Kikuya HAYASHI
| Department of Engineering Science | Assistant Professor |
| Cluster III (Fundamental Science and Engineering) | Assistant Professor |
Researcher Information
Field Of Study
Career
- Apr. 2025 - Present
The University of Electro-Communications, Graduate School of Informatics and Engineering Department of Engineering Science, Assistant Professor, Japan - Apr. 2022 - Mar. 2025
The University of Electro-Communications, Graduate School of Informatics and Engineering Department of Engineering Science, JSPS DC1, Japan - Sep. 2021 - Mar. 2025
The University of Electro-Communications, Graduate School of Informatics and Engineering Department of Engineering Science, JST FOREST RA, Japan
Educational Background
- Apr. 2022 - Mar. 2025
The University of Electro-Communications, Graduate School of Informatics and Engineering, Department of Engineering Science, Japan - Apr. 2020 - Mar. 2022
The University of Electro-Communications, Graduate School of Informatics and Engineering, Department of Engineering Science, Japan - Apr. 2016 - Mar. 2020
The University of Electro-Communications, School of Informatics and Engineering, Cluster III(Fundamental Science and Engineering), Japan
Research Activity Information
Award
- Sep. 2023
光化学協会
High-resolution Afterglow Patterning Using Cooperative Vapo- and Photo-chemical Reactions
Annual Meeting on Photochemistry 2023, Chemical Science Presentation Prize (RSC), Kikuya Hayashi - Apr. 2023
Chemical Society Japan
Photo-Induced Triplet Depletion Allowing Higher-resolution Afterglow
CSJ Student Presentation Award 2023, Kikuya Hayashi - Jun. 2021
光化学若手の会
ドナーアクセプター直交型キラル分子を利用した高効率遅延蛍光の発生要因の探求
第42回光化学若手の会 優秀ポスター発表賞, Kikuya Hayashi
Paper
- Selective Lower‐Occupied Through‐Bond Interactions for Efficient Organic Phosphorescence Enabling High‐Resolution Long‐Wavelength Afterglow
Rajashekhar K. Mulimani; Sakuya Ueda; Ryo Miyashita; Rana Tsuru; Kikuya Hayashi; Riku Shimura; Bahadur Sk; Shinji Matsuda; Shuzo Hirata
Advanced Materials, Wiley, 2502611, Apr. 2025, Peer-reviwed, Abstract
Persistent organic room‐temperature phosphorescence (RTP) enables high‐resolution afterglow bioimaging, independent of autofluorescence. However, the yield of organic RTP in the long‐wavelength region is generally low, which limits the high‐resolution information that can be obtained from the long‐wavelength region. Moreover, this makes it impossible to obtain multicolor and high‐resolution afterglow images. This report describes a molecule containing no atoms from the fourth or higher period that exhibits efficient red RTP in high yield. A molecule with red phosphorescent chromophores substituted with multiple phenylthio groups reached an RTP yield of 46.3% and an RTP lifetime of 0.43 s in an appropriate crystalline host medium. The selective lower‐occupied through‐bond or through‐space interactions among molecules significantly enhance the phosphorescence in the long‐wavelength region. The highly efficient and bright red persistent RTP induces a red afterglow from individual nanoparticles. Tuning the selective lower‐occupied through‐bond or through‐space interactions allows for the design of high‐performance RTP dyes and offers a novel approach to explore high‐resolution full‐color afterglow imaging.
Scientific journal - High‐Resolution Afterglow Patterning Using Cooperative Vapo‐ and Photo‐Stimulation
Kikuya Hayashi; Shuzo Hirata
Lead, Small, Wiley, 20, 16, Nov. 2023, Peer-reviwed, Abstract
Bright afterglow room‐temperature phosphorescence (RTP) soon after ceasing excitation is a promising technique for greatly increasing anti‐counterfeiting capabilities. The development of a process for rapid high‐resolution afterglow patterning of crystalline materials can improve both high‐speed fabrication of anti‐counterfeiting afterglow media and stable afterglow readout compared with those achieved with amorphous materials. Here, the high‐resolution afterglow patterning of crystalline materials via cooperative organic vapo‐ and photo‐stimulation is reported. A single crystal of (S)‐(−)−2,2’‐bis(diphenylphosphino)−5,5’,6,6’,7,7’8,8’‐octahydro‐1,1’‐binaphthyl [ (S)‐H8‐BINAP] doped with (S)‐(−)−2,2’‐bis(diphenylphosphino)−1,1’‐binaphthyl [ (S)‐BINAP] shows green afterglow RTP. Crystals of (S)‐BINAP‐doped (S)‐H8‐BINAP changed to an amorphous state with no afterglow capability on weak continuous photoirradiation under dichloromethane (DCM) vapor. Photoirradiation induced oxidation of the (S)‐H8‐BINAP host molecule in the crystal. The oxidized (S)‐H8‐BINAP forms on the crystal surface strongly interacted with DCM molecules, which induces melting of the (S)‐BINAP‐doped (S)‐H8‐BINAP crystal and trigger formation of an amorphous state without an afterglow capability. High‐resolution afterglow patterning of the crystalline film is rapidly achieved by using cooperative organic vapo‐ and photo‐stimulation. In addition to the benefit of rapid afterglow patterning, the formed afterglow images of the crystalline film can be repeatedly read out under ambient conditions without DCM vapor.
Scientific journal, English - Continuous Condensed Triplet Accumulation for Irradiance‐Induced Anticounterfeit Afterglow
Ende Hopsah Badriyah; Kikuya Hayashi; Bahadur Sk; Rina Takano; Takayuki Ishida; Shuzo Hirata
Advanced Science, Wiley, 10, 36, Oct. 2023, Peer-reviwed, Abstract
Afterglow room‐temperature emission that is independent of autofluorescence after ceasing excitation is a promising technology for state‐of‐the‐art bioimaging and security devices. However, the low brightness of the afterglow emission is a current limitation for using such materials in a variety of applications. Herein, the continuous formation of condensed triplet excitons for brighter afterglow room‐temperature phosphorescence is reported. (S)‐(‐)‐2,2′‐Bis(diphenylphosphino)‐1,1′‐binaphthyl ((S)‐BINAP) incorporated in a crystalline host lattice showed bright green afterglow room‐temperature phosphorescence under strong excitation. The small triplet–triplet absorption cross‐section of (S)‐BINAP in the whole range of visible wavelengths greatly suppressed the deactivation caused by Förster resonance energy transfer from excited states of (S)‐BINAP to the accumulated triplet excitons of (S)‐BINAP under strong continuous excitation. The steady–state concentration of the triplet excitons for (S)‐BINAP reached 2.3 × 10−2 M, producing a bright afterglow. Owing to the brighter afterglow, afterglow detection using individual particles with sizes approaching the diffraction limit in aqueous conditions and irradiance‐dependent anticounterfeiting can be achieved.
Scientific journal, English - Selective Triplet–Singlet Förster‐Resonance Energy Transfer for Bright Red Afterglow Emission
Bahadur Sk; Rana Tsuru; Kikuya Hayashi; Shuzo Hirata
Advanced Functional Materials, Wiley, 33, 11, Dec. 2022, Peer-reviwed, Abstract
Förster‐resonance energy transfer (FRETT‐S) from the lowest excited triplet state (T1) of a donating sensitizer to a fluorescence acceptor can be used to obtain bright room‐temperature afterglow emission at long wavelengths. However, the energy transfer from the lowest excited singlet state of the donor to the acceptor is an undesirable deactivation pathway that prevents FRETT‐S. Herein, heteroatoms in chromophores are shown to allow selective and efficient FRETT‐S for enhanced triplet emission for bright room‐temperature afterglow emission at long wavelengths. Different transition characteristics between the lowest singlet excited state and triplet states in heteroatom‐containing chromophores accelerate triplet generation, enabling near‐zero fluorescence yields. Out‐of‐plane vibrations of the heteroatoms in aromatic fused rings greatly enhance the radiative rate from T1 by a factor of 88 relative to non‐heteroatom‐containing fused chromophore. The compatibility of the near‐zero fluorescence and the enhanced triplet emission in a heteroatom‐containing fused chromophore enable selective and efficient FRETT‐S pathways, resulting in room‐temperature red afterglow emission with a yield of 17%. The bright emission at long‐wavelengths allows distinguishable, multiple spectral signals in ambient white light.
Scientific journal, English - Rational Design of a Triplet Afterglow Sensitizer Allowing for Bright Long-Wavelength Afterglow Room-Temperature Emission
Kikuya Hayashi; Kei Fukasawa; Takashi Yamashita; Shuzo Hirata
Lead, Chemistry of Materials, American Chemical Society (ACS), 34, 4, 1627-1637, Jan. 2022, Peer-reviwed
Scientific journal, English - Chiral approach to investigate mechanism of highly efficient thermally activated delayed fluorescence
Kikuya Hayashi; Arimasa Matsumoto; Shuzo Hirata
Lead, Chemical Communications, Royal Society of Chemistry (RSC), 57, 14, 1738-1741, Jan. 2021, Peer-reviwed,Cancellation of the Cotton effect depending on vibrations of a chiral orthogonal donor–acceptor structure identifies a mechanism of highly efficient delayed fluorescence.
Scientific journal, English
Lectures, oral presentations, etc.
- 蓄光の空間分解能を向上させる光誘起三重項消滅過程の研究
Kikuya Hayashi; Shuzo Hirata
Oral presentation, 第49回有機電子移動化学討論会
27 Jun. 2025
27 Jun. 2025- 28 Jun. 2025 - 固体結晶の微粒子化による長寿命りん光ディケイの酸素応答能の向上
Riku Shimura; Kikuya Hayashi; Shuzo Hirata
Oral presentation, Japanese, The 105th CSJ Annual Meeting
29 Mar. 2025 - Efficient red persistent room-temperature phosphorescence from a selenium substituted aromatic carbon
Kikuya Hayashi; Rajashekhar Mulimani Kashipati; Rana Tsuru; Sakuya Ueda; Shuzo Hirata
Oral presentation, English, Annual Meeting on Photochemistry 2024
05 Sep. 2024 - High-resolution oxygen sensing using persistent room-temperature phosphorescence from individual nanoparticles
Riku Shimura; Kikuya Hayashi; Shuzo Hirata
Poster presentation, English, Annual Meeting on Photochemistry 2024
03 Sep. 2024 - Photoinduced Triplet Depletion Allowing Higher-Resolution Afterglow
Kikuya Hayashi; Shuzo Hirata
Oral presentation, English, SPIE Photonics Europe 2024, Peer-reviewed
09 Apr. 2024 - Photoinduced Triplet Depletion Allowing Higher-Resolution Afterglow
Kikuya Hayashi; Shuzo Hirata
Oral presentation, English, SPIE Photonics West 2024, Peer-reviewed
30 Jan. 2024 - 共同刺激による高スピードアフターグロー光パターニングと高解像アフターグロー読み出し
Shuzo Hirata; Kikuya Hayashi
Invited oral presentation, 第72回高分子討論会, Invited
26 Sep. 2023 - High-resolution afterglow patterning using cooperative vapo- and photo-chemical reactions
High-resolution afterglow; patterning using cooperative vapo; photo-chemical reactions
Oral presentation, Annual Meeting on Photochemistry 2023
06 Sep. 2023 - 高輝度アフターグロー発光に向けた高濃度三重項蓄積挙動
Shuzo Hirata; Badriyah Ende Hopsah; Kikuya Hayashi; Sk Bahadur
Oral presentation, Japanese, Annual Meeting on Photochemistry 2023
05 Sep. 2023 - Photo-Induced Triplet Depletion Allowing Higher-Resolution Afterglow
Kikuya Hayashi; Keiki Fukumoto; Shuzo Hirata
Oral presentation, English, The 103rd CSJ Annual Meeting
22 Mar. 2023 - Key factor facilitating triplet-singlet resonance energy transfer for efficientt red afterglow emission
Kikuya Hayashi; Kei Fukasawa; Takashi Yamashita; Shuzo Hirata
Oral presentation, English, Web Annual Meeting on Photochemistry 2021
14 Sep. 2021 - ドナーアクセプター直交型キラル分子を利用した高効率熱活性化遅延蛍光発生要因の考察
Kikuya Hayashi; Arimasa Matsumoto; Shuzo Hirata
Oral presentation, Japanese, 2020年web光化学討論会
11 Sep. 2020
Research Themes
- 光誘起三重項消滅による超解像蓄光イメージングへの挑戦
林 希久也
日本学術振興会, 科学研究費助成事業, 電気通信大学, 特別研究員奨励費, Principal investigator, 本研究では、光の回折限界を超える空間分解能(超解像)で長寿命室温りん光を検出することを目的としている。研究代表者は、長寿命三重項励起子が色素の吸収波長よりも長波長域の光(刺激光)の照射により消去されることを見出している。本年度までに、この光誘起三重項消滅は、三重項励起子が刺激光によりイオン化し、その後高速で基底状態へと戻ることで生じていることを明らかにした。さらに、ドーナツ型に空間変調された刺激光を励起光と重ねて照射することで、長寿命室温りん光の空間分解能が向上することを実証し、学術論文および国内外の学会で報告した。一方で、長寿命室温りん光の超解像検出には、より高輝度な長寿命室温りん光体が必要であることが示唆された。 それゆえ、本年度は高輝度な赤色長寿命室温りん光体の開発を行った。既存の多環芳香族骨格に対し、最低三重項励起状態と高次一重項励起状態間のスピン軌道相互作用を大幅に増加させる置換基を導入することで、赤色領域において従来の材料を大幅に上回る長寿命室温りん光量子収率を有する材料を見出すことに成功した。この材料は回折限界サイズにおいてもCCDで十分検出可能なほど高輝度な赤色長寿命室温りん光を示すことを確認している。 また、高強度励起光照射下における長寿命室温りん光輝度の飽和要因を調査した。長寿命室温りん光の飽和挙動には、励起子間のエネルギー移動だけでなく高強度励起光による長寿命三重項励起子の光イオン化過程が含まれることを明らかにし、共著者として学術論文で発表している。, 22KJ1371
Apr. 2022 - Mar. 2025
