Kazuto Kayama

Kyoto University

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Masaki Sugimoto

Nagasaki University

Tsuneaki Sakurai

Kyoto Institute of Technology

D.K. Avasthi

University of Petroleum and Energy Studies

Shu Seki

Kyoto University

Shugo Sakaguchi

Kyoto University

G.B.V.S. Lakshmi

Jawaharlal Nehru University

Atsuya Chiba

National Institutes for Quantum and Radiological Science and Technology

Tetsuya Yamaki

National Institutes for Quantum and Radiological Science and Technology

Akifumi Horio

Osaka University

Yuichi Saitoh

National Institutes for Quantum and Radiological Science and Technology

Cooperative Institutions

Kyoto University

National Institutes for Quantum and Radiological Science and Technology

Osaka University

Takasaki Advanced Radiation Research Institute

Japan Atomic Energy Agency

Advanced Science Research Center

Japan Science and Technology Agency

Kyoto Katsura Hospital

Tohoku University

The University of Tokyo

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Remarkable effect of halogenation of aromatic compounds on efficiency of nanowire formation through polymerization/crosslinking by high-energy single particle irradiation

Radiation Physics and Chemistry (2017)

Akifumi Horio Tsuneaki Sakurai Kazuto Kayama G.B.V.S. Lakshmi D.K. Avasthi

Polystyrene

Particle (ecology)

10.1016/j.radphyschem.2017.02.052

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Citations (6)

Ubiquitous organic molecule-based free-standing nanowires with ultra-high aspect ratios

Nature Communications (2021)

Koshi Kamiya Kazuto Kayama Masaki Nobuoka Shugo Sakaguchi Tsuneaki Sakurai

Abstract The critical dimension of semiconductor devices is approaching the single-nm regime, and a variety of practical devices of this scale are targeted for production. Planar structures of nano-devices are still the center of fabrication techniques, which limit further integration of devices into a chip. Extension into 3D space is a promising strategy for future; however, the surface interaction in 3D nanospace make it hard to integrate nanostructures with ultrahigh aspect ratios. Here we report a unique technique using high-energy charged particles to produce free-standing 1D organic nanostructures with high aspect ratios over 100 and controlled number density. Along the straight trajectory of particles penetrating the films of various sublimable organic molecules, 1D nanowires were formed with approximately 10~15 nm thickness and controlled length. An all-dry process was developed to isolate the nanowires, and planar or coaxial heterojunction structures were built into the nanowires. Electrical and structural functions of the developed standing nanowire arrays were investigated, demonstrating the potential of the present ultrathin organic nanowire systems.

Coaxial

Aspect ratio (aeronautics)

10.1038/s41467-021-24335-x

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Porphyrin Nanowire Bundles for Efficient Photoconductivity, Photoemission, and Generation of Singlet Oxygens toward Photodynamic Therapy

ACS Applied Nano Materials (2020)

Tsuneaki Sakurai Shugo Sakaguchi Yuki Takeshita Kazuto Kayama Akifumi Horio

Energy released from an accelerated high-energy single/cluster particle triggers solid-state polymerization and cross-linking reactions of porphyrin-based π-conjugated monomers within a nanometer-scaled one-dimensional spatial area along the ion trajectory, resulting in the formation of an insoluble nanowire with a precise diameter and length. The nanowires are isolated by the development process—immersion of the irradiated film in organic solvents—and their shape and geometry are clearly characterized by atomic force microscopy. The obtained nanowire bundles, reflecting precisely the number of incident particles, show characteristic absorption spectra originating from porphyrin chromophores without significant degradation of the molecular cores. These porphyrin-based nanowires can be further functionalized into metallocomplexes by immersing the nanowires into solutions containing metal ion sources. The remarkable finding on the monomer structural parameters is that terminal alkyne groups are preferentially reacted and thus highly effective as a monomer structure for the present single particle-triggered linear polymerization method. The porphyrin-based nanowires show much higher photoconductivity than the precursor porphyrin films and enhanced fluorescence on silver nanoparticle layers via surface plasmon resonance. The porphyrin nanowires serve as photosensitizers mediating the generation of singlet oxygens, which is attractive for the use as a controlled nanosystem toward photocatalysis and photodynamic therapy.

Photoconductivity

Chromophore

10.1021/acsanm.0c01242

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Citations (12)