Research activity information

• Mar. 2024, 英国王立化学会 Nanoscale, Nanoscale 2024 Emerging Investigators
• Feb. 2022, 北海道大学電子科学研究所, 第51回 電子科学研究所 松本・羽鳥奨学賞
  岡本拓也, 32906734;32906733
• Oct. 2021, 北海道大学 遺伝子病制御研究所, 第7回北海道大学部局横断シンポジウムベストポスター賞
  「ハロゲン化鉛ペロブスカイト結晶におけるハロゲン欠陥回復」
  岡本拓也, 32906734
• Dec. 2020, 公益財団法人 井上科学振興財団, 第３７回（２０２０年度）井上研究奨励賞
  「液中レーザー誘起プラズマによるナノ粒子の生成」
  岡本拓也, 32906735
• Apr. 2020, 物質・デバイス領域共同研究拠点, 第２回 物質・デバイス共同研究賞
  「ナノ粒子生成における反応特異性を示す微小液滴のサイズ閾値の解明」
  岡本拓也;堀川雄輝;八ッ橋知幸;中村貴宏
• Dec. 2019, 東北大学多元物質科学研究所, 多元物質科学研究所長賞 (ポスター)
  「フェムト秒レーザーによる金ナノ粒子の生成：微小液滴表面を利用した粒径および分散制御」
  岡本拓也, 32906735
• Mar. 2017, 大阪市立大学, 研究業績優秀賞（若野賞）
  岡本拓也
• Sep. 2015, 光化学協会, 光化学討論会優秀学生発表賞 (ポスター)
  「レーザー誘起プラズマによるベンゼン水溶液からの親水性炭素ナノ粒子の生成」
  岡本拓也
• Feb. 2015, BCSJ Award Articles
  Synthesis of Hydrophilic and Hydrophobic Carbon Nanoparticles from Benzene/water Bilayer Solution with Femtosecond Laser Generated Plasma Filaments in Water
  Tomoyuki Hamaguchi;Takuya Okamoto;Koji Mitamura;Kimihiro Matsukawa;Tomoyuki Yatsuhashi

• Isomeric organic-inorganic indium bromide single crystals with delayed and dual colour emission
  Haichao Zhou; Kiyonori Takahashi; Takuya Okamoto; Jianguo Pan; Vasudevanpillai Biju
  MATERIALS HORIZONS, 29 Jan. 2026, [Peer-reviewed]
  English, Scientific journal
• Photoluminescence Enhancement in Zero-Dimensional Hybrid Copper Halide Single Crystals
  Rahul Ghosh Dastidar; Takuya Okamoto; Kiyonori Takahashi; Shailesh Rana; Kamlesh Awasthi; Nobuhiro Ohta; Challapalli Subrahmanyam; Vasudevanpillai Biju
  CHEMISTRY OF MATERIALS, 22 Dec. 2025, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• Photoluminescence enhancement by exciton-plasmon coupling in MAPbI₃ quantum dots on gold nanorods
  Tianci Wang; Tetsuro Katayama; Xu Shi; Akihiro Furube; Takuya Okamoto; Vasudevanpillai Biju
  NPG ASIA MATERIALS, 17, 1, 28 Nov. 2025, [Peer-reviewed]
  English, Scientific journal
• Amplified emission from halide perovskite quantum dots by exciton-plasmon-coupled energy transfer in the neutral and trion states on gold nanoparticles
  Bhagyashree Mahesha Sachith; Yifei Xia; Tianci Wang; Takuya Okamoto; Syoji Ito; Li Wang; Xu Shi; Naoto Tamai; Hiroshi Miyasaka; Hiroaki Misawa; Vasudevanpillai Biju
  JOURNAL OF MATERIALS CHEMISTRY A, 17 Nov. 2025, [Peer-reviewed], [Corresponding author]
  English, Scientific journal
• Modulating Band Alignment and Passivating Defects with In‐Situ Bi‐Substituted Cu₂ZnSnS₄ for Superior Photo‐/Electrochemical Water Splitting
  Mohit Kumar; Palak Chugh; Takuya Okamoto; Arup Mahata; Vasudevanpillai Biju; Subrahmanyam Challapalli
  Small, 21, 36, Wiley, 31 Jul. 2025, [Peer-reviewed]
  Scientific journal, Abstract
  
  Tailoring semiconductor properties through cation substitution is a promising strategy to improve the intrinsic properties of a photoabsorber material by improving charge carrier statistics, kinetics, and efficiency of photo‐/electrocatalytic conversions. In the current study, Cu₂ZnSnS₄ (CZTS) thin film photocathodes are investigated by partially replacing Zn with Bi by fabricating Cu₂Zn_1−xBi_xSnS₄ (x = 0.02, 0.04, 0.06, and 0.08) (x‐CZBTS; x: 2, 4, 6, and 8) thin films. Incorporating Bi replacing Zn reduce bulk defects, secondary phases, and Cu_Zn antisites and promote ease of crystallization with a decrease in crystallization temperature. Bi‐doping modulates the CZTS film band‐gap with a greater absorption coefficient, red shift, and charge collection. CZBTS coated with CdS/Pt (x‐CZBTS‐cp) films delivered photocurrent density (−4.0, −7.2, −5.2, and −1.3 mA cm⁻² at 0 V_RHE for x: 2, 4, 6, and 8, respectively). 4‐CZBTS‐cp with the highest J (η_STH = 1.62% at 0.45 V_RHE, 95 µmol cm⁻² h⁻¹ H₂ evolution, F.E. = 90%, and E_onset = 0.71V_RHE) showed 82% photocurrent density retention after 10h in 1 m kPi buffer (pH 7). DFT and experimental studies underscore improved PEC performance owing to significant Bi contribution in conduction band of CZBTS, lowering bandgap, elongating photogenerated charge carrier lifetime, rapid charge separation/transport, and charge accumulation at the Bi−S site on the surface with optimal Gibbs free energy (ΔG_H*) for CZBTS on photoexcitation.
• Organic Electron Acceptors for FAPbI3 Perovskites in Solutions and Solar Cells
  Kangjian Xu; Palyam Subramanyam; Takuya Okamoto; Ch Subrahmanyam; Vasudevanpillai Biju
  Journal of Physical Chemistry C, 129, 3, 1569, 1574, 23 Jan. 2025, [Peer-reviewed]
  Scientific journal
• Colloidally synthesized and bandgap-engineered luminescent titanium nitride quantum dots
  Aswathi Maladan; Takuya Okamoto; Mohit Kumar; Most Farida Khatun; Yasutaka Matsuo; Challapalli Subrahmanyam; Vasudevanpillai Biju
  Nanoscale, 17, 44, 25484, 25489, Royal Society of Chemistry (RSC), 2025, [Peer-reviewed], [Corresponding author]
  Scientific journal, We demonstrate the colloidal synthesis of luminescent titanium nitride (TiN) quantum dots with multicolor emission and tunable band gaps, providing safer alternatives to metal chalcogenides and halide perovskites for solar cells and LEDs.
• Distance-Dependent Energy Transfer under Modal Strong Coupling from CdSe/ZnS Quantum Dots to a Plasmonic Fabry–Pérot Cavity
  Takuya Okamoto; Azusa Onishi; Xu Shi; Tomoya Oshikiri; Kosei Ueno; Hiroaki Misawa; Vasudevanpillai Biju
  The Journal of Physical Chemistry C, 128, 10, 4208, 4214, American Chemical Society (ACS), 28 Feb. 2024, [Peer-reviewed], [Lead author, Corresponding author]
  Scientific journal
• Photosensitizer-singlet oxygen sensor conjugated silica nanoparticles for photodynamic therapy and bioimaging.
  Jeladhara Sobhanan; Kenji Ono; Takuya Okamoto; Makoto Sawada; Paul S Weiss; Vasudevanpillai Biju
  Chemical science, 15, 6, 2007, 2018, 07 Feb. 2024, [Peer-reviewed], [International Magazine]
  English, Scientific journal, Intracellular singlet oxygen (1O2) generation and detection help optimize the outcome of photodynamic therapy (PDT). Theranostics programmed for on-demand phototriggered 1O2 release and bioimaging have great potential to transform PDT. We demonstrate an ultrasensitive fluorescence turn-on sensor-sensitizer-RGD peptide-silica nanoarchitecture and its 1O2 generation-releasing-storing-sensing properties at the single-particle level or in living cells. The sensor and sensitizer in the nanoarchitecture are an aminomethyl anthracene (AMA)-coumarin dyad and a porphyrin or CdSe/ZnS quantum dots (QDs), respectively. The AMA in the dyad quantitatively quenches the fluorescence of coumarin by intramolecular electron transfer, the porphyrin or QD moiety generates 1O2, and the RGD peptide facilitates intracellular delivery. The small size, below 200 nm, as verified by scanning electron microscopy and differential light scattering measurements, of the architecture within the 1O2 diffusion length enables fast and efficient intracellular fluorescence switching by the tandem ultraviolet (UV)-visible or visible-near-infrared (NIR) photo-triggering. While the red emission and 1O2 generation by the porphyrin are continually turned on, the blue emission of coumarin is uncaged into 230-fold intensity enhancement by on-demand photo-triggering. The 1O2 production and release by the nanoarchitecture enable spectro-temporally controlled cell imaging and apoptotic cell death; the latter is verified from cytotoxic data under dark and phototriggering conditions. Furthermore, the bioimaging potential of the TCPP-based nanoarchitecture is examined in vivo in B6 mice.
• Dual-color photoluminescence modulation of zero-dimensional hybrid copper halide microcrystals
  Rahul Ghosh Dastidar; Takuya Okamoto; Kiyonori Takahashi; Yuta Takano; Chakkooth Vijayakumar; Challapalli Subrahmanyam; Vasudevanpillai Biju
  Nanoscale, 16, 10, 5107, 5114, Royal Society of Chemistry (RSC), 16 Jan. 2024, [Peer-reviewed], [Corresponding author]
  Scientific journal, Green–red dual emission in hybrid copper halides is controlled by a conducting surface-induced deactivation of the red-emitting state.
• Thermally Induced Reversible Fluorochromism by Self-Trapped Excitonic Emission in a Two-Dimensional Hybrid Copper(I)-Halide Single Crystal
  Amarjith V Dev; Manasa G. Basavarajappa; Swapnil S. Deshpande; Poulomi Mukherjee; Avija Ajayakumar; Chinnadurai Muthu; Takuya Okamoto; Sudip Chakraborty; D. D. Sarma; Vasudevanpillai Biju; Chakkooth Vijayakumar
  Chemistry of Materials, 2024, [Peer-reviewed]
  Scientific journal
• Self-assembled halide perovskite quantum dots in polymer thin films showing temperature-controlled exciton recombination
  Most Farida Khatun; Takuya Okamoto; Vasudevanpillai Biju
  Chemical Communications, 59, 93, 13831, 13834, Royal Society of Chemistry (RSC), 16 Oct. 2023, [Peer-reviewed], [Corresponding author]
  Scientific journal, Spontaneous assembly formation and thermal dissociation of self-assemblies of lead halide perovskite quantum dots embedded in a polymer host reversibly modulate the photoluminescence color, spectral maxima, and lifetime.
• Highly Luminescent and Stable Halide Perovskite Nanocrystals by Interfacial Defect Passivation and Amphiphilic Ligand Capping.
  Sushant Ghimire; Most Farida Khatun; Bhagyashree M Sachith; Takuya Okamoto; Jeladhara Sobhanan; Ch Subrahmanyam; Vasudevanpillai Biju
  ACS applied materials & interfaces, 15, 34, 41081, 41091, 30 Aug. 2023, [Peer-reviewed], [International Magazine]
  English, Scientific journal, Halide vacancies cause lattice degradation and nonradiative losses in halide perovskites. In this study, we strategically fill bromide vacancies in CsPbBr3 perovskite nanocrystals with NaBr, KBr, or CsBr at the organic-aqueous interface for hydrophobic ligand-capped nanocrystals or in a polar solvent (2-propanol) for amphiphilic ligand-capped nanocrystals. Energy-dispersive X-ray spectra, powder X-ray diffraction data, and scanning transmission electron microscopy images help us confirm vacancy filling and the structures of samples. The bromide salts increase the photoluminescence quantum yield (98 ± 2%) of CsPbBr3 by decreasing the nonradiative decay rate. Single-particle studies show the quantum yield increase originates from the poorly luminescent nanocrystals becoming highly luminescent after filling vacancies. Furthermore, we tune the optical band gap (ultraviolet-visible-near-infrared) of the hydrophobic ligand-capped nanocrystals by halide exchange at the toluene-water interface using saturated NaCl or NaI solutions, which completes in about 60 min under continuous mixing. In contrast, the amphiphilic ligand accelerates the halide exchange in 2-propanol, suggesting ambipolar functional groups speed up the ion-exchange reaction. The bromide vacancy-filled or halide-exchanged samples in a toluene-water biphasic solvent show higher stability than amphiphilic ligand-capped samples in 2-propanol. This strategy of defect passivation, ion exchange, and ligand chemistry to improve quantum yields and tune band gaps of halide perovskite nanocrystals can be promising for designing stable and water-soluble perovskite samples for solar cells, light-emitting diodes, photodetectors, and photocatalysts.
• Thermodynamically and Kinetically Controlled Nucleation and Growth of Halide Perovskite Single Crystals
  Dong Zhang; Takuya Okamoto; Vasudevanpillai Biju
  Small, 19, 48, Wiley, 25 Jul. 2023, [Peer-reviewed], [Corresponding author]
  Scientific journal, Abstract
  
  Halide perovskites are ideal for next‐generation optical devices and photovoltaics. Although perovskite single‐crystals show reproducible optoelectronic properties, significant variations in the crystal size, anisotropy, density, defects, photoluminescence (PL), and carrier lifetime affect the sample properties and device performances. Homogenous size and shape FA/MAPbBr₃ single microcrystals (MCs) with controlled edge lengths, crystal densities, PL lifetimes, and PL intensities are prepared by thermodynamically controlling and kinetically separating the crystal nucleation‐growth processes using optimum N‐cyclohexyl‐2‐pyrrolidone (CHP) concentration. The crystal growth kinetics at different CHP concentrations and temperatures are estimated spectroscopically by measuring the concentration of Pb (II). High‐density cubic MCs with a homogenous size distribution, high PL intensities, and long PL lifetimes are obtained within minutes at high temperatures by the controlled addition of the pyrrolidone derivative. Conversely, the crystal size nonlinearly increases with time at low temperatures. The isotropically grown high‐density single crystals at controlled nucleation‐growth rates at 190 °C with 20% CHP show the highest PL intensity and the longest PL lifetimes. This method offers thermodynamic and kinetic control of perovskite single‐crystal growth with shape control.
• Slipping‐Free Halide Perovskite Supercrystals from Supramolecularly‐Assembled Nanocrystals
  Takuya Okamoto; Vasudevanpillai Biju
  Small, 19, 32, Wiley, 12 May 2023, [Peer-reviewed], [Lead author, Corresponding author]
  Scientific journal, Abstract
  
  Supramolecularly assembled high‐order supercrystals (SCs) help control the dielectric, electronic, and excitonic properties of semiconductor nanocrystals (NCs) and quantum dots (QDs). Ligand‐engineered perovskite NCs (PNCs) assemble into SCs showing shorter excitonic lifetimes than strongly dielectric PNC films showing long photoluminescence (PL) lifetimes and long‐range carrier diffusion. Monodentate to bidentate ligand exchange on ≈ 8 nm halide perovskite (APbX₃; A:Cs/MA, X:Br/I) PNCs generates mechanically stable SCs with close‐packed lattices, overlapping electronic wave functions, and higher dielectric constant, providing distinct excitonic properties from single PNCs or PNC films. From Fast Fourier Transform (FFT) images, time‐resolved PL, and small‐angle X‐ray scattering, structurally and excitonically ordered large SCs are identified. An Sc shows a smaller spectral shift (<35 meV) than a PNC film (>100 meV), a microcrystal (>100 meV), or a bulk crystal (>100 meV). Also, the exciton lifetime (<10 ns) of an SC is excitation power‐independent in the single exciton regime 〈N〉<1, comparable to an isolated PNC. Therefore, bidentate‐ligand‐assisted SCs help overcome delayed exciton or carrier recombination in halide perovskite nanocrystal assemblies or films.
• Photoinduced interfacial electron transfer from perovskite quantum dots to molecular acceptors for solar cells.
  Bhagyashree Mahesha Sachith; Zhijing Zhang; Palyam Subramanyam; Challapalli Subrahmanyam; Akihiro Furube; Naoto Tamai; Takuya Okamoto; Hiroaki Misawa; Vasudevanpillai Biju
  Nanoscale, 15, 17, 7695, 7702, 04 May 2023, [Peer-reviewed], [International Magazine]
  English, Scientific journal, Bandgap-engineered inorganic and hybrid halide perovskite (HP) films, nanocrystals, and quantum dots (PQDs) are promising for solar cells. Fluctuations of photoinduced electron transfer (PET) rates affect the interfacial charge separation efficiencies of such solar cells. Electron donor- or acceptor-doped perovskite samples help analyze PET and harvest photogenerated charge carriers efficiently. Therefore, PET in perovskite-based donor-acceptor (D-A) systems has received considerable attention. We analyzed the fluctuations of interfacial PET from MAPbBr3 or CsPbBr3 PQDs to classical electron acceptors such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 1,2,4,5-tetracyanobenzene (TCNB) at single-particle and ensemble levels. The significantly negative Gibbs free energy changes of PET estimated from the donor-acceptor redox potentials, the donor-acceptor sizes, and the solvent dielectric properties help us clarify the PET in the above D-A systems. The dynamic nature of PET is apparent from the decrease in photoluminescence (PL) lifetimes and PL photocounts of PQDs with an increase in the acceptor concentrations. Also, the acceptor radical anion spectrum helps us characterize the charge-separated states. Furthermore, the PL blinking time and PET rate fluctuations (108 to 107 s-1) provide us with single-molecule level information about interfacial PET in perovskites.
• Halide Perovskite Single Crystals and Nanocrystal Films as Electron Donor-Acceptor Heterojunctions
  M. D. Shahjahan; Takuya Okamoto; Lata Chouhan; Bhagyashree Mahesha Sachith; Narayan Pradhan; Hiroaki Misawa; Vasudevanpillai Biju
  ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Dec. 2022, [Peer-reviewed]
  English, Scientific journal
• Mechano-optical Modulation of Excitons and Carrier Recombination in Self-Assembled Halide Perovskite Quantum Dots
  Zhijing Zhang; Sushant Ghimire; Takuya Okamoto; Bhagyashree Mahesha Sachith; Jeladhara Sobhanan; Challapalli Subrahmanyam; Vasudevanpillai Biju
  ACS Nano, 16, 1, 160, 168, 03 Jan. 2022, [Peer-reviewed], [Lead author]
  Scientific journal
• Long-Range Interfacial Charge Carrier Trapping in Halide Perovskite-C-60 and Halide Perovskite-TiO2 Donor-Acceptor Films
  Bhagyashree Mahesha Sachith; Takuya Okamoto; Sushant Ghimire; Tomokazu Umeyama; Yuta Takano; Hiroshi Imahori; Vasudevanpillai Biju
  JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 12, 35, 8644, 8651, Sep. 2021, [Peer-reviewed]
  English, Scientific journal
• Shape‐Dependent Kinetics of Halide Vacancy Filling in Organolead Halide Perovskites
  Takuya Okamoto; Md. Shahjahan; Vasudevanpillai Biju
  Advanced Optical Materials, 9, 19, 18 Jun. 2021, [Peer-reviewed], [Lead author, Corresponding author]
  Scientific journal
• Heterojunction Perovskite Microrods Prepared by Remote-Controlled Vacancy Filling and Halide Exchange
  Md Shahjahan; Ken-ichi Yuyama; Takuya Okamoto; Vasudevanpillai Biju
  ADVANCED MATERIALS TECHNOLOGIES, 6, 2, Feb. 2021, [Peer-reviewed]
  English, Scientific journal
• Synthesis of iron-based nanoparticles from ferrocene by femtosecond laser irradiation: Suppression of the particle growth in a mixture of water and hexane
  Yuki Horikawa; Takuya Okamoto; Takahiro Nakamura; Yuhei O. Tahara; Makoto Miyata; Shingo Ikeda; Kenji Sakota; Tomoyuki Yatsuhashi
  CHEMICAL PHYSICS LETTERS, 750, Jul. 2020, [Peer-reviewed]
  English, Scientific journal
• Effects of Ligand and Solvent on the Synthesis of Iron Oxide Nanoparticles from Fe(acac)(3) Solution by Femtosecond Laser Irradiation
  Takuya Okamoto; Takahiro Nakamura; Yuhei O. Tahara; Makoto Miyata; Kenji Sakota; Tomoyuki Yatsuhashi
  CHEMISTRY LETTERS, 49, 1, 75, 78, Jan. 2020, [Lead author]
  English, Scientific journal
• Synthesis of Single-Nanometer-Sized Gold Nanoparticles in Liquid–Liquid Dispersion System by Femtosecond Laser Irradiation
  Takuya Okamoto; Takahiro Nakamura; Kenji Sakota; Tomoyuki Yatsuhashi
  Langmuir, 35, 37, 12123, 12129, 26 Aug. 2019, [Peer-reviewed], [Lead author]
  Scientific journal
• Synthesis of Bare Iron Nanoparticles from Ferrocene Hexane Solution by Femtosecond Laser Pulses
  Takuya Okamoto; Takahiro Nakamura; Ryo Kihara; Tsuyoshi Asahi; Kenji Sakota; Tomoyuki Yatsuhashi
  ChemPhysChem, 19, 19, 2480, 2485, 18 Jul. 2018, [Peer-reviewed], [Lead author]
  Scientific journal
• Precipitation of dichloromethane as low-chlorine carbon nanoparticles from water by femtosecond laser pulses
  Takuya Okamoto; Erina Miyasaka; Koji Mitamura; Kimihiro Matsukawa; Tomoyuki Yatsuhashi
  JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 344, 178, 183, Jul. 2017, [Peer-reviewed], [Lead author]
  English, Scientific journal
• Synthesis of Fluorine‐Doped Hydrophilic Carbon Nanoparticles from Hexafluorobenzene by Femtosecond Laser Pulses
  Takuya Okamoto; Koji Mitamura; Tomoyuki Hamaguchi; Kimihiro Matsukawa; Tomoyuki Yatsuhashi
  ChemPhysChem, 18, 9, 1007, 1011, 06 Sep. 2016, [Peer-reviewed], [Lead author]
  Scientific journal
• Synthesis of Hydrophilic and Hydrophobic Carbon Nanoparticles from Benzene/Water Bilayer Solution with Femtosecond Laser Generated Plasma Filaments in Water
  Tomoyuki Hamaguchi; Takuya Okamoto; Koji Mitamura; Kimihiro Matsukawa; Tomoyuki Yatsuhashi
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 88, 2, 251, 261, Feb. 2015, [Peer-reviewed]
  English, Scientific journal

• Structural and Photoluminescence Control of Lead Halide Perovskites
  OKAMOTO Takuya, photochemistry, 57, 1, 16, 24, 24 Apr. 2026, [Peer-reviewed], [Lead author, Corresponding author]
  Lead halide perovskites have attracted much attention as semiconductor materials for applications in solar cells, light-emitting diodes, and photodetectors due to their facile synthesis, high photoluminescence (PL) quantum yields, and size- and halide-dependent tunable optical bandgaps. Recently, highly ordered assemblies of perovskite nanocrystals (PNCs), known as supercrystals, as well as ligand-stripped PNC assemblies have emerged as a topic of growing interest due to their unique optical properties, which differ from those of isolated PNCs or randomly aggregated PNC films. However, the correlation between the structural characteristics of such PNC assemblies and their PL properties remains unclear. It is crucial to gain a systematic understanding of the relationship between PNC alignment and exciton/carrier recombination dynamics in the PNC assemblies. This review introduces research on the control of PL properties in perovskite microcrystals and PNC films, as well as assembly structure and PL control of perovskite quantum dot assemblies and supercrystals., The Japanese Photochemistry Association, Japanese
• Defect Passivation Strategies in Halide Perovskite Solar Cells and LEDs
  Siddharth Singh; Arghya Sen; S. L. Aneesha; Woo Hyeon Jeong; Arup Ghorai; Junzhi Ye; Takuya Okamoto; Deepika Gaur; Subarna Samanta; Chun-Yun Wang; Sergio Gomez-Grana; Michael Saliba; Vishal Govind Rao; Pratik Sen; Robert L. Z. Hoye; Vasudevanpillai Biju; Lakshminarayana Polavarapu, ACS ENERGY LETTERS, 11, 4, 3060, 3120, 10 Apr. 2026
  English, Book review
• From halide perovskite nanocrystals to supercrystals: fundamentals and applications
  S. L. Aneesha; Yifei Xia; Takuya Okamoto; Deepika Gaur; Sudipta Seth; Johan Hofkens; Lakshminarayana Polavarapu; Vasudevanpillai Biju, Chemical Society Reviews, 54, 21, 9585, 9611, 2025, [Peer-reviewed], [Corresponding author]
  Halide perovskite supercrystals (or superlattices) are electronically coupled nanomaterials, such as nanocrystals, quantum dots, or nanoplatelets that offer collective optical and electronic properties distinct from those of their constituents., Royal Society of Chemistry (RSC)
• ハロゲン化鉛ペロブスカイトの電場変調吸収分光
  岡本 拓也, 分光研究 = Journal of the Spectroscopical Society of Japan / 日本分光学会 編, 73, 1, 18, 20, 2024, [Peer-reviewed]
  東京 : 日本分光学会, Japanese
• Lead-Free Halide Perovskite Materials and Optoelectronic Devices: Progress and Prospective
  Iago López-Fernández; Donato Valli; Chun Yun Wang; Subarna Samanta; Takuya Okamoto; Yi Teng Huang; Kun Sun; Yang Liu; Vladimir S. Chirvony; Avijit Patra; Juliette Zito; Luca De Trizio; Deepika Gaur; Hong Tao Sun; Zhiguo Xia; Xiaoming Li; Haibo Zeng; Iván Mora-Seró; Narayan Pradhan; Juan P. Martínez-Pastor; Peter Müller-Buschbaum; Vasudevanpillai Biju; Tushar Debnath; Michael Saliba; Elke Debroye; Robert L.Z. Hoye; Ivan Infante; Liberato Manna; Lakshminarayana Polavarapu, Advanced Functional Materials, 2023, [Peer-reviewed]
  Book review
• Laser Synthesis of Size-Regulated Metal Nanoparticles by Utilizing Liquid-Liquid Interface
  八ッ橋知幸; 岡本拓也; 堀川雄輝, 光学, 51, 2, 2022, [Peer-reviewed]
• Bottom-up Synthetic Approaches to Carbon Nanomaterial Production in Liquid Phase by Femtosecond Laser Pulses
  Tomoyuki Yatsuhashi; Takuya Okamoto, High-Energy Chemistry and Processing in Liquids, 331, 356, 2022, [Peer-reviewed]
  Springer Singapore
• Chemical Reactions and Nanomaterial Productions in Liquid Phase by Femtosecond Laser Pulses
  岡本拓也; 中島信昭; 八ッ橋知幸, レーザー研究, 45, 5, 2017, [Peer-reviewed], [Lead author]

• 機械的刺激によるハイブリッド金属ハライドの発光特性制御
  岡本 拓也
  フォトエキサイトニクス研究拠点 第8回研究会, 09 Apr. 2026, Invited oral presentation
  [Invited]
• Control of the Assembly and Optical Properties of Halide Perovskite Nanomaterials
  岡本 拓也
  日本化学会 第105春季年会 (2025) アジア国際シンポジウム―光化学ディビジョン―, Mar. 2025, Invited oral presentation
  [Invited]
• Emission Modulation of Zero-Dimensional Hybrid Copper Halides
  岡本 拓也
  The 2024 RIES-CEFMS (Research Institute for Electronic Science-Center for Emergent Functional Matter Science) Joint International Symposium, Dec. 2024, Invited oral presentation
  [Invited]
• Excitons in Halide Perovskite Assembly
  岡本 拓也
  The 2023 RIES-CEFMS (Research Institute for Electronic Science-Center for Emergent Functional Matter Science) Joint International Symposium, Dec. 2023, Invited oral presentation
  [Invited]
• フェムト秒レーザーによるナノ粒子の生成：有機金属錯体の分子構造によるナノ粒子のサイズ・形態制御
  岡本 拓也
  高分子・ハイブリッド材料研究センター（PHyM）講演会, Jan. 2018, Invited oral presentation
  [Invited]
• フェムト秒レーザーを用いたナノ粒子の表面および元素組成制御
  岡本 拓也
  高分子・ハイブリッド材料研究センター（PHyM）講演会, Mar. 2017, Invited oral presentation
  [Invited]

• 環境物質科学特別講義Ⅲ, 2024年, 修士課程, 環境科学院
• 英語演習, 2024年, 学士課程, 全学教育
• 一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), 2024年, 学士課程, 全学教育

• 日本分光学会
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• 日本化学会

• 液中レーザーアブレーションによる廃ガラス中有害金属の革新的定量・除去技術の開発
  環境研究総合推進費
  Apr. 2026 - Mar. 2029
  独立行政法人環境再生保全機構, 3RA-2601
• ペロブスカイト結晶-ナノ共振器を用いた低閾値かつ狭帯域ナノレーザーの開発
  科学研究費助成事業 若手研究
  01 Apr. 2021 - 31 Mar. 2024
  岡本 拓也
  本研究は、利得媒質のペロブスカイト結晶とファブリ・ペローナノ共振器の組み合わせによるサブnmオーダーのスペクトル半値幅と低閾値化、そしてレーザー発振波長の選択を同時に達成可能なナノレーザーの開発を目的とする。本年度は、ペロブスカイト結晶における自然放射増幅光の発振閾値制御に重要な、結晶のハロゲン欠陥密度の検討と、ペロブスカイトナノ結晶または市販の半導体量子ドットと金および酸化物の薄膜で構成されたナノ共振器の光学特性評価を行った。まず、ペロブスカイトマイクロ結晶への同種ハロゲンアニオンの添加および光照射を行った。結晶におけるハロゲン欠陥の回復速度および蛍光寿命の増加量は結晶のアスペクト比ではなく、比表面積の大きさに依存することを明らかにした。この研究に基づいた論文はWiley-VCHのAdvanced Optical Materialsに令和3年6月に掲載された。次に、ファブリ・ペローナノ共振器の薄膜材料および膜厚の最適化に向けて、ペロブスカイトナノ結晶および市販の半導体量子ドットを用いて金および酸化物の薄膜で構成されたナノ共振器の光学特性を評価した。しかし、どちらの量子ドットも共振器上では消光され、蛍光強度は減少した。そこで、ペロブスカイト量子ドットと薄膜材料の電荷移動について検討するため、ドナーであるペロブスカイト量子ドット薄膜とアクセプターとなる酸化チタンまたは比較としてフラーレンを組み合わせたヘテロ接合材料における光学特性について評価した。このようなヘテロ接合界面における電荷移動においてドナー・アクセプター界面に近づくにつれて動的な過程から静的な過程へと変化することが明らかとなった。この研究に基づいた論文はアメリカ化学会のThe Journal of Physical Chemistry Lettersに令和3年9月に掲載された。
  日本学術振興会, 若手研究, 北海道大学, 21K14580
• 光圧による局所濃縮を利用したハロゲン混合ペロブスカイト単一ナノ結晶形成機構の解明
  科学研究費助成事業 特別研究員奨励費
  24 Apr. 2020 - 31 Mar. 2023
  岡本 拓也
  本研究は、次世代発光材料である単一ペロブスカイトナノ結晶の形成機構、および結晶間の相互作用や反応機構を解明することを目的としている。本年度の研究では、主にペロブスカイトマイクロ結晶における欠陥回復速度の結晶形状依存性の解明と、自己組織化ペロブスカイトナノ結晶における結晶間相互作用の解明について研究活動を行った。まず、ハロゲン欠陥の少ないペロブスカイト結晶の形成に向け、結晶へのハロゲン化物の添加および光照射による結晶のハロゲン欠陥回復と、ハロゲン欠陥回復速度の結晶形状依存性について検討した。ペロブスカイトマイクロ結晶におけるハロゲン欠陥の回復速度および蛍光寿命の増加量は結晶のアスペクト比ではなく、比表面積の大きさに依存するということを明らかにした。この研究に基づいた論文はWiley-VCHのAdvanced Optical Materialsに令和3年6月に掲載された。次に、自己組織化ペロブスカイトナノ結晶における結晶間相互作用の解明に向けて、青色発光を示すペロブスカイト量子ドットを集積することで緑色発光を示す自己組織化ナノ結晶を形成した。緑色発光を示す自己組織化ナノ結晶の薄膜に機械的刺激を加えることで、薄膜は再び青色発光を示すことが分かった。機械的刺激を加える前後のナノ結晶および量子ドットの構造と発光特性について検討を行い、機械的刺激によってペロブスカイト量子ドットの集合状態が変化し、励起子閉じ込めおよび誘電遮蔽の強さに依存してバンドギャップエネルギーおよびキャリア拡散距離が変化することが明らかとなった。この研究に基づいた論文はアメリカ化学会のACS NANOに令和4年1月に掲載された。
  日本学術振興会, 特別研究員奨励費, 北海道大学, 20J00974
• 微小プラズマと微小液滴を融合したナノ粒子生成：微小反応場の特異性の解明
  科学研究費助成事業 特別研究員奨励費
  25 Apr. 2018 - 31 Mar. 2020
  岡本 拓也
  本研究は微小反応場におけるナノ粒子の生成、成長、そして凝集について基礎的な知見を得ることを目的とした。本年度は金属錯体の溶液試料と貧溶媒を撹拌試料して生じる微小液滴がナノ粒子の形態および粒子径に及ぼす効果の解明、およびマイクロ流路によりサイズを制御した液滴中での微小プラズマ発生について研究活動を行った。ヘキサン/塩化金酸水溶液、およびフェロセンヘキサン溶液/水の撹拌により水中油滴型のエマルションを形成し、原料が水に溶解する条件と有機溶媒に溶解する条件にてフェムト秒レーザーをそれぞれ照射した。ヘキサン/塩化金酸水溶液の水中油滴型エマルションへのレーザー照射では、キャッピング剤を用いることなく直径10 nm未満の大きさの金ナノ粒子の生成に成功した。レーザー照射時間にかかわらず平均粒子径は5 nm程度で一定であった。さらに、乾燥により金ナノ粒子は円形状に濃縮されつつも凝集しないことが分かった。金ナノ粒子の1次粒子が液滴表面に捕捉されることで粒子成長が抑制されると結論した。なお、この研究に基づいた論文はアメリカ化学会のLangmuirに掲載された。一方、フェロセンヘキサン溶液/水の水中油滴型エマルションへのレーザー照射では、油相側に原料分子が溶解しているにもかかわらず、レーザー照射後の水相において10 nm未満の鉄ナノ粒子が分散して得られることを見出した。また、原料濃度を10倍にしても、レーザーの照射時間にかかわらず、平均粒子径は10 nm未満のままであった。フェロセンを溶解したヘキサン液滴が微小な反応場として機能し、粒子および鉄原子の凝集が抑制されると結論した。さらに、市販のシリコン樹脂製マイクロ流路を用いて液滴のサイズ制御条件の検討を行った。微小液滴内でのナノ粒子生成に向けて、レーザー照射系の構築や、マイクロ流路内における各試料の流速条件およびレーザー照射条件の最適化を行った。
  日本学術振興会, 特別研究員奨励費, 大阪市立大学, 18J15442