研究者詳細 - 大須賀　秀次

論文 - 大須賀　秀次

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Spin dynamics of thiophene-fused π-systems with delayed emission

Hideto Matsuoka, Kazuki Shichida, Koki Tachibana, Hideji Osuga (担当区分：最終著者 )

The Journal of Chemical Physics ( AIP Publishing ) 162 ( 9 ) 094301 2025年03月 [査読有り]

Triplet excited states in organic molecules are generally optically inactive due to spin-forbidden transitions to the singlet ground state. Recent studies have extensively investigated triplet states to circumvent limitations imposed by spin statistics in organic light-emitting diodes. Room-temperature electrophosphorescence and electrofluorescence have previously been observed in thienyl-substituted phenazines without heavy metals; however, phosphorescence was absent when spin density was localized on the thiophene units, despite the expected heavy-atom effect from the sulfur atom. In this study, we investigate the spin dynamics of thiophene-fused π-systems lacking phenazine units to enable the effective utilization of triplet states in thiophene-containing π-systems. This investigation reveals delayed emission in the excited dimers of fused thiophenes, likely associated with triplet–triplet annihilation. Optical and EPR measurements, together with quantum chemical calculations, indicate that the fused thiophenes form head-to-tail dimers in both the ground and excited states.

STM/TERS observation of M-type diphenyl[7]thiaheterohelicene on Ag(111)

Sho Kimura, Takuma Hattori, Changqing Ye, Masaki Okada, Satoshi Kondo, Yui Sakurama, Akira Saito, Pawel Krukowski, Hideji Osuga, Yuji Kuwahara

Physical Chemistry Chemical Physics ( Royal Society of Chemistry (RSC) ) 26 ( 9 ) 7658 - 7663 2024年02月 [査読有り]

Chiral Recognition Mechanism of Two-Dimensional Self-Assembly Formed by [7]Thiaheterohelicene

Changqing Ye, Takuma Hattori, Yuji Hamamoto, Pawel Krukowski, Kouji Inagaki, Akira Saito, Hideji Osuga, Yoshitada Morikawa, Yuji Kuwahara

The Journal of Physical Chemistry C ( American Chemical Society (ACS) ) 127 ( 43 ) 21305 - 21312 2023年10月 [査読有り]

Light Emission from M-Type Enantiomer of 2,13-bis(hydroxymethyl)[7]-thiaheterohelicene Molecules Adsorbed on Au(111) and C60/Au(111) Surfaces Investigated by STM-LE

Paweł Krukowski, Takuma Hattori, Megumi Akai-Kasaya, Akira Saito, Hideji Osuga, Yuji Kuwahara

International Journal of Molecular Sciences ( MDPI AG ) 23 ( 23 ) 15399 - 15399 2022年12月 [査読有り]

Light emission from the M-type enantiomer of a helicene derivative (2,13-bis(hydroxymethyl)[7]-thiaheterohelicene) adsorbed on the clean Au(111) and the C60-covered Au(111) surfaces were investigated by tunneling-current-induced light-emission technique. Plasmon-originated light emission was observed on the helicence/Au(111) surface and it was strongly suppressed on the area where the helicene molecules were adsorbed at the edges of the Au(111) terraces. To avoid luminescence quenching of excited helicene molecules and to suppress strong plasmon light emission from the Au(111) surface, C60 layers were used as decoupling buffer layers between helicene molecules and the Au(111) surface. Helicene molecules were adsorbed preferentially on the Au(111) surface rather than on the C60 buffer layers due to the small interaction of the molecules and C60 islands. This fact motivated us to deposit a multilayer of helicene molecules onto the C60 layers grown on the Au(111) surface, leading to the fact that the helicene/C60 multilayer showed strong luminescence with the molecules character. We consider that such strong light emission from the multilayer of helicene molecules has a plasmon origin strongly modulated by the molecular electronic states of (M)-[7]TH-diol molecules.

Study of stereochemical crystallization of racemic mixtures of [5] and [7] thiaheterohelicene molecules on Ag(111) surface by scanning tunneling microscopy and Raman scattering spectroscopy

Pawel Krukowski, Takuma Hattori, Masaki Okada, Michal Piskorski, Iaroslav Lutsyk, Akira Saito, Hideji Osuga, Yuji Kuwahara

Applied Surface Science ( ELSEVIER ) 589 152860 2022年07月 [査読有り]

The crystallization of a racemic mixture of [5] and [7]thiaheterohelicene molecules into two-dimensional highly ordered molecular domains on a Ag(111) surface was investigated by scanning tunneling microscopy (STM) at 80 K. We observed that the crystallization of both thiaheterohelicene molecules on a Ag(111) surface was strongly affected by stereospecific interactions resulting from different numbers of aromatic rings incorporated into the helical skeletons of molecules. [5]Thiaheterohelicene molecules crystallized predominant into a few racemate polymorphic molecular domains, allowing us to obtain high-resolution STM images with the unambiguous identification of the absolute handedness of enantiomeric species. In contrast, the stereochemical chiral interactions among [7]thiaheterohelicene molecules led to the formation of one type of racemate molecular domain consisting of self-assembled zigzagged twin rows. X-ray photoelectron spectroscopy investigation strongly suggests weak interaction between thiaheterohelicene molecules and Ag(111) surface and lack of formation the S-Ag chemical bond. Surface-enhanced Raman spectroscopy combined with theoretical calculation based on a density functional theory was applied to the chemical verification of molecules adsorbed on a plasmonic silver surface for future tip-enhanced Raman spectroscopy.

Adsorption and Light Emission of a Racemic Mixture of [7]thiaheterohelicene-2,13-carboxaldehyde on Au(111), Cu(001), and NiAl(110) Surfaces Investigated Using a Scanning Tunneling Microscope

Pawel Krukowski, Songpol Chaunchaiyakul, Megumi Akai-Kasaya, Akira Saito, Hideji Osuga, Yuji Kuwahara

Journal of Physical Chemistry C ( AMER CHEMICAL SOC ) 125 ( 17 ) 9419 - 9427 2021年05月 [査読有り]

The coverage-dependent adsorption of a racemic mixture of [7]thiaheterohelicene-2,13-carboxaldehyde on Au(111), Cu(001), and NiAl(110) surfaces was investigated using a scanning tunneling microscope (STM). At a low coverage, the adsorption process for helicene molecules on Au(111) was strongly affected by surface reconstruction. At monolayer saturation coverage, the dominant molecular structure observed on Au(111) characteristically had separated self-assembled twin rows aligned in.112<overline>. directions. The helicene molecules within these separated twin rows are preferentialy arranged in a zigzag pattern with alternating (M)-and (P)-enantiomers. With increasing molecular coverage, the molecular structural transition from self-assembled twin rows to self-assembled single rows was observed. STM-induced light emission (STM-LE) investigation of helicene molecules on Au(111) showed the suppression of plasmon light emission over the molecules. The adsorption of helicene molecules on Cu(001) and NiAl(110) was quite different from that observed on Au(111). Neither the formation of self-assembled twin rows nor the molecular arrangement into different domains was observed. The formation of molecular clusters on Cu(001) and NiAl(110) was observed. STM-LE investigation of helicene molecules adsorbed on Cu(001) showed the suppression of plasmon light emission over these molecules. In contrast to metallic Au(111) and Cu(001) substrates, STM-LE investigations revealed the enhancement of light emission above the molecular clusters formed on metallic NiAl(110), suggesting plasmon-enhanced molecular light emission.

Nanoscale Dehydrogenation Observed by Tip-Enhanced Raman Spectroscopy

Songpol Chaunchaiyakul, Agung Setiadi, Pawel Krukowski, Francesca Celine I. Catalan, Megumi Akai-Kasaya, Akira Saito, Norihiko Hayazawa, Yousoo Kim, Hideji Osuga, Yuji Kuwahara

JOURNAL OF PHYSICAL CHEMISTRY C ( AMER CHEMICAL SOC ) 121 ( 33 ) 18162 - 18168 2017年08月 [査読有り]

This study shows evidence of nanoscale dehydrogenation occurring during tip-enhanced Raman spectroscopy (TERS) measurements. The near-field TERS spectra obtained locally on a self-assembled monolayer of 2,13-bis(aldehyde)[7]thiaheterohelicene molecules showed vibrational frequencies in good agreement with that predicted by density functional theory calculations, except for the L-mode at 1000 cm(-1), which is ascribed to a C C triple bond, implying that the benzene rings had been dehydrogenated during the experiments. Using peak analysis, incorporated with the molecular adsorption orientation deduced from high-resolution STM imaging, we conclude that one side benzene ring protruding upward was dehydrogenated as a result of pyrolysis, with the Ag tip serving as both local heat source and catalyst.

Organic thin-film transistors based on solution-processable benzodithiophene dimers modified with hexyl groups

Hirota Takeshi, Toake Hitoshi, Osuga Hideji, Uno Kazuyuki, Tanaka Ichiro

Jpn. J. Appl. Phys. ( Institute of Physics ) 56 ( 4 ) 048002 - 048002 2017年04月 [査読有り]

Benzodithiophene dimers modified with hexyl groups (2C<inf>6</inf>-BDT-dimer) were investigated as solution-processable organic semiconductors for organic thin-film transistors (OTFTs). Since 2C<inf>6</inf>-BDT-dimer crystals have an anisotropic shape, flow coating was adopted to grow polycrystalline films. The flow-coated films were inferior to the vacuum-evaporated ones in terms of their crystallinity estimated from X-ray diffraction data. However, the hole mobility of the OTFTs with the flow-coated films, which was 1.7 cm<sup>2</sup>V<sup>−1</sup>s<sup>−1</sup>at maximum, was higher than that of the OTFTs with vacuum-evaporated films because the one-dimensional thin crystals of the flow-coated films were aligned in the flow-coating direction.

探針増強ラマン分光測定中のヘリセンジアルデヒド分子の脱水素反応観察

高山正浩, チャウンチャイヤクルソンポル, セティアディアグン, クルコスキーパウエル, 赤井恵, 齋藤彰, 大須賀秀次, 桑原裕司

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2017 ( 0 ) 791 - 792 2017年

ナノスケールでの振動分光分析を可能にする探針増強ラマン分光法において観測されるシグナル強度の明滅現象は、孤立単分子由来のスペクトルの正確な解釈を困難にしている。本現象の解明のため、我々は金(111)基板上に自己組織化したヘリセンジアルデヒド分子についてSTM探針増強ラマン分光計測を行った。今回は、ラマン分光計測中の特異な化学反応について報告する。

Self-Assembly Formation of M‑Type Enantiomer of 2,13-Bis(hydroxymethyl)[7]-thiaheterohelicene Molecules on Au(111) Surface Investigated by STM/CITS

Songpol Chaunchaiyakul, Pawel Krukowski, Takuro Tsuzuki, Yuto Minagawa, Megumi Akai-Kasaya, Aldra Saito, Hideji Osuga, Yuji Kuwahara

The Journal of Physical Chemistry C ( AMER CHEMICAL SOC ) 119 ( 37 ) 21434 - 21442 2015年09月 [査読有り]

Adsorption of the M-type enantiomer of 2,13-bis(hydroxymethyl[7]-thiaheterohelicene molecules deposited on Au(111) was investigated by scanning tunneling microscopy (STM) and current imaging tunneling spectroscopy (CITS). We observed. preferential adsorption at step edges, fcc regions, and fcc elbow regions of the herringbone reconstruction at a low coverage after molecular deposition onto a substrate maintained at 150 +/- 20 K. Surprisingly, after molecular deposition onto a substrate maintained at 355 +/- 20 K, highly ordered islands exhibiting molecular self-assembly surrounded by disordered areas were observed. The islands consist of self-assembled zigzagged twin rows with the preferential direction tilted clockwise and anticlockwise from the < 1.1 (2) over bar > direction of the Au(111) substrate by an angle of 12 +/- 2 degrees. A detailed statistical analysis of the twin rows indicated that the unit cell lattice vectors a and b have lengths of 2.4 and 4.4 nm, respectively, with an angle between them of 77 degrees. We postulate an adsorption model without hydrogen bond formation between the hydroxyl groups of neighboring molecules or a strong pi-pi stacking interaction. We emphasize the advantages of this molecular system investigated for STM-induced luminescence experiments in the near future.

Evaluation of Stretching Properties of [7]Thiaheterohelicene Framework Called “Molecular Spring” Using AFM Force Measurements and Electrostatic State Calculations

Yoshio Nakahara, Minako Higashi, Ryoto Funayama, Yasuo Horii, Hideji Osuga, Hidefumi Sakamoto, Masato Oda, Shinpei Kado, Keiichi Kimura

Bulletin of the Chemical Society of Japan ( CHEMICAL SOC JAPAN ) 88 ( 4 ) 544 - 550 2015年04月 [査読有り]

The stretching properties of a [7]thiaheterohelicene framework, what we call molecular spring, have not been investigated so far, despite a variety of [7]thiaheterohelicene derivatives having very interesting characteristics due to both the rigidity arising from fused benzene rings and the flexibility like a spring originating from helical structure. In this study, a novel [7]thiaheterohelicene derivative, which has a disulfide moiety for bonding to a gold-coated substrate and a carboxy group for reacting with an amino-modified probe tip at each of its end groups, was synthesized in order to elucidate the elasticity of the [7]thiaheterohelicene framework by atomic force microscopy (AFM). The AFM force measurements were carried out using two carboxy-terminated disulfide derivatives with or without a [7]thiaheterohelicene moiety, and the deviation between two kinds of force-extension curves was related to the stretching originating from the [7]thiaheterohelicene framework here. Furthermore, its elasticity was compared to that of biphenyl, which is generally known as a rigid framework, using electrostatic state calculations.

キラル分子による金(111)表面上での分子アセンブリ形成と、キラル分子認識

桑原裕司, Krukowski Pawel, 都築拓朗, 皆川佑人, Chaunchaiyakul Songpol, 赤井恵, 齋藤彰, 大須賀秀次

精密工学会学術講演会講演論文集 ( 公益社団法人精密工学会 ) 2014 ( 0 ) 775 - 776 2014年

生体分子系を構成する有機分子はすべてキラルである。生体は、必ず右手系か左手系のどちらかのキラル分子（エナンチオマー）を活用しており、そのため、キラル分子間の相互作用は、さまざまな生体機能のもととなっている。本研究では、表面上で自己組織化したヘリセン分子の分子間相互作用を評価するため、STM、STSの詳細に分析し、キラル分子認識に関する情報を得た。

Growth of pentacene crystallinity control layers for high mobility organic field-effect transistors based on benzodithiophene-dimer films

Tomoya Sakai, Y. Matsumoto, K. Shibamoto, H. Osuga, K. Uno, Ichiro Tanaka

JOURNAL OF CRYSTAL GROWTH ( ELSEVIER SCIENCE BV ) 378 347 - 350 2013年09月 [査読有り]

We have investigated the growth process of benzodithiophene (BDT)-dimer films deposited on similar to 1.1-monolayer-thick pentacene layers used as crystallinity control layers (CCLs). It has been found that the BDT-dimer film shows, on their initial stage, two-dimensional growth with the 2nd-layer pentacene islands of the CCLs working as the growth nuclei. Thus, we considerably reduced the density of the 2nd-layer pentacene islands of the CCLs by lowering their growth rate because the density is determined by the migration length of the pentacene molecules on the surfaces. As a result, we obtained BDT-dimer films consists of enlarged grains, and lowered the channel resistance of the pentacene-CCL/BDT-dimer FETs. (c) 2013 Elsevier B.V. All rights reserved.

Investigation of yellow emission from a co-polymer utilizable as an emitting material for white OLED

Akimoto, I.; Uzawa, H.; Hinatsu, M.; Nishide, Y.; Osuga, H.; Sakamoto H.

Physics Procedia 29 46-49 2012年01月

Complexation and fluorescence behavior of a copolymer bearing azacrown ether and anthracene moieties

Hidefumi Sakamoto, Tomohiro Anase, Hideji Osuga, Keiichi Kimura

Reactive and Functional Polymers 71 ( 5 ) 569 - 573 2011年05月 [査読有り]

Copolymers bearing azacrown ether and anthracene moieties were synthesized using methacrylates of N-2-ethyl-azacrown ether or 9-hydroxymethylanthracene. Their fluorescence behaviors in the presence of alkali metal ions were measured in THF:H2O = 10:1 solution. Maximum fluorescence intensities for copolymers bearing aza-12-crown-4, 15-crown-5 and 18-crown-6 were observed for with Na+, K+ and K+, respectively. The largest change in fluorescence behavior was observed for the copolymer bearing aza-18-crown-6 in the presence of K+. The magnitude of the increase in the fluorescence intensity was related to the content of the crown ether moiety. The time-dependent changes in the fluorescence spectra using photo-irradiation were also investigated. Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved.

Origin of yellow emission in white OLED with single emitting material

Ikuko Akimoto, Sayaka Tsuzuki, Hidetoshi Uzawa, Masako Hinatsu, Yosuke Nishide, Hideji Osuga, Hidefumi Sakamoto

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 1 ( WILEY-V C H VERLAG GMBH ) 8 ( 1 ) 2011年 [査読有り]

The photo-luminescence (PL) and electro-luminescence (EL) of a novel organic material, benzodithiophene/triphenylamine copolymer (P-PBTx, n=5-6) were investigated. The PL exhibited wide blue emission at room temperature, which is attributed to fluorescence from a chromophore, benzodithiophene moiety, from results of spectral analysis and decay profile. The EL, however, exhibited white emission consisting of wide blue (B) and yellow (Y) bands, although it was prepared with P-PBTx as a single emitting material. The Y-band was slightly observed at 7 K and found to possess long lived component of 19 ms lifetime. The origin of the Y-band efficiently stimulated by carrier injection is supposed to be a charge-transfer state between benzodithiophene and triphenylamine moieties. The long lived component could be explained by lowered transition probability caused by charge separation. (c) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A Chiral Wedge Molecule Inhibits Telomerase Activity

Ken-ichi Shinohara, Yuta Sannohe, Shuji Kaieda, Ken-ichi Tanaka, Hideji Osuga, Hidetoshi Tahara, Yan Xu, Takashi Kawase, Toshikazu Bando, Hiroshi Sugiyama

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY ( AMER CHEMICAL SOC ) 132 ( 11 ) 3778 - 3782 2010年03月 [査読有り]

In addition to the Watson-Crick double helix, secondary DNA structures are thought to play important roles in a variety of biological processes. One important example is the G-quadruplex structure that is formed at the chromosome ends, which inhibits telomerase activity by blocking its access to telomeres. G-quadruplex structures represent a new class of molecular targets for DNA-interactive compounds that may be useful to target telomeres. Here, we reported the first example of enantioselective recognition of quadruplex DNA by a chiral cyclic helicene. We propose a new ligand-binding cleft between two telomeric human G-quadruplexes linked by a TTA linker. We found that the cyclic helicene M1 exhibited potent inhibitory activity against telomerase.

Highly silver ion selective fluorescence ionophore: Fluorescent properties of polythiazaalkane derivatives bearing 8-(7-hydroxy-4-methyl)coumarinyl moiety in aqueous solution and in liquid-liquid extraction systems

Hidefumi Sakamoto, Junichi Ishikawa, Hideji Osuga, Kunio Doi, Hiroko Wada

Analyst 135 ( 3 ) 550 - 558 2010年 [査読有り]

Two novel fluoroionophores, N-(7-hydroxy-4-methylcoumarin-8-ylmethyl)-3,9- dithia-6-azaundecane (1) and N-(7-hydroxy-4-methylcoumarin-8-ylmethyl)-3,9- dithia-6-azaundecane (2), were synthesized as fluorescence extractants for selective silver determination. The absorption and fluorescence spectra were measured in aqueous 1,4-dioxane solution (28 v/v%) in the absence and presence of silver ion, and their acid dissociation constants were determined from the pH-dependent spectral changes. In the liquid-liquid extraction of some metal ions from neutral aqueous solution into dichloromethane phase, compounds 1 and 2 exhibited excellent silver ion selectivity, and dramatic fluorescence spectral changes were observed in the dichloromethane solutions containing these compounds. The determination limit of 2 for silver ion was 2.0 × 10 -8 mol dm-3 in the liquid-liquid extraction. © 2010 The Royal Society of Chemistry.

Development of a High-Performance Liquid Chromatography Method to Determine the Fagopyrin Content of Tartary Buckwheat (Fagopyrum tartaricum Gaertn.) and Common Buckwheat (F-esculentum Moench)

Kentaro Eguchi, Tomohiro Anase, Hideji Osuga

PLANT PRODUCTION SCIENCE ( CROP SCIENCE SOC JAPAN ) 12 ( 4 ) 475 - 480 2009年10月 [査読有り]

Buckwheat contains fagopyrin, which induces photosensitization in light-skinned livestock Mien exposed to sunlight. Here, we developed a high-performance liquid chromatography (HPLC) method to measure the fagopyrin content: of buckwheat.. The HPLC profile Of the fagopyrin extract purified from Tartary buckwheat 'Rotundatum' had 3 apparent, peaks. The Ultraviolet-visible (UV-vis) absorption spectrum of each peak yielded absorbance maxima (lambda(max)) at 547 nm and 591 inn, indicating that these peaks corresponded to fagopyrin and unidentified fagopyrin derivatives. We considered the total Content reflected by the 3 peaks to be the fagopyrin content of buckwheat. We determined the fagopyrin content in the leaves of Tartary buckwheat 'Rotundatum' and common buckwheat 'Miyazakiootsubu' both by UV-vis photometric analysis and the newly developed HPLC method. The fagopyrin content is overestimated by UV-vis photometry because the extracts; contain a considerable amount of chlorophyll. Thus, HPLC analysis is more efficacious for fagopyrin-content measurements than UV-vis photometric analysis. The HPLC analysis of fagopyrin is easy, quick and efficacious for screening buckwheat varieties with trace or no fagopyrin. There are only a few reports on the accumulation sites of fagopyrin in buckwheat. We revealed that in Tartary and common buckwheat., fagopyrin is present mainly in the leaves and flowers and slightly in the stems, hulls, and groats. The fagopyrin contents of the leaves and flowers of Rotundatum were approximately 2.6 and 2.8 times higher than those in Miyazakiootsubu, respectively.

Carrier transport in benzodithiophene-dimer field-effect transistors with pentacene crystallinity control layers

Y. Matsumoto, S. Takamiya, A. Kurokawa, H. Osuga, K. Uno, Ichiro Tanaka

APPLIED PHYSICS LETTERS ( AMER INST PHYSICS ) 94 ( 20 ) 203305 2009年05月 [査読有り]

The carrier transport in the benzodithiophene (BDT)-dimer films plays significant role for high carrier mobility of BDT-dimer field-effect transistors (FETs) using very thin pentacene layers as crystallinity control layers (CCLs). When the grains of the BDT-dimer films are small, the carrier mobility is not only low but also depends on the average thickness of the pentacene-CCLs. However, it is independent from the thickness of the CCLs when the grain size of the BDT-dimer films is large enough, and becomes as high as 0.76 cm(2) V(-1) s(-1). This result shows that the high carrier mobility of pentacene-CCL/BDT-dimer FETs is due to the carrier transport in the BDT-dimer films.

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