Inorganic materials and properties

  • Nanotechnology/Materials / Nanobioscience (Nano Materials/Nano Bioscience)

Research Keywords 【 Display / hide

  • Phosphors

  • Nanophosphor

  • Luminescent nanomaterials

  • Nanocomposite materials

 

Books 【 Display / hide

  • 次世代ディスプレイへの応用に向けた材料、プロセス技術の開発動向

    磯 由樹, 磯部 徹彦, 技術情報協会, 2020.02

    Scope: 第8章 第4節 完全無機ペロブスカイトナノ結晶蛍光体の特性、合成法および耐久性の改善

  • 量子ドット材料の技術と応用展開: ディスプレイ・照明・バイオ応用から太陽電池まで

    磯 由樹, 磯部 徹彦, 情報機構, 2017.06

    Scope: 第4章第2節 ペロブスカイト型量子ドット蛍光体

  • 次世代蛍光体材料の開発

    磯 由樹, 磯部 徹彦, シーエムシー出版, 2016.07

    Scope: 第4編 第1章 CdフリーCuInS2量子ドット,第2章 ドープ型量子ドット,第3章 ナノシート蛍光体

  • ナノ粒子の表面修飾と分析評価技術~各種特性を向上するためのナノ粒子表面関連技術とその評価~

    磯部 徹彦, 情報機構, 2016.01

    Scope: 第4章 第6節 蛍光ナノ粒子の表面修飾

  • 近赤外・紫外線-波長変換と光吸収増大による太陽電池の高効率化技術

    磯 由樹, 磯部 徹彦, S&T出版, 2016.01

    Scope: 第1章 第1節 ナノ蛍光体による近紫外線→可視光・近赤外線変換と結晶シリコン太陽電池への応用

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Papers 【 Display / hide

  • Bandgap-tuned fluorescent CuGaS<inf>2</inf>/ZnS core/shell quantum dots for photovoltaic applications

    Hase S., Iso Y., Isobe T.

    Journal of Materials Chemistry C (Journal of Materials Chemistry C)  10 ( 9 ) 3523 - 3530 2022.02

    Joint Work

     View Summary

    This work investigated CuGaS2 (CGS)/ZnS quantum dots (QDs) as fluorescent materials for a luminescent downshifting (LDS) layer and a luminescent solar concentrator (LSC) with a single-crystalline silicon (sc-Si) solar module. The bandgap of the CGS/ZnS QDs was adjusted to ∼3.1 eV by changing the molar ratio of Cu/Ga, and in so doing a transparent and colorless LDS layer that converted near-ultraviolet (UV) light to visible light was fabricated. The resulting QDs, which exhibited a high photoluminescence quantum yield of 73%, were embedded in ethylene-vinyl acetate (EVA) copolymer resin to fabricate a QDs@EVA film. The short-circuit current (ISC) of the sc-Si solar module under simulated solar light decreased from 39.35 mA to 38.30 mA (−2.7%) by using the QDs@EVA film instead of an EVA film without QDs. Correspondingly, the photoelectronic conversion efficiency (η) changed from 18.07% to 17.56% (−2.8%). The decreased photocurrent was because of light scattering by aggregated QDs, and overcame the wavelength-conversion effect of the LDS film. In contrast, the QDs@EVA film was effective for LSC because the ISC and η relatively increased by +77.7% and +96.2%, respectively. The visible light emitted by the UV-excited QDs and the visible light scattered by the QDs contributed to the photoelectric conversion.

  • Implications of gas-barrier properties in realizing the self-recovery of photodegraded CsPbBr<inf>3</inf>perovskite nanocrystals

    Enomoto I., Iso Y., Isobe T.

    Journal of Materials Chemistry C (Journal of Materials Chemistry C)  10 ( 1 ) 102 - 107 2022.01

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  20507534

     View Summary

    Fluorescent CsPbBr3perovskite nanocrystals (NCs) degraded by photoinduced desorption of surface ligands can exhibit self-recovery; however, irreversible oxidative damage from oxygen in the atmosphere must be avoided. In this work, gas-barrier polymer films made of ethylene vinyl alcohol (EVOH) and ethylene vinyl acetate (EVA) copolymers were investigated as sealing materials for CsPbBr3NC films. The NC film covered with EVOH showed photodegradation with blackening and photoluminescence quenching under light excitation, while self-recovery of the optical properties was observed during dark storage. These phenomena were attributed to the photoinduced desorption of surface ligands (and thus the formation of surface defects) and their re-adsorption, respectively. In contrast, self-recovery did not occur when an EVA film was used. X-ray photoelectron spectroscopy indicated the formation of Pb-O bonds for the EVA-coated film. Thus, EVOH, which has a lower oxygen permeability than EVA, successfully prevented irreversible damage by permeated oxygen. This is an important finding for the reuse or lifetime-extension of CsPbBr3NCs.

  • Formation Process of Y<inf>2</inf>O<inf>3</inf>:Bi<sup>3+</sup>,Eu<sup>3 +</sup>Nanosheets from Hydroxide Precursor Nanosheets

    Matsunaga T., Iso Y., Isobe T.

    ECS Journal of Solid State Science and Technology (ECS Journal of Solid State Science and Technology)  10 ( 9 )  2021.09

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  21628769

     View Summary

    We studied the formation of Y2O3:Bi3+,Eu3+ nanosheets from different Y2O3 precursors to propose a mechanism for their formation. One limitation of solar cells is their low sensitivity to near-ultraviolet light, which may be improved by including a phosphor to convert near-ultraviolet light to visible light, which can be readily absorbed. An attractive phosphor for this role is Y2O3:Bi3+,Eu3+; however, it remains unclear how Y2O3:Bi3+,Eu3+ forms from Y2O3 precursor nanosheets. Therefore, we studied the formation of Y2O3:Bi3+,Eu3+ nanosheets from Y2O3 precursors fabricated under various conditions including different pH, base type, and autoclave duration. We found that single-crystalline Y2O3:Bi3+,Eu3+ nanosheets formed from Y2O3 precursor nanosheets produced under suitable conditions. The Y2O3:Bi3+,Eu3+ nanosheets retained the crystallographic orientation of the precursor Y2O3 nanosheets. The formation of these nanosheets did not require the presence of organic ligands. Our findings indicate that Y2O3:Bi3+,Eu3+ nanosheet formation involved anisotropic assembly of crystallized nanoparticles and a subsequent dissolution-recrystallization process. The Y2O3:Bi3+,Eu3+ nanosheets fabricated under certain conditions displayed absorption and emission properties suitable for use as solar converters.

  • Glycothermally Synthesized Carbon Dots with Narrow-Bandwidth and Color-Tunable Solvatochromic Fluorescence for Wide-Color-Gamut Displays

    Yoshinaga T., Shinoda M., Iso Y., Isobe T., Ogura A., Takao K.I.

    ACS Omega (ACS Omega)  6 ( 2 ) 1741 - 1750 2021.01

    Research paper (scientific journal), Joint Work, Accepted

     View Summary

    © 2021 The Authors. Published by American Chemical Society. Fluorescent carbon dots (CDs) represent a promising eco-friendly next-generation phosphor. However, most CDs exhibit broad photoluminescence (PL) spectra [full width at half-maximum (fwhm) over 60 nm]; few works on CDs with sharp PL spectra (fwhm less than 40 nm) have been reported. In addition, their syntheses and color tuning require harsh conditions of high temperatures, long reaction times, and high pressures with catalysts. Here, we successfully prepared narrow-bandwidth emissive CDs (fwhm of 27-40 nm) from phloroglucinol in a glycol solvent of 1,2-pentanediol at temperatures as low as 180 °C for a reaction duration of as short as 6 h under ambient conditions without any catalysts via an open reaction system in which dehydration and condensation reactions among phloroglucinol molecules were enhanced. We shifted the emission peak from 463 to 511 nm by selecting seven kinds of solvents with different polarities, that is, emission colors could be tuned from blue to green by taking advantage of fluorescence solvatochromism. The CD-dispersed polymer films showed a similar solvatochromic behavior and sharp PL spectra, verifying the feasibility of applying the CDs to displays with a wide color gamut.

  • Effects of Halide Composition on the Self-Recovery of Photodegraded Cesium Lead Halide Perovskite Nanocrystals: Implications for Photoluminescence Applications

    Miyashita K., Kidokoro K., Iso Y., Isobe T.

    ACS Applied Nano Materials (ACS Applied Nano Materials)  4 ( 11 ) 12600 - 12608 2021

    Research paper (scientific journal), Joint Work, Accepted

     View Summary

    Photodegraded CsPbBr3 perovskite nanocrystals (NCs) can exhibit complete self-recovery following storage in the dark. This behavior results from the readsorption of surface ligands that experienced photoinduced desorption under UV light excitation. In the present work, mixed-halide CsPb(Cl0.4Br0.6)3, CsPb(Cl0.2Br0.8)3, and CsPb(Br0.7I0.3)3 NCs were prepared via ion exchange to evaluate the influence of halide composition on the photodegradation and self-recovery of NCs. Partially substituting Cl- for Br- enhanced the photoactivation, which improved the photoluminescence properties by optimizing the adsorption state of the surface ligands during light excitation. In contrast, partially substituting I- for Br- reduced the stability of the cubic crystal structure, thus subjecting the NCs to irreversible degradation (likely including a partial phase transition) and preventing their self-recovery. Cycle tests confirmed the reversibility of the photodegradation/self-recovery of CsPbBr3 NCs; however, this behavior was disturbed by irreversible surface oxidation reactions when the sample was exposed to ambient air. Therefore, it was concluded that ambient air must be excluded to effectively take advantage of the self-recovery phenomenon for practical applications.

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Papers, etc., Registered in KOARA 【 Display / hide

Reviews, Commentaries, etc. 【 Display / hide

  • 単結晶シリコン太陽電池の波長変換材料を目指した量子ドットの開発

    磯 由樹,磯部 徹彦

    機能材料 (シーエムシー出版)  41 ( 4 ) 19 - 27 2021.04

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media), Joint Work

  • 新しい蛍光体材料カーボンドットとは?─緑色や赤色に発光するナノ炭素材料

    磯 由樹,磯部 徹彦

    化学 (化学同人)  76 ( 3 ) 68 - 69 2021.03

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media), Joint Work

  • ナノ蛍光体:発光する半導体量子ドット

    磯 由樹,磯部 徹彦

    粉体工学会誌 57 ( 12 ) 641 - 646 2020.12

    Article, review, commentary, editorial, etc. (scientific journal), Joint Work

  • 新たなナノ蛍光体の台頭─ペロブスカイトナノ結晶とカーボンドット─

    磯 由樹,磯部 徹彦

    セラミックス 55 ( 11 ) 796 - 799 2020.11

    Article, review, commentary, editorial, etc. (scientific journal), Joint Work

  • ナノ蛍光体が透明に分散した波長変換TMAS誘導シリカプレート

    磯 由樹, 磯部 徹彦

    Material Stage 16 ( 9 ) 81 - 83 2016.09

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media), Joint Work

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Presentations 【 Display / hide

  • 量子ドットとカーボンドットの開発の最前線

    磯部 徹彦

    新化学技術推進協会 電子情報技術部会 ナノフォトニクスエレクトロニクス交流会 講演会 「ディスプレイの今と未来」, 

    2021.04

    Oral presentation (invited, special)

  • リガンド交換によるCuInS2/ZnS量子ドットのインクへの分散性の向上

    白石 萌々,磯 由樹,磯部 徹彦, 藤波 哲郎, 野田 国宏, 塩田 大

    第81回応用物理学会秋季学術講演会 (オンライン) , 

    2020.09

    Oral presentation (general)

  • ハロゲン交換によるCsPbBr3ペロブスカイトナノ結晶の光劣化と自己回復への影響

    宮下 聖規,磯 由樹,磯部 徹彦

    第81回応用物理学会秋季学術講演会 (オンライン) , 

    2020.09

    Oral presentation (general)

  • CsPbBr3ペロブスカイトナノ結晶膜の自己回復機能の探究

    榎本 郁弥,磯 由樹,磯部 徹彦

    第81回応用物理学会秋季学術講演会 (オンライン) , 

    2020.09

    Oral presentation (general)

  • 量子ドットおよびカーボンドット蛍光体の表面修飾エンジニアリング

    磯部 徹彦,磯 由樹

    第380回蛍光体同学会講演会 (オンライン) , 

    2020.09

    Oral presentation (invited, special)

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • Development of advanced liquid-phase synthesis of carbon dots with controlled photoluminescence properties

    2019.06
    -
    2022.03

    Keio University, Challenging Research (Exploratory), Research grant, Principal investigator

     View Summary

    従来の無機蛍光体の主流は、希土類元素や遷移金属を結晶にドープし、f軌道やd軌道の準位間での遷移を通じて発光するタイプである。近年、バンドギャップで発光し、量子サイズ効果によって粒子径制御で発光色を調整できる量子ドット(QD)が台頭している。しかし、QD材料として、CdSe、InP、CsPbBr3などが開発されているが、毒性や安定性の面で問題がある。このような背景のもと、本研究では、資源として豊富に存在する炭素材料を用いて、高色純度かつ高効率で発光するカーボンドット(CD)を液相中で合成する指針を構築することを目指す。

  • Improvement of properties of solar cells by quantum dots with the function of UV - visible wavelength conversion

    2018.04
    -
    2021.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, ISOBE Tetsuhiko, Grant-in-Aid for Scientific Research (B), Research grant, Principal investigator

     View Summary

    An ultraviolet light absorber is used in a photovoltaic module to protect its parts from ultraviolet light. As a result, in photovoltaic modules, the spectral sensitivity of wavelengths below 400 nm is reduced. If a phosphor converting ultraviolet light into visible light is used instead of the ultraviolet light absorber, it is possible to protect the photovoltaic module from ultraviolet light and at the same time to improve the spectral sensitivity of the photovoltaic module in ultraviolet range. In this research, we have developed core / shell type CuInS2/ZnS and CuGaS2/ZnS quantum dot phosphors that convert ultraviolet light to visible light and have high transparency to visible light with high spectral sensitivity of photovoltaic modules. We investigated the improvement of photoelectric conversion efficiency of the photovoltaic module by wavelength conversion of these quantum dots.

  • Preparation, characterization, and application of near-UV -> red conversion fluorescent nanosheets and their composite films

    2015.04
    -
    2018.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, ISOBE Tetsuhiko, Grant-in-Aid for Scientific Research (C), Research grant, Principal investigator

     View Summary

    Y2O3:Bi3+,Eu3+ nanosheets, which emit red light under near-UV irradiation, were obtained by calcining hydroxide precursor nanosheets synthesized through a hydrothermal method. An aqueous dispersion of positively charged Y2O3:Bi3+,Eu3+ nanosheets with polyethyleneimine adsorbed to the surface was prepared for their deposition. Fluorescent nanosheets were electrophoretically deposited on a transparent conductive substrate under a constant voltage. Next, polyvinylpyrrolidone was coated on the film. The effects of the PVP-coated film samples on the properties of a commercial monocrystalline silicon photovoltaic module were evaluated.

  • Preparation and characterization of biocompatible composite beads with fluorescent nanoparticles

    2011.04
    -
    2014.03

    Keio University, ISOBE Tetsuhiko, Grant-in-Aid for Scientific Research (B), Research grant, Principal investigator

     View Summary

    Preparation of chitosan beads by cross-linking method through electrostatic interaction with tripolyphosphate ions, combined with emulsification method using SPG membrane was studied. Next, hybridizations between green-emitting YAG:Ce3+ nanoparticles and chitosan beads, and between red-emitting Eu3+-doped apatite nanoparticles and chitosan beads were studied. Hybridizations between Eu3+-doped apatite nanoparticles and silica beads, and between YAG:Ce3+ nanoparticles and alginate beads were also studied.

  • Preparation and characterization of composites consisting of nanoparticles with dual functions of fluorescence and magnetism

    2008
    -
    2010

    Keio University, ISOBE Tetsuhiko, Grant-in-Aid for Scientific Research (B), Research grant, Principal investigator

     View Summary

    YVO_4:Bi^<3+>,Eu^<3+> nanoparticles emitting red under the excitation of ultraviolet light were hybridized with PMMA mirobeads through electrostatic interaction. In addition, YAG:Ce^<3+> nanoparticles emitting green under the excitation of blue light as well as YAG/YIG core/shell nanoparticles were hybridized with PMMA mirobeads through electrostatic interaction.

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Works 【 Display / hide

  • 早慶交換講義「無機ナノ蛍光体の研究開発への挑戦」

    ISOBE TETSUHIKO

    2013.04

    Other, Single

  • 慶應義塾大学メディアセンターMediaNet, No.18, p.25, ティールーム「電子化でちょっと気になること」

    ISOBE TETSUHIKO

    2011.11

    Other, Single

  • ソニーケミカル&インフォメーションデバイス株式会社 鹿沼事業所における講演 「ドープ型ナノ蛍光体に関する研究動向と展望」

    ISOBE TETSUHIKO

    2011.09

    Other, Single

  • 関東学院六浦高等学校 模擬授業 「身近で活躍する発光材料」

    磯部 徹彦

    2011.06

    Other, Single

Intellectual Property Rights, etc. 【 Display / hide

  • 発光体の製造方法

    Date applied: 特願平9-212171  1997.08 

    Date announced: 特開平10-310770  1998.11 

    Patent

  • 発光体の製造方法

    Date applied: 特願平10-273596  1998.09 

    Date announced: 特開2000-104058  2000.04 

    Patent

  • ハイドロキシアパタイトの合成方法,ハイドロキシアパタイト複合体およびその製造方法

    Date applied: 特願2000-607922  1999.03 

    Date announced: WO00/58209  2000.10 

    Patent

  • リン酸カルシウム粉体の製造方法

    Date applied: 特願2000-607923  1999.03 

    Date announced: WO00/58210  2000.10 

    Patent

  • はんだ粉末とその製造方法、およびソルダーペースト

    Date applied: 特願平11-187637  1999.07 

    Date announced: 特開2000-317682  2000.11 

    Patent

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Awards 【 Display / hide

  • Outstanding Poster Paper Award

    T. Watanabe, Y. Iso, T. Isobe, H. Sasaki, 2017.12, The 24th International Display Workshops(IDW'17), Improved Photostability of Tetramethyl Orthosilicate-Modified InP/ZnS Quantum Dots

    Type of Award: Award from international society, conference, symposium, etc.

  • The Poster Award

    Kenji Akisada, Yusuke Noguchi, Tetsuhiko Isobe, 2010.11, The 3rd International Congress on Ceramics (ICC3) Symposim 5 "Hybrid and Nano-Structured Materials", Preparation of composite PMMA microbeads hybridized with fluorescent YVO4:Bi3+,Eu3+

    Type of Award: Award from international society, conference, symposium, etc.

  • Best Paper Award

    Wakana Kichikawa, Fumiaki Nishimura, Tetsuhiko Isobe, 2006.09, The International Union Materials Research Society - International Conference in Asia 2006 (IUMRS-ICA 2006), Photoluminescence of the Highly Transparent Colloidal Solution of LaPO4:Ce3+, Tb3+ Nanocrystal Phosphors Synthesized by Low-Temperature Solvothermal Method : Effect of Polyphosphate Additive

    Type of Award: Award from international society, conference, symposium, etc.

 

Courses Taught 【 Display / hide

  • SEMINAR IN APPLIED CHEMISTRY

    2022

  • NANO SCALE SCIENCE JOINT SEMINAR

    2022

  • MATERIAL DESIGN SCIENCE JOINT SEMINAR

    2022

  • LABORATORIES IN APPLIED CHEMISTRY A

    2022

  • INTRODUCTION OF MATERIAL DESIGN 2

    2022

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Courses Previously Taught 【 Display / hide

  • 総合デザイン工学特別研究第2

    慶應義塾大学大学院

    2018.04
    -
    2019.03

  • 化学B

    慶應義塾大学

    2018.04
    -
    2019.03

  • マテリアルデザイン概論2

    慶應義塾大学

    2018.04
    -
    2019.03

  • 応用化学実験A

    慶應義塾大学

    2018.04
    -
    2019.03

  • 無機化学基礎

    慶應義塾大学

    2018.04
    -
    2019.03

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Memberships in Academic Societies 【 Display / hide

  • 蛍光体同学会, 

    2001.01
    -
    Present
  • 応用物理学会, 

    1996.02
    -
    Present
  • 日本希土類学会, 

    2005.01
    -
    Present
  • 電気化学会, 

    2011.01
    -
    Present
  • 日本セラミックス協会, 

    2011.04
    -
    Present

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Committee Experiences 【 Display / hide

  • 2022.01
    -
    Present

    会長, 蛍光体同学会

  • 2007.01
    -
    Present

    幹事, 蛍光体同学会

  • 2004.06
    -
    Present

    委員, 日本学術振興会 光電相互変換第125委員会

  • 2014.04
    -
    Present

    代議員, 電気化学会

  • 2017.10
    -
    Present

    Luminescence and Display Materials Division, Executive Committee Member-at-Large, Electrochemical Society

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