Publications (International)


(The University of Electro-Communications)

  1. T. Uematsu, K. Wajima, D. K. Sharma, S. Hirata, T. Yamamoto, T. Kameyama, M. Vacha*, T. Torimoto*, S. Kuwabata*, Narrow band-edge photoluminescence from AgInS2 semiconductor nanoparticles by the formation of amorphous III–VI semiconductor shells, NPG Asia Mater. 2018, DOI 10.1038/s41427-018-0067-9.
  2. S. Hirata*, J. Phys. Chem. Lett. 2018, 9, 4251-4259.
  3. T. Hori, K. Totani*, S. Hirata, T. Watanabe*, Large refractive index variations induced by accumulating triplet excitons under photoexcitation at low power, Chem. Phys. Lett. 2018, 704, 5-10.
  4. N. Nakamura, D. K. Sharma, S. Hirata, M. Vacha*, Intra-chain aggregates as the origin of green emission in polyfluorene studied on ensemble and single chain level, J. Phys. Chem. C 2018, 122, 8137-8146.
  5. M. Liu, S. Hirata, T. Iyoda, M. Vacha, P. Piotrowiak*, Excited state behavior of single strand and bulk P3HT in contact with an Au nanowire array, J. Phys. Chem. C 2018, 122, 7925-7933.
  6. B. J. Lidster, S. Hirata, S. Matsuda, T. Yamamoto, V. Komanduri, D. R. Kumar, Y. Tezuka, M. Vacha*, M. L. Turner*, Macrocyclic poly(p-phenylenevinylene)s by ring expansion metathesis polymerisation and their characterization by single-molecule spectroscopy, Chem. Sci. 2018, 9, 2934-2941.

(Tokyo Institute of Technology, Prof. Vacha Group)

  1. Ł. Bujak*, K. Narushima, D. K. Sharma, S. Hirata, M. Vacha*, Plasmon enhancement of triplet excitons diffusion revealed by nanoscale imaging of photochemical fluorescence upconversion, J. Phys. Chem. C 2017, 121, 25479-25486.
  2. S. Hirata*, M. Vacha, Large reverse saturable absorption at sunlight power level using the ultralong lifetime of triplet excitons, J. Phys. Chem. Lett. 2017, 8, 3683-3689.
  3. K. Narushima, S. Hirata*, M. Vacha*, Nanoscale triplet exciton diffusion via imaging of up-conversion emission from single hybrid nanoparticles in molecular crystals, Nanoscale 2017, 9, 10653-10661.
  4. D. K. Sharma*, S. Hirata, Ł. Bujak, V. Biju, T. Kameyama, M. Kishi, T. Torimoto, M. Vacha*. Influence of Zn on the photoluminescence of colloidal (AgIn)xZn2(1-x)S2 nanocrystals, Phys. Chem. Chem. Phys. 2017, 19, 3963-3969.
  5. K. Kamada*, Y. Sakagami, T. Mizokuro, Y. Fujiwara, K. Kobayashi*, K. Narushima, S. Hirata, M. Vacha, Efficient triplet-triplet annihilation upconversion in binary crystalline solids fabricated by solution casting and operated in air, Mater. Horiz. 2017, 4, 83-87.
  6. Ł. Bujak*, T. Ishii, D. K. Sharma, S. Hirata, M. Vacha*, Selective turn-on and modulation of resonant energy transfer in single plasmonic hybrid nanostructures, Nanoscale 2017, 9, 1511-1519.
  7. S. Hirata*, M. Vacha, White afterglow room‐temperature emission from an isolated single aromatic unit under ambient condition, Adv. Opt. Mater. 2017, 5, 1600996.
  8. D. K. Sharma*, S. Hirata, Ł. Bujak, V. Biju, T. Kameyama, M. Kishi, T. Torimoto, M. Vacha*, Single-particle spectroscopy of I-III-VI semiconductor nanocrystals: spectral diffusion and suppression of blinking by two-color excitation, Nanoscale 2016, 8, 13687-13694.
  9. S. Hirata*, K. Shizu, Organic Light-Emitting Diodes: High-throughput virtual screening, Nat. Mater. 2016, 15, 1056-1057. News & Views.
  10. S. Hirata*, M. Vacha, Circularly polarized persistent room-temperature phosphorescence from chiral aromatics in air, J. Phys. Chem. Lett. 2016, 7, 1539-1545.
  11. S. Hirata*, M. Vacha, Large transmittance change induced by exciton accumulation under weak continuous photoexcitation, Adv. Opt. Mater. 2016, 4, 297-305.
  12. Y. Katsurada, S. Hirata*, K, Totani, T. Watanabe, M. Vacha, Photoreversible on-off recording of persistent room-temperature phosphorescence, Adv. Opt. Mater. 2015, 3, 1726-1737. Back Cover, Highlighted by Materials Views, Feb. 17, 2016.
  13. T. Fukushima, J. Yamamoto, M. Fukuchi, S. Hirata, H. H. Jung, O. Hirata, Y. Shibano, C. Adachi, H. Kaji*, Material degradation of liquid organic semiconductors analyzed by nuclear magnetic resonance spectroscopy, AIP Advances 2015, 5, 087124.
  14. T. Imagawa, S. Hirata*, K. Totani, T. Watanabe, M. Vacha, Thermally activated delayed fluorescence with circularly polarized luminescence characteristics, Chem. Commun. 2015, 51, 13268-13271. Inside Back Cover.
  15. Y. Tsubomoto, S. Hirata*, K. Totani, M. Vacha, T. Watanabe, Long-lived triplet excitons allowed by intermolecular hydrogen bonding in amorphous matrix, J. Photo. Sci. Tech. 2015, 28, 573-577.
  16. K. Shizu, Y. Sakai, H. Tanaka, S. Hirata, C. Adachi, H. Kaji*, Meta-linking strategy for small singlet-triplet energy gap of thermally activated delayed fluorescence emitters, ITE Trans. on MTA 2015, 3, 108-113.
  17. S. Lee, K. Noda, S. Hirata, M. Vacha*, Position-dependent three-dimensional diffusion in nematic liquid crystal monitored by single-particle fluorescence localization and tracking, J. Phys. Chem. Lett. 2015, 6, 1403-1407.
  18. S. Hirata, K. Sakai, K. Masui, H. Tanaka, S. Y. Lee, H. Nomura, N. Nakamura, M. Yasumatsu, H. Nakanotani, Q. Zhang, K. Shizu, H. Miyazaki, C. Adachi*, Highly efficient blue electroluminescence based on thermally activated delayed fluorescence, Nat. Mater. 2015, 14, 330-336. Highlighted by Chemistry World, Dec. 8, 2014.
  19. S. Hirata*, K. Totani, T. Yamashita, C. Adachi, M. Vacha*, Large reverse saturable absorption under weak continuous incoherent light, Nat. Mater. 2014, 13, 938-946. Highlighted by Nat. Mater., 13, 917-918, 2014 and Noteworthy Chemistry, Oct. 27, 2014.
  20. Y. Honmou, S. Hirata, H. Komiyama, J. Hiyoshi, S. Kawauchi, T. Iyoda, M. Vacha*, Single molecule electroluminescence and photoluminescence of polyfluorene unveils the photophysics behind the green emission band, Nat. Commun. 2014, 5, 4666.
  21. K. Katayama, S. Hirata, M. Vacha*, Circularly polarized luminescence from individual microstructures of conjugated polymer aggregates with solvent-induced chirality, Phys. Chem. Chem. Phys. 2014, 16, 17983-17987.
  22. S. Furumaki, F. Vacha, S. Hirata, M. Vacha*, Bacteriochlorophyll aggregates self-assembled on functionalized gold nanorod cores as mimics of photosynthetic chlorosomal antennae: a single molecule study, ACS Nano 2014, 8, 2716-2182.
  23. S. Hirata*, K. Totani, H. Kaji, T. Watanabe, M. Vacha, Relationship between room temperature phosphorescence and deuteration position in a purely aromatic compound, Chem. Phys. Lett. 2014, 591, 119-125.
  24. 平田修造*, 安達千波矢, 渡辺敏行, 戸谷健朗, 常温大気中で高効率蓄光機能を示す有機材料, 高分子論文集 2013, 70, 623-636. in Japanese.
  25. H. Kobayashi, S. Hirata, M. Vacha*, Mechanical manipulation of photophysical properties of single conjugated polymer nanoparticles, J. Phys. Chem. Lett. 2013, 4, 2591-2596.
  26. S. Hirata*, K. Totani, H. Kaji, M. Vacha, C. Adachi*, Reversible thermal recording media using time-dependent persistent room temperature phosphorescence. Adv. Opt. Mater. 2013, 1, 438-442. Front Cover Picture.
  27. K. Totani*, Y. Okada, S. Hirata*, M. Vacha, T. Watanabe, Thermoresponsive persistent phosphorescent color change using efficient thermally activated reverse energy transfer with a large energy difference, Adv. Opt. Mater. 2013, 1, 283-288. Front Species.
  28. S. Hirata*, K. Totani, T. Yamashita, H. Kaji, S. R. Marder, T. Watanabe*, C. Adachi*, Efficient persistent room temperature phosphorescence in organic amorphous materials under ambient conditions, Adv. Funct. Mater. 2013, 23, 3386-3397.

(Kyushu University, Prof. Adachi Group)

  1. S. Hirata*, T. Tsuji, Y. Kato, C. Adachi*, Reversible coloration enhanced by electrochemical deposition of an ultra-thin zinc layer onto an anodic nanoporous alumina layer, Adv. Funct. Mater. 2012, 22, 4195-4201.
  2. K. Kubota, S. Hirata, Y. Shibano O. Hirata, M. Yahiro, C. Adachi*, Liquid carbazole substituted with a poly(ethylene oxide) group and its application for liquid organic light emitting diodes, Chem. Lett. 2012, 41, 934-936.
  3. Q. Zhang, J. Li, K. Shizu, S. Huang, S. Hirata, H. Miyazaki, C. Adachi*, Design of efficient thermally activated delayed fluorescence materials for pure blue organic light emitting diodes, J. Am. Chem. Soc. 2012, 134, 14706-14709.
  4. C. H. Shim, S. Hirata, J. Oshima, T. Edura, R. Hattori, C. Adachi*, Uniform and refreshable liquid electroluminescent device with a back side reservoir, Appl. Phys. Lett. 2012, 101, 113302.
  5. S. Hirata, H. J. Heo, Y. Shibano, O. Hirata, M. Yahiro, C. Adachi*, Improved device lifetime of organic light emitting diodes with an electrochemically stable-conjugated liquid host in the liquid emitting layer, Jpn. J. Appl. Phys. 2012, 51, 041604.
  6. S. Hirata, K. Kubota, H. H. Jung, O. Hirata, K. Goushi, M. Yahiro, C. Adachi*, Improvement of electroluminescence performance of organic light emitting diodes with a liquid emitting layer by introduction of electrolyte and a hole-blocking layer, Adv. Mater. 2011, 23, 889-893.
  7. M. Kashiwagi, S. Hirata, K. Harada, Y. Zheng, K. Miyazaki*, M. Yahiro, C. Adachi*, Enhanced figure of merit of a porous thin film of bismuth antimony telluride, Appl. Phys. Lett. 2011, 98, 023114.

(Ph. D course in Tokyo University of Agriculture and Technology, Prof. Watanabe Group)

  1. S. Hirata*, M. Vacha, T. Watanabe: Investigation of quenching mechanism in thermoreversible fluorescent recording materials of fluorescence using thermochromic fluorescence resonance energy transfer, Jpn. J. Appl. Phys. 2010, 49, 052501.
  2. S. Hirata, K. S. Lee, T. Watanabe*, Reversible fluorescent on–off recording in a highly transparent polymeric material utilizing fluorescent resonance energy transfer (FRET) induced by heat treatment, Adv. Funct. Mater. 2008, 18, 2869-2879.
  3. S. Hirata, T. Watanabe*, Reversible thermoresponsive recording of fluorescent images (TRF), Adv. Mater. 2006, 18, 2725-2729.



  1. S. Hirata*, Ultralong-lived room temperature triplet excitons: Molecular persistent room temperature phosphorescence and nonlinear optical characteristics with continuous irradiation, J. Mater. Chem. C 2018, doi: 10.1039/C8TC01417E, 2018 Emergence Investigator Issue.
  2. M. Vacha*, D. K. Sharma, S. Hirata, Single-molecule studies beyond optical imaging: Multi-parameter single-molecule spectroscopy, Journal of Photochemistry and Photobiology C: Photochemistry 2017, 34, 121-136.
  3. S. Hirata*, Recent advances in materials with room‐temperature phosphorescence: Photophysics for triplet exciton stabilization, Adv. Opt. Mater. 2017, 5, 1700116, Back Cover Picture.
  4. 平田修造*, 分子性室温りん光と三重項の光物理化学, 光化学協会誌, 2016, 47, 2, 84-91. in Japanese.


Representative Awards



  1. 17th The Japanese Photochemistry Association Award for Young Scientist
  2. 65th Chemical Society Japan (CSJ) Award for Young Chemists
  3. 29th Young Scholar Lectures of Chemical Society Japan (CSJ)