Shugo Sakaguchi

Kyoto University

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Tsuneaki Sakurai

Kyoto Institute of Technology

Shu Seki

Kyoto University

Masaki Sugimoto

Nagasaki University

Koshi Kamiya

Kyoto University

Akira Idesaki

National Institutes for Quantum and Radiological Science and Technology

Hiroshi Koshikawa

National Institutes for Quantum and Radiological Science and Technology

Masaki Nobuoka

Panasonic (Japan)

Tetsuya Yamaki

National Institutes for Quantum and Radiological Science and Technology

D.K. Avasthi

University of Petroleum and Energy Studies

G.B.V.S. Lakshmi

Jawaharlal Nehru University

Cooperative Institutions

Kyoto University

Osaka University

National Institutes for Quantum and Radiological Science and Technology

Takasaki Advanced Radiation Research Institute

Japan Atomic Energy Agency

Advanced Science Research Center

Japan Science and Technology Agency

Tohoku University

The University of Tokyo

Kyoto Katsura Hospital

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Conjugated Nanowire Sensors via High-Energy Single-Particle-Induced Linear Polymerization of 9,9′-Spirobi[9H-fluorene] Derivatives

The Journal of Physical Chemistry B (2018)

Shugo Sakaguchi Tsuneaki Sakurai Jun Ma Masaki Sugimoto Tetsuya Yamaki

Nanostructures composed of conjugated polymers or π-conjugated molecules provide sensing platforms with large specific surface areas. One of the feasible approaches to accessing such nanostructured miniaturized sensors with ultrahigh sensitivity is to develop a network of organic nanowires with optical/electronic properties that can measure signals upon interacting with the analytes at their surfaces. In this work, organic nanowires with controlled number density and uniform length were fabricated by one-dimensional solid-state polymerization of 9,9′-spirobi[9H-fluorene] (SBF) derivatives triggered by high-energy single particles. SBF was chosen as a conjugated molecular motif with the interplay of high density of π-electrons, high solubility, and uniform solid-state structures, allowing us to fabricate sensing platforms via solution processing. The as-deposited energy density in linear polymerization nanospace was theoretically analyzed by a collision model, interpreting nanowire sizes at subnanometer levels. The substitution of bromine atoms was confirmed to be effective not only for the higher collision probability of the incident particles but also for the remarkable increase in radiolytic neutral radical yield via C–Br cleavages or electron-dissociative attachments onto the bromine atoms. The fluorescence spectra of SBF-based nanowires were different from those of SBF derivatives due to extended bond formation as a result of polymerization reactions. Fluorescence was quenched by the addition of nitrobenzene, indicating the potential use of our nanowires for fluorometric sensing applications. Microwave-based conductivity measurements revealed that the SBF-based nanowires exhibited charge carrier transport property upon photoexcitation, and that the conductivity was changed upon treatment with nitrobenzene vapors. The presented strategy of bromination of aromatic rings for efficient fabrication of controlled nanowire networks with favorable fluorescent and charge transport properties of nanowires advances the development of nanostructured sensing systems.

10.1021/acs.jpcb.8b06310

Cite

Citations (9)

Interactions of Single Particle with Organic Matters: A Facile Bottom-Up Approach to Low Dimensional Nanostructures

Quantum Beam Science (2020)

Shugo Sakaguchi Koshi Kamiya Tsuneaki Sakurai Shu Seki

A particle induces a pack of chemical reactions in nanospace: chemical reactions confined into extremely small space provide an ultimate technique for the nanofabrication of organic matter with a variety of functions. Since the discovery of particle accelerators, an extremely high energy density can be deposited, even by a single isolated particle with MeV-ordered kinetic energy. However, this was considered to cause severe damages to organic molecules due to its relatively small bond energies, and lack of ability to control the reactions precisely to form the structures while retaining physico-chemical molecular functionalities. Practically, the severely damaged area along a particle trajectory: a core of a particle track has been simply visualized for the detection/dosimetry of an incident particle to the matters, or been removed to lead nanopores and functionalized by refilling/grafting of fresh organic/inorganic materials. The use of intra-track reactions in the so-called “penumbra” or “halo” area of functional organic materials has been realized and provided us with novel and facile protocols to provide low dimensional nano-materials with perfect size controllability in the 21st century. These protocols are now referred to as single particle nanofabrication technique (SPNT) and/or single particle triggered linear polymerization technique (STLiP), paving the way towards a new approach for nanomaterials with desired functionalities from original molecules. Herein, we report on the extremely wide applicability of SPNT/STLiP protocols for the future development of materials for opto-electronic, catalytic, and biological applications among others.

Particle (ecology)

Nanomaterials

10.3390/qubs4010007

Cite

Citations (6)

Oriented Nanowire Arrays with Phthalocyanine – C₆₀ Multi-Heterojunctions

Journal of Photopolymer Science and Technology (2021)

Masaki Nobuoka Koshi Kamiya Shugo Sakaguchi Akira Idesaki Tetsuya Yamaki

One dimensional nanowires systems with programmed multi-heterojunction along their axes have been presumed as an ideal nanomaterials platform for quantum confinements exhibiting novel electronic/photonic functions. Herein we have successfully produced free-standing nanowires with multi-heterojunctions of which spatial alignments are perfectly under control on a substrate by a facile protocol referred to as Single Particle Triggered Linear Polymerization method. Uniform nanowires were well-vertically aligned on substrates with tightly bound bases, and represented by the sequential bottom-up of ~ 10 nano-segments from copper phthalocyanine and Buckminster fullerene molecules. Efficient polymerization/crosslinking reactions with high enough G values of 20-40 (100 eV)-1 were rationalize the formation of the nano-segments with significant changes in their radial thickness. Although the released energy density by the employed high energy charged particle was extremely high, which is presumed from the value of linear energy transfer of 1 – 1.4 ×104 eV nm-1, however electronic and Raman spectroscopies confirmed clearly that the nano-segments in nanowires reflected well opto-electronic characteristics of molecules at least the outer boundaries, suggesting the future application of the present multi-heterojunction systems as magneto-optical nanomaterials. We are able to make our own choices of the molecules with designed electronic states, and program them to 0-1 dimensional nanomaterials with sequential connection along a direction by the present technique.

Nanomaterials

Particle (ecology)

10.2494/photopolymer.34.167

Cite

Citations (0)

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

Cite

Citations (5)

Donor/Acceptor Segregated π-Stacking Arrays by Use of Shish-Kebab-Type Polymeric Backbones: Highly Conductive Discotic Blends of Phthalocyaninatopolysiloxanes and Perylenediimides

Macromolecules (2017)

Tsuneaki Sakurai Satoru Yoneda Shugo Sakaguchi Kenichi Kato Masaki Takata

Construction of large-area electron donor–acceptor (D–A) interfaces and hole/electron pathways is important for photoconducting and photovoltaic functions. Although blends of D- and A-type discotic π-systems have a possibility to realize one-dimensional charge carrier pathways as well as heterointerfaces, D–A segregated structures are difficult to develop by self-assembly because they are entropically unfavored structures. Here we report the use of shish-kebab-type hole-transporting discotic columns fixed by a self-threading polysiloxane chain and approach to such segregated nanostructures. Electron-donor/acceptor blends of soluble phthalocyaninatopolysiloxanes (Poly-SiPcs) and perylenedicarboximides (PDIs) were prepared, and their photoconductive property was investigated. Although Poly-SiPc1 shows a photoinduced charge separation with PDI1 analogous to the corresponding monomeric phthalocyanines (SiPc1 and H2Pc1), the Poly-SiPc1/PDI1 system displays a remarkably larger photoconductivity than SiPc1/PDI1 and H2Pc1/PDI1, which mostly results from the presence of hole-transporting pathways with the mobility μh,1D ∼ 0.1 cm2 V–1 s–1 in Poly-SiPc1 along the polysiloxane covalent bonds even upon mixing with PDI1. When π-stackable PDI2 is used instead of PDI1, X-ray diffraction analysis disclosed obvious signs of π-stacking periodicities for both Pc and PDI planes in the mixture, indicating the presence of donor–acceptor segregated domains of columnar structures. As a result, photoexcitation of Poly-SiPc1/PDI2 generates highly mobile holes and electrons, leading to the observation of a much larger conductivity.

Discotic liquid crystal

Acceptor

Electron acceptor

Electron donor

Photoconductivity

Photoexcitation

Electron Mobility

10.1021/acs.macromol.7b02020

Cite

Citations (17)

Ubiquitous Organic Molecule-based Free-standing Nanowires with Ultra-high Aspect Ratios

Research Square (Research Square) (2021)

Koshi Kamiya Kazuto Kamiya 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 this decade. 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 device integration; however, the steep increase in the number of surfaces and their interaction in 3D nanospace make it hard to integrate nanostructures with aspect ratios over ~ 10. We report herein a unique technique to produce uniform free-standing 1D nanostructures with extremely high aspect ratios over 100, borrowing from technology developed for cancer radiotherapy with high-energy charged particles. Along the straight trajectory of particles penetrating the condensed phase of a variety of sublimable organic molecules, 1D nanowires were formed with single-nm thickness and perfectly controlled length. An all-dry process was developed to isolate the nanowire plexus, and hetero-junction structures could be facilely built into the nanowires by the new technique. Coaxial extension of nanowires by a chemical process allowed us to freely design the nanowires both in axial and radial directions.

Coaxial

10.21203/rs.3.rs-364552/v1

Cite

Citations (0)

Highly Efficient Solid-State Intra-Track Polymerization of Ethynyl-Substituted Spirobifluorenes Triggered by Swift Heavy Ion Irradiations

Journal of Photopolymer Science and Technology (2020)

Shugo Sakaguchi Tsuneaki Sakurai Akira Idesaki Hiroshi Koshikawa Masaki Sugimoto

Acetylenes are the first monomer to polymerize by the energy deposited by ionizing radiations. Herein we report an extremely efficient solid state polymerization of ethynyl-substituted 9,9'-spirobi[9H-fluorene]s (SBFs) via a unique nano-fabrication technique referred to as Single Particle Trigged Linear Polymerization (STLiP) initiated by high energy charged particles. The resulted nanowires of polymerized/crosslinked SBFs show a gradual transformation from flexible to rigid rod-like with an increase in the reaction efficiency mediated by the ethynyl substitution. The overall efficiency of initiation/propagation/crosslinking reactions is remarkably high even in comparison with the primary yield of ionization events in the radiation chemical processes, marking up to G > 80 (100 eV)-1, which is suggestive of efficient chain reactions in the propagation steps. The present results demonstrate efficient solid-state polymerization reactions, which are neither topochemical polymerization reactions nor acid/base catalyzed reactions, expand the versatility of STLiP technique to fabricate 1D nanomaterials based on a variety of organic compounds.

10.2494/photopolymer.33.91

Cite

Citations (2)

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

Cite

Citations (12)