Faculty Profiles - NAKAHARA Yoshio

Published Papers - NAKAHARA Yoshio

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多波長励起光を備えた光熱変換顕微鏡による水中でのチオリンゴ酸修飾銀ナノ粒子の凝集挙動の定量評価

中原佳夫, 宮崎淳, 廣野碧唯, 家永隆史, 矢嶋摂子（Part： Lead author,　Corresponding author )

分析化学 74 ( 1-2 ) 23 - 28 2025.01 [Refereed]

Polydopamine-Coated Solid Silica Nanoparticles Encapsulating IR-783 Dyes: Synthesis and NIR Fluorescent Cell Imaging

Yoshio Nakahara, Haruki Nakabayashi, Jun Miyazaki, Mitsuru Watanabe, Toshiyuki Tamai, Setsuko Yajima （Part： Lead author,　Corresponding author )

ACS Omega 9 19932 - 19939 2024.04 [Refereed]

Properties of surface layers of polyethylene naphthalate substrates modified by ultraviolet light irradiation for their electroless deposition

Toshiyuki Tamai, Mitsuru Watanabe, Rie Kakehashi, Yoshio Nakahara, Setsuko Yajima

Colloid and Polymer Science 302 433 - 448 2024.04 [Refereed]

The properties of thin surface layers of polymer substrates should be investigated and controlled for their application in electroless deposition. In this paper, polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) substrates were modified by plasma treatment, ultraviolet (UV)/ozone treatment, or UV (254 nm) irradiation. The chemical and physical properties of the modified layer were studied by measuring contact angle and zeta potential, field-emission scanning electron microscope (FE-SEM) imaging, and infrared spectroscopy. The condition of the surface modification affected oxygenation of the polymer chains. The oxygenation formed hydrophilic surface functional groups and relatively polar low-molecular-weight fragments resulting from the scission of the polymer chains. The surface functional groups and the fragments governed the properties of the modified layer. Adhesive metal films were electrolessly deposited on the thinner modified layer having the hydrophilic functional groups. In contrast, the thicker modified layer containing the fragments decreased the adhesion of the metal films. For example, UV/ozone treatment of the PEN substrate formed the thicker modified layer, on which no adhesive metal films were deposited. These findings illustrate that optimizing the condition of the surface modification thoroughly is feasible to form the modified layer having the chemical and physical properties appropriate for depositing adhesive metal films.

Polysilsesquioxane Gate Dielectric Layers Cured by Ultra‐Violet Light Irradiation Using Thiol‐Ene Reaction for Organic Thin‐Film Transistors

Yoshio Nakahara, Ken-ichiro Yamane, Tomoaki Nakagami, Kazuyuki Uno, Ichiro Tanaka （Part： Lead author,　Corresponding author )

physica status solidi (a) ( Wiley ) 2200895 2023.04 [Refereed]

Quantitative Discrimination of Silver and Gold Nanoparticles Immobilized in Transparent Plastic Film by Photothermal Microscopy with Multiwavelength Excitation

Yoshio Nakahara, Jun Miyazaki, Aoi Hirono, Takashi Ienaga, Setsuko Yajima （Part： Lead author,　Corresponding author )

Chemistry Letters 52 ( 2 ) 113 - 115 2023.02 [Refereed]

Fluorescent sensing with nanoparticles

Yoshio Nakahara （Part： Lead author,　Last author,　Corresponding author )

Analytical Sciences 38 ( 11 ) 1369 - 1370 2022.11 [Refereed]

Influencing foam properties of aqueous bis(2-ethylhexyl)sulfosuccinate solutions by addition of polypropylene-glycol-modified and amino-modified silica nanoparticles

Keita Aono, Hiroya Shiba, Furitsu Suzuki, Yoshihiro Yomogida, Motomitsu Hasumi, Shinpei Kado, Yoshio Nakahara, Setsuko Yajima

Colloids and Surfaces A: Physicochemical and Engineering Aspects 655 130228 2022.09 [Refereed]

Room-temperature coalescence of Pd nanoparticles with sacrificial templates and sintering agents, and their catalytic activities in the Suzuki coupling reaction.

Soichiro Okada, Yoshio Nakahara, Mitsuru Watanabe, Toshiyuki Tamai, Yasuyuki Kobayashi, Setsuko Yajima （Part： Corresponding author )

RSC Advances 12 14535 - 14543 2022.05 [Refereed]

Synthesis of Silica Nanoparticles with Physical Encapsulation of Near-Infrared Fluorescent Dyes and Their Tannic Acid Coating

Yoshio Nakahara, Yukiho Nakajima, Soichiro Okada, Jun Miyazaki, Setsuko Yajima （Part： Lead author,　Corresponding author )

ACS Omega ( American Chemical Society (ACS) ) 6 ( 27 ) 17651 - 17659 2021.07 [Refereed]

Relationship between air-water interfacial dilational viscoelasticity and foam property in aqueous solutions of sodium alkylsulfates with different hydrocarbon chains

Keita Aono, Furitsu Suzuki, Yoshihiro Yomogida, Tetsuya Okano, Shinpei Kado, Yoshio Nakahara, Setsuko Yajima

JOURNAL OF DISPERSION SCIENCE AND TECHNOLOGY ( TAYLOR & FRANCIS INC ) 42 ( 8 ) 1218 - 1224 2021.06 [Refereed]

The influence of alkyl chain structures in sodium alkylsulfates (ASs) on their rheological properties was investigated in this study. Dilational viscoelasticity at the air-water interface, dynamic surface tension, and foam property were quantitatively evaluated in aqueous solutions of ASs with different hydrocarbon chains, and the relationship was systematically discussed. The experimental results show that the alkyl chain plays an important role in the interfacial dilational properties. For ASs with straight alkyl chains, AS with the longer alkyl chain showed the maximum value of the interfacial dilational viscoelasticity at the lower concentration. The longer the alkyl chain of AS was the larger the maximum value of the interfacial dilational viscoelasticity was. The frequency dependence of the interfacial dilational viscoelasticity was confirmed only in the range of high surfactant concentrations, suggesting that the interfacial relaxation process is mainly controlled by the diffusion of the surfactants. As for the relationship between interfacial dilational viscoelasticity and foam property, it was found that the maximum value of the interfacial dilational viscoelasticity was correlated with the foam stability under the conditions.

Room-Temperature Coalescence of Tri-n-Octylphosphine-Oxide-Capped Cu-Ag Core-Shell Nanoparticles: Effect of Sintering Agent and/or Reducing Agent

Soichiro Okada, Yoshio Nakahara, Mitsuru Watanabe, Toshiyuki Tamai, Yasuyuki Kobayashi, Setsuko Yajima （Part： Corresponding author )

Bulletin of the Chemical Society of Japan 94 ( 5 ) 1616 - 1624 2021.06 [Refereed]

Room-Temperature Coalescence of Tri-n-Octylphosphine-Oxide-Capped Cu-Ag Core-Shell Nanoparticles: Effect of Sintering Agent and/or Reducing Agent

Soichiro Okada, Yoshio Nakahara, Mitsuru Watanabe, Toshiyuki Tamai, Yasuyuki Kobayashi, Setsuko Yajima

Bulletin of the Chemical Society of Japan 64 ( 5 ) 1616 - 1624 2021.05 [Refereed]

Metal nanoparticle pastes are useful for nanoinks to form fine conductive patterns in printed electronics. This study reports a novel method for room-temperature coalescence of Cu-Ag core-shell nanoparticles (Cu@Ag NPs), which are expected to have the properties of both migration and oxidation resistance originating from Cu and Ag, respectively. First, oleylamine/oleic-acid capped Cu@Ag NPs were synthesized by the galvanic replacement method. Second, the ligand exchange reaction to tri-n-octylphosphine oxide (TOPO) was carried out on the surface of Cu@Ag NPs. Finally, TOPOcapped Cu@Ag NPs were dipped into methanol containing a sintering agent and/or a reducing agent. When HCl was added as a sintering agent to methanol, the crystallite size of Cu@Ag NPs significantly increased. Furthermore, the almost complete removal of organic compounds and suppression of significant oxidation of Ag and Cu were observed. In consideration of these results, a Cu/Ag conductive thin film was prepared from TOPO-capped Cu Ag NPs by dipping into methanol containing HCl at room temperature under air atmosphere. Electrical resistivity of the obtained Cu/Ag thin film was (5.1 « 1.7).

Foam Destabilization Effect of Sodium Bis(2-ethylhexyl)sulfosuccinate on Sodium Alkylsulfate Aqueous Solutions Based on Its Fast Surface Tension Gradient Relaxation

Keita Aono, Furitsu Suzuki, Yoshihiro Yomogida, Motomitsu Hasumi, Shinpei Kado, Yoshio Nakahara, Setsuko Yajima

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( The Chemical Society of Japan ) 94 ( 2 ) 542 - 548 2021.02 [Refereed]

Investigation of Photo-Initiators for Ultra-Violet Light Cured Polysilsesquioxane Gate Dielectric Layers of Organic Thin Film Transistors

秦野航輔, 中原佳夫, 宇野和行, 田中一郎

材料 69 ( 10 ) 712 - 716 2020.10 [Refereed]

Effects of Polypropylene Glycol at Very Low Concentrations on Rheological Properties at the Air–Water Interface and Foam Stability of Sodium Bis(2-ethylhexyl)sulfosuccinate Aqueous Solutions

Keita Aono, Furitsu Suzuki, Yoshihiro Yomogida, Motomitsu Hasumi, Shinpei Kado, Yoshio Nakahara, Setsuko Yajima

Langmuir ( American Chemical Society (ACS) ) 36 ( 34 ) 10043 - 10050 2020.09 [Refereed]

Preparation of Ag2Se QDs with excellent aqueous dispersion stability by organic coating with aqueous ATRP

Nakahara Yoshio, Kunitsu Yuki, Ozaki Nobuhiko, Tanaka Mutsuo, Yajima Setsuko （Part： Lead author,　Corresponding author )

POLYMER BULLETIN ( Springer Science and Business Media LLC ) 76 ( 9 ) 4753 - 4768 2019.09 [Refereed]

Surface modification of polyethylene naphthalate substrates by ultraviolet light-irradiation and assembling multilayers and their application in electroless deposition: The chemical and physical properties of the stratified structure

T. Tamai, M. Watanabe, Y. Kobayashi, J. Kobata, Y. Nakahara, S. Yajima

Colloids and Surfaces A: Physicochemical and Engineering Aspects 575 230 - 236 2019.08 [Refereed]

© 2019 Elsevier B.V. Electroless metal deposition on polymer surface is useful for fabricating metallic patterns. The surfaces of polyethylene naphthalate (PEN) substrates were modified by ultraviolet (UV) light -irradiation and layer-by-layer assembly of polyelectrolyte multilayer thin films, and then nickel and copper films were electrolessly deposited on the substrate surfaces to form the stratified structure, PEN-substrate/multilayer/metal-film. The chemical and physical properties of the modified layer in the substrate surfaces were studied by X-ray photoelectron spectroscopy, nanoindentation test, and measuring contact angle. The properties of the UV-irradiated surface layer depended on the condition of surface modification and affected the adhesion of the deposited metal film. Adhesive nickel films were deposited on the UV (254 nm)-irradiated PEN substrates that have thin modified layers compatible with the multilayers. In contrast, no adhesive nickel films were deposited on the substrate surfaces having thicker and fragile modified layers. These contrasting results are originated from the oxygenation and crosslinking of the polymer chains in the substrate surface layers, and reactive species formed by the UV irradiation induce the oxygenation and crosslinking. The properties of the modified substrate-surface play an important role for depositing adhesive metal films.

Crystallite Size Increase of Silver Nanoparticles by Ligand Exchange and Subsequent Washing Process with Antisolvent

Okada Soichiro, Nakahara Yoshio, Watanabe Mitsuru, Tamai Toshiyuki, Yajima Setsuko （Part： Corresponding author )

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 19 ( 8 ) 4565 - 4570 2019.08 [Refereed]

Room-Temperature Sintering of Tri-n-Octylphosphine-Oxide-Capped Silver Nanoparticle Paste by Dipping into an Organic Solvent Containing a Sintering Agent

Okada Soichiro, Nakahara Yoshio, Watanabe Mitsuru, Tamai Toshiyuki, Kobayashi Yasuyuki, Yajima Setsuko （Part： Corresponding author )

JOURNAL OF PHYSICAL CHEMISTRY C ( American Chemical Society (ACS) ) 123 ( 23 ) 14118 - 14125 2019.06 [Refereed]

A tetraester derivative of fluorescent calix[4]arene bearing a proton-ionizable moiety for highly sensitive extraction-fluorometric determination of sodium ion

Yoshio Nakahara, Yuta Furuno, Hitoshi Iwamoto, Setsuko Yajima, Keiichi Kimura （Part： Lead author,　Corresponding author )

Supramolecular Chemistry ( Taylor and Francis Ltd. ) 30 ( 8 ) 697 - 705 2018.08 [Refereed]

In this study, we report the highly sensitive extraction-fluorometric detection system of Na+ using flow injection analysis with a tetraester derivative of fluorescent calix[4]arene. In liquid-liquid extraction experiments, the fluorescent intensity of calix[4]arene derivative 1 bearing a p-nitrophenol moiety was highly dependent on pH and the Na+ concentration in the aqueous phase. On the other hand, such phenomenon was not observed in the case of calix[4]arene derivative 2, which is almost the same structure as 1 except for a p-nitrophenol moiety. These results show that the proton dissociation of the p-nitrophenol moiety decisively affects the fluorescence intensity of 1. Owing to these fluorescence responsiveness, a calibration graph of the Na+ concentration could be successfully prepared using flow injection analysis with good linearity at the tens of nanomolar level. The tetraester scaffold of calix[4]arene was essential to the detection of Na+ in such a very low concentration range.

Ester-free cross-linker molecules for ultraviolet-light-cured polysilsesquioxane gate dielectric layers of organic thin-film transistors

Shuichi Okada, Yoshio Nakahara, Kazuyuki Uno, Ichiro Tanaka

Japanese Journal of Applied Physics ( Japan Society of Applied Physics ) 57 ( 4 ) 2018.04 [Refereed]

Pentacene thin-film transistors (TFTs) were fabricated with ultraviolet-light (UV)-cured polysilsesquioxane (PSQ) gate dielectric layers using cross-linker molecules with or without ester groups. To polymerize PSQ without ester groups, thiol-ene reaction was adopted. The TFTs fabricated with PSQ layers comprising ester-free cross-linkers showed a higher carrier mobility than the TFTs with PSQ layers cross-linked with ester groups, which had large electric dipole moments that limited the carrier mobility. It was demonstrated that the thiol-ene reaction is more suitable than the conventional radical reaction for UV-cured PSQ with small dielectric constant.

Near-Infrared Dye Immobilized in Porous Silica Layer on Gold Nanorod and Its Fluorescence Enhancement by Strengthened Electromagnetic Field Based on Surface Plasmon Resonance

Yoshio Nakahara, Ryoko Takeda, Toshiyuki Tamai, Setsuko Yajima, Keiichi Kimura （Part： Lead author,　Corresponding author )

Plasmonics ( Springer New York LLC ) 13 ( 2 ) 645 - 652 2018.04 [Refereed]

We report immobilizing Nile Blue A, which is a cationic fluorescent dye emitting in the near-infrared region, in the porous silica layer on gold nanorod and its fluorescence enhancement by strengthened electromagnetic field based on surface plasmon resonance. The effect of the spacer corresponding to the silica layer on the metal-enhanced fluorescence effect is also discussed in detail. Hollow silica nanorod was in advance prepared, and then the silica layer was partly etched to increase the porosity for the improvement of the mass transfer. Subsequently, gold nanorod was fabricated in the restricted space of hollow silica nanorod. Finally, Nile Blue A was physically immobilized in the porous silica layer on gold nanorod through electrostatic interactions. The fluorescence enhancement of Nile Blue A based on surface plasmon resonance was semi-quantified by comparative experiments using hollow silica nanorod, which is exactly the same structure except for gold as silica-coated gold nanorod. Since our results demonstrated that the porosity degree of the silica layer significantly affected the fluorescence enhancement of Nile Blue A, it is hopeful that our design concept, distinct from the conventional one, can lay a foundation for further development of near-infrared fluorescence nanomaterials.

Effect of Protective Agents on Silver Nanoparticle Preparation by Vacuum Evaporation on Running Hydrocarbon Solution

Ienaga Takashi, Nakahara Yoshio, Yajima Setsuko, Kimura Keiichi （Part： Corresponding author )

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 18 ( 4 ) 2547 - 2554 2018.04 [Refereed]

Comparison of Physical Adsorption Strength of Protective Agents via Ligand Exchange of Silver Nanoparticles Prepared by Vacuum Evaporation on Running Oil Substrate (vol 90, pg 1251, 2017)

Ienaga Takashi, Okada Soichiro, Nakahara Yoshio, Watanabe Mitsuru, Tamai Toshiyuki, Yajima Setsuko, Kimura Keiichi

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 91 ( 3 ) 506 2018.03 [Refereed]

Comparison of Physical Adsorption Strength of Protective Agents via Ligand Exchange of Silver Nanoparticles Prepared by Vacuum Evaporation on Running Oil Substrate

Takashi Ienaga, Soichiro Okada, Yoshio Nakahara, Mitsuru Watanabe, Toshiyuki Tamai, Setsuko Yajima, Keiichi Kimura （Part： Corresponding author )

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( CHEMICAL SOC JAPAN ) 90 ( 11 ) 1251 - 1258 2017.11 [Refereed]

We compared adsorption strength of protective agents via ligand exchange of silver nanoparticles synthesized by the improved vacuum evaporation on running oil substrate (VEROS) method. This comparison concerns physical adsorption of protective agents on the surface of silver nanoparticles instead of chemisorption. Clean surfaces of silver nanoparticles synthesized by the improved VEROS method were suitable for this investigation. All the experiments in this study were designed so that as far as possible protective agents did not ionize. Thus, oleic acid capped silver nanoparticles were synthesized by the improved VEROS method. Next, octanoic acid, n-octylamine and oleic acid were used as additive protective agents in ligand exchanges. The ligand exchange is also closely related to physical adsorption strength of protective agents on the surface of metal nanoparticles. Oleic acid on the surface of silver nanoparticles was exchanged by octanoic acid and vice versa under the same experimental conditions. On the other hand, oleic acid on the silver surface was not exchanged by n-octylamine. These results were remarkably different from those reported in general chemical synthetic methods but they were well consistent with our previous study on performance of protective agents in the synthesis of silver nanoparticles with the improved VEROS method.

Improving the carrier mobility of pentacene thin film transistors by surface flattened polysilsesquioxane gate dielectric layers

Daisuke Michiura, Yoshio Nakahara, Kazuyuki Uno, Ichiro Tanaka

Zairyo/Journal of the Society of Materials Science, Japan ( Society of Materials Science Japan ) 66 ( 9 ) 644 - 647 2017.09 [Refereed]

The surface flatness of photo-curable polysilsesquioxane (PSQ) films for gate dielectric layers of pentacene thin film transistors (TFTs) was considerably improved by ultra-violet light (UV)/O3 treatment
the root-mean-squared (RMS) roughness was improved from 0.35 to 0.23 nm after 40-minute treatment. However, the PSQ surfaces became hydrophilic because hydroxyl groups, which degraded transistor performances, replaced the organic functional groups such as methyl groups by the UV/O3 treatment. Therefore, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) treatment was successively performed after the UV/O3 treatment to replace the hydroxyl groups with hydrophobic silyl groups. It was found that four-hour HMDS treatment under dry nitrogen was enough to reduce off current of pentacene TFTs. As a result, the carrier mobility of the pentacene TFT fabricated with UV/O3 and HMDS-treated PSQ layers became 0.59 cm2V-1s-1, which was more than seven times higher than that of the pentacene TFTs with untreated PSQ layers.

Surface modification of PEN and PET substrates by plasma treatment and layer-by-layer assembly of polyelectrolyte multilayer thin films and their application in electroless deposition

T. Tamai, M. Watanabe, Y. Kobayashi, Y. Nakahara, S. Yajima

RSC ADVANCES ( ROYAL SOC CHEMISTRY ) 7 ( 53 ) 33155 - 33161 2017 [Refereed]

The surfaces of the polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) substrates were modified by plasma treatment and then layer-by-layer (LbL) assembly of polyelectrolyte multilayer thin films from two oppositely charged polyelectrolytes. Negatively or positively charged palladium complex ions bound to oppositely charged multilayer surfaces and were reduced to form palladium nanoparticles and then a nickel film was electrolessly deposited on the substrate surfaces. The multilayers on PEN and PET substrate surfaces are suitable for supporting palladium nanoparticle catalysts and their properties can be controlled by the conditions of LbL assembly.

Improving the carrier mobility of pentacene thin film transistors by surface treatment of polysilsesquioxane gate dielectric layers

Daisuke Michiura, Yoshio Nakahara, Kazuyuki Uno, Ichiro Tanaka

Zairyo/Journal of the Society of Materials Science, Japan ( Society of Materials Science Japan ) 65 ( 9 ) 652 - 655 2016.09 [Refereed]

We improved the carrier mobility of the pentacene thin film transistors (TFT), which were fabricated with polysilsesquioxane (PSQ) gate dielectric layers, from 0.082 to 0.31 cm2V-1s-1 by treating the PSQ surface with ultra-violet irradiation (UV)/O3 and 1,1,1,3,3,3-hexamethyldisilazane (HMDS). It was found that the PSQ layers were flattened by the UV/O3 treatment, and the PSQ surface became hydrophilic at the same time because the organic functional groups on the PSQ surface were changed to hydroxyl groups. The grains of the pentacene films deposited on the UV/O3-treated PSQ surfaces were found to be as large as a few microns. However, the carrier mobility of the pentacene TFTs was not so much improved as expected from the largely grown pentacene grains probably because the hydroxyl groups scattered the charged carriers. In addition, the off-current of the pentacene TFTs increased by 4 orders of magnitude. It is thus considered that the hydroxyl groups also worked as hopping sites for the increased off-current which flew without the gate voltage. On the other hand, the carrier mobility of the pentacene TFTs fabricated with the PSQ dielectric layers of which surfaces were treated with UV/O3 and HMDS became ∼4 times larger than that without any surface treatment of the PSQ layers, and also the off-current decreased by 3 orders of magnitude because the hydroxyl groups were changed with silyl groups by the HMDS treatment.

Investigation of Ultraviolet Light Curable Polysilsesquioxane Gate Dielectric Layers for Pentacene Thin Film Transistors

Hideto Shibao, Yoshio Nakahara, Kazuyuki Uno, Ichiro Tanaka

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY ( AMER SCIENTIFIC PUBLISHERS ) 16 ( 4 ) 3327 - 3331 2016.04 [Refereed]

Polysilsesquioxane (PSQ) comprising 3-methacryloxypropyl groups was investigated as an ultraviolet (UV)-light curable gate dielectric material for pentacene thin film transistors (TFTs). The surface of UV-light cured PSQ films was smoother than that of thermally cured ones, and the pentacene layers deposited on the UV-light cured PSQ films consisted of larger grains. However, carrier mobility of the TFTs using the UV-light cured PSQ films was lower than that of the TFTs using the thermally cured ones. It was shown that the cross-linker molecules, which were only added to the UV-light cured PSQ films, worked as a major mobility-limiting factor for the TFTs.

High-Mobility 6,13-Bis(triisopropylsilylethynyl) Pentacene Transistors Using Solution-Processed Polysilsesquioxane Gate Dielectric Layers

Yu Matsuda, Yoshio Nakahara, Daisuke Michiura, Kazuyuki Uno, Ichiro Tanaka

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY ( AMER SCIENTIFIC PUBLISHERS ) 16 ( 4 ) 3273 - 3276 2016.04 [Refereed]

Polysilsesquioxane (PSQ) is a low-temperature curable polymer that is compatible with low-cost plastic substrates. We cured PSQ gate dielectric layers by irradiation with ultraviolet light at similar to 60 degrees C, and used them for 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) thin film transistors (TFTs). The fabricated TFTs have shown the maximum and average hole mobility of 1.3 and 0.78 +/- 0.3 cm(2)V(-1)s(-1), which are comparable to those of the previously reported transistors using single-crystalline TIPS-pentacene micro-ribbons for their active layers and thermally oxidized SiO2 for their gate dielectric layers. It is therefore demonstrated that PSQ is a promising polymer gate dielectric material for low-cost organic TFTs.

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 （Part： Lead author )

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( CHEMICAL SOC JAPAN ) 88 ( 4 ) 544 - 550 2015.04 [Refereed]

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.

Synthesis of Spherical SiO2@TiO2 Core-Shell Nanoparticles with Anatase-Type Crystallinity and High Aqueous Dispersibility and Their Photocatalytic Properties

Yoshio Nakahara, Masahiro Hayashizaki, Mitsuru Watanabe, Toshiyuki Tamai, Keiichi Kimura （Part： Lead author )

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( CHEMICAL SOC JAPAN ) 88 ( 1 ) 133 - 138 2015.01 [Refereed]

Up to date, the development of TiO2 nanoparticles with well-defined morphology, crystallinity, and high solvent dispersibility has been still a big challenge. In this study, monodisperse and spherical SiO2@TiO2 core shell nanoparticles, whose diameter was 20.7 +/- 2.7 nm, with anatase-type crystallinity and high aqueous dispersibility were fabricated by a simple and facile method combing a sol gel reaction using tetrabutyl orthotitanate as a precursor in the presence of colloidal SiO2 nanoparticles and a very mild crystallization process of the TiO2 layer. Transmission electron microscope measurements showed that the size and shape of the obtained core shell nanoparticles were considerably uniform. The anatase crystallinity of the TiO2 layer on the particle surface was endowed by heating at 100 degrees C in the acidic aqueous solution under atmospheric pressure. Also, they maintained high aqueous dispersibility even after the crystallization process. Most importantly, their photocatalytic ability towards methylene blue was comparable to that of commercially available pure TiO2 nanoparticles. The SiO2@TiO2 core shell nanoparticles developed in this study are highly expected to be membranous materials for very thin TiO2 films due to their high aqueous dispersibility and shape homogeneity.

Fluorescent silica nanoparticles modified chemically with terbium complexes as potential bioimaging probes: their fluorescence and colloidal properties in water

Yoshio Nakahara, Yoichi Tatsumi, Ikuko Akimoto, Shusuke Osaki, Motomichi Doi, Keiichi Kimura （Part： Lead author )

NEW JOURNAL OF CHEMISTRY ( ROYAL SOC CHEMISTRY ) 39 ( 2 ) 1452 - 1458 2015 [Refereed]

It generally requires a complicated reaction protocol for the synthesis of silylated fluorescent lanthanide complexes. In this study, a silylated terbium complex was prepared by a very simple procedure through formation of a Schiff base between a terbium complex bearing a formyl group and 3-aminopropyltriethoxysilane. Using the silylated terbium complex, highly fluorescent silica nanoparticles modified chemically with terbium complexes (Tb-SNPs) were efficiently synthesized by a reverse micelle method with Triton X-100 as a surfactant in cyclohexane. The fluorescence properties of Tb-SNPs were remarkably improved by photostability, pH dependence and fluorescence lifetime, compared to free terbium complexes. Also, Tb-SNPs hardly aggregated under aqueous conditions with different salt concentrations and pHs. From these results, it was found that Tb-SNPs are applicable under physiological aqueous conditions. Furthermore, as an application model, Tb-SNPs were used as the fluorescent label for the imaging of African green monkey kidney cells.

Synthesis and Characterization of Silver Nanoparticles by Vacuum Evaporation on Running Hydrocarbon Solution Containing Nonionic Surfactant in Cylindrical Glass Chamber

Takashi Ienaga, Yoshio Nakahara, Keiichi Kimura

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) 43 ( 12 ) 1893 - 1895 2014.12 [Refereed]

A single-molecule force-spectroscopic study on stabilization of G-quadruplex DNA by a telomerase inhibitor

Ryoto Funayama, Yoshio Nakahara, Shinpei Kado, Mutsuo Tanaka, Keiichi Kimura

ANALYST ( ROYAL SOC CHEMISTRY ) 139 ( 16 ) 4037 - 4043 2014.08 [Refereed]

Single-molecule force spectroscopy was carried out using AFM force measurements for the purpose of direct observation of the stabilization of G-quadruplex DNA by a telomerase inhibitor, which is 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin tetrakis(p-toluenesulfonate) (TMPyP). In AFM force measurements, we used an AFM tip and an Au substrate modified chemically with terminal-biotinylated telomere DNA and streptavidin, respectively. The telomere DNA was fully stretched by the AFM tip based on the bridge formation between the AFM tip and the Au substrate through the streptavidin-biotin interaction. The force-extension curves, which reflected the stretching of a single DNA molecule, were distinguished from all of the curves, judging from the rupture force and the contour length. The selected curves were analyzed using a worm-like chain model, and one of the fitting parameters, persistence length (l(p)), was used as an index for the stabilization of the G-quadruplex structure. Consequently, the l(p) value was significantly increased by the addition of TMPyP under the experimental conditions where the G-quadruplex structure could be formed. On the other hand, the value was hardly changed by the addition of TMPyP under the conditions except the above. Furthermore, the methodology developed and demonstrated in this work was applied to evaluate the stabilization of G-quadruplex DNA by other telomerase inhibitors such as ethidium bromide and p-xylene-bis(N-pyridinium bromide).

Single-molecule force spectroscopic study on chiral recognition of cysteine derivatives immobilized on a gold substrate by using AFM tips chemically modified with optically active crown ethers

Yoshio Nakahara, Hitoshi Mitani, Shinpei Kado, Keiichi Kimura （Part： Lead author )

RSC ADVANCES ( ROYAL SOC CHEMISTRY ) 4 ( 101 ) 57850 - 57854 2014 [Refereed]

The chiral recognition of cysteine derivatives immobilized on a gold substrate using atomic force microscopy (AFM) tips chemically modified with optically active crown ethers was quantitatively investigated with single-molecule force spectroscopy (SMFS). Interestingly, the chiral recognition ability of the optically active crown ether-modified tip was entirely opposite to that of its optical isomermodified tip. The difference of rupture forces for the chiral recognition was determined to be about 40 pN under our experimental conditions.

原子間力顕微鏡を用いるカチオン性ポルフィリンによるグアニン四重鎖構造の安定化効果の定量評価

舩山遼斗, 中原佳夫, 門晋平, 田中睦生, 木村恵一

日本分析化学会講演要旨集 ( (公社)日本分析化学会 ) 62年会 65 - 65 2013.08

Synthesis of Silicon Quantum Dots Functionalized Chemically with Monosaccharides and Their Use in Biological Fluorescence Imaging

Yoshio Nakahara, Kazuki Machiya, Toshiyuld Sato, Ni Tar Nwe, Tetsuya Furaike, Hiroshi Tamura, Keiichi Kimura （Part： Lead author )

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) 42 ( 5 ) 498 - 500 2013.05 [Refereed]

Novel water-dispersible, pH-stable, and biocompatible quantum dots were synthesized through the surface modification of silicon quantum dots (SiQDs) with monosaccharides. The presence of the monosaccharide on the surface of the SiQDs was recognized by fluorescence measurements using its complementary lectin (concanavalin A). The fluorescence cell imaging was carried out by using SiQDs functionalized chemically with D-glucosamine, and it was shown that the SiQDs developed in this study are applicable as blue chromophores for biological fluorescence imaging.

Highly selective sensing of hydrophilic anions based on structural-color change of inverse opal hydrogel functionalized with a thiourea group

Shinpei Kado, Haruka Otani, Yoshio Nakahara, Keiichi Kimura

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY ( AMER CHEMICAL SOC ) 245 2013.04 [Refereed]

Highly selective recognition of acetate and bicarbonate by thiourea-functionalised inverse opal hydrogel in aqueous solution

Shinpei Kado, Haruka Otani, Yoshio Nakahara, Keiichi Kimura

CHEMICAL COMMUNICATIONS ( ROYAL SOC CHEMISTRY ) 49 ( 9 ) 886 - 888 2013 [Refereed]

Ultra-thin films of polysilsesquioxanes possessing 3-methacryloxypropyl groups as gate insulator for organic field-effect transistors

Yoshio Nakahara, Haruna Kawa, Jun Yoshiki, Maki Kumei, Hiroyuki Yamamoto, Fumio Oi, Hideo Yamakado, Hisashi Fukuda, Keiichi Kimura （Part： Lead author )

THIN SOLID FILMS ( ELSEVIER SCIENCE SA ) 520 ( 24 ) 7195 - 7199 2012.10 [Refereed]

Polysilsesquioxanes (PSQs) possessing 3-methacryloxypropyl groups as an organic moiety of the side chain were synthesized by sol-gel condensation copolymerization of the corresponding trialkoxysilanes. The ultra-thin PSQ film with a radical initiator and a cross-linking agent was prepared by a spin-coating method, and the film was cured integrally at low temperatures of less than 120 degrees C through two different kinds of polymeric reactions, which were radical polymerization of vinyl groups and sol-gel condensation polymerization of terminated silanol and alkoxy groups. The obtained PSQ film showed the almost perfect solubilization resistance to acetone, which is a good solvent of PSQ before polymerization. It became clear by atomic force microscopy observation that the surface of the PSQ film was very smooth at a nano-meter level. Furthermore, pentacene-based organic field-effect transistor (OFET) with the PSQ film as a gate insulator showed typical p-channel enhancement mode operation characteristics and therefore the ultra-thin PSQ film has the potential to be applicable for solution-processed OFET systems. (C) 2012 Elsevier B.V. All rights reserved.

Synthesis of Amphiphilic Copolymers Bearing a Spirobenzopyran Moiety at the End Group and Their Photoresponsive Micellar Behaviors in Water

Yoshio Nakahara, Jin Nakamura, Naoya Shirotani, Keiichi Kimura （Part： Lead author )

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) 41 ( 10 ) 1142 - 1144 2012.10 [Refereed]

Novel photoresponsive amphiphilic copolymers, poly{methoxy[oligo(ethylene glycol)] methacrylate-co-styrene}, were synthesized using a spirobenzopyran initiator by atom transfer radical polymerization. The spiropyran and merocyanine forms of the spirobenzopyran moiety at the end group successfully underwent photoisomerization under the conditions of micelle formation, which resulted in a drastic change in micellar properties, e.g., in the assembly state and the hydrophobic environment.

Ion-selective imaging by frictional force microscopy based on ion recognition of ionophores attached to probe tips

Shinpei Kado, Yoshio Nakahara, Keiichi Kimura

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY ( AMER CHEMICAL SOC ) 244 2012.08 [Refereed]

Self-assembly of benzo-18-crown-6/crowned-spirobenzopyran copolymers in water and controlled release of entrapped organic dyes by photoirradiation

Yoshio Nakahara, Yuki Okazaki, Keiichi Kimura

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY ( AMER CHEMICAL SOC ) 244 2012.08 [Refereed]

Investigation of polysilsesquioxane as a gate dielectric material for organic field-effect transistors

M. Kawamura, Yoshio Nakahara, Mitsuhiro Ohse, Maki Kumei, K. Uno, Hidefumi Sakamoto, Keiichi Kimura, Ichiro Tanaka

APPLIED PHYSICS LETTERS ( AMER INST PHYSICS ) 101 ( 5 ) 2012.07 [Refereed]

We fabricated pentacene field-effect transistors using polysilsesquioxane (PSQ) as a gate dielectric material that can be cured at sufficiently low temperatures for low cost plastic substrates. The surface roughness of the PSQ films were reduced by the introduction of 3-methacryloxypropyl groups, and their surface energy was controlled to match with that of the pentacene layers by the introduction of phenyl groups. Consequently, the carrier mobility was improved by two orders of magnitude and reached 0.38 cm(2) V-1 s(-1). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742891]

Ultra-High-Sensitive Extraction-Photometric Determination of Sodium Ion Using Flow Injection Analysis with a Chromogenic Calix[4]arene Derivative and a Laser Interferometric Photothermal Detector

Daisuke Tsuda, Yoshio Nakahara, Koji Machitani, Masato Kannaka, Eiji Takahashi, Keiichi Kimurar

ANALYTICAL CHEMISTRY ( AMER CHEMICAL SOC ) 84 ( 8 ) 3710 - 3715 2012.04 [Refereed]

A novel flow injection analysis (FIA) system for ultra-high-sensitive determination of Na+, which involves laser interferometric photothermal equipment as the detector, was designed using a proton-dissociable chromogenic calix[4]arene derivative with a dinitrophenol moiety as the extraction-photometric reagent. The chromogenic calix[4]arene derivative showed an excellent extractability toward Na+, which reflected the cation-complexing property of the tetraethyl ester derivative of calix[4]arene. As the calibration graph of the Na+ concentration could be successfully obtained at the nanomolar level by this method, the proposed FIA system was found to be promising for highly sensitive determination of Na+ in very dilute samples such as supply water and cooling water in power plants.

Potassium-ion-selective sensing based on selective reflection of cholesteric liquid crystal membranes

Shinpei Kado, Yuuhei Takeshima, Yoshio Nakahara, Keiichi Kimura

JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY ( SPRINGER ) 72 ( 1-2 ) 227 - 232 2012.02 [Refereed]

It is well-known that cholesteric liquid crystals have an optical property, selective reflection, due to changes in the pitch of their helical structure. This unique property of cholesteric liquid crystals can be used to attain a visual sensing system showing color changes as the detection signal. In this paper, we report a visual sensing membrane comprising cholesteric liquid crystals, in which a 15-crown-5 derivative was incorporated as ion recognizing sites, for K+ in aqueous solution. The resulting CLC membrane showed a shift of the reflection peak sensitive to K+ in water. We have also designed polymer-dispersed liquid crystal membranes that showed ion-selective reflection peak shifts with improved response time.

Potassium-ion-selective sensing based on selective reflection of cholesteric liquid crystal membranes

Shinpei Kado, Yuuhei Takeshima, Yoshio Nakahara, Keiichi Kimura

Journal of Inclusion Phenomena and Macrocyclic Chemistry 72 ( 1-2 ) 227 - 232 2012.02 [Refereed]

It is well-known that cholesteric liquid crystals have an optical property, selective reflection, due to changes in the pitch of their helical structure. This unique property of cholesteric liquid crystals can be used to attain a visual sensing system showing color changes as the detection signal. In this paper, we report a visual sensing membrane comprising cholesteric liquid crystals, in which a 15-crown-5 derivative was incorporated as ion recognizing sites, for K+ in aqueous solution. The resulting CLC membrane showed a shift of the reflection peak sensitive to K+ in water. We have also designed polymer-dispersed liquid crystal membranes that showed ion-selective reflection peak shifts with improved response time. © 2011 Springer-Verlag.

Two-Dimensional Nanoscale Imaging of Sugar Distribution Using AFM Force Sensing with Probe Modified by Concanavalin A

Inoue Shigeto, Nakahara Yoshio, Kado Shinpei, Tanaka Mitsuo, Kimura Keiichi

Journal of Surface Analysis ( The Surface Analysis Society of Japan ) 18 ( 3 ) 164 - 173 2012

We have recently realized the two-dimensional visualization of a oligoethyleneglycol (OEG)/mannose (Man)-terminated pattern surface by performing AFM force measurements using a concanavalin A (ConA)-modified AFM tip. To extend the visualization technique, various types of patterned surfaces with localized sugar chains were fabricated by lithography and their two-dimensional visualizations were challenged in a phosphate-buffered saline solution by AFM force measurements using a ConA-modified AFM tip in this study. The adhesion force based on the interaction of ConA with Man was much larger than that based on the interaction of ConA with phosphorylcholine or galactose. The spatial resolution of this method was evaluated using a nanopatterned surface fabricated using silica nanoparticles. Man-terminated regions were clearly distinguishable from OEG-terminated regions on a nanometer scale.

Self-assembling phenomena of benzo-18-crown-6/crowned-spirobenzopyran copolymers in aqueous solution and controlled release of entrapped organic dyes using external stimuli

Yoshio Nakahara, Yuki Okazaki, Keiichi Kimura （Part： Lead author )

SOFT MATTER ( ROYAL SOC CHEMISTRY ) 8 ( 11 ) 3192 - 3199 2012 [Refereed]

A novel amphiphilic vinyl copolymer incorporating benzo-18-crown-6 (BC) and crowned spirobenzopyran (cSP) in the side chain [poly(BC-co-cSP)] was synthesized by free radical copolymerization. The spectroscopic measurements made it clear that poly(BC-co-cSP) forms a micelle in water and that its cSP moiety can bind a metal ion in the micelle. Photochromism based on the spirobenzopyran moiety was successfully observed even under conditions of micelle formation. These results indicate that two external stimuli, metal ions and light, can cause significant changes in the assembly state and physical properties of poly(BC-co-cSP). Release behaviors of encapsulated organic dyes from polymeric micelles consisting of poly(BC-co-cSP) were investigated in Tris-HCl buffer solution (pH 7.4) before and after addition of external stimuli. As a result, it was shown that the performances were largely affected by metal-ion addition and photoirradiation. Thus, controlled release of organic dyes from polymeric micelles was realized using a combination of UV-light and visible-light irradiation in water containing BaCl2.

Effect of photoirradiation on chromatographic separation of alkali metal ions using crowned-spirobenzopyran-immobilized silica

Yoshio Nakahara, Yuki Yamaguchi, Hitoshi Iwamoto, Hidefumi Sakamato, Keiichi Kimura （Part： Lead author )

ANALYTICAL METHODS ( ROYAL SOC CHEMISTRY ) 4 ( 12 ) 4025 - 4029 2012 [Refereed]

We successfully developed a novel photocontrollable chromatographic system for separation of alkali metal ions. Based on the finding that the metal-ion complexation of spirobenzopyran derivatives bearing a crown ether moiety, which we call crowned spirobenzopyran, can be drastically changed by photoirradiation, crowned spirobenzopyrans were immobilized covalently onto silica gels for stationary phases of ion chromatography. Under dark or UV-light irradiation conditions, a marked separation between Li+ and K+ was attained by silica gels modified chemically with crowned spirobenzopyran bearing an 18-crown-6 ring. On the other hand, no significant separation between the two metal ions was found under visible-light irradiation conditions. This result originates from the fact that the K+-complexing ability of crowned-spirobenzopyran-immobilized silica is switched by photoisomerization of the spirobenzopyran moiety from its merocyanine form to spiropyran form. Furthermore, computer simulations of separation of alkali metal ions by crowned spirobenzopyrans in the silica phase were conducted using molecular dynamics calculations.

AFM Observation of Stimuli-Responsive Stretching Behavior for Spirobenzopyran/Crown-Ether Copolymer

Shinpei Kado, Kunika Uehara, Yoshio Nakahara, Keiichi Kimura

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( CHEMICAL SOC JAPAN ) 84 ( 4 ) 422 - 426 2011.04 [Refereed]

We have observed stretching behavior of a stimuli-responsive polymer chain bearing two functional groups, spirobenzopyran (SP) and crown ether (CR), at the side chain (SP/CR copolymer) by atomic force microscopy (AFM). The spirobenzopyran side chain can undergo photoisomerization from its electrically neutral spiropyran form to zwitterionic merocyanine by UV irradiation. The crown ether side chain can complex with metal ions. These reactions in the side chains would cause changes in their geometric structure and/or physical properties, resulting in the enhanced bifunctionality of SP/CR copolymer based on their stimuli-responsive ability. In this study, SP/CR copolymer, which was adsorbed on mica substrate, was stretched by AFM tip, when external stimuli (i.e., photoirradiation or metal ion addition) were applied. The force-extension curves of SP/CR copolymer were then analyzed by curve fitting based on a theoretical model of polymer chain elasticity to elucidate the external-stimuli effect on the polymer stretching behavior at the single molecule level.

Alkali Metal Ion Sensing Using Absorbance Changes Based on Aggregation of Silica Nanoparticles Modified Chemically with Crown Ethers

Yoshio Nakahara, Takafumi Hayashi, Haruna Kawa, Keiichi Kimura （Part： Lead author )

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) 40 ( 4 ) 348 - 350 2011.04 [Refereed]

Crown-ether-modified silica nanoparticles (Crown SNPs) were successfully prepared by simple chemical modifications of silica nanoparticles. The organic moiety introduced into silica nanoparticles was characterized by solid-state C-13 NMR and elemental analysis. No morphological damage of silica nanoparticles was recognized according to SEM observation. When an alkali metal salt was added to a solution containing Crown-SNPs, the absorbance changes, whose extent was dependent on the kind and the concentration of a metal ion, were observed.

Quantitative H-1 NMR analysis of reacted silanol groups in silica nanoparticles chemically modified with monochlorosilanes

Yoshio Nakahara, Tsutomu Takeuchi, Shoutaro Yokoyama, Keiichi Kimura （Part： Lead author )

SURFACE AND INTERFACE ANALYSIS ( WILEY-BLACKWELL ) 43 ( 4 ) 809 - 815 2011.04 [Refereed]

Quantitative analysis of reacted silanol groups in silica nanoparticles modified chemically with monochlorosilanes was performed by H-1 NMR after treatment with cesium fluoride. Silica nanoparticles were modified chemically by the reaction between the silanol groups and monochlorosilanes, and the structure of the organic moiety anchored onto the silica surface was confirmed with solid-state C-13 NMR. As monochlorosilanes react with silanol groups at 1:1 ratio unlike di-or trichlorosilanes, the number of the silanes introduced into silica nanoparticles equals that of reacted silanol groups. Organically modified silica nanoparticles were dissolved using cesium fluoride, and the amount of the soluble organic compounds originated from the introduced silanes was determined by a H-1 NMR internal standard method using pyrene as the reference. Those values determined by H-1 NMR were in good agreement with those determined by elemental analysis. Thus, the number of reacted silanol groups per one particle was calculated on the basis of the results obtained by the H-1 NMR method, and the values were highly dependent on the steric structure of the introduced silanes. Copyright (C) 2010 John Wiley & Sons, Ltd.

Synthesis of Novel Photochromic Calix[4]arene Ligand Bearing a Spirobenzopyran and Three Ethyl-Ester Moieties and Photocontrol of Its Alkali Metal Ion Extractability

Koji Machitani, Megumi Saeda, Yoshio Nakahara, Keiichi Kimura

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( CHEMICAL SOC JAPAN ) 83 ( 9 ) 1107 - 1112 2010.09 [Refereed]

A novel photochromic calix[4]arene ligand bearing a spirobenzopyran and three ethyl-ester moieties (compound 1) was synthesized, and photocontrol of its alkali metal ion extractability was studied. In the dark, compound 1 showed the largest changes of absorption spectra for Na+ among alkali metal ions. When Na+ was gradually added to the solution of compound 1, its complexation behavior was evaluated by H-1 NMR, which suggests that Na+ was taken into the cavity formed by four carbonyl oxygens and four ether oxygens, and that compound 1 formed a 1:1 complex with Na+. The proton signals originating from the spirobenzopyran moiety were slightly changed by metal-ion complexation. This means that the spirobenzopyran moiety was not very close to Na+ under dark conditions. Liquid liquid extraction experiments with alkali metal ion using compound 1 made it clear that the extractability of Na+ was enhanced under UV-light irradiation, compared with that under visible-light irradiation. This suggests that the electrostatic interaction between a phenolate anion of the merocyanine moiety generated by UV-light irradiation and Na+ promotes the extractability to some extent.

Morphological Changes in Vesicles and Release of an Encapsulated Compound Triggered by a Photoresponsive Malachite Green Leuconitrile Derivative

Ryoko M. Uda, Eri Hiraishi, Ryo Ohnishi, Yoshio Nakahara, Keiichi Kimura

LANGMUIR ( AMER CHEMICAL SOC ) 26 ( 8 ) 5444 - 5450 2010.04 [Refereed]

Photoinduced morphological changes in phosphatidylcholine vesicles are triggered by a Malachite Green leuconitrile derivative dissolved in the lipidic membrane, and are observed at Malachite Green derivative/lipid ratios < 5 mol%. This Malachite Green derivative is a photoresponsive compound that undergoes ionization to afford a positive charge on the molecule by UV irradiation. The Malachite Green derivative exhibits amphiphilicity when ionized photochemically, whereas it behaves as a lipophilic compound under dark conditions. Cryo-transmission electron microscopy was used to determine vesicle morphology. The effects of the Malachite Green derivative on vesicles were studied by dynamic light scattering and fluorescence resonance energy transfer. Irradiation of vesicles containing the Malachite Green derivative induces nonspherical vesicle morphology. fusion of vesicles, and membrane solubilization, depending on conditions. Furthermore, irradiation of the Malachite Green derivative induces the release of a vesicle-encapsulated compound.

A Novel Method to Prepare Polysilsesquioxane Nanoparticles Possessing Bromoalkyl Groups

Yoshio Nakahara, Chenghuan Ma, Hiroyuki Yamamoto, Fumio Oi, Keiichi Kimura （Part： Lead author )

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) 38 ( 9 ) 876 - 877 2009.09 [Refereed]

Photochemical Modulation of Europium Ion Fluorescence Using a Tetraazamacrocyclic Derivative Bearing a Spirobenzopyran and Three Carboxymethyl Moieties

Koji Machitani, Yoshio Nakahara, Keiichi Kimura

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN ( CHEMICAL SOC JAPAN ) 82 ( 4 ) 472 - 474 2009.04 [Refereed]

Application of Gold Nanoparticles to Spectrophotometric Sensing of Hydrophilic Anions Based on Molecular Recognition by Urea Derivative

Shinpei Kado, Ayumi Furui, Yu Akiyama, Yoshio Nakahara, Keiichi Kimura

ANALYTICAL SCIENCES ( JAPAN SOC ANALYTICAL CHEMISTRY ) 25 ( 2 ) 261 - 265 2009.02 [Refereed]

We have prepared gold nanoparticles (GNPs) modified with a thiol compound that possesses a phenylurea moiety for the spectrophotometric sensing of hydrophilic anions, such as dihydrogen phosphate, based on changes in the surface plasmon absorption of the GNP. We examined the spectral change of phenylurea-modified GNP in dichloromethane upon the addition of various anions as tetrabutylammonium salts to the Solution. The GNP showed increasing plasmon intensity with the concentration of dihydrogen phosphate. For a control experiment with an inactive hexanethiolate-modified GNP, such an ion-selective change in the plasmon band was not observed. Furthermore, in order to realize the spectrophotometric detection of hydrophilic anions in water using GNP with the urea functionality, we attempted to prepare bifunctional GNP modified with both the phenylurea derivative and a water-soluble thiol (e.g., L-Cysteine). The resulting bifunctional GNP showed anion-selective changes in the plasmon band accompanied by increasing absorbance at a longer wavelength due to GNPs aggregation.

Ion-selective Imaging by Atomic Force Microscopy with a Crown-ether-modified Tip

Shinpei Kado, Hitoshi Yano, Yoshio Nakahara, Keiichi Kimura

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) 38 ( 1 ) 58 - 59 2009.01 [Refereed]

Analytical and Separation Chemistry by Taking Advantage of Organic Photochromism Combined with Macrocyclic Chemistry

Keiichi Kimura, Yoshio Nakahara

ANALYTICAL SCIENCES ( JAPAN SOC ANALYTICAL CHEMISTRY ) 25 ( 1 ) 9 - 20 2009.01 [Refereed]

Photochromic crown compounds, such as monomeric and polymeric crown compounds incorporating spirobenzopyran, spironaphthooxazine, spirobenzothiapyran, Malachite Green, and Crystal Violet moieties, were synthesized for applications in the fields of analytical and separation chemistry. The photochromic crown compounds, especially crowned spirobenzopyran derivatives, were applied to metal ion extraction, extraction spectrophotometry, membrane transport, and ion chromatography, the sensitivity and selectivity of which were controlled and enhanced photochemically. Also, micelles and vesicles containing lipophilic crowned spirobenzopyrans and Malachite Greens were tested for their usefulness in spectrophotometric and fluorometric metal-ion determination and photocontrol of organic substance in aqueous systems. The polymeric crowned spirobenzopyrans were tried to use as a photochemical valve based on photochemical rheology changes. Moreover, attempts were made to directly observe photoinduced aggregation of the spirobenzopyran moiety and photoresponsive rheology changes of the polymeric crowned spirobenzopyran, by using chemical force microscopy.

Molecular design of tetraazamacrocyclic derivatives bearing a spirobenzopyran and three carboxymethyl moieties and their metal-ion complexing behavior

Koji Machitani, Hidefurni Sakamoto, Yoshio Nakahara, Keiichi Kimura

ANALYTICAL SCIENCES ( JAPAN SOC ANALYTICAL CHEMISTRY ) 24 ( 4 ) 463 - 469 2008.04 [Refereed]

Tetraazacyclododecane and tetraazacyclotetradecane derivatives bearing a spirobenzopyran and three carboxymethyl moieties, I and 2, and a diethylenetriamine derivative bearing a spirobenzopyran and four carboxymethyl moieties 3 were synthesized. The isomerization behaviors based on the spirobenzopyran moiety of these ligands were studied by UV-visible spectrophotometry in aqueous solutions containing various metal ions at neutral pH. These ligands formed stable 1:1 complexes with lanthanide ions, while the spirobenzopyran moiety was isomerized to its corresponding merocyanine form even under dark conditions. In aqueous solutions containing a lanthanide ion, the absorption spectra of 1 or 2 showed remarkable blue shifts, while absorbances at the maximum absorption wavelengths in the visible region were enhanced; such changes are attributable to the isomerization to the merocyanine form of the spirobenzopyran moiety. These results suggest that the phenolate anion of the merocyanine moiety interacts very strongly with a lanthanide ion bound by the complexing moiety because of the high charge density of lanthanide ions. In contrast, the absorbance of merocyanine form was decreased by the complexation of the macrocyclic ligand with transition metal ions, such as Cu2+ and Zn2+. This result indicates that macrocyclic ligands, 1 and 2, formed complexes with transition metal ions only by the aminocarboxylate moieties, and the phenolate ion of merocyanine moiety was not able to participate in the complexation. This conclusion was also demonstrated by density functional theory calculations.

Photoinduced micelle-to-vesicle transition and encapsulation of glucose by photoresponsive Malachite Green leuconitrile derivative

Ryoko M. Uda, Tomoyuki Tanabe, Yoshio Nakahara, Keiichi Kimura

SOFT MATTER ( ROYAL SOC CHEMISTRY ) 4 ( 3 ) 560 - 563 2008 [Refereed]

De-tert-butylation of p-tert-Butylcalix[4]arene Using Sulfated Zirconia as a Solid Superacid Catalyst

M. Takagaki, E. Nomura, T. Kobata, H. Mori, Y. Nakahara, H. Taniguchi, K. Kimura

ITE-IBA Letters on Batteries, New Technologies & Medicine ( 1 ) 388 - 391 2008 [Refereed]

Facile synthesis of C-2-Symmetric chiral crown ethers with two reactive hydroxymethyl groups

Yohji Nakatsuji, Yoshio Nakahara, Katsumori Nagamiya, Yuki Itoh, Kentaro Uesugi, Naohisa Ishida, Masahiro Muraoka, Toshiyuki Kida, Mitsuru Akashi

SYNTHESIS-STUTTGART ( GEORG THIEME VERLAG KG ) ( 19 ) 2973 - 2978 2007.10 [Refereed]

Fabrication of celtular multilayers with nanometer-sized extracellular matrix films

Michiya Matsusaki, Koji Kadowaki, Yoshio Nakahara, Mitsuru Akashi

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION ( WILEY-V C H VERLAG GMBH ) 46 ( 25 ) 4689 - 4692 2007 [Refereed]

Fabrication and enzymatic degradation of fibronectin-based ultrathin films

Yoshio Nakahara, Michiya Matsusaki, Mitsuru Akashi （Part： Lead author )

JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION ( VSP BV ) 18 ( 12 ) 1565 - 1573 2007 [Refereed]

Novel fibronectin (FN)-based ultrathin films were prepared by layer-by-layer (LbL) assembly. Among the various combinations of extracellular matrix (ECM) proteins and glycosamino-glycans (GAGs) such as FN, gelatin (G), alpha-elastin (E) and heparin (Hep), FN/Hep, FN/G and FN/E nanofilms were successfully fabricated in phosphate buffer solutions (pH 7.4). The film thickness of the nanofilms, in which each component can interact with each other by FN-specific interactions, was larger than that of other LbL films (E/Hep, G/E and G/Hep) prepared by electrostatic interactions. The FN/G film was rapidly decomposed by treatment with elastase, thus demonstrating, the enzymatic biodegradability of the nanofilm. We prepared the FN/heparinoid multilayers composed of FN and dextran sulfate (Dex), and its thickness was much larger than that of the FN/alpha-poly(L-lysine hydrochloride) (PLL) film prepared by LbL assembly using common electrostatic interactions. Furthermore, the FN/G and FN/Dex nanofilms prepared by FN-specific interaction were more stable in Eagle's MEM with 10% fetal bovine serum (FBS) than the electrostatic assembling films, FN/PLL and PLL/Dex. FN-based multilayers composed of FN and ECM components can be useful as artificial ECM films for tissue engineering and other biomedical applications.

PMSE 160-Design and characterization of novel membrane materials from imidazolium-based room temperature ionic liquids and liquid crystal structures

Michiya Matsusaki, Yoshio Nakahara, Mitsuru Akashi

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY ( AMER CHEMICAL SOC ) 232 545 - 545 2006.09 [Refereed]

3D-cell assembly by preparing of polymeric nanofilms on cell surface

Michiya Matsusaki, Yoshio Nakahara, Mitsuru Akashi

Polymer Preprints, Japan 55 ( 2 ) 5397 - 5398 2006

Controlling of 3D-cell assembly for in vitro tissue engineering by bio-nanofilms

Michiya Matsusaki, Yoshio Nakahara, Mitsuru Akashi

Polymer Preprints, Japan 55 ( 1 ) 1994 2006

We have studied 3D-cell assembly by preparing of nano-sized extra cellular matrix (bio-nanofilm) onto cell surface as novel cell assembling technology for tissue engineering field. Alternate immersion of adhered 1 st layer cells into fibronectin and gelatin/Tris buffer solution can prepare nano-ECM onto cell surfaces. 2 nd layer cells can adhere and extend onto bio-nanofilm. Continuation of these steps, 3D-cell layers can be fabricated. We have successfully prepared mouse L929 fibroblast and human SMC four layers by preparing of 15-20 nm of bio-nanofilm. The 3D-cell assembly technology would be useful for not only fabricating of vessel or skin like cell layers but also clarification of basic science of ECM for cell lamination.

Formation of protein nano-films for in vitro tissue engineering

Yoshio Nakahara, Michiya Matsusaki, Mitsuru Akashi

Polymer Preprints, Japan 55 ( 1 ) 1993 2006

The development of multilayer ultrathin films containing proteins (bio-nanofilm) is one of the focal subjects in biomaterials science and technology. In particular, a layer-by-layer (LbL) assembly via bio-specific interactions for the immobilization of proteins onto a substrate has attracted much attention as driving forces due to their high affinity and specificity. In this study, the various combinations of LbL assemblies among extracellular matrix proteins and glycosaminoglycans including fibronectin (FN), gelatin (G), α-elastin (E), heparine (Hep), and dextrane sulfate (Dex) were analyzed quantitatively by a quartz crystal microbalance (QCM). And then, their enzymatic degradation behaviors and stabilities in cell culture medium (E-MEM + FBS) were investigated. In addition, it was confirmed that such bio-nanofilms could be formed on a phospholipid bilayer, which is postulated as a model of cell membranes.

Fluorometric sensing of alkali metal and alkaline earth metal cations by novel photosensitive monoazacryptand derivatives in aqueous micellar solutions

Y Nakahara, T Kida, Y Nakatsuji, M Akashi

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY ( AMER CHEMICAL SOC ) 230 U3013 - U3014 2005.08 [Refereed]

New fluorescence method for the determination of the critical micelle concentration by photosensitive monoazacryptand derivatives

Y Nakahara, T Kida, Y Nakatsuji, M Akashi （Part： Lead author )

LANGMUIR ( AMER CHEMICAL SOC ) 21 ( 15 ) 6688 - 6695 2005.07 [Refereed]

A novel fluorescence method for the determination of the critical micelle concentration (cmc) is reported. The cmc values of nonionic and anionic surfactants were evaluated utilizing a photosensitive monoazacryptand-Ba2+ complex, whose fluorescence intensity is sensitively changed by environmental conditions based on the photoinduced electron transfer (PET) mechanism as a fluorescent probe (PET method). Based on a comparison of the cmc values obtained by the PET method versus those obtained by conventional fluorescence-based methods as well as the values reported in the literature, one can conclude that the PET method is useful for the cmc determination. In particular, the PET method was more effective for the cmc determination of nonionic surfactants with very low cmc values (< 10(-5) M) than any other fluorescence-based method. In the cases of anionic surfactants, the PET method revealed the formation of the premicellar aggregates comprised of surfactant molecules and fluorescent probes below the cmc. Moreover, the hydrophobicity around the monoazacryptand-Ba2+ complex incorporated into various nonionic surfactant micelles was evaluated by this PET method.

Novel C-2-symmetric chiral 18-crown-6 derivatives with two aromatic sidearms as chiral NMR discriminating agents

Y Nakatsuji, Y Nakahara, A Muramatsu, T Kida, M Akashi

TETRAHEDRON LETTERS ( PERGAMON-ELSEVIER SCIENCE LTD ) 46 ( 25 ) 4331 - 4335 2005.06 [Refereed]

Fluorometric sensing of alkali metal and alkaline earth metal cations by novel photosensitive monoazacryptand derivatives in aqueous micellar solutions

Y Nakahara, T Kida, Y Nakatsuji, M Akashi （Part： Lead author )

ORGANIC & BIOMOLECULAR CHEMISTRY ( ROYAL SOC CHEMISTRY ) 3 ( 9 ) 1787 - 1794 2005 [Refereed]

Novel monoazacryptand-type fluorescent chemosensors, I (derived From an 18-crown-6) and 2 (derived from a 15-crown-5) both with a pyrene ring as their photoresponsive moiety, were synthesized. Their fluorescence properties for alkali metal and alkaline earth metal cations in water were then examined. The detection of metal cations was accomplished by a change in the fluorescence intensity of the host compounds, based on a photoinduced electron transfer (PET) mechanism. In aqueous solution, I showed little fluorescence upon the addition of Ba2+ because of the very weak complexation with Ba2+, but the presence of micelles of polyoxyethylene(10) isooctylphenyl ether (Triton X-100) enabled I to show highly sensitive and selective Ba2+ detection among alkali metal and alkaline earth metal cations. With respect to the selective fluorescent detection of important metal cations (Na+, K+, Mg2+, Ca2+) relevant to living organisms, 2 was found to detect K+ with high selectivity in aqueous micellar solutions of polyoxyethylene(20) sorbitan rnonostcarate (Tween-60). The selectivity for metal cations was mainly dependent oil the goodness of fit of the host cavity and the metal cation size. In the presence of anionic surfactants, 2 detectcd alkaline earth metal cations mori effectively than alkali metal cations.

Synthesis of double-armed lariat ethers with pyrene moieties at each end of two sidearms and their fluorescence properties in the presence of alkali metal and alkaline earth metal cations

Y Nakahara, T Kida, Y Nakatsuji, M Akashi （Part： Lead author )

JOURNAL OF ORGANIC CHEMISTRY ( AMER CHEMICAL SOC ) 69 ( 13 ) 4403 - 4411 2004.06 [Refereed]

Two types of double-armed lariat ether derivatives having pyrene moieties at each end of two sidearms, (3x + 1)-crown-x derivatives 1 (x = 5), 2 (x = 6), and 3 (x = 4) (type A) and 3y-crown-y derivatives, 6 (y = 5) and 7 (y = 6) (type B), were synthesized, and their complexation behavior toward alkali metal and alkaline earth metal cations was examined by fluorescence spectroscopy. Pyrene excimer emission decreased accompanied by an increase in monomer emission upon metal ion complexation. This finding is ascribed to the change of the spatial distance of two pyrene rings by movement suppression of both the crown ring and one of the two sidearms based on complexation with the metal cation. The selectivity for alkaline earth metal cations was highly dependent on the fitness of the host cavity and the guest size. Although most of the fluorophores did not respond to alkali metal cations, only trans-7a containing an 18-crown-6 ring showed K+ selectivity.

A novel fluorescent indicator for Ba2+ in aqueous micellar solutions

Y Nakahara, T Kida, Y Nakatsuji, M Akashi （Part： Lead author )

CHEMICAL COMMUNICATIONS ( ROYAL SOC CHEMISTRY ) pp 224-225 ( 2 ) 224 - 225 2004.01 [Refereed]

Fluorometric sensing of alkaline earth metal cations by new lariat ethers having plural pyrenylmethyl groups on the electron-donating sidearms

Y Nakahara, Y Matsumi, WB Zhang, T Kida, Y Nakatsuji, Ikeda, I （Part： Lead author )

ORGANIC LETTERS ( AMER CHEMICAL SOC ) 4 ( 16 ) 2641 - 2644 2002.08 [Refereed]

[GRAPHICS]
New fluorescent compounds (1), lariat ethers having plural pyrenylmethyl groups on the sidearms, were prepared, and their complexation behavior with alkaline earth metal cations was examined by fluorescence spectrometry. The pyrene excimer emission decreased accompanied with an increase in the monomer emission upon complexation with the metal ion. This finding is ascribed to the cooperative participation of one of the two sidearms in the complexation of the crown ring with the metal ion.

Adsorption Mechanism of Poly (Ammonium Carboxylate) onto Phthalocyanine Blue Pigment Deduced by 1H NMR Spin-Lattice Relaxation Time

Taizo Mohri, Yoshio Nakahara, Wanbin Zhang, Toshiyuki Kida, Yohji Nakatsuji, Isao Ikeda

Journal of Oleo Science 50 ( 11 ) 857 - 863 2001 [Refereed]

1H NMR spin-lattice relaxation time of ethylenediammonium dioctanoate (EDADO), a model dispersant (MD) for phthalocyanine blue (PhB) pigment, was examined with a high-resolution magic angle spinning (MAS) 1H NMR probe (1H Nano-nmrTM Probe). The adsorption mechanism of EDADO onto PhB was discussed on the basis of the spin-lattice relaxation time obtained by changing the polarity of the solvent and the temperature in the 1H NMR measurement. In addition to the deduction shown in our previous report that the adsorption of the MD molecule onto the pigment is induced by the coordination of a lone electron pair of a nitrogen atom of the amino group onto Cu (II) of PhB, it became clear that equilibrium among a diammonium salt, a half-salt, and diamine (ethylenediamine, EDA) is an important factor in the adsorption behavior. A comparison of measurements in chloroform-d and in methanol-d4 suggests that the complex of PhB and a half-salt composed of EDA and octanoic acid still has interaction with a carboxylic acid molecule through proton-transfer from the carboxylic acid to PhB (PhB of the complex and/or free PhB) and successive hydrogen bonding which may effect the dispersion of pigment in a nonpolar medium. The results obtained in this model system may afford a basis for explaining the good dispersing ability of poly (ammonium carboxylate), that is, polymeric dispersants in practical use. © 2001, Japan Oil Chemists’ Society. All rights reserved.

Study on the Adsorption Behavior of Dispersants onto Pigment Using 1H NMR Spin-Lattice Relaxation Time

Taizo Mohri, Yoshio Nakahara, Wanbin Zhang, Toshiyuki Kida, Yohji Nakatsuji, Isao Ikeda

Journal of Oleo Science 50 ( 8 ) 623 - 631 2001 [Refereed]

In order to obtain information concerning the function of the polar group of polymeric dispersants generally used for pigment particles in a non-aqueous medium, alkylamine, alkylammonium salt, amide, and carboxylic acid were selected as the model dispersants and their adsorption behavior onto the phthalocyanine blue (PhB) pigment was studied by means of 1H NMR spin-lattice relaxation time using a high-resolution magic angle spinning 1H NMR probe. The amino group, particularly the primary amino group, was found to be the most effective as the adsorption site for the pigment among the functional groups examined in this study. The results obtained in this work suggest that the coordination of a lone electron pair on the nitrogen atom of an amino group to the Cu(II) of PhB is the driving force for the adsorption. © 2001, Japan Oil Chemists’ Society. All rights reserved.

The first study on the mobility of surface-adsorbed molecules using H-1 NMR spin-lattice relaxation time

T Mohri, Y Nakahara, WB Zhang, Y Nakatsuji, T Muneishi, Y Miyaji, Ikeda, I

CHEMISTRY LETTERS ( CHEMICAL SOC JAPAN ) ( 9 ) 988 - 989 2000.09 [Refereed]

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