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

  • Improving the thermal resistance of fluorescent CsPb(Br,I) 3 perovskite quantum dots by surface modification with perfluorodecanoic acid

    Iso Y., Eri M., Hiroyoshi R., Kano K., Isobe T.

    Royal Society Open Science (Royal Society Open Science)  9 ( 8 )  2022.08

    Joint Work

     View Summary

    CsPb(Br,I) 3 quantum dots (QDs) show application potential for optoelectronic devices. However, their thermal degradation is a significant problem. In this work, the effects of perfluorodecanoic acid (PFDA) modification on the photoluminescence (PL) and thermal resistance of CsPb(Br,I) 3 QDs were evaluated. The PL intensity of oleic-acid-modified quantum dots (OA-QDs) in toluene decreased drastically upon heating at 100°C. The PL quantum yield of the QDs increased from 69.6% to 77.4% upon modification with PFDA. Furthermore, the PL intensity of the QDs modified with PFDA (PFDA-QDs) increased to 140.6% upon heating, because of the reduction of surface defects upon adsorption of PFDA and its optimized adsorption state. A solid-film PFDA-QDs sample heated at 80°C for 4 h showed temporary PL enhancements for the OA-QDs and PFDA-QDs films to 445% and 557% of their initial values, respectively, upon heating for 0.25 h. This was attributed to the optimized adsorption states of the surface ligands. PFDA-QDs film maintained 354% after 4 h of heating, whereas that of OA-QDs film was 104%. Thus, PFDA modification enhances PL intensity and suppresses PL degradation under heating, which is important for wavelength converters for optoelectronic device applications.

  • 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.

  • Surface-Modified Carbon Dots with Improved Photoluminescence Quantum Yield for Color Conversion in White-Light-Emitting Diodes

    Sato K., Katakami R., Iso Y., Isobe T.

    ACS Applied Nano Materials (ACS Applied Nano Materials)  5 ( 6 ) 7664 - 7669 2022

    Joint Work

     View Summary

    Surface modification of p-phenylenediamine-derived carbon dots using 4-morpholinoaniline with an electron-donating and rigid structure followed by purification using silica gel column chromatography increased the photoluminescence quantum yield from 28.3 to 41.8% in chloroform. The improved photoluminescence quantum yield was observed for the surface modification by postaddition of the surface modifier after the formation of the π-conjugated structure of the carbon dot core but was not observed for the carbon dots prepared from a mixture of p-phenylenediamine and 4-morpholinoaniline. The finding of this work gives us an idea to design carbon dots with high photoluminescence quantum yield for application of color conversion in white-light-emitting diodes.

  • Transparent Nanocomposites Comprising Ligand-Exchanged CuInS<inf>2</inf>/ZnS Quantum Dots and UV-Cured Resin for Wavelength Converters

    Shiraishi M., Iso Y., Isobe T.

    ACS Omega (ACS Omega)   2022

    Joint Work

     View Summary

    Quantum dots (QDs) dispersed in UV-curable resin are used for patterning in photolithography and inkjet printing. However, low affinity between the main component of UV-curable resins known as celloxide, an alicyclic diepoxy compound, and QD surface ligands with alkyl chains causes significant aggregation of QDs. In this study, the dispersibility of core/shell CuInS2/ZnS QDs with adsorbed 1-dodecanethiol and oleic acid in celloxide was improved using the ligand exchange method to prepare transparent fluorescent nanocomposites. Cyclohexyl 3-mercaptopropionate (MPACH) and 3-mercaptopropionic acid (MPA) were successfully adsorbed onto the QDs. MPACH-modified QDs (QD-MPACH) were well dispersed in the UV-curable resin, whereas MPA-modified QDs (QD-MPA) exhibited significant aggregation. Nanocomposite plates containing dispersed QDs were prepared by UV irradiation. The QD-MPACH nanocomposite plate was transparent, while the QD-MPA nanocomposite plate was turbid. The homogeneous dispersion of QD-MPACH was attributed to the similarity in the molecular structure between MPACH and celloxide. The photoluminescence (PL) peak of the QD-MPA nanocomposite occurred at a longer wavelength than that of the QD-MPACH nanocomposite. Furthermore, compared with the absolute photoluminescence quantum yield (PLQY) of the as-prepared QDs in toluene (55%), that of the QD-MPA nanocomposite was smaller (46%), and that of the QD-MPACH nanocomposite was higher (61%). An enhanced self-absorption effect was observed for the QD-MPA nanocomposite because of significant light scattering by the aggregates and concentration quenching, resulting in the PL redshift and decreased PLQY. Moreover, the PL intensity of the QD-MPACH nanocomposite was maintained at 98% of the initial value after continuous excitation-light irradiation for 5 h. The high PLQY and photostability of the QD-MPACH nanocomposite are beneficial in 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

  • 狭帯域赤色蛍光を示すカーボン量子ドットの液相合成

    片上 凜香,佐藤 康平,小椋 章弘,高尾 賢一,磯 由樹,磯部 徹彦

    第12回CSJ化学フェスタ2022 (タワーホール船堀,東京) , 

    2022.10

    Poster presentation

  • 臭化セシウム鉛ナノキューブの配列制御による光安定性の向上

    橋本 翔太,佐々木 萌香,磯 由樹,緒明 佑哉,磯部 徹彦,今井 宏明

    第12回CSJ化学フェスタ2022 (タワーホール船堀,東京) , 

    2022.10

    Poster presentation

  • 狭帯域蛍光および蛍光ソルバトクロミズムを示すグラフェン量子ドットの大量液相合成

    越智 幸乃,片上 凜香,小椋 章弘,高尾 賢一,磯 由樹,磯部 徹彦

    第12回CSJ化学フェスタ2022 (タワーホール船堀,東京) , 

    2022.10

    Poster presentation

  • Surface Engineering of Fluorescent CsPbBr3 and Carbon Quantum Dots by Perfluorocarboxylic Acid

    Tetsuhiko Isobe, Yoshiki Iso

    242nd ECS Meeting (Atlanta, USA) , 

    2022.10

    Oral presentation (invited, special)

  • CsPbX3ペロブスカイト量⼦ドットの光劣化と⾃⼰回復の探究

    磯 由樹,磯部 徹彦

    第83回応用物理学会秋季学術講演会 (東北大学川内北キャンパス,仙台) , 

    2022.09

    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

  • ADVANCED COURSE OF PHOSPHOR MATERIALS

    2022

  • SEMINAR IN APPLIED CHEMISTRY

    2022

  • NANO SCALE SCIENCE JOINT SEMINAR

    2022

  • MATERIAL DESIGN SCIENCE JOINT SEMINAR

    2022

  • LABORATORIES IN APPLIED CHEMISTRY A

    2022

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Courses Previously Taught 【 Display / hide

  • 無機化学基礎

    慶應義塾大学

    2018.04
    -
    2019.03

  • 固体の機能設計

    慶應義塾大学大学院

    2018.04
    -
    2019.03

  • 機能デザイン工学

    慶應義塾大学大学院

    2018.04
    -
    2019.03

  • 総合デザイン工学特別研究第1

    慶應義塾大学大学院

    2018.04
    -
    2019.03

  • 総合デザイン工学課題研究

    慶應義塾大学大学院

    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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