星野 勝義

It is empirically known that titanium dioxide nanoparticles stabilize the contact and frictional charge of the host polymers to which they are added. However, the mechanism for the stabilization process has not yet been elucidated. In this study, polyester films doped with titanium dioxide nanoparticles of different crystalline forms were triboelectrically charged and the effect of humidity on their charging characteristics was subsequently investigated to elucidate the charge stabilization mechanism. Our first finding was that the rutile-, rutile–anatase mixed crystal (P25)-, and amorphous-dominant-type titanium dioxide nanoparticles reduced the sensitivity of the films to humidity (humidity dependence), while the anatase-type titanium dioxide enhanced the humidity dependence. This difference in action was explained by associating it with the different water adsorption forms on the major crystalline surface of each titanium dioxide type. The second finding was that doping with titanium dioxide nanoparticles, particularly rutile and P25 nanoparticles, reduced fluctuations in the amount of tribocharges of the polyester film. This crystalline-form-dependent difference in action was considered to be based on the depth of the electron traps involved in each titanium dioxide type. The above two findings have allowed us to propose the first mechanism of tribocharge stabilization by titanium dioxide.

The achievement of molecular orientation control by rubbing and pressing poly(3-alkylthiophene)s is a powerful technique to improve the performance of organic electronic devices. We report here that the rubbing and pressing of blackish-brown 3-methoxythiophene oligomer powders yield layer and tablet samples with gold tones, respectively. Specular reflectivity, colorimetric, and X-ray diffraction measurements reveal that this gold tone is caused by an increase in the ratio of edge-on lamellar crystallites to face-on ones, which is promoted by rubbing/pressing. In contrast to the 3-alkylthiophene polymer, which develops a dominant face-on lamellar structure, rubbing of the 3-methoxythiophene oligomer increases the relative amount of edge-on lamellar crystallites to face-on lamellar ones. Furthermore, gold tone development in the tablet samples is limited to the near-surface area, despite the fact that pressure is also applied to the tablet bulk. These specific chemical events are explained by considering the repulsive interactions between the 3-methoxythiophene backbone and the functional groups on the surface of the substrate employed during the rubbing/pressing processes. Despite the lower applied pressure, gold tone development by rubbing is accompanied by a higher reflective property than by pressing because of the formation of larger relative amounts and sizes of edge-on lamellar crystallites, which are responsible for the gold tone.

Solution-cast coating films of perchlorate-doped oligo(3-methoxythiophene) exhibited a gold-like luster similar to that of metallic gold despite the involvement of no metals. However, the development mechanism of the luster remains ambiguous. To understand the mechanism, we performed scanning electron microscopic analysis, variable-angle spectral reflectance measurements, and ellipsometry measurements on ClO4−-doped oligo(3-methoxythiophene) cast film with a gold-like luster. The results revealed that the lustrous color of the film was not induced by the submicron-sized regular structures (structural color), nor by the high-density free electrons (reflective response based on Drude model), but by the large optical constants (refractive index and extinction coefficient) of the film, as speculated previously.

<p>著者らはこれまで，過塩素酸イオンがドープされた3-メトキシチオフェン重合体の塗布膜が，金色調光沢を示すことを示してきた．本研究では，過塩素酸イオンの代わりにテトラフルオロホウ酸イオンをドーパントに用いたところ，膜の色および光学物性が異なる結果が得られた．具体的には，ドーパントが過塩素酸イオンの場合は，膜が黄色みの強い金色調光沢色を示すのに対して，テトラフルオロホウ酸イオンの場合は，緑色みの反射が加わることで，より白色に近い金色調光沢色となった．また後者の膜の正反射率は，過塩素酸イオンドープ膜に比べて増加した．それぞれの重合体の分子量およびドープ率に大きな差は見られなかった．一方，各膜のX線回折測定の結果から，テトラフルオロホウ酸イオンの場合には，金色調光沢発現の要因の一つであるedge-onラメラ構造の割合が高いことが判明した．これらのことから，色調の違いおよび正反射率の増加が生じたのは，テトラフルオロホウ酸イオンの存在により膜中のedge-onラメラ結晶の存在割合が増加したためであることが示唆された．</p>

Metal-free, metal-like lustrous films may find applications in a variety of fields, and a study of the factors affecting their stability is highly desirable. In particular, chemical events occurring in the coating solutions might affect the supramolecular organization of the films and therefore the metal-like luster. Herein, the chemical events occurring in acetonitrile and nitromethane coating solutions of oligo(3-methoxythiophene) and their effect on the optical properties of the films were investigated by X-ray diffraction, UV-vis absorption, and viscosity measurements. In acetonitrile, the oligomers underwent gradual dedoping with time, but only small changes in viscosity were observed. The solution was applied to a glass plate to yield a dark brown film, which turned into a goldlike lustrous film by rubbing. In nitromethane, the supramolecular structure of the oligomers changed with time from the nonaggregated state to π-dimers and then to π-stacks, and the viscosity increased. The properties of the goldlike films prepared from this solution were greatly affected by this chemical event. Remarkably, the π-dimer solution provided the film with the highest specular reflectance, yellowness, greenness, brightness, and crystallinity.

Electropolymerization of 3-methoxythiophene in the presence of tetramethylammonium tetrafluoroborate produced gold-like lustrous films with a deeper yellowish tone and higher specular reflectance as compared to the previously reported films prepared in the presence of lithium perchlorate. The improved optical properties were attributed to the increased film crystallinity induced by the action of dodecylsulfate ions incorporated in the films and the lower polydispersity of the BF4 1doped oligomers comprising the film.

Novel electropolymerized films that naturally appeared gold-like and possessed lustrous green color tones were prepared by the cyclic potential-sweep electropolymerization of 3-methoxythiophene. The polymerized products were characterized by different instrumentation techniques, which identified them as oligo(3-methoxythiophene) containing perchlorate and dodecyl sulfate anions. The optical and structural analyses demonstrated that the films consisted of edge-on and face-on lamellar structures of the oligomers, and that the edge-on structures contributed to the development of the gold-like luster. The role of the cyclic potential sweep was interpreted as the preferential destruction of the face-on lamellar structures and a contribution to the increasing effects of the edge-on lamellar structures.

Mixed-valence bicarbazyl nano/microtubes and wires were embedded in conventional transparent polymer films, and their transparent conductive properties were compared. Though the outer diameter and length of the two fibers are comparable, the former exhibited much higher electric conductivity and visible-light transmittance than the latter. This was explained in terms of the differences in supermolecular ordering and doping level between the two fillers. Additionally, the transparent conductive features of films on which the nano/microtubes were supported were also described.

The electrode reactions of tetrabutylammonium bromide (TBABr) and tetrabutylphosphonium bromide (TBPBr) were investigated in the presence of LiBr. The cyclic voltammograms of TBABr and TBPBr exhibited a white-colored state (white film formation) and a transparent colorless state (film dissolution). Fourier transform infrared spectroscopic and X-ray photoelectron spectroscopic measurements of the white films revealed that TBA(+) and TBP+ formed water-insoluble ion pairs with the tribromide generated by the electrooxidation of Br- to produce the white-colored TBABr(3) and TBPBr3 films, respectively. The films were reversibly decolored electrochemically to the initial transparent state. In addition, the cyclic voltammetry with different alkylammonium salts ((CnH2n+(1))(4)N+Br-, n=2, 4, 5, and 6) suggested that hydrophile-lipophile balance (HLB) was closely related to the white film formation, and that the HLB corresponding to the tetrabutylammonium made possible the formation of the stable white film with a long memory life time (recording) and the complete dissolution of the white film with a low applied potential (erasing). The morphological observation of the white films demonstrated that the white-colored appearance was attributed to the effect of light scattering by their coarse structures. (C) 2015 Elsevier B.V. All rights reserved.

An ITO (indium-tin-oxide)-nanoparticle film electrode was prepared by applying an ITO nanoparticle-dispersed solution to an ITO planar plate and then sintering it. The electrochromic properties of 1,1'-dibenzyl-4,4'-bipyridinium (DBV2+) were examined at the nanoparticle film electrode. The one-electron reduction of DBV2+ produced a filmy purple deposit of DBV+, and electrochromism between the white and purple appeared. An incomplete vanishing (ghost image), which often occurs when an ITO planar electrode is used, was not observed at the nanoparticle film electrode. The successful ghost-free electrochromism was explained in terms of the much lower molecular density of the deposited DBV+ per unit real surface area compared to that on the ITO planar electrode. Also, it was demonstrated that the coloration-decoloration cycle was significantly improved by the effect of the ghost-free electrochromism. (C) 2014 Elsevier B.V. All rights reserved.

Perchlorate-doped 3-methoxythiophene oligomer was chemically synthesized, and its solutions were applied to produce films characterized by their gold-like luster which showed no degradation in the ambient atmosphere for at least one year. The oligomer is characterized by its good solvent-soluble, good film-forming, and moderate electrical conducting properties. More importantly, wide-angle and grazing incidence X-ray diffraction measurements revealed that the gold-like films have a compact periodic layered structure with a lamellar interlayer spacing of 1.10 nm and an intralayer spacing of 0.34 nm, though the oligomer involves no long alkyl chains. It was proposed that the strong gold-like luster could be related to the highly regular and compact nature of the lamellae in the oligomer films.

The triboelectrification behavior of polymer films when in contact with iron carrier beads was investigated using a homemade special instrument which can control relative humidity under a nitrogen atmosphere. The films showed a large humidity-dependent charging behavior; the charge amount increases with the ambient humidity in the range of a few percent RH to ca. 60% RH. This dependence is explained in terms of the model based on the water charging during the friction and the penetration of the positively charged water into the film. However, it was found that the humidity dependence is significantly depressed by the doping of carboxylic acids into the film or by the introduction of a carboxyl group in the polymer backbone. This depression is again explained by the above charged-water penetration model in which carboxylate ions trap the positively charged water on the film surface.

One-dimensional copper nanomaterials are expected to play important roles in fabricating nanoscale electronic devices. In this study, we show that the electro-reduction of copper compounds in water at room temperature produces dendritic copper nanowires in the presence of ammonia without using templates. The nanowires consist of a stalk part (500 nm thick and 80 mu m long on average) and a branch part (250 nm thick and 40 mu m long on average). Microanalyses revealed that the nanowires are mainly composed of metallic copper. A preliminary study of the electrochemical capacitor properties of the copper nanowire electrode demonstrated its specific capacitance of 117 F g(-1). (C) 2012 Elsevier B.V. All rights reserved.

One of the nanocarbons, graphene, was added to a Diphenylamine-4-diazoniuin sulfate/formaldehyde condensate/polyvinyl alcohol (DSR/PVA) resist films. Conductivity of the DSR/PVA cured films was increased by the incorporation of graphene. The Conductivity was larger than that with multi-walled carbon nanotube (CNT) and fulleren C-60 (weight ratio of graphene, CNT or C-60 to DSR = 1.00 : 1.00). The conductivity of the DSR/PVA films with graphene depended on the dispersion method. The values of electric conductivity (sigma) for the thin cured films (3 mu m) were ca. 1.5 times larger than those for the thick films (4 mu m). Photodecomposition of DSR/PVA coated films with graphene was accelerated. It is considered that diazocompounds were reductively decomposed by the electrons evolved from graphene which absorbed light energy. Electron rich characteristics of graphene may play an important role in enhancing of electric conductivity and photo decomposition rate. Hardness of the DSR/PVA cured films with graphene was higher than that without additives. Conductivity and hardness of the DSR/PVA cured films containing graphene is higher than those with long CNT and round C-60 which seems to be due to more polarity edge parts of graphene.

Nanostructured composite electrodes were prepared by dip-coating a mixed dispersion of ITO nanoparticles and 1,1'-didodecyl-4,4'-bipyridinium (DDV2+) dibromide on an ITO-coated glass plate, and their electrochromic properties were investigated in a 0.1 M Li2SO4 aqueous solution. The electrodes showed a color change from pale white to violet as they were oxidized and reduced, respectively, and good electrochromic performances; i.e., switching times of coloration (500 ms) and decoloration (380 ms), coloration efficiency of 140 cm(2) C-1, long-term stability (&gt;500 test cycles), and a memory life time greater than at least 24 h.

Cobalt compound nanowires were dispersed in a transparent nonconductive polymer film by merely stirring, and the film's transparency and electrical conductivity were examined. This composite film is a unique system in which the average length of the nanowires exceeds the film's thickness. Even in such a system, a percolation threshold existed for the electric conductivity in the direction of the film thickness, and the value was 0.18 vol%. The electric conductivity value changed from similar to 1 x 10(-12) S/cm to similar to 1 x 10(-3) S/cm when the volume fraction exceeded the threshold. The electric conductivity apparently followed the percolation model until the volume fraction of the nanowires was about 0.45 vol %. The visible light transmission and electric conductivity of the composite film of about 1 vol % nanowires were 92% and 5 x 10(-3) S/cm, respectively. Moreover, the electric conductivity in the direction parallel to the film surface did not depend on the amount of the dispersed nanowires, and its value was about 1 x 10(-14) S/cm. Even in a weak magnetic field of about 100 mT, the nanowires were aligned in a vertical and parallel direction to the film surface, and the electric conductivity of each aligned composite film was 2.0 x 10(-2) S/cm and 2.1 x 10(-12) S/cm. The relation between the average wire length and the electric conductivity was examined, and the effect of the magnetic alignment on that relation was also examined.

The capacitor properties of cobalt compound nanowire (CCNW) electrodes, prepared by the one-step electroreduction of [Co(NH3)(6)](3+) in water, have been investigated. The CCNW electrode changes its various properties during its growth. During the initial growth stage, the CCNW electrodes consist of nanowires with smooth surfaces and have a specific capacitance (C-m) of 310 Fg(-1). During the middle stage, prickles grow on the CCNW surface, leading to a reduction in its real surface area and its C-m value to 230 F g(-1). During the final stage, further growth of the prickles is accompanied by the fusion of the CCNWs, and hence, a drastic decrease in the real surface area. However, a maximum capacitance of C-m = 420 Fg(-1) was obtained during this stage. This unexpected capacitance change was discussed in terms of the effects of rapid ion transfer and the electroactive material/electrolyte interface area. In addition, the aging effect and the cycle life of the CCNW electrode were also investigated. (C) 2011 Elsevier B.V. All rights reserved.

An electrochromic-type electronic paper was prepared using nanocomposites that consisted of silica nanoparticles (silica 60 wt %) and polyamide pulp. Its light scattering, ion transport, and aqueous electrolyte retention characteristics were examined. As a result, the shape of the nanocomposites was completely self-standing, though it could be impregnated with about nine times as much water on a weight basis. Moreover, its light scattering property was extremely similar to paper. Because of the impregnation of a large amount of water, the ion transport property of the nanocomposites was the same as that of the electrolyte solution without the nanocomposites. The nanocomposites was impregnated using an aqueous solution in which bismuthyl perchlorate (redox species), copper perchlorate, perchloric acid, sodium perchlorate, hydroquinone (electron mediator) and 2-buthyne-1,4-diol (leveling agent) were dissolved. The electronic paper was then prepared by sandwiching the nanocomposites between an indium tin-oxide transparent electrode and a copper sheet. This electronic paper utilizes the reversible codeposition reaction of black Bi-Cu from bismuthyl perchlorate and copper(II) ions. The characteristics of this electronic paper were examined, and excellent characteristics with a white reflectivity of 65%, black reflectivity of 6.4%, contrast ratio of 10:1, operating life of over 1 x 10(6) cycles and open-circuit memory of at least 1 month were obtained. In addition, its driving voltage was 1.2 V, and the write time was 500 ms.

The preparation and characterization of conducting polycarbazole (PCz) hybrid films with a colorless transparency are described. They were prepared by the vacuum evaporation of tin, aluminum, or gallium onto anion-doped green-colored PCz films, or by applying gallium to the films, followed by their exposure to ambient air. The resultant hybrid films consisting of an undoped PCz backbone and metal compounds exhibited good transparencies (90-95% at a wavelength of 550 nm). The hybrid films have a specific cross-sectional structure in which the small regions of the metal compounds are dispersed in the PCz backbone. The, hybridization reaction was mechanistically explained on the basis of the combination of a metal corrosion reaction and polymer dedoping reaction, which was successfully supported by the chemical analyses of the hybrid films. The electric conductivities of the hybrid films, measured by a four-point-probe method, ranged from 2.2 x 10(-4) to 6.0 x 10(-3) S cm(-1). which are considered to be the lowest limit because the use of the hybrid films as an electrochemical electrode reveals that a network of conductive paths is preferentially formed in the film thickness direction rather than in the in-plane direction.

Electro-conductivity of a thick Diphenylamine-4-diazonium sulfate/formaldehyde condensate/polyvinyl alcohol (DSR/PVA) resist layers increased by the incorporation of multi-walled carbon nanotube (CNT) and fulleren C(60) (weight ratio of CNT or C(60) to DSR = 1.00 : 1 similar to 3.00:1). Conductivity of DSR/PVA film with CNT was one order larger than that with C(60). The larger conductivity depends on the charge leakage through the network or thread-bundle structure of multi-walled CNT. Conductivity of shorter CNT (3 similar to 20 nm) was larger than that with long CNT (40 similar to 70 nm). The a values for the thin films ( 6 mu m) were ca. two times larger than those for the thick films ( 12 mu m). Photo decomposition of DSR/PVA resist with CNT was accelerated reductively by the electrons evolved from CNT, absorbing light energy. Electron rich characteristics of CNT may play an important role in the enhancement of electric conductivity and photo decomposition rate.

The electrochromic properties of 1,1&apos;-dibenzyl-4.4&apos;-bipyridinium and 1,1&apos;-diheptyl-4,4&apos;-bipyridinium were investigated in the presence of MBr (M = Li(+), Na(+), and K(+)). The cyclic voltammograms of these viologens showed a white-coloured state in addition to the usual violet one-electron reduction state and the colourless divalent state. Chemical analyses (FT-IR and XPS spectra) of the white film and some control experiments with different supporting electrolytes, MX (X = Cl(-) and I(-)), revealed that the viologens formed water-insoluble ion pairs with tribromide generated by the electrooxidation of monobromide to produce a white film. The film was reversibly decolourized electrochemically to the initial transparent state, providing the polyelectrochromism using the simple viologen/MBr systems. The colouration efficiencies for the violet and the white-coloured states were 170 cm(2)/C and 104 cm(2)/C, respectively. (C) 2009 Elsevier Ltd. All rights reserved.

Titanium oxide layers prepared by hard (rutile and anatase types) and soft processes (anodic amorphous oxides prepared in an aqueous phosphoric, TiOxw, and a dichloromethane/electrolyte solution, TiOxo) were brought into contact with the ClO4--doped poly(3-methylthiophene) (P3MeT) film, and their ability to photofix atmospheric dinitrogen was compared. The comparisons revealed that the latter junctions using amorphous oxides produced larger amount of N-2-fixation products than the former two junctions and that the P3MeT/TiOxw junction exhibited a higher N-2-fixation rate than the P3MeT/TiOxo cell. The TiOxw and TiOxo layers were characterized by transmission electron microscopic observations, X-ray electron dispersive analysis, and selected area electron diffraction measurements, and the higher activity of the TiOxw layer was rationalized on the basis of the contact potential difference measurements. Additionally, the dependences of the N-2-fixation yield on the photoirradiation time, P3MeT film thickness, and anodizing potential during the formation of the TiOxw were investigated using the most active P3MeT/TiOxw junction cell. (C) 2007 Elsevier B.V. All rights reserved.

An electropolymerized polyindole film was solubilized into a dichloromethane solution by its electrochemical reduction, and the electrochemical reoxidation of the soluble species produced the film again on the electrode surface. These dissolution and redeposition behavior were investigated by using cyclic voltammetry, UV-vis, NMR, FT-IR, and MALDI-TOFMS measurements.