研究テーマ

パイ共役分子(有機低分子・高分子)や生体分子からなる超分子ナノ構造体の構築、および作製した分子集合体によるナノデバイスの作製と光電子機能・エネルギー変換に関する研究を行っています。特に、分子の集合構造や配置・配向制御と機能発現に関して重点的に研究を進めています。

最近の発表論文

J. Phys. Chem. Lett. 2017, 8, 4580–4586. 

“From Linear to Foldamer and Assembly: Hierarchical Transformation of a Coplanar Conjugated Polymer into a Microsphere” 

リニアーからフォルダマーを介して集合化:平面状共役ポリマーの階層的構造変形による球体形成

Abstract: Despite the coplanar structure, a conjugated alternating copolymer forms amorphous, well-defined microspheres without π-stacked crystalline domains. Here, we gain insights into the mechanism of how the coplanar conjugated polymer forms amorphous microspheres by means of spectroscopic studies on the assembly/disassembly processes. The difference of the spectral profiles of photoabsorption and photoluminescence with varying the solvent/nonsolvent composition clarifies that stepwise assembly takes place through the microsphere formation; [1] intrapolymer linear-to-folding transformation upon diffusion of polar nonsolvent and [2] interpolymer assembly of the foldamers upon further addition of the nonsolvent to form microspheres. As shown in various biopolymers such as proteins and DNA, such stepwise folding and assembly behaviors of conjugated polymers from primary to secondary and tertiary structure open a new way to create transformable functional materials.












Adv. Opt. Mater. 2017, 5, 1700123/1–7. 

“Low-Threshold Whispering Gallery Mode Lasing from Self-Assembled Microspheres of Single-Sort Conjugated Polymers” 

単一の共役ポリマーからなる自己組織化球体からの低閾値WGMレーザー発振

Abstract: Low-threshold organic microlasers are demanded for advanced optical applications such as nano/micrometer scale memory, sensing, and communication tools, and further valuable for future electrically-driven laser applications. In this paper, we demonstrate that various highly-fluorescent conjugated polymers self-assemble to form single-component microspheres that exhibit, upon femtosecond pumping to a single microsphere, whispering gallery mode (WGM) lasing with blue, green, and red emission colors. In particular, the microsphere consisting of polyfluorene shows the lowest threshold fluence as low as 1.5 μJ cm^–2 and high photostability against successive pumping of > 10^5 pulse. The threshold fluence was further reduced by one fourth (0.37 μJ cm^–2) by mounting the microspheres on a Ag-coated substrate, where a mirror effect of the Ag layer enhances efficiency of the PL confinement with a minor effect of plasmonic near field. Considering the intrinsic charge injection and transport properties, π-conjugated polymer microsphere resonators will be possible materials for electrically pumped WGM luminescence.















ACS Appl. Mater. Interfaces 2017, 9, 9996–10002. 

“Peptide Cross-linkers: Immobilization of Platinum Nanoparticles Highly Dispersed on Graphene Oxide Nanosheets with Enhanced Photocatalytic Activities” 

ペプチドクロスリンカー:酸化グラフェン表面への白金ナノ粒子の高分散な固定化と増強光触媒効果

Abstract: For exerting potential catalytic and photocatalytic activities of metal nanoparticles (MNPs), immobilization of MNPs on a support medium in highly dispersed state is desired. In this article, we demonstrated that surfactant-free platinum nanoparticles (PtNPs) were efficiently immobilized on graphene oxide (GO) nanosheets in a highly dispersed state by utilizing oligopeptide β-sheets as a cross-linker. The fluorenyl-substituted peptides were designed to form β-sheets, where metal-binding thiol groups and protonated and positively charged amino groups are integrated on the opposite sides of the surface of a β-sheet, which efficiently bridge PtNPs and GO nanosheet. In comparison to PtNP/GO composite without the peptide linker, the PtNP/peptide/GO ternary complex exhibited excellent photocatalytic dye degradation activity via electron transfer from GO to PtNP and simultaneous hole transfer from oxidized GO to the dye. Furthermore, the ternary complex showed photoinduced hydrogen evolution upon visible light irradiation using a hole scavenger. This research provides a new methodology for the development of photocatalytic materials by a bottom-up strategy on the basis of self-assembling features of biomolecules.













Chem. Lett. 2017, 46, 423–425. 

“Controlled Self-Assembly of Oligopeptides Bearing Electron Donor and Acceptor Units on the Side Chains to Form β-Sheets with Selective π-Stacking Configuration” 

電子供与体および受容体を側鎖に有するオリゴペプチドの自己組織化による選択的なπスタック様式をもつβシート形成

Abstract: We describe the β-sheet formation from heptapeptides bearing one electron-donating free-base porphyrin and two electron-accepting naphthalenediimides on the side chains. The porphyrin units in the resultant β-sheet fibers form J- or H-type aggregates, depending on the protonated state of the porphyrin unit in the assembling process.











Polym. J. 2016, 48, 1045–1050. 

“Spherical resonators from π-conjugated polymers” (Focus Review) 

π共役ポリマーからなる球体共振器

Abstract: Optical resonators play an important role in optical devices; they confine, sharpen, and amplify light. Self-assembled polymer resonators are advantageous for their simple, low-cost, and low-energy fabrication processes. In this Focus Review, we show recent advances in the self-assembly of π-conjugated polymers to form microspheres that act as optical resonators. The key factors in sphere assembly are low crystallinity of the polymers and slow diffusion of polar nonsolvent during the assembling process. Focused laser excitation of a single isolated microsphere excites whispering gallery modes (WGMs), in which sharp and periodic lines are observed in the photoluminescence (PL) spectrum; these are characterized as transverse electric and magnetic modes. Efficient intrasphere energy transfer occurs in the case of microspheres composed of energy-donating and -accepting polymer blends. Furthermore, WGM-mediated long-range intersphere PL propagation and subsequent color conversion were observed in the case of linearly coupled microspheres. Conjugated polymer microspheres are beneficial as optical resonators in terms of their high refractive indices, high absorptivity, and high PL efficiency, which are achieved by using simple fabrication processes.













ACS Nano 2016, 10, 7058–7063. 

“Color-Tunable Resonant Photoluminescence and Cavity-Mediated Multistep Energy Transfer Cascade” 

発光色を変調可能な共鳴発光とキャビティーを介した多段階エネルギー移動カスケード

Abstract:  Color-tunable resonant photoluminescence (PL) was attained from polystyrene microspheres doped with a single polymorphic fluorescent dye, boron-dipyrrin (BODIPY) 1. The color of the resonant PL depends on the assembling morphology of 1 in the microspheres, which can be selectively controlled from green to red by the initial concentration of 1 in the preparation process of the microspheres. Studies on intersphere PL propagation with multicoupled microspheres, prepared by micromanipulation technique, revealed that multistep photon transfer takes place through the microspheres, accompanying energy transfer cascade with stepwise PL color change. The intersphere energy transfer cascade is direction selective, where energy donor-to-acceptor down conversion direction is only allowed. Such cavity-mediated long-distance and multistep energy transfer will be advantageous for polymer photonics device application.
















RSC Adv. 2016, 6, 52854–52857.

“Self-assembled polycarbazole microspheres as single-component, white-colour resonant photoemitters” 

単一の構成要素で白色共鳴発光を示す自己組織化ポリカルバゾールマイクロ球体

Abstract: Self-assembled polycarbazole (PCz) microspheres exhibit whispering gallery mode photoluminescence (PL), where resonant PL lines appear at the whole visible spectral range. The ultra-wide-range PL results from a partial oxidation of PCz upon strong photoexcitation. The single component micro-photoemitters, preparable with simple and inexpensive process, is applicable as full-colour, narrow-width light emission sources.











Chem. Lett. 2016, accepted.

“Enwrapping Conjugated Polymer Microspheres with Graphene Oxide Nanosheets” 

酸化グラフェンナノシートによる共役ポリマー球体の被覆

Abstract: Water-dispersible conjugated polymer microspheres were obtained by enwrapping with graphene oxide (GO) nanosheets. Simply mixing the polymer microspheres and GO in water results in an exclusive formation of GO-wrapped microspheres. Photoluminescence (PL) spectra of the GO-wrapped single microsphere show whispering gallery modes, in which the PL lines are broadened in comparison with bare microspheres without GO. The broadening is attributed to scattering and reabsorption of the confined PL.












ACS Nano 2016, 10, 5543–5549.

“Conjugated Polymer Blend Microspheres for Efficient, Long-Range Light Energy Transfer” 

効率的で長距離の光エネルギー移動が可能な共役ポリマーブレンドマイクロ球体

Abstract: Highly luminescent π-conjugated polymeric microspheres were fabricated through self-assembly of energy-donating and energy-accepting polymers and their blends. To avoid macroscopic phase separation, the nucleation time and growth rate of each polymer in the solution were properly adjusted. Photoluminescence (PL) studies showed that efficient donor-to-acceptor energy transfer takes place inside the microspheres, revealing that two polymers are well-blended in the microspheres. Focused laser irradiation to a single microsphere excites whispering gallery modes (WGMs), where PL generated inside the sphere is confined and resonates. The wavelengths of the PL lines are finely tuned by changing the blending ratio, accompanying the systematic yellow-to-red color change. Furthermore, when several microspheres are coupled linearly, the confined PL propagates the microspheres through the contact point, and a cascade-like process converts the PL color while maintaining the WGM characteristics. The self-assembly strategy for the formation of polymeric nano- to microstructures with highly miscible polymer blends will be advantageous for optoelectronic and photonic device applications.













Thin Solid Films 2016, 603, 408–412.

“Enhancement of grain size and crystallinity of thin layers of pentacene grown under magnetic field” 

磁場下で成長したペンタセン薄膜におけるグレインサイズと結晶性の向上

Abstract: Field-effect mobilities (µ) of pentacene films, prepared by a thermal deposition under a magnetic field (H-field), were largely enhanced, in comparison with that prepared without an H-field.  Under a perpendicular H-field with respect to the substrate surface, the crystallinity of the edge-on pentacene orientation is enhanced, resulting in the 9-fold enhancement of µ.  Furthermore, under parallel H-field with respect to the substrate surface, µ of the pentacene films were 23-fold greater than that prepared without the H-field.  The surface morphology studies by atomic force microscopy of the ultra thin films of pentacene clarified that the grain size of the pentacene at the interface with the substrate is larger for films under parallel H-field than that prepared without an H-field.  The simple and effective method for enhancing the semiconducting properties of the organic thin films gives high technological impact in its application to organic electronics.
















Sci. Rep. 2016, 6, 19635/1–6.

“Optically induced mode splitting in self-assembled, high quality-factor conjugated polymer microcavities” 

高いQ値を示す自己組織化共役ポリマーマイクロ共振器における光誘起モード分裂

Abstract: We investigate the whispering gallery modes (WGMs) of self-assembled single microspheres. They consist of a recently developed highly fluorescent π-conjugated copolymer and exhibit excellent optical properties with Q-factors up to 10^4. Under continuous laser irradiation, we observe a splitting of the highly degenerate spherical WGMs into a multiplet of lines. Comparison with the calculated spectral response of a weakly distorted sphere shows that the optical excitation induces a change of the optical path length in the microcavity so that it resembles a prolate spheroid. The separation of the lines is given by the ellipticity and the azimuthal mode number. Measurements in various gaseous environments suggest that the distortion is caused by light induced oxidation of the polymer. Our findings show that photooxidation can be a beneficial mechanism for in-situ tuning of optically active polymer structures.








J. Mater. Chem. A 2015, 3, 17612–17619.

“Cysteine-containing oligopeptide β-sheets as redispersants for agglomerated metal nanoparticles” 

凝集した金属ナノ粒子を再分散させるシステイン含有オリゴペプチドβシート

Abstract: Oligopeptide β-sheets comprising fluorenyl methoxy carbonyl (Fmoc) group on its N-terminus and five amino acid residues of cysteine, lysine and valine displays redispersive properties of agglomerated metal nanoparticles (MNPs, M = Au, Cu, Pt and Pd). The ligand-free MNPs prepared by laser ablation technique in liquid keep high dispersion state due to the inherent surface charges delivered by anionic species present in solution but may agglomerate after the preparation which depends on concentration or salinity. We show how the agglomerated MNPs can be returned to the dispersive state by adding the Fmoc-oligopeptide β-sheets in methanol, which is characterized by photoabsorption spectroscopy and transmission electron microscopy. Systematic studies varying the concentration, the amino acid sequences and secondary structures of a series of the oligopeptides clarify that the β-sheet structure is essential for the redispersion of the MNPs, where metal-binding thiol groups are integrated on one side and positively charged amino groups are located on the other side of the β-sheet. A possible mechanism for the redispersion may be that the agglomerated MNPs are subsequently enwrapped by the flexible β-sheets and gradually separated due to the reconstruction of peptide β-sheets under the assembly/disassembly equilibrium.










Macromolecules 2015, 48, 3928–3933.

“Whispering Gallery Resonance from Self-Assembled Microspheres of Highly Fluorescent Isolated Conjugated Polymers” 

高発光性孤立π共役高分子の自己組織化マイクロ球体からのウィスパリングギャラリー共鳴

Abstract: Self-assembly of highly fluorescent isolated conjugated polymers (ICPs), comprising alternating phenylene moieties with an insulating cyclic side chain and different arylene moieties, was comprehensively studied. Two out of nine ICPs were identified to form well-defined spheres of 1–6 μm diameter. The degree of twisting of the main chains was found to be an important structural factor enabling formation of spheres, for which dihedral angles >50° between the neighboring arylene moieties were required. A single microsphere with high sphericity exhibited whispering gallery mode (WGM) photoemission upon excitation with a focused laser. In this emission, sharp and periodic emission lines were superimposed on a broad photoemission spectrum. The WGM spectral profiles were very sensitive to the integrity of the spherical geometries and surface smoothness, which depends on the self-assembling condition as well as the structure of the polymer backbone. Microspherical optical resonators consisting of such highly fluorescent conjugated polymers are novel. They also present advantages in that (i) there is no need for a light waveguide and fluorescent-dye doping, (ii) its high refractive index is beneficial for light confinement, and (iii) the fabrication process is simple, not requiring sophisticated, costly microfabrication technology.












Macromolecules 2015, 48, 2570–2575.

“Colloidal Crystallization and Ionic Liquid Induced Partial β-Phase Transformation of Poly(vinylidene fluoride) Nanoparticles” 

ポリフッ化ビニリデンナノ粒子によるコロイド結晶化とイオン液体誘起による部分的β相化

Abstract: Colloidal crystallization of poly(vinylidene fluoride) (PVDF) nanoparticles (NPs) and its β-phase transformation were studied. The pristine PVDF NPs with an average diameter of 230 nm consist of 46% α-phase and 54% amorphous PVDF. The PVDF NPs were assembled on a quartz substrate by means of vertical deposition method from a tetrahydrofuran dispersion of PVDF NPs with a few volume percentage of n-alkane. The resultant colloidal thin films displayed a pale-greenish structural color with the selective reflection at around 550 nm wavelength due to closely packed PVDF NPs. The colloidal thin films were immersed into an acetonitrile solution containing 2 wt % ionic liquid, subsequently air-dried, and thermally annealed at 140 °C, just below the melting point of the PVDF–IL blends. After annealing, the PVDF NPs partially transformed into its β-phase with the volume percentages of α-, β-, and amorphous phases of 22, 32, and 46%, respectively. The postannealed colloidal films still maintained the face-centered-cubic assembling structure of PVDF NPs, thus displaying the greenish structural color and selective reflection.










Chem. Commun. 2015, 51, 1206–1209.

“Translation of Assembling Trajectory by Preorganisation: A Study of the Magnetic Properties of 1D Polymeric Unpaired Electrons Immobilised on a Discrete Nanoscopic Scaffold” 

事前組織化による集合化軌跡の翻訳:ナノサイズの土台へ固定した1次元不対電子ポリマーの磁気特性

Abstract: A nitronyl nitroxide (NN)-appended hexabenzocoronene (HBCNN), when allowed to coassemble with bis(hexafluoroacetylacetonato)cobalt(II), forms a coaxial nanotubular architecture featuring NN-Co(II) coordinated copolymer chains immobilised on the outer and inner nanotube surfaces.  Upon lowering the temperature, this nanotube has enhanced magnetic susceptibility below 10 K.












Asian J. Org. Chem. 2014, 3, 1182–1188. 

“Charge-Separated Fmoc-Peptide β-Sheets: Sequence-Secondary Structure Relationship for Arranging Charged Side Chains on Both Sides” 

電荷分離型Fmocペプチドβシート:荷電側鎖を両面に配置するためのシーケンスと2次構造の関連性

Abstract:  β-Sheet formation from fluorenylmethoxycarbonyl (Fmoc)-substituted polar oligopeptides was demonstrated, where acidic and basic side chains are located separately on either side of the β-sheet surfaces. For yielding such charge-separated β-sheets, self-assembly of 18 pentapeptides was studied, all of which contain glutamic acid (E), lysine (K), and valine (V). Fmoc-pentapeptides containing one E and one K all formed fibrillar nanostructures consisting of stacked β-sheets. On the other hand, Fmoc-pentapeptides containing two E and two K formed β-sheet fibrils only when V was located at the center and separated two EK pairs. Photoluminescence studies of these peptides in a glycine buffer containing thioflavin T revealed a clear relationship between the amino acid sequence and secondary structure, where the location of neutral V plays a pivotal role for the β-sheet formation. The β-sheet formation propensity was further supported by computer simulation studies with the TANGO algorithm.












Sci. Rep. 2014, 4, 5902/1–5. 

“Self-Assembled Conjugated Polymer Spheres as Fluorescent Microresonators” 

発光性共振器としての自己組織化共役系高分子マイクロ球体

Abstract:  Confinement of light inside an active medium cavity can amplify emission. Whispering gallery mode (WGM) is one of mechanisms that amplifies light effectively by confining it inside high-refractive-index microstructures, where light propagates along the circumference of a sphere via total internal reflection. Here we show that isolated single microspheres of 2–10 μm diameter, formed from self-assembly of π-conjugated alternating copolymers, display WGM photoemission induced by laser pumping. The wavelengths of the emission peaks depend sensitively on the sphere size, position of the excitation spot and refractive index of each polymer. The Q-factor increases with increasing sphere diameter and displays a linear correlation with the reciprocal radius, indicating that the small curvature increases the efficacy of the total internal reflection. WGM photoemission from π-conjugated polymer microspheres is unprecedented and may be of high technological impact since the microspheres fulfill the role of fluorophores, high-refractive-index media and resonators simultaneously, in addition to their simple fabrication process.














Thin Solid Films 2014, 562, 467–470. 

“Control of Molecular Orientation and Morphology in Organic Bilayer Solar Cells: Copper Phthalocyanine on Gold Nanodots” 

有機積層太陽電池内の分子配向と形状制御:金ナノドット上の銅フタロシアニン

Abstract:  Molecular orientation, morphology of donor (D)/acceptor (A) interface and photoabsorptivity in organic bilayer solar cells were controlled using Au nanodots with ~20 nm diameter inserted between the bottom electrode and the organic layer.  Copper phthalocyanine (CuPc) molecules deposited onto the Au nanodot-coated electrode were mostly oriented face-on with large surface roughness, which is beneficial for photoabsorption, charge separation and transport.  Furthermore, Au nanodots exhibit blue-shifted plasmon bands so that CuPc absorbs light more efficiently than that on thin Au layer.  Bilayer C60/CuPc solar cells containing Au nanodots exhibited 1.4 times higher photoelectric conversion efficiency than those without Au nanodots.  Factors for the enhanced efficiency are (i) improvement of the optical absorption characteristics by face-on orientation of CuPc and (ii) increase of the D/A heterointerface area.  In addition, the shift of the plasmon absorption band of Au by the formation of nanodots makes absorption of the CuPc layer much more efficiently, resulting in better photovoltaic output.











Polym. Chem. 2014, 5, 3583–3587. 

“Tetramethylbithiophene in π-Conjugated Alternating Copolymers as Effective Structural Component for the Formation of Spherical Assemblies” 

球状集合体形成のための効果的な構造要素としてのパイ共役交互共重合体中のテトラメチルビチオフェン

Abstract:  π-Conjugated alternating copolymers containing a tetramethylbithiophene unit show a strong tendency to form well-defined, sub- to several-micrometer-sized spheres. The twisted bithiophene unit inhibits interchain stacking and anisotropic crystal growth of these copolymers, leading to the formation of structurally isotropic spheres by means of a slow diffusion of nonsolvent into a solution of the copolymers. These micrometer-sized spheres display extremely long photocarrier lifetimes (~ 10^-3 s) in comparison with cast films from the solutions of the polymers and those of the irregular aggregates (< 10^-6 s).













Appl. Phys. Lett. 2013, 103, 043301/1–4. 

“Magnetic-field-induced enhancement of crystallinity and field-effect mobilities in phthalocyanine thin films” 

磁場誘起によるフタロシアニン薄膜の結晶性と電界効果移動度の向上

Abstract:  Organic semiconductor thin films were fabricated by thermal deposition of free-base and metal phthalocyanines under a static magnetic field. A vertical magnetic field enhanced the crystallinity of the edge-on orientation of the phthalocyanine discs, whereas a horizontal magnetic field had a minimal effect on the crystallinity. The major factor for the orientation change is attributed to the diamagnetic anisotropies of p -electrons in the phthalocyanine macrocycles. Field-effect transistors of phthalocyanine films fabricated under a vertical magnetic field exhibited better hole mobilities and on-current values with smaller threshold voltages than those of phthalocyanine films fabricated without a magnetic field.











J. Am. Chem. Soc. 2013, 135, 870–876. 

“Spherical Assemblies from π-Conjugated Alternating Copolymers: Toward Optoelectronic Colloidal Crystals” 

パイ共役交互共重合ポリマーからの球状集合体:光電子機能をもつコロイド結晶の実現に向けて

Abstract: Self-assembly of conducting polymers, which are often used as photoabsorbing, charge-transporting, and photoemission layers of organic photovoltaic and light-emitting devices, were comprehensively studied by means of slow precipitation from polymer solutions upon addition of a vapor of nonsolvents.  Polymers such as polyfluorene and polythiophene having a single monomer component hardly formed defined and discrete objects but only gave ill-defined aggregates.  In contrast, alternating copolymers typically having both fluorene and thiophene components in their repeating unit self-assembled into well-shaped spheres with diameters ranging from several hundreds of nanometers to several micrometers.  Such clear differences in terms of the assembling geometries derive from the rigidity and crystallinity of the polymers, where the copolymers possess large steric hindrance on their backbone that reduces planarity of the polymers and inhibits anisotropic crystal growth, leading to the formation of structurally isotropic spheres.  Changing the assembling parameters can systematically control diameter and deviation of the spheres.  Furthermore, photocarrier lifetimes of the spheres were markedly enhanced by more than three orders of magnitude in comparison with those of cast films from their solutions.  This research gives a useful guide for preparation of colloidal crystals from π-conjugated polymers toward their optoelectronic applications.












Angew. Chem. Int. Ed. 2012, 51, 8490–8494. 

“Discotic Ionic Liquid Crystals of Triphenylene as Dispersants for Orienting Single-Walled Carbon Nanotubes” 

カーボンナノチューブを配向可能な分散剤としてのディスク状イオン液晶

Abstract: Triphenylene-based discotic ionic liquid crystals (ILCs) with six imidazolium ion pendants can disperse pristine single-walled carbon nanotubes (SWNTs) 2–3 orders of magnitude better than reported LCs.  When ILC is columnarly assembled, doping with SWNTs results in homeotropic columnar orientation up to a macroscopic length scale.  Combination of shear and annealing treatments gives rise to three different states in terms of the orientations of the LC columns and SWNTs, where the anisotropy of electrical conduction is determined predominantly by whether SWNTs are unidirectionally oriented or not.











J. Am. Chem. Soc. 2012, 134, 2524–2527. 

“Segregated and Alternately Stacked Donor/Acceptor Nanodomains in Tubular Morphology Tailored with Zinc Porphyrin-C60 Amphiphilic Dyads:  Clear Geometrical Effects on Photoconduction” 

亜鉛ポルフィリンーフラーレン連結分子の自己組織化による、チューブ状構造体への分離積層型および交互積層型D/Aナノドメインの選択的作りわけと明確な光伝導性への影響

Abstract: Amphiphilic zinc porphyrin (PZn; electron donor, D)–fullerene (C60; electron acceptor, A) dyads 2 and 3, bearing an identical hydrophilic wedge with triethylene glycol chains but different linkers between the PZn and C60 units, self-assemble into nanotubes with essentially different dimensional and geometrical features from one another. The nanotube from dyad 2 with an ester linker consists of a bilayer wall formed with coaxially segregated D and A nanodomains along the tube axis (coaxial D–A heterojunction), thereby displaying explicit photoconductivity with ambipolar carrier transport properties. In contrast, the nanotube from dyad 3 with a rigid arylacetylene linker consists of a monolayer wall with an alternate geometry of D/A stacking, resulting in poor photoconducting outputs. Such a geometrical difference also significantly affects the photovoltaic properties.













Sci. Technol. Adv. Mater. 2012, 13, 033001/1–15. (Review)

“Programmed Self-Assembly of Large π-Conjugated Molecules into Electroactive One-Dimensional Nanostructures”

大きなπ共役分子の電子活性1次元ナノ構造へのプログラム自己組織化

Abstract: Electroactive one-dimensional (1D) nano-objects possess inherent unidirectional charge and energy transport capabilities along with anisotropic absorption and emission of light, which are of great advantage for the development of nanometer-scale electronics and optoelectronics. In particular, molecular nanowires formed by self-assembly of π-conjugated molecules attract increasing attention for application in supramolecular electronics. This review introduces recent topics related to electroactive molecular nanowires. The nanowires are classified into four categories with respect to the electronic states of the constituent molecules: electron donors, acceptors, donor–acceptor pairs and miscellaneous molecules that display interesting electronic properties. Although many challenges still remain for practical use, state-of-the-art 1D supramolecular nanomaterials have already brought significant advances to both fundamental chemical sciences and technological applications.














Bull. Chem. Soc. Jpn. 2011, 84, 17–25. (Account)

“Electroactive Nanotubes from π-Conjugated Discotic Molecules”

パイ共役ディスク状分子からなる電子活性ナノチューブ

Abstract: Self-assembly of π-conjugated molecules is attractive for construction of well-defined, nanometer-scale electroactive materials. This account describes our developments on self-assembled nanotubes from Gemini-shaped hexa-peri-hexabenzocoronenes (HBCs). At first, detailed molecular arrangement in the nanotube is presented, which is perfectly revealed by a synchrotron radiation X-ray diffraction analysis of a macroscopic fiber consisting of highly aligned HBC nanotubes. Next, electroconductive properties of the HBC nanotubes are investigated. By means of direct current and noncontact methods, anisotropic charge-transport properties in the nanotubes are confirmed. The effect of the surface oligoether chains on intertubular conduction is also examined by field-effect transistor measurements. Finally, optoelectronic applications are developed by constructing newly designed nanotubes. These nanotubes possess a coaxial configuration, where an electron-donating graphitic bilayer of π-stacked HBC arrays is laminated by an electron accepting molecular layer. Due to the molecular-layer donor/acceptor heterojunction, the nanotubes exhibit remarkable photoconduction and photovoltaic outputs. Furthermore, the optoelectronic properties are modulated by changing the density of electron acceptors on the nanotube surfaces by coassembly of multiple components or utilizing photochromism. These results will advance to electronic and optoelectronic applications of supramolecular nanomaterials.