Synthetic Metals (v.153, #1-3)

Contents (vii-xiii).

Preface (xvii).

Direct Formation of Pentacene Thin Films by Solution Process by Takashi Minakata; Yutaka Natsume (1-4).
Solution processing of pentacene (PEN) thin films has been studied and authors found that PEN could form solution and PEN films directly formed by developing solution of PEN onto substrates without using precursor molecules. The solution processed PEN films showed both highly crystallized structure and good transport properties of FETs with the field-effect mobility of 0.45 cm2/Vs.
Keywords: Solution processing; Semiconductor films; Organic semiconductors based on conjugated molecules (not polymers);

The aqueous solution of poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) containing various organic solvents was coated on a poly(ethyleneterephthalate) film as a substrate and carrier transport properties were investigated. It was found that an addition of ethylene glycol lowered the sheet resistance by two or three orders of magnitude. The temperature dependence of conductivity of various PEDOT/PSS coatings was described one-dimensional variable range hopping where ethylene glycol was crucial to reduce the effective energy barrier for hopping of charge carriers between localized states.
Keywords: Solution processing; Transport measurements; Conductivity; Hall effect; Magnetotransport; Grain boundaries; Amorphous thin films; Coatings; Polythiophene and derivatives;

Preparation of ITO Thin Films by Sol-Gel Process and Their Characterizations by C. Su; T.-K. Sheu; Y.-T. Chang; M.-A. Wan; M.-C. Feng; W.-C. Hung (9-12).
Indium-tin-oxide (ITO) has attracted intense interest due to some of its unique characteristics; it has high optical transmittance in the visible region, low electric resistivity, and chemical stability. Therefore, ITO thin films have been found to play an important role in opto-electronic applications. In this work, uniform and transparent ITO films were deposited onto glass substrates using a sol-gel process. The initial sols were prepared by mixing solutions of indium nitrate prepared in anhydrous ethanol with tin chloride and mechanically stirring the resultant mixture until a clear and sticky coating sol was obtained. The glass substrates were dip-coated and annealed at 550 °C. Because annealing conditions affect the microstructures, the properties of the resultant ITO films can be controlled. Depending on annealing time and film thickness, the electrical resistivity of the ITO coating varied from 27000 to 1400 Ω/□ for 8% by wt. Sn-content The optical transmittance of 200 nm thick ITO film was more than 80% in the visible region. The surface morphology examined by SEM appears to be uniform over large surface areas. Possible correlations among the film properties and film preparation conditions are discussed.
Keywords: ITO; Coatings; Sol-gel methods; Scanning electron microscopy;

We electrochemically prepared phosphate doped polyaniline films on stainless steel surface in the electrolytic solution containing various aniline concentrations and 1.0 M phosphoric acid solutions by applying a constant potential of 1.2 V (vs. SCE) for an hour at room temperature. Aniline concentrations of 0.1 M and 0.2 M were observed as optimising conditions in the phosphoric acid solution for electrodeposition. The mechanical properties of the doped polyaniline films on stainless steel revealed a strong adhesiveness and excellent uniformity. The CV diagrams of the films showed the characteristic redox couples around 0.2 V and 0.6 V. Corrosion characteristics of the coating on stainless steel (SS) 304 were investigated by polarization measurements and open-circuit potential measurements. In order to understand capability and applicability of the polyaniline coating as a protective coating against corrosion on SS 304 in acidic chloride environments, the present results were compared with the other cases. The electrolytes for corrosion test were neutral 3 wt.% NaCl, 0.5 M HCl, 0.1 M HCl + 0.4 M NaCl and 0.2 M H2SO4  + 0.2 M NaCl acidic solutions. The corrosion characteristic of the phosphate doped polyaniline films on SS resulted in not only dramatic increases in both corrosion potential and film breaking potential, but also large drop in corrosion current. The present results suggest that phosphate doped polyaniline coating on SS 304 is a strong candidate for corrosion protection of SS 304 in acidic chloride environments.
Keywords: Polyaniline; Protective coating; Phosphate; Stainless steel; Corrosion protection;

Electrosynthesis and Characterization of Composite Polypyrrole-Dextran-Sulfite Oxidase Films by Samuel B. Adeloju; Anita Ohanessian; Nguyen N. Duc (17-20).
The electrosynthesis of a composite polypyrrole-dextran-sulphite oxidase (PPy-Dex-SOx) film was carried out by galvanostatic polymerisation. The simultaneous formation of a conducting polypyrrole support and the entrapment of sulfite oxidase (SOx) on a platinum electrode was accomplished in an aqueous solution which contained 0.5 M pyrrole, 0.02 g/1 dextran and 8 units/ml SOx at an applied current density of 0.25 mA/cm2 and a polymerization time of 25 sec. The conductivity of the resulting composite PPy-Dex-SOx film was as high as that of polypyrrole- sulfite oxidase (PPy-SOx) film, but the presence of dextran improved the mechanical stability of the composite film. The presence of SOx in the composite film was confirmed by scanning electron microscopy and arnperometric measurement of sulfite.
Keywords: Electrochemical polymerization; Control of interface structure and morphology; Scanning electron microscopy; Electrochemical methods; Polypyrrole and derivatives; Detectors;

Microcontact printing of metalloproteins by Adriana Biasco; Dario Pisignano; Blandine Krebs; Roberto Cingolani; Ross Rinaldi (21-24).
The morphological investigation by scanning probes techniques, and especially Atomic Force Microscopy (AFM) allow to measure the surface roughness of immobilized proteins with unequalled vertical spatial resolution. This is particularly important, since the biological role of proteins is closely related to their physiological folding architectures. In particular, metalloproteins, such as blue copper proteins, revealed to be good candidates for biomolecular electronics by virtue of their natural electron transfer activity, which is exploitable in molecular switches whose conduction state can be controlled by gating their redox state. The interest in these molecules is indeed motivated by the possibility of eliciting current flow through the redox level of single molecules. Printing metalloproteins can be an advantageous approach for the easy realization of bioelectronic circuits. We implemented and developed the selective deposition of the metalloprotein Azurin (Az) from Pseudomonas aeruginosa by microcontact printing, and investigated by AFM the surface morphology of the printed Az layers.
Keywords: Metalloproteins; Microcontact printing; Self-assembly using surface chemistry; Atomic force microscopy;

Incorporation of Glucose Oxidase into Conducting Organic Langmuir-Blodgett Films by Nobuaki Watanabe; Hitoshi Ohnuki; Takafumi Saiki; Hideaki Endo; Mitsuru Izumi; Tatsuro Imakubo (25-28).
Conducting organic Langmuir-Blodgett films (LB) were prepared and their ability to immobilize a protein molecule was discussed. The conducting LB films are obtained by mixing bis-ethylenedioxy-tetrathiafulvalene (BO) molecule with fatty acid (FA). As an enzyme, glucose oxidase (GOD) was immobilized on the conducting LB film. Molecular orientations and other characterization of GOD-LB complexes were investigated by infrared absorption technique. To discuss the use of the conducting LB films for fabricating a glucose sensor, we investigate the change of the FT-IR in GOD-LB complexes after injection of glucose. GOD is absorbed in the LB films and maintains its bioactivity and sensitivity. The present technique with highly ordered conducting LB films is to be used as a suitable platform for immobilization of the enzyme for sensor architecture.
Keywords: Langmuir-Blodgett techniques; Infrared and Raman spectroscopy; Semiconducting films; Organic conductors based on radical and/or anion salts; BEDO-TTF; Glucose oxidase;

Light-emitting diodes fabricated from cytochrome c and myoglobin by H. Tajima; S. Ikeda; K. Shimatani; M. Matsuda; Y. Ando; J. Oh; H. Akiyama (29-32).
We have fabricated ITO-insulator-Al junctions using cytochrome c and myoglobin as insulating layers. The junctions act as light-emitting diodes. The electro-luminescence (EL) spectra of these diodes exhibit broad peaks around 530 and 700 nm, and a weak shoulder around 410 nm. These features are consistent with the absorption spectra. Although the reproducibility of the data is quite poor for the current and the EL intensity, the external quantum efficiency obtained from the two quantities are well expressed by a function of the applied voltage. The quantum efficiency almost linearly increases above the applied voltage of 7 V and reaches to ∼1 × 10−7 at V  = 14 V for both cytochrome c and myoglobin diodes.
Keywords: Atomic force microscopy; Optical absorption and emission spectroscopy; Electroluminescence; Metal/insulator interfaces;

Near-infrared luminescent bis-squaraine dyes linked by a thiophene or pyrene spacer for noncovalent protein labeling by Hiroyuki Nakazumi; Taishi Ohta; Hiroyuki Etoh; Takaaki Uno; Christa L. Colyer; Yutaka Hyodo; Shigeyuki Yagi (33-36).
Novel bis-squaraine fluorophores with near-infrared emissions have been synthesized, in which two squaraine moieties are conjugatively linked by a thiophene, oligothiophene or pyrene spacer. Bis-squaraine dyes linked by a monothiophenc or pyrene spacer exhibit enhanced fluorescence by the formation of 1:1 dye-protein complexes when bound as noncovalent labeling probes to human serum albumin (HSA) and bovine serum albumin (BSA).
Keywords: Photoluminesccnce; UV-Vis-NIR absorption; Polythiophcne and derivatives; Coupling reactions;

Photodynamic effect of hydrophilic C60-derived nanostructures for catalytic antitumoral antibacterial applications by Chi Yu; Taizoon Canteenwala; Long Y. Chiang; Brian Wilson; Kenneth Pritzker (37-40).
Appreciable production rate of singlet oxygen (1O2) from water-soluble molecular micelle-like hexa(sulfo-n-butyl)[60]fullerene upon laser irradiation at 500–600 nm was detected via 1O2 emission at 1270 nm, that was correlated to its involvement in photodynamic therapy (PDT) for antitumoral and antibacterial treatments.
Keywords: C60 derivative; Hexa(sulfo-n-butyl)[60]fullerence; Singlet oxygen; Photodynamic therapy; Antitumor; Antibacteria;

Polymer FET with a conducting channel by S. Ashizawa; Y. Shinohara; H. Shindo; Y. Watanabe; H. Okuzaki (41-44).
Metal-insulator-semiconductor field effect transistor (MISFET) using poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) as an active channel was fabricated by multiple line patterning, one of the most simple, rapid, and inexpensive methods capable of making patterns of conducting polymers, insulators, and metals using a standard laser printer. The MISFET operated both in the depletion and enhancement modes in response to positive and negative gate voltages, respectively, where the gate current was crucial to the performance of the device. Furthermore, a novel device, metal-semiconductor field effect transistor (MESFET) using a Schottky barrier formed at the interface between aluminum and PEDOT/PSS instead of the polymer insulator, was fabricated.
Keywords: Polythiophenc and derivatives; Metal/insulator interfaces; Metal/semiconductor interfaces; Schottky barrier;

Conjugated polymers encapsulated with microspheres of polyvinyl alcohol by Edelma E. da Silva; Luiz A. Cury; Luiz O. Ladeira; Nathan B. Viana; Oscar N. Mesquita; Luiz G. Guimaraes (45-48).
The synthesis and characterization of fluorescent microspheres of poly(2-methoxy,5-(2’ethyl-hexiloxy)-p-phenilene vinylene) MEH-PPV conjugated polymer encapsulated with polyvinyl alcohol (PVA) are presented. Comparison between the emission spectra obtained for MEH-PPV in chloroform solution and for a single PVA/MEH-PPV microsphere is done. The broadening and the enhancement of the vibronic peaks observed in the isolated microsphere spectrum are interpreted as due to confinement effects. Quality factors, of the order of 104 to 105, were estimated for microspheres radius ranging from 12 to 17 μm, which strongly indicate that PVA/MEH-PPV microspheres are potential candidates for high gain spherical cavity lasers.
Keywords: Photoluminescence; Poly(phenylene vinylene) and derivatives; Lasers;

The need for building an infrastructure of embedded passive technology for electronic devices has become important due to the relentless push toward “smaller”, “smarter”, “cheaper”, and “faster”. Both embedded capacitors and resistors have been developed to fill the material gaps stated in the NEMI roadmap. In this presentation, we would like to introduce the development of embedded resistors by utilizing some conducting polymers along with their packaging technologies such as, integrating and embedding, lamination and chemical etching, screen printing and ink jetting. Those material properties and processing as well as the device performance and challenges will be addressed in the paper.
Keywords: Conducting polymers; Embedded resistor; Nano-particles; Electronic packaging;

Light emission in the channel region of a thin-film transistor using the semiconducting polymer Super Yellow as the emissive material is reported The transistor structure was fabricated with light emission as the goal. To accomplish this, gold, which is a good hole injector into the organic layer, was patterned for one electrode, while aluminum, which has been shown to function as an electron injecting contact in sandwich and planar organic light emitting diodes, was patterned for the other electrode. The channel length was ∼1 micrometer and the channel width was −4000 micrometers. The data demonstrate that the magnitude of the gate bias influences the brightness of the emission zone. The location of the emission zone and the possible mechanism of operation will be discussed.
Keywords: Polymer field effect transistor; Light emission; Gold; Aluminum;

Development of Integrally Skinned Asymmetric Polyaniline Hollow Fibers for Membrane Applications by I.D. Norris; A.G. Fadeev; J. Pellegrino; B.R. Mattes (57-60).
Fabricating integrally-skinned asymmetric hollow fiber membranes from concentrated polyaniline solutions is technically challenging due to the complex issues associated with rapid gelation of the polymer solution and controlling the phase inversion process to create porous structures. Different processing parameters, such as solution composition, coagulants, and spinning conditions were shown to dramatically affect the morphology of immersion-precipitated polyaniline hollow fiber membranes. This study revealed that it is possible to minimize macrovoid formation while controlling the thickness of the selective layer and the porosity of the support layer. Asymmetric polyaniline hollow fibers with morphologies that range from a highly permeable microporous interface to a dense selective layer have been successfully produced. The membrane properties can be tailored by doping the polyaniline hollow fiber with the desired dopant acid during the fiber-spinning process. Asymmetric integrally-skinned polyaniline hollow fiber membranes with an ultra-thin (<1 μm), defect-free selective layer have been produced on a continuous basis (150 m/h). Furthermore, the thickness of the dense layer can be systematically increased up to 30 μm for combined heat-mass transfer applications such as the dehumidification of air.
Keywords: Polyaniline and derivatives; Solution processing; Manipulation of surface structure and morphology;

Electrically conducting polypyrrole fibers spun by electrospinning by Tae Su Kang; Soong Wook Lee; Jinsoo Joo; Jun Young Lee (61-64).
Electrospinning is a process that produces continuous fibers with the diameters in the range of micron or sub-micron, where many solution jets are split by the repulsive electric force imposed on a polymer solution or melt. In this study we fabricated electrically conducting polypyrrole (PPy) fiber nonwoven web using the electrospinning technique and investigated the properties of the fiber and the web. Highly conducting soluble PPy was first chemically polymerized using ammonium persulfate (APS) as the oxidant and dodecylbenzene sulfonic acid (DBSA) as the dopant source. Electrical conductivity and solubility of the resulting PPy powder significantly varied with the polymerization conditions such as the concentration of the oxidant, polymerization temperature and time. PPy solution with the appropriate concentration for the electrospinning was prepared by dissolving PPy powder in chloroform with extra DBSA. Electrospinning of the PPy fiber was then carried out under applying electrical voltage of 30 to 45 kV. The electrospun PPy fiber nonwoven web was finally washed with methanol to remove the remaining extra DBSA in the fiber, resulting in electrically conducting PPy nonwoven web. The PPy fibers exhibited circular cross-section and the extraordinarily smooth surface and the diameter of the fibers was about 3 μm. The electrical conductivity of the compressed PPy nonwoven web was about 0.5 S/cm, which is slightly higher than those of the powder or the cast films, possibly because of molecular orientation induced during the electrospinning.
Keywords: Polypyrrole; Solubility; Electrospinning; Electrically conducting fiber; Electrically conducting nonwoven web;

Conducting Polymers on Paper Fibres by James H Johnston; John Moraes; Thomas Borrmann (65-68).
Conducting polymers have generated a great deal of interest because of their physical and chemical properties as well as their potential in industrially useful materials. However, one of the shortcomings of most conducting polymers is that they are often formed as intractable films that are difficult to process [1]. To overcome this problem we have incorporated various conducting polymers into sheets of paper in order to create new composite materials which combine the universal properties of a paper sheet or paper products with the chemical and electrically conducting properties of the conducting polymer.Various composite paper – conducting polymer products have been prepared by polymerizing polypyrrole and polyaniline directly onto the paper sheet using ferric chloride as the oxidant. Electronmicroscopy shows that the polymers comprise spheres of about 50–150 nanometers in size fused together such that they fully encapsulate the individual cellulose fibres in the paper sheet. The open matrix of fibres characteristic of the original paper sheet is maintained and hence provides a much greater specific surface area for the conducting polymer than that of a continuous flat sheet which would be the case if the polymer simply formed a laminar coating on the paper surface. In the case of polyaniline, it was also possible to form a different morphology of the polymer comprising a mix of nano-size spheres, rods and plates using ammonium persulfate as the oxidant. Conductivities of up to 6 S cm−1 have been measured for paper-polypyrrole composites and up to 2x10−3 S cm−1 for paper-polyaniline composites.
Keywords: Polyaniline; Polypyrrole; Paper; Fibres; Redox; Conductivity;

A Simple Approach to Control the Growth of Polyaniline Nanofibers by Nan-Rong Chiou; Arthur J. Epstein (69-72).
Polyaniline nanofibers are synthesized via controlled chemical oxidative polymerization. The interconnected, branched network-like nanostructures are demonstrated through scanning electron microscopy (SEM). Using different synthetic conditions as well as different dopant acids we can control the diameters of polyaniline nanofibers ranging from 30 nm to 80 nm. UV/vis spectra of polyaniline nanofibers are consistent with nonfibrous polyaniline powders prepared by the conventional chemical synthesis. The nanofibrous morphology has no significant change when redoped/dedoped multiple times by the acid/base solutions. The formation mechanism of the nanofibers is discussed.
Keywords: Polyaniline; Nanofiber; Nanostructure; Chemical polymerization; Dilute polymerisation;

Electroabsorption (EA) and photocurrent measurements are carried out for a Au/Zn-phthalocyanine(ZnPc)/C60/In/Al heterojunction cell in order to elucidate the effect of photoexcitation of ZnPc or C60 on the inner electric field E 0. By a pumping excitation of either the ZnPc or C60 layer, the E 0 of the pumped layer is decreased and that of the other layer is increased. The photocurrent due to a probing-light illumination besides the pumping-light illumination has a good correlation with E 0 under the pumping excitation of ZnPc but has no correlation under the pumping excitation of C60.
Keywords: Electroabsorption; Solar cells; Fullcrenes and derivatives; Organic semiconductors based on conjugated molecules;

New application of electrospun TiO2 electrode to solid-state dye-sensitized solar cells by Mi Yeon Song; Do Kyun Kim; Kyo Jin Ihn; Seong Mu Jo; Dong Young Kim (77-80).
A new application of electrospun TiO2 nanofibers was reported for an electrode for dye-sensitized solar cells (DSSCs). TiO2 nanofiber electrode was electrospun directly onto a FTO substrate from a mixture of titanium propoxide and poly(vinyl acetate) (PVAc) in dimethyl formamide. The TiO2 nanofibers are composed of one-dimensionally aligned fibrils ca. 20-nm thick with an islands-in-a-sea morphology, which was obtained from the phase separation of TiO2 gel and PVAc during solidification process. The pretreatment of the electrospun web by exposing it to solvent vapor prior to calcination at 450 °C in air was found to result in a stable electrode that could be used in a DSSC. The electrospun TiO2 electrode could be efficiently penetrated by a viscous polymer gel electrolyte because of its porous structure. The DSSC with electrospun TiO2 electrode with gel electrolyte based on PVDF-HFP reveals the conversion efficiency of 3.8 % with the global AM 1.5 illumination of 100 mW/cm2. The overall conversion efficiency of gel electrolyte system was found to be over 90 % of liquid electrolyte.
Keywords: Electrospinning; Titanium dioxide; Nanofibers; Dye-sensitized solar cell; Gel electrolyte;

Novel Regiospecific MDMO-PPV Polymers with Improved Charge Transport Properties for Bulk Heterojunction Solar Cells by A.J. Mozer; P. Denk; M.C. Scharber; H. Neugebauer; N.S. Sariciftci; P. Wagner; L. Lutsen; D. Vanderzande; A. Kadashchuk; R. Staneva; R. Resel (81-84).
A series of novel regiospecific MDMO-PPV polymers have been synthesized by the copolymerization of the mixture of the two isomers of the asymmetrically substituted monomer via the sulphinyl precursor route. As the weight percent of either one of the two isomers is increased above ∼80 percent, the solubility of the resulting polymer is reduced. This is attributed to enhanced interchain ordering in the solid as evidenced by X-ray diffraction measurements. The hole mobility of the polymer prepared by the copolymerization of the 70:30 weight percent mixture of the two isomers (70:30 RS-MDMO-PPV) is found to be a factor of ∼3.5 higher at all measured electric fields at room temperature as compared to the regiorandom MDMO-PPV (RRa-MDMO-PPV). The electric field and temperature dependence of the hole mobility is discussed in the framework of disorder formalism and reveals an interplay between the one order of magnitude higher prefactor mobility and the slightly increased energetic disorder. Such behavior is attributed to the presence of ordered regions embedded in an otherwise amorphous matrix. The mobility is expected to increase within the ordered regions due to better electronic coupling. On the other hand, such regions may act as traps for the charge carriers, as it is supported by thermally stimulated luminescence measurements. Finally, bulk heterojunction photovoltaic devices based on the blends of 70:30 MDMO-PPV and the methanofullerene PCBM with improved power conversion efficiency and a high (0.71) filling factor have been fabricated.
Keywords: Photoconductivity; Transport measurements; Poly(phenylcne vinylenc) derivatives; Fullerenes and derivatives; Solar cells;

Screening for artifacts in near-field scanning photocurrent microscopy images of polymer solar cells by C.R. McNeill; C.J.R. Fell; J.L. Holdsworth; P.C. Dastoor (85-88).
We present the results of an investigation to screen for the presence of artifacts in near-field scanning photocurrent microscopy (NSPM) images of polymer solar cells caused by variations in tip-sample separation. We show that by increasing the size of the probe tip we are able to deliberately degrade the surface topographical image without altering the photocurrent image. This work demonstrates that NSPM images of polymer solar cells reliably probe the local charge generation properties of the device and are not significantly influenced by the presence of artifacts. Polyfluorene blend solar cells are used as a model system for this study.
Keywords: Solar cells; Polyfluorene blends; NSOM;

Electrochemical capacitor with chemically polymerized conducting polymer based on activated carbon as hybrid electrodes by Kwang Sun Ryu; Young-Gi Lee; Kang Man Kim; Yong Joon Park; Young-Sik Hong; Xianglan Wu; Man Gu Kang; Nam-Gyu Park; Rak Young Song; Jang Myoun Ko (89-92).
ACP/PAn hybrid electrodes for surpercapacitors were fabricated by adsorption of aniline monomers on the surface of activated carbon powders (ACP) and their polymerization by using a chemical method. Their capacitance performances were investigated in the 1M H2SO4 aqueous electrolyte solution by means of cyclic voltammetry and impedance spectroscopy. The cyclic voltammetric results showed that the ACP/PAn electrodes gave an increased specific capacitance value of 273 F/, which was larger than the capacitance of the ACP, approximately 193 F/g. However, impedance spectroscopic data showed better response time and higher frequency capacitance performance in ACP than ACP/PAn electrodes. This result means that the redox reaction of PAn is rate-determined step and can not contribute for charge storage at high frequency range over 1 Hz.
Keywords: Dual-layer; Polymer electrolyte; Compatible layer; Inorganic single ion conductor; Ionic conductivity; High rate capability;

A new type of polythiophene derivatives, regioregular side-chain conjugated polythiophene (rr-PsccPH), was synthesized. The absorption spectrum of the rr-PsccPH film was red-shifted by ca. 80 nm in comparison with that of poly (3-arylthiophene). The photovoltaic cells based on the blend of the polymer and C60 were fabricated and characterized. Energy conversion efficiency of the photovoltaic cell under a white light (70 mW/cm2) was 0.54%, when the weight ratio of the polymer to C60, equals to 1:2.
Keywords: Polythiophene; Side-chain conjugated; Solar cells;

The effect of a buffer layer on the photovoltaic properties of solar cells with P3OT:fullerene composites by Insun Yoo; Munjae Lee; Changhee Lee; Dae-Won Kim; In Sik Moon; Do-Hoon Hwang (97-100).
We have studied the effect of buffer layers such as poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), copper phthalocyanine (CuPC), and gold metal on the photovoltaic properties of solar cells with poly(3-octylthiophene) (P3OT):fullerene composites. The device structure is ITO/buffcr/P3OT:C60/BCP/LiF/Al where bathocuproine (BCP) was used as an exciton-blocking layer. The cell with a PEDOT:PSS buffer layer exhibits an open circuit voltage of Voc  ∼ 0.4 V and the power conversion efficiency of η ∼ 1.8%. The incident photon to collected election efficiency (IPCE) is about 30% at 520 nm. The cell with a CuPC buffer layer exhibits slightly higher Voc  ∼ 0.46 V and power efficiency of η ∼ 2.1%. This result indicates that a good buffer layer at the polymer/electrode interfaces can enhance the Voc. and die power conversion efficiency.
Keywords: Organic solar cell; Photovoltaic properties; Buffer layer;

The humido-responsive behavior of polypyrrole films at different temperatures under various humidities was investigated. The motion of film lay in the anisotropic expansion due to the sorption of water vapor from one side of the film, where the degree of bending was in proportion to the relative humidity change regardless of the temperature or absolute humidity. On the other hand, the film bent more quickly at higher temperatures, which was associated with the large diffusion coefficient for water vapor molecules in the film. The apparent activation energy in the sorption and desorption processes was found to be 46.0 kJ mol−1and 44.6 kJ mol−1, respectively.
Keywords: Electrochemical polymerization; Semiconducting films; Polypyrrole and derivatives;

Electrically induced contraction of zone-drawn polypyrrole films by H. Okuzaki; T. Hattori; H. Morikage; Y. Yamada (105-108).
The zone-drawing method was applied to electrochemically synthesized polypyrrole films at different heater temperatures under various applied tensions. It was found that the film could be zone-drawn by a factor of 1.4 at the drawing temperatures of 150–200 °C. The electrical conductivity and Young's modulus increased to 327 S cm−1 and 3.6 GPa from 145 S cm−1 and 0.9 GPa of the as-synthesized film, respectively. When dc 3 V was applied in the drawing direction, the zone-drawn film exhibited contraction of 0.3% parallel to the electric field, while that perpendicular to the electric field reached 1.4%. The large anisotropy in contraction was explained by the orientation of polymer chains: the water vapor molecules sorbed on the conducting paths of polypyrrole chains aligned in the direction of the current flowing might desorb by the local Joule heating, thereby contracting the film in the lateral direction. The anisotropy, defined as the ratio of contractions between parallel and perpendicular to the electric field, was 4.6 under 3 V.
Keywords: Electrochemical polymerization; Tensile drawing; Semiconducting films; Polypyrrole and derivatives;

The polypyrrole films doped with tetrafluoroborate were electrochemically synthesized and contractile behavior was measured in air under ac voltages. It was found that the film did not respond at MHz frequencies but underwent gradual contraction where the changes in the strain, electric current, and temperature of the film were independent on the frequency in a range from dc to 1 MHz under the same effective value of the electric field. The resistance of the film was constant about 35 Ω but the capacitance decreased with the frequency, indicating that the electrically induced contraction of the film under ac voltage could be explained by the same mechanism under dc voltage where the dehydration of polymer chains and/or dopant ions due to the Joule heating.
Keywords: Electrochemical polymerization; Semiconducting films; Polypyrrole and derivatives;

Carbon-enriched Li0.98Mg0.02FePO4 compounds were prepared by a novel modified solid-state reaction method Citric acid added to the precursors works as a particle size growth inhibitor as well as a carbon source. Electrochemical evaluation of the Li0.98Mg0.02FePO4 reveals a lithium insertion plateau around 3.4 V vs. Li together with a specific capacity of over 160 mAh/g at the C/20 rate. Differential capacity data confirm the two-phase nature of the insertion reactions as well as outstanding ionic reversibility.
Keywords: Carbon-enriched; Li0.98Mg0.02FePO4 compounds; modified solid-state reaction;

Electrochemical synthesis of polypyrrole films using stainless steel mesh as substrate for battery application by J. Wang; J. Chen; C.Y. Wang; D. Zhou; C.O. Too; G.G. Wallace (117-120).
The effect of synthesis conditions of polypyrrole films, using stainless steel mesh as electrode substrate, on the capacity of batteries has been investigated. The polypyrrole films were prepared using different solvents, different polymerization methods, and different deposition time. The results show that the performance of the cell with stainless steel mesh is similar to the cell using platinum mesh, but stainless steel mesh is lighter and cheaper than that of platinum mesh.
Keywords: Electrochemical polymerization; Substrate material; Polypyrrole electrode; Batteries; Capacity;

Fabrication and evaluation of actuators based on polymer electrolyte membranes by T. Nakano; Y. Takeoka; M. Rikukawa; K. Sanui (121-124).
Actuators based on hydrocarbon polymer electrolyte membranes having phosphoric acid groups were fabricated to investigate the correlation between the chemical properties and the actuation. The bending size and velocity of actuation were measured and compared with the values for fluorocarbon polymers, Nafion®-based actuators. The actuators were fabricated by coating polymer electrolyte membranes with gold using dichlorophenanthrolinegold (III) chloride. The actuators bent toward the anode when the applied voltage was over 1 kV. Nafion®-based actuators reached the maximum displacement size within 1 s, while the hydrocarbon polymer-based actuators took over 60 s. The difference in the velocity of actuation was caused by the difference in the proton conductivity of polymer electrolyte membranes. The maximum displacement size of hydrocarbon polymer-based actuators was nearly equal to that of Nations-based actuators.
Keywords: Conducting polymer; Amorphous thin films; Metal/electrolyte interfaces; Switches;

Synthesis of optically active regioregular poly(thiophene) by Fumihiko Saito; Yuko Takeoka; Masahiro Rikukawa; Kohei Sanui (125-128).
A regioregular polythiophene bearing an optically active substituent at the 3-position of thiophene ring, Head-to-Tail poly(3-[2-((S)-1-methyloctyloxy)ethyl]thiophene) (HT-P(S)MOET), was synthesized using highly reactive zinc. HT-P(S)MOET had more than 95% Head-to-Tail coupling with a Mw of 3.72 × 104 (Mw/Mn = 1.20) as estimated by 1H-NMR spectroscopy and gel permeation chromatography. HT-P(S)MOET had strong negative Cotton effect at about 560 and 610 nm and positive Cotton effect at about 490 nm. The presence of circular dichroism effect shows that the chirality of side chains induces the optical activity in poly(thiophene) main chains. The Langmuir-Blodgett films of HT-P(S)MOET exhibited well-defined layer structure and unique optical properties.
Keywords: Polythiophene and derivatives; Langmuir-Blodgett techniques; Coupling reactions;

In order to improve the processibility of polyaniline (PANI), poly(o-ethoxyaniline) (PEOA) is grafted with ethoxy group on the PANI backbone and synthesized via an emulsion polymerization. The electric conductivity of PEOA is lower than that of PANI due to the interference of ethoxy side group in the electronic conjugation of polymer backbone. However, PEOA has better solubility than PANI in common organic solvents. PEOA/organically modified montmorillonite (OMMT) nanocomposites were thereby prepared via a solvent intercalation method, using an OMMT. The electrical conductivity of PEOA/OMMT nanocomposites was controlled via OMMT contents. The internal structures, electrical properties, and thermal properties of these nanocomposites were examined via wide angle X-ray diffraction (WAXD), transmission electron microscope (TEM), scanning electron microscope (SEM), two probe conductivity measurement, and thermogravimetric analyzer (TGA). The intercalated nanostructures analysed via WAXD and TEM were correlated with the electrical and thermal properties change originated from the nanoscale interaction between OMMT and PEOA.
Keywords: Conducting polymer; Poly(o-ethoxyaniline); Nanocomposite; OMMT;

Polyanilines containing transition metal ions were synthesized by oxidizing the complex of aniline with the corresponding metal chloride in solution. The influence of the synthetic conditions such as reaction medium, the molar ratio of reactants, temperature and time on the polymer yield and electrical conductivity was discussed. The products were characterized by elemental analysis, FT-IR spectroscopy and in-situ UV/Vis spectroscopy. Scanning electron micrograph was employed to examine the morphology of polyanilines synthesized in the presence of different transition metals. Experimental results showed that transition metal ions had been successfully incorporated into the polymer, and there was a strong interaction between the transition metal ions and polyaniline chains. Thermogravimetric analysis demonstrated that the thermal stability of polyaniline containing transition metal ions was lower than that of emeraldine base of polyaniline.
Keywords: Polyaniline; Transition metal ions; Synthesis; Characterisation;

In search for polymers with tunable spectroscopic and electrochemical properties, suitable for application in organic electronics, we have elaborated two new families of proccssible conjugated polymers containing electroactive side chain chromophores of oligoaniline type. Random copolymers of 3-alkylthiophenes and 3-oligoaniline thiophenes can be prepared in a three-step procedure. First, 3-alkylthiophene and ethyl-3-thiopheneacetate are copolymerized to give poly(3-alkyl-2,5-thienylene-co-3-methyiene-ethylcarboxylate-2,5-thienylene)-the precursor polymer. The precursor is then hydrolyzed and, in the last step, aniline oligomers are attached to it via amidation reaction. Regioregular copolymers with oligoaniline pendant groups are prepared by post-polymerization functionalization of regioregular precursor copolymers, namely poly(dialkyl-2,2′-bithiophene-alt-2,7-fluoren-9-one)s by grafting aniline oligomers via the carbonyl groups of the fluoren-9-one subunit The properties of the precursors as well as oligoaniline containing polymers are determined by electrochemical methods and UV-Vis-NIR, EPR and FTIR spectroscopy.
Keywords: Polythiophene; Oligoaniline; In situ electrochemical spectroscopy; UV-Vis-NIR absorption;

Third-order nonlinear optical spectroscopy in charge-transfer type conjugated polymers by Hideo Kishida; Keisuke Hirota; Takeru Wakabayashi; Hiroshi Okamoto; Ban-Lin Lee; Hisashi Kokubo; Takakazu Yamamoto (141-144).
We have investigated the linear and third-order nonlinear optical properties in a charge-transfer (CT) type conjugated copolymer, PThQx, which is composed of an electron-donating molecule, thiophene (Th), and electron-accepting one, quinoxaline (Qx), by using the linear absorption, two-photon absorption (TPA), and third-harmonic generation (THG) spectroscopies. In comparison with a homopolymer, polythiophene, the absorption coefficient α of PThQx is significantly reduced, while its third-order nonlinear susceptibility (χ(3)) is unchanged. This indicates that the figure of merit for the nonlinear optical materials, defined as χ(3)/α, is enhanced in PThQx. This enhancement comes from the CT character of the excited states in PThQx, in which a hole and an electron are created on different molecules.
Keywords: (Polythiophene and derivatives; Non-linear optical methods);

We report on fast transient photoconductivity measurements on highly oriented films of poly(p-phenylene vinylene) at various excitation densities and temperatures via linear (400 nm) or two-photon (800 nm) excitation. The photocurrent waveform is found to be independent of the applied electric field (up to F ∼ 3 × 105  V/cm) but strongly dependent on excitation density. A significant reduction of the photocurrent lifetime is observed at higher light intensities, clearly indicating carrier bimolecular recombination. A transport mechanism mediated by traps is also evident by the long-lived (up to 1 μs) photocurrent ‘tail’ that diminishes at low temperatures. We have fitted the transient photocurrent waveforms to a kinetic model from which the dynamics of carrier recombination, trapping and de-trapping were deduced.
Keywords: Photoconductivity; Poly(phenylene vinylene);

Poly (3,4-ethylenedioxythiophene)/gold (PEDOT/Au) nanocomposites were prepared using a redox cycle system. In the redox system, PEDOT films in the neutral state reacted with AuCl3 producing an oxidized PEDOT film, where metallic gold nanoparticles were collectively deposited onto the films. The redox process was repeated on the same film. More homogenous gold particles (10–20 nm) were deposited on top of the PEDOT film as the number of redox cycle was increased. XPS and SEM were used to identify the formation of gold particles. The oxidation process of neutral PEDOT in the AuCl3 solution was monitored by UV-vis spectroscopy. The rapid drop in the film resistance was also monitored during the deposition redox-process of the gold nanoparticles.
Keywords: Pedot; Gold; Nanocomposite; Electroless plating;

Free radical scavenging and antioxidant properties of conducting polymers examined using EPR and NMR spectroscopies by P.A. Kilmartin; M. Gizdavic-Nikolaidis; Z. Zujovic; J. Travas-Sejdic; G.A. Bowmaker; R.P. Cooney (153-156).
Conducting polymers are being considered for a range of applications in which they will come into contact with biological tissues, such as artificial muscles, in drug release, nerve regeneration and as scaffolds for cell attachment. The radical scavenging properties of antioxidants consumed in the diet are often assessed by their ability to neutralise stable free radicals such as α,α-diphenyl-β-picrylhydrazyl (DPPH). Commercially available soluble polyaniline and polypyrrole were found to be efficient and rapid scavengers of DPPH radicals, as monitored by EPR spectroscopy. Further experiments using solid polyaniline samples, in the partially oxidised or fully reduced state, using solid state 13C NMR (CP MAS, NQS and Polarization Inversion) showed that the polyaniline was oxidised through its interaction with DPPH radicals. Aniline and pyrrole monomers also reacted with DPPH radicals but at a much slower rate, consistent with their lower reducing strengths.
Keywords: Polyaniline; Polypyrrole; Nuclear magnetic resonance spectroscopy; Electron paramagnetic resonance spectroscopy;

Electric Field Control of Charge Transport in Doped Polymers by V.N. Prigodin; F.C. Hsu; Y.M. Kim; J.H. Park; O. Waldmann; A.J. Epstein (157-160).
Recent observation of a large “field effect” for conducting polymers is in conflict with a fact that the electric field cannot penetrate in a conductor further than the molecular scale Debye radius. We review the experimental results for gate voltage control of conductivity in a FET structure. We propose that the field effect is related to inhomogeneous structure and remnant ions. The free space within the polymer network enables ions to move in and out. The electronic screening at the dielectric/conducting polymer boundary transforms the electric potential into the shift of chemical potential for ions inside leading to ionically charging/discharging of the polymer film. The ionic charge is compensated by the variation of the electron concentration. In the linear response to the gate voltage, the charging capacity is c = ε ε 0 ( r i 2 + r e 2 ) , where ri,e is the Debye radius for ionic and electronic subsystems. For low concentration of ions (ri  ≫ re) the charging response increases exponentially with applied voltage and approaches saturation c0  = e2N(EF) that is a few hundred F/cm3. Surprisingly, the experimental “off state” is reached with only a few percent of compensation. Therefore we propose that the main effect of the ionic invasion is suppression of the charge conduction between metallic grains of the inhomogeneous polymers.
Keywords: Transport measurements; Metal/electrolyte interfaces; Conducting polymers; Polymer field effect transistors;

The poly(p-phenylene) films were electrochemically synthesized by anodic oxidation of benzene on a stainless steel electrode in borontrifluoride diethyl etherate as a solvent. It was found that a rise in the polymerization potential and/or temperature increased the polymerization rate, solvent remained in the film, and Young's modulus, while the degree of polymerization, electrical conductivity, tensile strength, and elongation at break decreased. The degree of polymerization and electrical conductivity respectively attained 25 and 1.7 S cm−1 for the film polymerized at −15 °C under 1.55 V vs. SCE.
Keywords: Electrochemical polymerization; Semiconducting films; Other conjugated and/or conducting polymers;

The doping of highly oriented poly(p-phenylene vinylene) films prepared by the zone-reaction method was performed with various acids, HCl, H2SO4, and H3PO4. The changes in the microstructure, electrical, tensile, and viscoelastic properties of the resulting films were studied. It was found that the doping of HCl and H2SO4 increased the electrical conductivity to 186 and 61 S cm−1 at the doping time of 6 and 1.5 h, respectively. A further doping, however, lowered the conductivity, which was associated with the relaxation of molecular orientation. The zone-reacted film doped with HCl preserved Young's modulus and tensile strength as high as 44.7 and 0.73 GPa, where dynamic storage modulus was 49 GPa at 25 °C and held 21 GPa at 400 °C.
Keywords: Tensile drawing; Semiconducting films; Poly(phenylene vinylene) and derivatives;

Heat capacity, electron paramagnetic resonance, and dc conductivity investigations of dispersed polyaniline and poly(ethylene dioxythiophene) by P.K. Kahol; J.C. Ho; Y.Y. Chen; C.R. Wang; S. Neeleshwar; C.B. Tsai; B. Wessling (169-172).
Dispersible polyaniline (PANI) exhibits a dc conductivity σ ≈ 0.1 S/cm when it's doped with poly(styrene sulfonic acid) (PSS) such that the number of sulfate ions per two-ring PANI unit (y) is 2. On increasing the dopant amount to y = 12 the conductivity σ drops to 10−5  S/cm. The EPR magnetic susceptibility results on these samples give nearly the same density of states at the Fermi level N(EF) ≈ 0.65 states/eV 2-rings. With y′ defined as the number of sulfate groups per three-ring PEDOT unit, PSS doping of poly(ethylene dioxythiophene) (PEDOT) gives σ ≈ 10−1  S/cm at y′ = 5.7 and σ ≈ 10−5  S/cm at y′ = 45.9. Like PANI, N(EF) ≈ 0.55 states/eV 3-rings is same at both the doping levels. The EPR linewidth for these samples in the less conducting state is found to be large compared with the mote conducting state, although the overall temperature dependence in the two states is qualitatively the same. These results are consistent with the inhomogeneous disorder models.
Keywords: Polyaniline and derivatives; Conductivity; Electron Spin Resonance; Specific heat; magnetic Measurements;

We have tried to confirm the sign inversion of electronic photocarrier in a fusible conducting polymer, regiorandom poly(3-octadecylthiophene), PAT18 associated with the solid-liquid phase transition by means of the time-of-flight (TOF) method. It was found that the hole mobility decreases with increasing temperature. At the temperature near the solid-liquid phase transition, the hole mobility decreases drastically, and eventually the melting temperature, it was impossible to evaluate the hole mobility from noisy transient photocurrent. On the other hand, transient photocurrent based on electron transport are observed above the melting point. The negative carrier mobility was evaluated in the range from 10−6 to 10−5  cm2/Vs, which is comparably the hole mobility at solid state. This fact suggests that the same mechanism, for example interchain hopping limits carrier transport, and the negative carrier is electron. This unique phenomenon is interpreted as modulation of electronic energy state caused by conformational change of the main chain. That is, the drastic conformational change of polymer backbone induced by the thermal activation of side chain vibration, which is responsible for the thermochromism in poly(3-alkylthiophene)s, may play a key role for this unique phenomenon.
Keywords: Polythiophene and derivatives; Transport measurement; Optical absorption and emission spectroscopy; Solid-liquid phase transition; Photoconductivity;

Conducting polymers as substrates for surface-mounted molecular devices by Timothy Hanks; Laura Glish; Sarbjit Singh; David Johnson; Laura Wright (177-180).
Thin films of poly(3,4-diethoxythiophene), PEDOT, were prepared by vacuum sublimation/polymerization of 2,5-dibromo-3,4-ethylenedioxythiophene onto freshly cleaved mica. AFM studies show that the films are exceptionally smooth and contain both highly crystalline and amorphous regions. Exposure of the film to polar solvents for one hour causes an increase in the surface roughness, while exposure to non-polar solvents or thermal annealing decreases surface roughness. Ary thiols linked to diazo dye labels can be covalently bound to the films by simple exposure in dilute methylene chloride solutions. This provides a convenient way to functionalize PEDOT surfaces with molecular devices.
Keywords: Sublimation; Polymerization; Atomic force microscopy; Self-assembly using surface chemistry; Special purpose functionalized conjugated polymers;

Purification and characterisation of poly(2-methoxyaniline-5-sulfonicacid acid) by F. Masdarolomoor; P.C. Innis; S. Ashraf; G.G. Wallace (181-184).
The chemical oxidative synthesis of water soluble sulfonated polyaniline, poly (2-methoxy aniline-5-sulfonic acid) (PMAS) has been shown to result in an impure mixture of polymeric isomers. A tangential cross flow dialysis system has been developed to rapidly and efficiently separate high molecular weight polymer from low molecular weight oligomers, and results compared to conventional tubing dialysis. Characterisation of the purified polymer fractions has been made using UV-vis spectroscopy, gel permeation chromatography, cyclic voltammetry, conductivity measurement and thermal analysis. Results indicate that while the conventional dialysis tubing is not able to separate the mixture of high and low molecular weight materials efficiently, the cross flow dialysis is able to separate them more rapidly and efficiently. Purified high molecular weight PMAS exhibited enhanced electrical conductivity and significant property changes with respect to tubing dialysed PMAS. The pure PMAS, which is the high molecular weight species (Mw 10157 Da) obtained from the cross flow dialysis, has a twofold higher conductivity than the impure PMAS dialysed by the conventional method.
Keywords: Conducting polymer; Water-soluble; Self-doping;

An HRP based biosensor using sulphonated polyaniline by Orawan Ngamna; Aoife Morrin; Simon E. Moulton; Anthony J. Killard; Malcolms R. Smyth; Gordon G. Wallace (185-188).
The properties of poly (2-methoxyaniline-5-sulfonic acid) (PMAS), a water-soluble polymer, has been investigated as a potential mediator for biosensors. Addition of poly (L-Lysine) (PLL) to the PMAS renders this material water-insoluble; an important feature for aqueous based biosensors. Characterisation of various PMAS/PLL mixtures showed that a uniform and stable film could reproducibly be fabricated on ITO coated Mylar using 0.1% (w/v) PMAS and 0.05% (w/v) PLL. Immobilisation of enzyme horseradish peroxidase (HRP) onto the PMAS/PLL film was also investigated. Amperometric detection (−0.1 V vs. Ag/AgCl reference electrode) of hydrogen peroxide was investigated using the PMAS/PLL/HRP electrode as the working electrode in a three electrode cell containing phosphate buffer saline (pH 6.4) solution. Amperometric responses were observed upon the addition of hydrogen peroxide. HRP immobilised concentration was optimised to be 0.35% (w/v) at 35 μL. Loading volume was also studied and optimised to be 35 μL. The optimal condition for amperometric test was using constant applied potential at −100 mV. Detection limit of the sensor in PBS solution was 0.01 mM H2O2. Calibration curve in PBS pH 6.4 shows a linear response range between 0.01 and 0.1 mM H2O2 with a sensitivity of 24.91 μA/cm2  mM−1 and correlation coefficient of 0.9966.
Keywords: Polyaniline and derivatives; Conducting polymers; HRP biosensors;

Synthesis of electrophosphorescent polymers based on para-phenylenes with iridium complexes by W. Yang; H.Y. Zhen; C.Y. Jiang; L.J. Su; J.X. Jiang; H.H. Shi; Y. Cao (189-192).
A series of hyper-branched and linear-type conjugated polymers based on substituted para-phenylenes with iridium complexes was synthesized by Yamamoto polycondensation. The efficient energy transfer from polypara-phenylene segments to iridium complex is observed. EL emission from PPP segments is completely quenched at as low as 0.5 mol % of the Ir complex content in feed ratio. The hyper-branched copolymers emit green light, and the maximal external quantum efficiencies are around 1.5% for BHPPPIrPPy copolymers. CNPPPIrMPPy(acac)-1 copolymer emits yellow light with a maximal external quantum efficiency of 1.3%.
Keywords: Para-phenylene; Ir-complex; Phosphorescent copolymer;

A series of novel soluble conjugated copolymers derived from 9,9-dioctylfluorene (DOF) with metal-free and Pt (II) tetraphenylporphyrin (TPP) were synthesized via palladium-catalyzed Suzuki coupling reaction, with TPP content in the copolymers of 0.5%, 1%, 5%, 20% and 50% respectively. Platinum (II) (Pt) were incorporated into the copolymers by reaction of the copolymers with PtCl2. Emission from DOF segment was completely quenched at very low metal-free TPP content (1%). The copolymers of DOF-co-TPP emit saturated red emission that is red-shifted slightly with increasing the TPP contents. After Introducing Pt, the emission peak of the copolymers is blue-shifted. Electroluminescent (EL) quantum efficiency of the devices based on the copolymers was 0.12% for copolymer with 5% TPP content and EL efficiency PFO-PtTPP was 0.15% for metal complex with 1% PtTPP content.
Keywords: Polyfluorene; Metal-Free Tetraphenylporphyrin; Pt (II)-Tetraphenylporphyrin; Electroluminescence;

Efficient electron injection from bilayer cathode with aluminum as cathode by Hongbin Wu; Fei Huang; Junbiao Peng; Yong Cao (197-200).
A new bilayer cathode has been developed for varieties of RGB emitting polymers to form an effective electron injector. An effective electron injection from high work function metal, such as Al cathode can be realized by incorporation of a thin layer of amino-ended alkyl-substituted polyfluorene copolymer and corresponding ammonium salt-cationic polyelectrolyte between metal cathode and emitting layer. The performance of polymer light emitting-diodes (PLEDs) fabricated with such bilayer cathodes can be enhanced to the levels comparable or even higher than that obtained by using Ca and Ba as the cathode (for red QE = 2–3%, for green 5–8%, for blue 1–2% respectively). The new electron-injection layer can be processed from environment-friendly solvents such as alcohol or water in which most of light-emitting polymers are insoluble. The mechanism of lowering the barrier height for electron injection from Al is discussed based on I-V characteristics, build-in potential, and X-ray diffraction data.
Keywords: Electroluminescent; Polyelectrolyte; Polymer light-emitting diode; Schottky barrier; Metal/semiconductor interfaces;

Synthesis and EL properties of aluminum and α-pyridoin complex by Won Sam Kim; Burm-Jong Lee; Yunghee Oh; Young-Soo Kwon (201-204).
A novel light emitting aluminum complex containing the dihydroxy derivative of trans-1,2-dipyridylethene (PAl), α-pyridoin, was synthesized and its electroluminescent (EL) properties were characterized. The structure of complex PAl was elucidated by FT-IR, solid state 1H-NMR, UV-Vis and XPS. The complex PAl showed thermal stability up to 350 °C under nitrogen flow, which was measured by TGA and DSC. The photoluminescence (PL) was measured from the PAl film on quartz substrate. The PL emission exhibited green light centered at about 490 nm. Electroluminescent (EL) devices were fabricated by the vacuum deposition. The EL devices having the structure of ITO/TPD/PAl/Al were studied, where N,N-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) was used as a hole transporting layer. TPD hole transport layer was 40 nm thick and PAl emitting layer 60 nm thick. The PAL device showed yellow emission at 575 nm. The maximum brightness of 91 cd/m2 was observed from the PAl EL device.
Keywords: OLED; electroluminescence; photoluminescence; X-ray photoelectron spectroscopy;

Fabrication and characterization of OLEDs using MEH-PPV and SWCNT nanocomposites by Young-Geun Ha; Eun-Ah You; Byung-Jin Kim; Jong-Ho Choi (205-208).
Optoelectronic devices based upon poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene](MEH-PPV)-single-walled carbon nanotube (SWCNT) nanocomposites have been fabricated and characterized. SWCNTs were synthesized by the laser ablation method, and organic thin films were produced by spin-coating and cluster beam deposition (CBD) methods. The hole-only-type devices with the structure of ITO-coated glass/PEDOT:PSS/nanocomposite/Au demonstrate that the transport characteristics are improved due to the efficient hole injection and percolative conduction in the range of 0–1.0 SWCNT wt. % relative to MEH-PPV. Studies of luminescence and device characteristics for the double-layer-type devices of ITO-coated glass/PEDOT:PSS/nanocomposite/(DCM-doped)Alq3/Li:Al exhibit that the incorporation of SWCNT into MEH-PPV and of DCM into Alq3 enhances the transport characteristics and device performance, respectively
Keywords: OLED; CBD; MEH-PPV; SWCNT; Alq3; DCM;

Characterizaton of tetracene-based electroluminescent devices produced by cluster beam deposition methods by Eun-Ah You; Young-Geun Ha; Young-Sang Choi; Jong-Ho Choi (209-212).
We have fabricated and characterized heterojunction electroluminescent devices with the structure of ITO-coated glass/tetracene/(DCM-doped)Alq3/Li:Al. The organic thin films of tetracene, Alq3, and dye dopant DCM were deposited by applying the cluster beam deposition (CBD) methods. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements show that the flat and smooth thin tetracene films are close to a highly ordered, single crystal. Photoluminescence (PL), electroluminescence (EL) and device characteristics such as current density-voltage (J  −  V), EL intensity-voltage (L  −  V), and external quantum efficiency-current (EQE-I) were examined for undoped and DCM-doped devices.
Keywords: Tetracene; Alq3; DCM; Cluster beam deposition; OLED;

Rheofluorescence studies of poly(p-phenylenevinylene) derivatives in simple shear flow by Elisabeth K. Hill; Khai Leok Chan; Andrew B. Holmes; Dave E. Dunstan (213-216).
Common manufacturing approaches for polymer displays expose light emitting polymer solutions (LEPs) to high shear rates during film deposition. Little is yet known about the effects of shear on LEP conformation and alignment; the ability to manipulate these polymers in flow may prove critical for enhanced device performance.A novel spectroscopic approach that employs an optically accessible Couette cell has been developed to investigate the effects of a uniform shear field on LEP luminescence. Orientation and deformation in polymer solutions are observed as shear-dependent changes in fluorescence emission. We report the influence of simple shear flow on steady state fluorescence emission from MEH-PPV and two other poly(p-phenylenevinylene) derivatives, in dilute solution and a polystyrene matrix. Rheochromism, a shear-induced red shift of 4–6 nm in spectra recorded at shear rates of 100–1000 s−1, indicates a small extension of conjugated polymer coils. Changes in fluorescence emission intensity as a function of shear rate and observation geometry are attributed to alignment of prolate polymer coils in the flow field.
Keywords: Photoluminescence; Poly(phenylene vinylene) and derivatives; Solution processing;

Periodic multilayer structures of poly(p-phenylenevinylene)s have been fabricated by a self-assembly method on quartz or indium-tin- oxide-coated glass substrates. Alternating multilayers consisting of poly(P-phenylenevinylene) (PPV) and PPV derivatives which possess polyanion properties were adsorbed onto positively charged substrates. Periodic multilayers with a microdisk geometry have also been fabricated on quartz or indium-tin-oxide-coated glass substrates, and the optical properties and a yellow electroluminescence from a light- emitting device with a microdisk geometry have been studied.
Keywords: Poly(phenylene vinylene) and derivatives; Photoluminescence; Electroluminescence; Etching; Coupling reactions; Self-assembly;

Electrophoretic response of poly(methyl methacrylate) coated TiO2 nanoparticles by J.Y. Lee; J.H. Sung; I.B. Jang; B.J. Park; H.J. Choi (221-224).
A microcapsule-based electronic ink display technique, which uses the microencapsulation of electrophoretic dispersion, is being developed for direct-view portable displays. Microcapsules of titanium dioxide (TiO2) electrophoretic nanoparticle suspension were prepared using amino precondensates via in-situ polymerization. The amino prepolymers were synthesized from melamine-urea formaldehyde resin at 60 °C. However, since TiO2 has a relatively high density (4.28 g/cm3), the density mismatch causes severe sedimentation problem in the suspended media. In order to lower its density, TiO2 was coated with poly(methyl methacrylate) via a dispersion polymerization method prior to being used for an electronic ink material. In order to improve their mobility, a charge control agent was also added to the suspension of synthesized nanoparticles in the dielectric medium. Electrophoretic mobility of the synthesized particles was investigated via electrophoretic light scattering. The morphology of the synthesized microcapsule was also characterized by optical microscopy, and scanning electron microscopy.
Keywords: Electronic ink; Microencapsulation; Nanoparticle; Electrophoresis; Microsphere;

Experimental and Computational Studies of Substituted Terthiophene Oligomers as Electroluminescent Materials by Keith C. Gordon; Samuel MacArthur; Gabrielle David; Tracey M. Clarke; David L. Officer; Pawel Wagner; Simon B. Hall (225-228).
Density functional calculations at the B3LYP/6-31G(d) level are used to predict the vibrational spectra for a series of substituted thiophenes and terthiophenes containing the emitter unit diethenylbenzene (DEB). The calculations show that cyano substitution induces non-planarity, particularly for the terthiophene compound. This was verified by the absorption and emission data, which suggest that the ground state is less planar than the excited state. The solution phase electronic spectroscopy reveals that some of the compounds are very emissive; however, CN substitution quenches this emission. Electroluminescent devices may be constructed using these emitter materials and it is found that the efficiency of the CNDEB compounds may be improved with the introduction of a different hole transporting layer.
Keywords: Infrared and Raman spectroscopy; Ab initio quantum chemical methods and calculations; Electroluminesence;

High efficiency polymeric light-emitting diodes with a blocking layer by Sang Yeol Kim; Taeyong Noh; Soo-Hyoung Lee (229-232).
In this paper, we describe a simple method for fabrication of high efficiency multilayered polymeric light-emitting diodes (PLEDs). In the device configuration of ITO/HIL/BL/EML/BaF2:Ca:Al (ITO: indium tin oxide, BL: blocking layer, HIL: hole injection layer as PEDOT:PSS, EML: emitting layer as poly(alkylfluorene) derivative), poiy(9-vinyl carbazole) (PVK) was selected as an BL because it has a hole transporting property and a relatively higher band gap, especially a lower LUMO level than the emitting polymer and higher HOMO level than PEDOT:PSS. As a result, the PVK layer could effectively block the electrons from metal cathode and confine them in the emitting polymer layer. In addition, it could properly control the amount of holes from ITO anode by partial blocking. The charge balance was achieved and the device with a PVK. layer exhibits a higher brightness and luminance efficiency than those in devices without PVK. Also, the thickness of PVK was easily controlled by solvents for emitting polymer and the device with a thicker PVK layer shows better performance.
Keywords: Organic light-emitting device; Conjugated polymer; Charge balance; Blocking layer;

Photoemission and X-ray absorption spectroscopies of phosphorescent organic iridium complexes by J. Thompson; V. Arima; F. Matino; S. Berkebile; G. Koller; F.P. Netzer; M.G. Ramsey; R. Cingolani; R.I.R. Blyth (233-236).
Phosphorescent materials represent an attractive route to high-efficiency organic LEDs, since their maximum theoretical quantum efficiency is 100%, compared to the 25% of fluorescent materials. We have studied the electronic structure of three phosphorescent iridium complexes, the red-emitter Iridium bis (2-(2′-benzothienyl) pyridinato-N, C3′) (acetylacetonate), the blue emitter, Iridium bis(2-(4,6- difluorophenyl) pyridinato-N,C2′) picolinate, and the green emitter Iridium tris (2-(4-totyl)pyridinato N,C2) using electron spectroscopies. The materials were evaporated in-situ onto a clean gold substrate in ulta-high vacuum. The valence band electronic structures were investigated using resonant photoemission, with the unoccupied states determined using X-ray absorption. The data suggests a hybridisation of the Ir 5d states with the π orbitals of the ligand. NEXAFS spectra are shown to be highly sensitive to the local environment.
Keywords: Photoelectron spectroscopy; X-ray absorption spectroscopy; Organic semiconductors based on conjugated molecules;

First-order imprinted organic distributed feedback lasers by Dario Pisignano; Luana Persano; Elisa Mele; Paolo Visconti; Marco Anni; Giuseppe Gigli; Roberto Cingolani; Laura Favaretto; Giovanna Barbarella (237-240).
The excellent luminescence and gain properties of substituted oligothiophenes are exploited to imprint one-dimensional photonic crystals for the fabrication of printed distributed feedback (DFB) cavities. We demonstrate the dry-printing of organic semiconductor lasers, carrying out the realization of a complete device by a single nanofabrication step, which can be perfectly integrated with other existing planar semiconductor processing and etching technologies. In particular, a thiophene-based pentamer with very good amplified spontaneous emission and optical gain properties was used to fabricate a single-mode, first-order DFB lasers exhibiting an emission with a linewidth of 1.1 nm at about 636 nm for excitation fluences larger than 27 μJ/cm2. These results clearly indicate that substituted oligothiophene-S,S- dioxides are promising candidates for solid-state lasers realizable by emerging nanopatteming technologies.
Keywords: Lasers; Stimulated luminescence; Spin wasting; Manipulation of surface structure and morphology;

High Efficiency Blue Organic Electroluminescent Devices Having a Metal-Doped Electron Injection Layer by Yasuhisa Kishigami; Kenji Tsubaki; Yukihiro Kondo; Junji Kido (241-244).
We report high efficiency blue organic electroluminescent (OEL) devices having a metal-doped electron injection layer at the cathode interface. The typical device structure is an indium-tin oxide (IIO)/arylamine derivative (α-NPD)/blue emitting distyrylarylene derivative/metal-doped organic electron injection layer/Al. The device efficiency is dependent on the work function of the dopant metals and the host organic materials composing the metal-doped layer. A device having Cs-doped bathophenanthroline (Bphen) layer as the cathode interface layer exhibited a high luminous efficiency of 9 lm/W and an external quantum efficiency of 6.5% at luminance of 300 cd/m2, which are the highest values reported for blue organic EL devices
Keywords: Organic semiconductors based on conjugated molecules; Electroluminescence; Organic/Inorganic Interfaces;

Synthesis, spectroscopy and quantum chemical DFT studies on new pleiadene-based materials by J. Casado; M.C. Ruiz Delgado; V. Hernández; J.T. López Navarrete; C. Parejo; F. Fernández-Lázaro; Á. Sastre-Santos; F. Wudl (245-248).
The synthesis and characterisation of poly-vinyl-6b,10b-dihydrobenzo[j]cyclobut[a]accnaphthylenc (PVDBCA) and the poly- vinylpleiadene dimer (PVPD) have been accomplished. Raman spectroscopy, electrochemistry, X-ray diffraction and density functional theory calculations of model systems have been combined in order to address the evolution of the structural and electronic parameters upon polymerization relative to specific through-space interactions between the monomeric units in the macromolecules. These studies could have some significance for wire-like materials from the point of view of electron or hole transporting.
Keywords: Synthesis; Poly-vinyl-6b; 10b-dihydrobenzo[j]cyclobut[a]acenaphthylene; Poly-vinylpleiadene dimer; Density functional calculation; Raman spectroscopy; X-ray diffraction; Electrochemistry;

In this work we study three homologues of terthiophene in which the innermost sulphur atom has been replaced by a phosphorous one, namely, 2,5-bis(2-thienyI)phospholes. This strategy pursuits to improve the optical and electronic properties of oligomers derived from thiophene by means of the modulation of their conjugational properties. The assignment of the Raman bands of the phosphole derivatives and their correlation among the series of molecules allows to compare their electronic structures with that of the thiophene counterparts. We have found a disruption of the whole electronic structure on passing to the phospholes, which can be in agreement with the already well known lacking of aromatic character of phosphole as compared with thiophene. Raman spectroscopy also proves effective in addressing σ-π conjugation between π-chromophorcs of a dimer connected through a P-P bond in neutral state.
Keywords: Density functional calculations; Raman spectroscopy; Phospholes; π-elcctron delocalisation;

Displacement Current Measurement as a Tool to Characterize Organic Field Effect Transistors by Satoshi Ogawa; Tatsuo Naijo; Yasuo Kimura; Hisao Ishii; Michio Niwano (253-256).
In spite of recent extensive studies of organic field effect transistors (OFETs), the operation mechanism is not yet clear. Especially the origin of the carriers accumulated in channel of OFET should be clarified to discuss the performance of OFETs. We have to take care of impurity-induced-carriers as well as carriers injected from source and drain electrodes. The spread of the charge sheet at organic/dielectric interface is also critical to the PET performance. Thus an experimental technique to probe such behavior of carriers is highly required. In this study, we have proposed displacement current measurement (DCM) method as a tool to characterize OFETs. We found that this technique enables us to probe various properties in OFETs; the carrier injection from metal electrodes to organic materials, the effective area of charge sheet in the channel, and the amounts of carriers accumulated in the device. The results for pentacene and poly-3- hexylthiophene FETs are reported to discuss the relation between the carrier generation and FET performance.
Keywords: Schottkey barrier; Metal/Semiconductor interface; Organic semiconductors based on conjugated molecules. Switches; Field Effect Transistors; Carrier injection properties;

Investigation of the electropolymerisation of EDOT in ionic liquids by Klaudia Wagner; Jennifer M. Pringle; Simon B. Hall; Maria Forsyth; Douglas R. MacFarlane; David L. Officer (257-260).
Poly(3,4-ethylenedioxythiophene) (PEDOT) has been successfully synthesised using ionic liquids as both the growth medium and the electrolyte. Both imidazolium and pyrrolidinium-based TFSA ionic liquids were used to assess the influence of the nature of the medium on the morphology and electrochemical activity of the resulting materials.
Keywords: Polythiophenc and derivatives; Electrochemical polymerization;

Synthesis and properties of new luminescent poly(arylenevinylene) copolymers containing spirobifluorene by Bing Huang; Jun Li; Pin Shao; Jingui Qin; Zuoquan Jiang; Gui Yu; Yunqi Liu (261-264).
Two new light-emitting polymers, poly[2,2′-spirobifluorylene vinylene-alt-2,5-di-(n-buthoxy)-1,4-phenylene vinylene] (PSBF-PV) and poly[2,2′-spirobifluorylene vinylene-alt-9,9′-di-(fl-hexyl)-2,7-fluorenyl vinylene] (PSBF-FV) have been synthesized through the well-known Homer-Emons condensation between appropriate diphosphonates and dialdehydes. The polymers consist of arylenevinylene chromophores linked through 9,9′-spirobifiiorene to control the effective conjugation length and to suppress interchain aggregation. Photoluminescence maxima of PSBF-PV and PSBF-FV in thin solid film were shown at 512 and 446 nm, corresponding to green and blue-green emission, respectively. The single-layer light-emitting diodes of the two copolymers were fabricated in the configuration of ITO (indium-tin oxide)/polymer/Al, exhibiting weak emission. Better performance (luminance maxima is 846 cd/m2) was achieved using Alq3 as electron injection layer in double layer LEDs for PSBF-PV.
Keywords: Poly(phenylenc vinylene) and derivatives;

Nonvolatile memory effect of an Al/2-Amino-4,5-dicyanoimidazole/Al structure by Masataka Kano; Seiko Orito; Yoshiaki Tsuruoka; Nobuo Ueno (265-268).
We studied electrical properties of 2-Amino-4,5-dicyanoimidazole (AIDCN), which has a very large electric dipole moment, using a simple Al/AIDCN/Al structure. The measured current-voltage characteristics showed that the device is switched from low-conductivity state (off-state) to high-conductivity state (on-state) at threshold voltage of 2.3 V. On/off ratio of the current was 103 at the bias of 1V. The device remained the on-state for two weeks even when the bias voltage was turned off. Furthermore, the on-state could be switched back to the off-state by applying a negative bias voltage. The switching time for transitions was estimated to be below 40 ns by using the transient technique. These results demonstrate that a nonvolatile memory device can be realized by the simple MIM structure. We will also show the temperature dependence of the electrical conductivity, ultraviolet photoemission spectra (UPS) to discuss mechanisms of the switching phenomena.
Keywords: Transport measurements; Organic/inorganic interfaces; Photoelectron spectroscopy;

We synthesized a dendrimer with 16 terpyridine-platinum-pyridine groups on the dendritic periphery. The terpyridine-platinum (I) complex on the periphery of the dendritic carbosilane has been prepared from the reaction of Pt(COD)Cl2 and the 2,2′:6′,2′′-terpyridine groups. The terpyridine-platinum-pyridine complexes on the dendritic surface were prepared from ligand exchange of the platinum (I) complex from chloride ions to 4-(6-mercapto-l-thiohexa)pyridine. The chemical structure of the dendrimer was verified by using NMR and UV spectroscopy. The actual shape and size of individually dispersed dendrimers on the substrate were investigated by using tapping mode atomic force microscopy (TM-AFM). As a result, the dendrimers were domed shaped on the substrate and regular in size, respectively.
Keywords: Dendrimer; Terpyridine; Platinum; Silane; Tapping mode AFM;

Near infrared detection by means of coordination complexes by M. Caironi; D. Natali; M. Sampietro; M. Ward; A. Meacham; F.A. Devillanova; M. Arca; C. Denotti; L. Pala (273-276).
We report on the detection of near infrared (NIR) radiation in the range 900–1600 nm by means of coordination complexes such as [M(RtR’timdt)2]x− (M = Ni, Pd, Pt; R,R’timdt = formally monoreduced disubstituted imidazolidine-2,4,5-trithione; x = 0, 1), and [{Ru(bipy)2}2(μ-L)]x+ (H3L = 9-phenyl-2,3,7-trihydroxy-6-fluorone; x = 1, 3). By exploiting these stable coordination complexes absorbing in the visible and NIR region, the poor stability to air and light usually found in low band-gap organic semiconductors can be overcome. [M(R,R’timdt)2] and [{Ru(bipy)2}2(μ-L)]1+ complexes show π-π* transitions in the range 700-1000 nm, which can be bathochromically shifted by changing their oxidation state. Taking profit of this feature, we prepared photodetecting devices operating in the NIR region up to 1600 nm, thus reaching the appealing spectral range of telecommunications. NIR quantum efficiencies of these preliminary photodetectors, made by simple casting from solution, are comparable to those in the visible of most devices based on pristine organic materials. We succeeded in detecting train pulses with a repetition frequency of about 200 kHz at 960 nm and 80 kHz at 1450 nm, to our knowledge an unprecedented result that demonstrates the possibility to enter the NIR region by organic molecular-based devices.
Keywords: Detectors; Photoconductivity; Semiconducting films; Organic semiconductors based on conjugated molecules (not polymers);

The organic photoreceptor devices were fabricated with a planar configuration and were investigated the photoelectric properties. The optimization of the device structure was examined in terms of decrease of the dark current. In this study, the Au or Al electrode was prepared with planar configuration on the substrate and then organic semiconductor layer was successively prepared. The organic layer of p- or n-type semiconductor was prepared and it was consecutively over-coated with n- or p-type semiconductor, respectively. Since the difference between the work functions of Au and Al, the influence of the contact barrier on dark current was expected. The influence of the contact between an organic layer and an electrode was examined. The results indicated that the dark current is mainly due to the hole injection from the electrode and transport into the p-type layer. In the device without the contact between p-type semiconductor and electrode, the performance of the device was considerably improved by reducing the dark current.
Keywords: Control of interface structure and morphology; Heterojunction; Semiconductor/semiconductor interface;

Polarized optical and photoluminescence properties of highly oriented poly(p-phenylene-vinylene) by D. Comoretto; C. Soci; F. Marabelli; A. Mikhailovsky; D. Moses (281-284).
We report on the anisotropic reflectance (R), transmittance (T) and photoluminescence (PL) properties of stretch-oriented free standing films of poly(p-phenylene-vinylene) (PPV) at different temperatures. The PL quantum efficiency is strongly dependent on the pump polarization, being higher when the pump is polarized perpendicular to the polymer chain orientation. Independently of the pump polarization, we find that the PL emission spectra are mainly polarized along the polymer chain direction. The PL spectra have been corrected both for the number of absorbed photons and for self-absorption of the emitted light. Frank-Condon analysis of the oscillator strength for absorption and corrected emission spectra suggest that two different “chromophores” contribute to the optical properties.
Keywords: Poly(phenylene vinylene); Optical absorption and emission spectroscopy; Infrared and Raman spectroscopy;

Utilizing roll-to-roll techniques for manufacturing source-drain electrodes for all-polymer transistors by T. Mäkelä; S. Jussila; H. Kosonen; T.G. Bäcklund; H.G.O. Sandberg; H. Stubb (285-288).
The first all-polymer field effect transistor was reported already ten years ago. In the last few years rapid progress has been made in the field of plastic electronics. This progress has been based on developments in materials and in fabrication technology. In this work we report an all-polymer transistor in which source and drain electrodes are printed by using flexographic printing. This method is widely used in the printing industry. In the all-polymer transistor device, polyaniline (PANI), regio-regular poly(3-hexylthiophene) (rr-PHT), poly(vinylphenol) (PVP) and poly(3,4)ethylenedioxythiophene/potystyrenesulfonate (PEDOT/PSS) are used as source and drain electrodes, active channel semiconductor material, insulator and gate electrode, respectively. Flexible polyethylene terephthalate (PET) and poly(ethylene-2,6-naphthalate) (PEN) sheets are used as substrates. First, source and drain electrodes are printed by using a laboratory scale FLEXO printing machine, rr-PHT and PVP are spin coated and finally PEDOT/PSS is drop cast. As a result, conductivity, spreading, optical quality and thickness of the produced source-drain electrode pairs are measured and the transistor devices are characterized. Manufacturing of organic transistors entirely by a roll-to-roll process is evaluated.
Keywords: Solution processing; Polymer/polymer interfaces; Polyaniline and derivatives; Polythiophene and derivatives; Reel-to-reel production;

Structure Property Relationships in Conjugated Organic Systems by L. O’Neill; P. Lynch; M. McNamara; H.J. Byrne (289-292).
A series of π conjugated oligomers were studied by absorption and photoluminescence spectroscopy. A linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transition energies, it was observed that the Stokes shift also exhibited a well-defined relationship with increasing conjugation length, implying a correlation between the electron-vibrational coupling and chain length. This correlation is further examined using Raman spectroscopy, whereby the integrated Raman scattering is seen to behave superlinearly with chain length. There is a clear indication that the vibrational activity and thus nonradiative decay processes are controllable through molecular structure. The correlations between the Stokes energies and the vibrational structure are also observed in a selection of PPV based polymers and a clear trend of increasing luminescence efficiency with decreasing vibrational activity and Stokes shift is observable. The implications of such structure property relationships in terms of materials design are discussed.
Keywords: Oligomers and polymers; Electron-photon coupling; Raman Spectroscopy;

Organic nano-transistor fabricated by co-evaporation method under alternating electric field by Masatoshi Sakai; Masaaki Iizuka; Masakazu Nakamura; Kazuhiro Kudo (293-296).
We have fabricated the organic conductive wires and nano-transistors using co-evaporation method of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) under AC electric field. Needle-like crystals of TTF-TCNQ charge transfer complex grow from an edge of gold electrodes along the electric field. The frequency dependence of the growth time of molecular wires indicates that AC electric field around 100 Hz is the most effective for making connected wires. Many connected wires were highly conductive which did not show any modulation of electrical conductivity with the gate voltage. However N-channel field effect transistor characteristics were observed with improvements of growth sequence. It is suggested that a tiny semiconductor area is formed at the connecting point of two conductive molecular wires.
Keywords: Metal/semiconductor interfaces; Organic conductors based on radical cation and anion salts;

Carrier transport properties of self-organized oligosilanes with different lengths of terminal alkyl-chains were investigated by the time-of-flight transient photocurrent technique. The self-organized oligosilane thin films possess a high molecular order, which generates well-ordered carrier hopping sites. The order of the hopping sites enables us to control hopping distance by the terminal chains, resulting in systematic change of the carrier mobility.
Keywords: Photoconductivity; Carrier transport; Conjugated molecules. Self-organization;

Electro-optical properties of poly(N-alky1-2-ethynylpyridinium bromide)s by K.T. Lim; S.H. Jin; H.J. Lee; J.W. Park; S.Y. Kim; W.C. Lee; Y.S. Gal (301-304).
Poly(N-alkyl-2-ethynylpyridinium bromides)s with different alkyl chains were synthesized in high yields by the activated polymerisation of 2-ethynylpyridine with various alkyl bromides in the absence of any additional initiator or catalyst The polymer structures were characterized by various instrumental methods such as NMR, IR, and UV-visible spectroscopies to confirm the conjugated polymer backbone system having N-alkylpyridinium moieties. The polymers were completely soluble in such organic solvents as DMF, DMSO, and DMAc. The photoluminescence spectra of poly(N-dodecyl-2-ethynylpyridinium bromide) and poly(2-ethynyl-N-octadecylpyridinium bromide) showed that the photoluminescence peaks are located at 600 and 596 nm corresponding to the photon energy of 2.07 and 2.08 eV, respectively.
Keywords: Polyacetylene and derivatives; Semiconducting films; Photoluminescence; Ionic polymers;

Fabrication of field effect transistor based on deuterated glycinium phosphite crystal and pentacene by Hironori Yamada; Yasumitsu Matsuo; Junko Hatori; Zbigniew Czapla; Seiichiro Ikehata (305-308).
We have fabricated a field effect transistor (FET) based on an organic ferroelectric insulator, a deuterated glycinium phoshite (D-GPI) and a pentacene film and have investigated electrical properties on the prepared FETs. It is observed that the FET based on D-GPI and pentacene film becomes a normally-on p-type FET. Moreover, we have observed that the gate electric field E G dependence of drain current i DS in the prepared FET displays the characteristics of hysteresis. This result indicates that the FET based on the D-GPI and pentacene film shows a memory effect Furthermore, we have found that the area of the i DS -E G hysteresis curve in the FET based on the D-GPI and pentacene film is determined by the magnitudes of the spontaneous polarization and coercive electric field of the D-GPI. On the basis of these results, it is also ascertained that the spontaneous polarization in the D-GPI insulator is responsible for the surface charge at the interface between the D-GPI and pentacene film. Furthermore, these results indicate that the values of i DS and the formation of the depletion layer largely depend on the spontaneous polarization and coercive field of the D-GPI insulator. Moreover, it is deduced that we can control the appearance of the depletion layer by controlling the deuterated ratio, which is responsible for the spontaneous polarization and coercive field of GPI insulator.
Keywords: Molecular conductor; Field effect transistor; Memory effect;

New Mo6S3−xSexI6 (x = 0.05) nanowires by A. Mrzel; J. Kovač; M. Remškar; A. Jesih; D. Mihailović (309-312).
We report on the synthesis and characterization of new air-stable nanowire material with a chemical formula Mo6S3−xSexI6 (x  = 0.05). The material can be synthesized in a single step reaction from the elements in bulk quantities. There are almost no impurities in the as-grown material, such as catalysts and the bundles can be dispersed using an ultrasonic bath in some polar solvents like water or isopropyl alcohol. The material has a fur-like appearance, with individual needles having a diameter of about 100 nm to 1000 nm while majority of them have diameter around 400 nm and a wide range of lengths. The material has similar structure as Mo6S3I6 and is composed of nanowires weakly bound in bundles. X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and electron microscopy were used to characterize the new nanowires.
Keywords: High temperature method for material preparation; Electron microscopy;

Fabrication and Applications of Conducting Polymer Nanotube, Nanowire, Nanohole, and Double Wall Nanotube by J. Joo; B.H. Kim; D.H. Park; H.S. Kim; D.S. Seo; J.H. Shim; S.J. Lee; K.S. Ryu; K. Kim; J.-I. Jin; T.J. Lee; C.J. Lee (313-316).
We fabricated nanotubes, nanowires, and double wall nanotubes (DWNTs) of (semi) conducting poly (3,4- ethylenedioxythiophene) (PEDOT), poly (p-phenylenevinylene) (PPV), and polypyrrole (PPy) through electrochemical polymerization or chemical vapor deposition method by using Al2O3 nanoporous template. The formation of the nanotubes, nanowires, and DWNTs was confirmed by SEM and TEM images. The formation of tube or wire, the length, and the thickness of wall of the nanotubes were controlled through various synthetic conditions, such as polymerization time and applied current (or voltage). Inorganic ferromagnetic Ni or organic light emitting PPV materials was synthesized outside or inside the conducting polymer nanotube as the form of DWNT. Two PL peaks were observed for carbonized PPV/light emitting PPV DWNTs. We fabricated nanoholes on the surface of conducting PEDOT-PSS [poly (4-styrenesulfornate)] films through high-energy ion irradiation. For electrical and optical properties of the nano-systems, I-V characteristics curves and UV/Vis absorbance spectra were measured. The UV/Vis absorbance spectrum of PPy nanowires varied with the dissolving solvent of template. The applications of the nanotubes, nanowires, and nanoholes of conducting polymers to electrode of capacitor and to nanotip emitters of field emission (FE) are presented.
Keywords: Conducting polymer; Nanotube; Nanowire; Double wall nanotube; Nanohole; Nanotip;

Synthesis and Self-Assembled Film Fabricated from Water-Soluble Poly(P-phenylene vinylene) and Fullerene Derivative by Fushen Lu; Yuliang Li; Huibiao Liu; Junpeng Zhuang; Liangbing Gan; Daoben Zhu (317-320).
Fullerene-containing ammonium was synthesized and the photocurrent generation of self-assembled multilayer film fabricated from [ll-(2,2-dimethyl-[60]fulleropyrrolidin-l-yl)-undecyl]-trimethyl-animonium (FA) and water-soluble poly(P-phenylene vinylene) using alternate deposition method was also investigated. The self-assembled film exhibits a steady and rapid anodic 2.5 μA cm−2 photocurrent response.
Keywords: Solution processing; Self-assembly using surface chemistry; Atomic force microscopy; Fullerene and derivatives; Solar cells;

Synthesis and characterization of novel conductive star polymers containing PSS/PANI arms by Chih-Chien Chu; Yih-Wen Wang; Leeyih Wang; Tong-Ing Ho (321-324).
Novel multistep procedures for preparing water-soluble, conducting star-shaped polyaniline/poly(styrenesulfonate) complex are presented. Star poly(styrenesulfonate) which serves as a template for generating the electroactive polymer complex was synthesized by sequential atom transfer radical polymerization (ATRP) and Makowski's sulfonating method of styrene. The characterization by GPC and 1H-NMR showed that each polymeric arm of the star polyelectrolyte exhibited a well-defined chain length and a well-controlled charge fraction. The conducting polymer complex prepared by the polyelectrolyte-guided polymerization of aniline was highly stable in aqueous solution.
Keywords: Conducting polymer; Star polymer; Atom transfer radical polymerization; Polyacid; Polyaniline;

Real-time monitoring of microfluidic lithography by Dario Pisignano; Francesca Di Benedetto; Luana Persano; Elisa Mele; Roberto Cingolani (325-328).
In order to observe in real-time and to accurately measure the filling speed during the capillary process in planar microfluidic devices, we integrated a ruler in the silicon master structures, side by side with the channels, and replicated it into the elastomeric elements. The time dependence of the covered length (z, t) and of the filling rate (v, t) under different temperature and surface functionalization conditions was then exactly determined by optical microscopy. This allowed us to quantitatively assess the strong dependence of v on the process environmental conditions, and to discard in real-time the presence of impurities on employed substrates, thus allowing one to strongly improve the throughput of the microfluidic-based soft lithography for nanotechnology applications.
Keywords: Microfluidics; Polyurethane; Polymer-polymer interfaces; Interface preparation; Control of interface structure and morphology;

Polymer microcavities by room temperature electron-beam evaporation of TiOx and SiOx by Luana Persano; Elisa Mele; Dario Pisignano; Vanessa Frascerra; Roberto Cingolani (329-332).
We report on monolithic symmetric vertical microcavities exploiting two TiCx/SiOx distributed Bragg reflectors (DBRs), realized by means of electron-beam evaporation. The whole nanofabrication process is carried out without heating the chamber atmosphere, thus allowing the direct evaporation of the top dielectric mirror onto the organic layer previously spin-cast on the bottom DBR stack. The high adhesion to the substrate, the possibility of employing active media of low softness temperature, and the absence of any degradation of the emission properties of the organic compound opens the way for novel vertical emitting resonators and monolithic photo-and electroluminescent microcavities. Our mirrors exhibit a stop-band reflectivity higher than 95% and a spectral width of more than 170 nm.
Keywords: Polymeric microcavities; Organic microcavity; Photoluminescence; Multilayer structures;

We report on the doping dependence of the valence band of mats of potassium intercalated single wall carbon nanotubes (SWCNT) using high resolution photoemission spectroscopy as probe. For the pristine SWCNT about one third are metallic Tomonaga-Luttinger-Liquids (TLL) which can be directly monitored by a power law scaling in the density of states close to the Fermi level. Upon potassium doping the charge transfer to the conduction band of the fraction of semiconducting SWCNT within the bundle leads to a crossover from the TLL scaling to a normal Fermi liquid behaviour. This can be explained by an increased intertube interaction and/or by an increased screening of the neighboring metallic tubes within the bundle.
Keywords: Photoemission; Carbon nanotubes; Tomonaga-Luttinger liquid;

Morphological and electrical characteristics of polyaniline nanofibers by Roch Chan Yu King; Frédérick Roussel (337-340).
Polyaniline nanofibers with an average diameter of <100 nm were synthesized from two different polymerization processes. They were fabricated either (a) via a template-tree procedure at the interface of a heterogeneous (biphasic) medium composed of an organic solvent (toluene or CCI4) containing the monomer (aniline) and an aqueous layer containing the oxidizing agent (ammonium peroxydisulfate, APS) and camphorsulfonic acid (HCSA) as the dopant or (b) in a homogeneous (monophasic) medium in which nanofiber growth is promoted by the presence of a small amount (<1% by wt.) of single-walled carbon nanotubes as an added polymerization “seed” template. UV/Vis spectra of the nanofibers were obtained from pressed pellets or solution-cast thin films on glass slides confirming the conducting (doped) state of polyaniline. The electrical properties of the as-synthesized nanofibers (press pellets) were obtained via the conventional four-probe technique. Linear voltage-current (V-I) characteristics were recorded providing an estimated value of the electrical conductivity. The morphology and average diameter of the obtained nanofibers were investigated by Scanning Electron Microscopy (SEM).
Keywords: Polyaniline and derivatives; Interface preparation; Scanning transmission electron microscopy; UV-Vis-NIR absorption;

Synthesis and Characterization of Polythiophene and Poly (3-methylthiophene) Nanotubes and Nanowires by D.H. Park; B.H. Kim; M.K. Jang; K.Y. Bae; S.J. Lee; J. Joo (341-344).
We synthesized nanotubes and nanowires of π-conjugated polythiophene (PT) and poly (3-methylthiophene) (P3MT) by using nanoporous anodic aluminum oxide (A12O3) template through electrochemical polymerization method From SEM and TEM photographs, we observed the formation of nanotubes with diameters of 100 ∼ 200 nm and wall thicknesses of 5 ∼ 10 nm. The length of PT and P3MT nanotubes and nanowires was up to ∼40  μm. To discern the structural and optical properties of the systems, we measured UV/Vis absorbance and FT-IR spectra. We observed that the doping level, the π-π* transition peak, and bipolaron peaks in P3MT nanotubes varied with synthetic temperature. Based on measured I-V characteristic curves with gate bias for a single strand of PT nanotube, the systems should be considered to exhibit p-type nature.
Keywords: polythiophene; poly (3-methylthiophene); nanotube; nanowire;

Formation of novel nanostructures using carbon nanotubes as a frame by E. Borowiak-Palen; M. Rümmeli; T. Gemming; M. Knupfer; R.J. Kalenczuk; T. Pichler (345-348).
Molecular nanostructures, such as nanotubes and nanorods, represent ideal building blocks for nanoelectronic devices due to their unique electronic properties. We present recent progress in the formation of novel nanostructures which have been produced by substitution reaction from carbon nanotube templates. We report on the synthesis of boron doped single wall carbon nanotubes with different substitution levels, multiwall boron nitride nanotubes, boron nitride nanocapsules, silicon carbide nanostructures and gallium nitride nanostructures. The morphology, crystal structure and atomic ratio of the samples have been characterized by various techniques.
Keywords: Electron energy loss spectroscopy; Graphite and related compounds; Scanning transmission electron microscopy;

Modification of SiC based nanorods via a hydrogenated annealing process by M. Rümmeli; E. Borowiak-Palen; T. Gemming; A. Huczko; M. Knupfer; S. Cudziło; R.J. Kalenczuk; T. Pichler (349-352).
We present a novel and simple method to modify silicon carbide nanorods coated in quartz by annealing in an ammonia atmosphere. The process allows the coaxial nanorod to be restructured such that the core becomes quartz with a thick silicon carbide sheath. The nanorods were analysed using bulk sensitive EELS and Raman spectroscopy and on a local scale using TEM imaging and spectroscopy.
Keywords: Electron energy loss spectroscopy; Raman Spectroscopy; Semiconductor-semiconductor heterostructure; Scanning transmission electron microscopy;

Hydrogen absorption of the polymer-coated Pd nanoparticle by Miho Yamauchi; Hiroshi Kitagawa (353-356).
Mono-dispersed palladium nanoparticles, which were coated with polymer, were prepared and their hydrogen absorption properties were investigated. The averaged diameter of the prepared particles was estimated to be 2.6 ± 0.4 nm from a TEM photograph. By measurement of hydrogen pressure-composition isotherms, the hydrogen solubility of the Pd particles was determined to be 0.5 H per Pd. In the isotherms, plateau-like region was observed in the temperature rang of 303 to 393 K, indicating the coexistence of solid solution and hydride phases in the Pd nanoparticles in this temperature range.
Keywords: Hydrogen absorption; Pd nanoparticle; Polymer-coated particle; PCT curve;

Interaction of Carbon Nanotubes with Sugar Complexes by A. Casey; G.F. Farrell; M. McNamara; H.J. Byrne; G. Chambers (357-360).
The interaction of carbon nanotubes with soft organic molecules such as cyclodextrins and other saccarides has recently been shown to produce water soluble composites. Such systems offer considerable advantages over polymer based composites due to their biocompatibility and noncovalent coupling which can potentially preserve the unique properties of the tubes. The mechanism of interaction for such systems has been proposed to be dominated by hydrophobic and hydrophilic interactions along the surface of the tube. However efforts to characterise and rationalise such noncovalent interactions between the sugar-based materials and the carbon nanotubes have been slow to emerge. In this study a composite system has been formed using HiPco Single Walled Carbon Nanotubes (HCNT) and starch (extracted from rice). This composite was characterised using a range of spectroscopic techniques, which showed clear evidence of an intermolecular interaction between the HCNT and starch. The characterisation of these systems will be presented and evidence to support the notion of a noncovalent interaction is clear.
Keywords: Fullerenes and derivatives; UV-Vis-NIR absorption; Infrared and Raman Spectroscopy;

Charge Density Wave to Mixed Density Wave Phase Transition at High Fields in (Per)2M(mnt)2 (M = Au, Pt) by D. Graf; E.S. Choi; J.S. Brooks; J.C. Dias; R.T. Henriques; M. Almeida; M. Matos; D. Rickel (361-364).
The ground states of the quasi-one-dimensional organic metal (Per)2M(mnt)2 (where M = Au and Pt) were investigated by transport and magnetization measurements in magnetic fields of 33 and 45 tesla. The low field charge density wave transition temperature is suppressed by applied fields and a high field insulating state is introduced. We also report preliminary results of the effect of quasi-hydrostatic pressure on the charge density wave ground state and high field insulating state. The results will be discussed within the context of a contemporary model of high field density wave behavior.
Keywords: Q1D organic conductors; Charge density wave; Charge transfer salts;

EMR Measurements of Field-Induced Superconductor λ-(BETS)2FexGa1−xCl4 by Y. Oshima; E. Jobiliong; J.S. Brooks; S.A. Zvyagin; J. Krzystek; H. Tanaka; A. Kobayashi; H. Cui; H. Kobayashi (365-368).
We have performed high-field Electron Magnetic Resonance (EMR) measurements of λ-(BETS)2FexGa1−xCl4 to clarify the role of π- and d-electrons in the paramagnetic (PM) and field-induced superconducting (FISC) phases. We found that this system has a non-negligible π-d interaction that is very sensitive to the sample cooling rate. The π-d interaction is weaker when the sample is rapidly cooled which might affect its FISC phase. The results of the organic alloy λ-(BETS)2FexGa1−xCl4 (x  = 0.6) will be presented in this paper. © 2005 Elsevier Science. All rights reserved
Keywords: Electron spin resonance; Organic conductors based on radical cation and/or anion salts; Superconducting phase transitions;

Fermi Surface Study of β′′-(BEDT-TTF)(TCNQ) by Magnetooptical Measurements by M. Kimata; Y. Oshima; K. Koyama; H. Ohta; M. Motokawa; H.M. Yamamoto; R. Kato (369-372).
We have performed magnetooptical measurements of β′′-(BEDT-TTF)(TCNQ) using a cavity perturbation technique with a millimeter vector network analyzer (MVNA) and a 14 T superconducting magnet at IMR, Tohoku University. The results of ADMRO and SdH measurements at low temperatures are not consistent with the band calculation result. Therefore, we are interested in Fermi surfaces at low temperatures and have performed magnetooptical measurements of β′′-(BEDT-TTF)(TCNQ). Although the band calculation and ADMRO results suggest the existence of Q1D FS, our results suggest the existence of Q2D FS only. From the results of magnetooptical measurements, we discuss the FS topology of this system at low temperatures.
Keywords: Transport measurements; Magnetotransport; Organic conductors based on radical cation and/or anion salt; Other phase transition;

Crystal structures and physical properties of new BDA-TTP conductors by J. Yamada; K. Fujimoto; H. Akutsu; S. Nakatsuji; H. Nishikawa; K. Kikuchi (373-376).
The TaF6 and FeBr4 salts of BDA-TTP [2,5-bis(13-dithian-2-ylidene)-l,3,4,6-tetrathiapcntalene] have been prepared and characterized as β-(BDA-TTP)2TaF6 and β-(BDA-TTP)2FeBr4, respectively. The crystal structure of β-(BDA-TTP)2TaF6 is isostructural to those of the ambient-pressure superconductors β-(BDA-TTP)2X (X  = SbF6, AsF6 and PF6), but this salt undergoes an MI (metal-to-insulator) transition instead of a superconducting transition at ambient pressure. The β-(BDA-TTP)2FeBr4 salt, which is tsomorphous to the superconductors β-(BDA-TTP)2MCl4 (M  = Fe and Ga) under applied pressures, exhibits a phase transition near 170 K and antiferromagnetic ordering with the Néel temperature (T N) of about 9.5 K at ambient pressure.
Keywords: Magnetic measurements; Transport measurements; Conductivity; Metal-insulator phase transitions; Magnetic phase transitions; Organic conductors based on radical cation and/or anion salts;

Study of rapid oscillations in (TMTSF)2FSO3 under pressure and under very high magnetic fields by W. Kang; Y.J. Jo; Haeyong Kang; Ok-Hee Chung; D. Vignolles; M. Nardone; A. Audouard (377-380).
(TMTSF)2FSO3 is very special in that its electric transport properties are described by electrons from two-dimensional Fermi surfaces (FS) whereas those in most other Bechgaard salts are intrinsically explained with electrons from weakly warped quasi-one- dimensional FS. Conventional Shubnikov-dc Haas oscillations, described with the Lifshitz-Kosevich formula, has been observed. In this study, we measured magnetoresistance along the least conducting direction (c *) under pressures of up to 11 kbars and magnetic fields of up to 55 T, generated in a pulsed magnet, and found that the oscillations preserved two-dimensional nature to the highest measured field. There is no field-induced electronic transition. Pressure dependence and magnetic field dependence of parameters of oscillations are presented and discussed.
Keywords: Organic superconductors; Transport measurements; Conductivity; Hall effect; Magnetotransport;

The cyclotron effective mass is obtained by fitting a temperature-dependence of the Fourier transform integrals of the dc Haas-van Alphen (dHvA) oscillation with Lifehitz-Kosevich (LK) formula. However, the LK formula should be applied carefully in two-dimensional (2D) and quasi-two-dimensional (Q2D) systems at low temperatures, where the magnetic-field-dependence of the chemical potential cannot be neglected. We derive a cross-over temperature above which we can use the LK formula for the estimation of the cyclotron mass even in 2D and Q2D systems. We also show the cross-over temperature of κ-(BEDT-TTF)2Cu(NCS)2 which is known as the quasi-two-dimensional organic conductor.
Keywords: Organic superconductors;

The anion radical salts in the TCNQ system with 1-ethy1-3-methylimidazolium (EMI) and l-butyl-3-methylimidazolium (BMI) were prepared The 1:1 salts of EMI-TCNQ (1) and BMI-TCNQ (3) melted at 145 and 155 °C, respectively, and were stable even in the liquid state. The conductivity of 1 increased by four orders of magnitude at melting owing to the carrier generation by the dissociation of TCNQ dimers and decreased by three orders of magnitude at freezing.
Keywords: TCNQ; Alkyl-imidazolium cations; Ionic liquid; Anion radical salt; Conductivity in the liquid state;

TTF derivatives containing fused-pyrazine rings for novel donor- acceptor systems by Naraso; Jun-ichi Nishida; Masaaki Tomura; Yoshiro Yamashita (389-392).
In this work, novel TTF derivatives fused with electron-accepting pyrazine rings are described. We have succeeded in preparing two kinds of TTF derivatives containing two pyrazine rings. Furthermore, we have prepared asymmetrical TTF derivatives containing one pyrazine ring to increase the electron-donating properties. In some cases, hydroxyl groups were introduced to induce intcrmolecular hydrogen bonds. Oxidation of hydroquinone derivatives afforded a new type of donor-acceptor compounds with quinone units, which showed both oxidation and reduction potentials. The electrical conductivity of the D-A compound was about 10−8  S/cm as single component. We have also prepared several CT complexes based on the new TTF derivatives and investigated the structures and properties.
Keywords: Heterocyclc synthesis; UV-Vis-NIR absorption; Organic conductors based on radical cation and/or anion salts; Electro-optical modulator;

Uniaxial strain investigation on the metal-insulator transition of (EDO-TTF)2PF6 by M. Sakata; M. Maesato; A. Ota; H. Yamochi; G. Saito (393-396).
The quasi-one dimensional organic conductor (EDO-TTF)2PF6 shows the novel metal-insulator transition, which complies with the cooperative features of the tetramerization of EDO-TTF, the charge ordering of 0110 pattern, and the ordering of anion at ca. 280 K. In this paper, the effect of the uniaxial strain on the metal-insulator transition of (EDO-TTF)2PF6 was investigated by means of the transport measurement. In low pressure region, the transport behavior was differently modified depending on the direction of the compression. In the cases that the strain was applied along the b and a′ axes within the donor layer (intralayer), the transition temperature (T MI) was slightly decreased or not changed and the jump of resistivity was suppressed with increasing the strain. Contrary, the T MI was enhanced remarkably to above 340 K by the strain along the interlayer direction. The present results indicate that the strain along the interlayer direction is more effective for stabilization of insulating phase than those along the interlayer directions. It has been reported that the intralayer direction is expanded while the interlayer distance is shortened below T MI because the anion slightly inserts into the donor layer by means of the low temperature X-ray measurement at ambient pressure. The enhancement of the metal-insulator transition by the uniaxial strain along the interlayer direction is consistent with this anisotropic distortion of the unit cell through the transition. With applying the large strain along each direction, the insulating phase was suppressed and the metallic phase appeared around the room temperature. The metal-insulator transition occurred below about 200 K with the feature of the second-order.
Keywords: Metal-insulator phase transition; EDO-TTF; Transport measurement; Uniaxial strain;

Pressure effects on β′-type Pd(dmit)2 anion radical salts, which belong to a strongly correlated electron system with a quasi-triangular lattice of dimerized Pd(dmit)2 units, were studied with X-ray crystal structure analysis and resistivity measurements. The electronic state of this system is governed by various parameters including the effective on-site Coulomb energy on the dimer (U eff.), the band width (W), the degree of frustration, and the degree of band-filling. X-ray crystal structure analysis under hydrostatic pressure at low temperatures was performed for the Et2Me2P salt The tight-binding band calculations based on structural data indicate that the application of hydrostatic pressure reduces the electron correlation effect and leads the system from the Mott insulating state to the metallic state accompanied by the superconductivity. Further application of hydrostatic pressure induces another non-metallic behavior. This would originate from a partial nesting of the anisotropic Fermi surface associated with a structural transition which removes the glide plane and the two-fold axis. Based on cation dependence in the pressure effect, we propose a possible interplay of the correlation and the frustration, and discuss the uniaxial strain effect for this unique strongly correlated electron system.
Keywords: Organic conductors based on radical anion salts; Metal-insulator phase transitions; Structural phase transitions; X-ray diffraction; Semi-empirical models and model calculations;

Electronic Properties of a New Layered Organic Conductor, (BEDT-TTF)3Br(pBIB) by T. Takahashi; S. Suzuki; K. Hiraki; H.M. Yamamoto; R. Kato (401-404).
The electronic properties of a novel 3:1 BEDT-TTF salt were investigated by 13C-NMR measurements on a single crystal sample based on selectively 13C-enriched BEDT-TTF molecule. Static suscptibitity, Knight shift and relaxation rate were measured and a Korringa relation was confirmed. The correlation enhancement of Korringa co-efficient was found very small in comparison to the usual 2:1 BEDT-TTF salts.
Keywords: Nuclear magnetic resonance spectroscopy; Magnetic measurements; Organic conductors based on radical cation salts;

The organic FET with poly(peptide) derivatives and poly(methyl-methacrylate) gate dielectric by S. Uemura; A. Komukai; R. Sakaida; T. Kawai; M. Yoshida; S. Hoshino; T. Kodzasa; T. Kamata (405-408).
The field effect transistor (FET) was fabricated with pentacene as an active layer and polymer insulator as a gate dielectric. Poly(γ-methyl-L-glutamate) [PMLG] and poly(methyl-methacrylate) [PMMA] were used as one of the polymeric gate dielectric. PMLG has the large dipole moment along the rod-like main chain and the small dipole moment in the side chain. The effect of the main chain dipole and/or the side chain dipole on the FET was compared with that of PMMA gate dielectric, which has dipole moment only at side chain. When PMLG gate dielectric was used, the hysteresis in the transfer characteristics was considerably increased as compared with that in the case of other polymeric gate dielectrics. It is considered that the large hysteresis behavior is taken place by both the dipole moments of the side chain and the main chain.
Keywords: Solution processing; Insulating film; Semiconductor/insulator interfaces;

Scanning Tunneling Spectroscopy on κ-(BEDT-TTF)2Cu[N(CN)2]Br by K. Ichimura; S. Higashi; K. Nomura; A. Kawamoto (409-412).
We report the electron tunneling spectroscopy on partially deuterated κ-(BEDT-TTF-d[3,3])2Cu[N(CN)2]Br using a low temperature STM. In the superconducting state, tunneling spectra show the energy gap structure clearly; the conductance around the zero bias voltage is well reduced. V-shaped tunneling conductance curve inside the gap edge suggests the gap anisotropy. The linear dependence on the energy near zero bias is explained by the d-wave pairing with line nodes. By fitting to the d-wave gap model, we obtain the gap parameter as Δ=1.4–3.3 meV. Correspondingly, 2Δ/kT c is estimated as 2.7–6.4. The value is almost the same as that in κ-(BEDT-TTF)2Cu(NCS)2, d[0,0] and d[2,2] salts. The zero bias anomaly, which is an evidence for nodes of the superconducting gap, was found. The d-wave symmetry is strongly supported.
Keywords: Atomic force microscopy; Scanning tunneling microscopy; Single-crystal surfaces; Superconducting phase transitions; Organic superconductors;

One-dimensional strongly correlated electron system, which is accompanied by the interaction with the lattice, has attracted a great deal of interest. At half-filling, this system is a Mott insulator when the electron-lattice interaction is weak. We performed theoretical investigation of the stable ground state of the one-dimensional strongly correlated electron system in which one electron was doped from half-filling. We found that a polaron solution appears under conditions of comparatively strong electron-lattice interaction and the polaron delocalizes under conditions of weak electron-lattice interaction in the Mott phase. [R. Shirasaki, and K. Iwano, J. Phys. Soc. Jpn. 72 (2003) 2902.] Moreover, we investigated the optical conductivity in the appearance of the polaron in the Mott phase. We used the phase Hamiltonian which described the physical properties of the strongly correlated electron system. Our calculation shows that the optical absorption peak in the electron gap appears when the polaron is induced in the strongly correlated electron system.
Keywords: Models of non-linear phenomena; Mani-body and quasiparticle theories; Photoluminescence;

NMR Studies of Exotic Members of Bechgaard Salt with Non- centrosymmetric Anions under Pressure by Hidetaka Satsukawa; Haeyong Kang; Ko-Ichi Hiraki; Toshihiro Takahashi; Younjung Jo; Woun Kang; Ok-Hee Chung (417-420).
The electronic properties of (TMTSF)2FSO3 have been investigated under pressure of 0.65 GPa by measuring 77Se-NMR lineshape, spin-lattice relaxation rate ( T 1 − 1 ) and spin-spin relaxation rate ( T 1 − 1 ) measurements on a single crystal sample. The NMR signal was found abnormally broadened below 90 K. Below 40 K, a narrow component appears and coexists with the broader one. The temperature dependence of T 1 − 1 suggests that the broader component comes from a metallic phase and the narrow one from an insulating phase. The activation energy determined for the insulating component was found three times lower than the value found at ambient pressure. From the T 1 − 1 measurements, the broadening of the metallic component was confirmed as inhomogeneous. An unusual double peak anomaly of T 1 − 1 suggests the existence of extremely slow fluctuations of the inhomogeneous local fields below 90 K at this pressure.
Keywords: Nuclear magnetic resonance spectroscopy; Metal-insulator phase transition. Organic conductors based on radical cation and/or anion salts;

Highly conducting ionic liquids based on l-ethyl-3-methylimidazolium cation by Y. Yoshida; J. Fujii; K. Muroi; A. Otsuka; G. Saito; M. Takahashi; T. Yoko (421-424).
Highly conducting EMI-based room-temperature (RT) ionic liquids containing transition metals [EMI][M(III)Cl4] (M = Fe, Fe0.5Ga0.5 and Ga) were prepared, and their thermal and physical properties were well investigated, where EMI is l-ethyl-3-methylimidazolium, All the salts are liquid at RT and show a wide liquid range. High ionic conductivities (1.8-2.0x10−2 S cm−1 at 20 °C) and low viscosities (12–14 cP at 30 °C) are comparable to those of N(CN)2 and C(CN)3 salts. The FeCU and Fco.5Gao.5Cl4 melts exhibit a Curie-like behavior arising from the = 5/2 spins on iron(III) ions, indicating the first conductive-paramagnetic biftinctional RT ionic liquids. On cooling, the solidified FeCl4 salt passes through an antiferromagnetic transition at 4.2 K. On the basis of sixteen EMI-based RT ionic liquids including the present salts, it has become apparent that the conductivity is proportional to the reciprocal of the product of the anion weight and the viscosity.
Keywords: Room-temperature ionic liquid; 1-ethy l-3-methylimidazolium; Ionic conductivity; Viscosity; Walden plot; Magnetic susceptibility;

Structures and electrical conductivities of cation radical salts based on unsymmetrical [Au(III)(C-N)(S-S)] type dithiolate complexes by Kazuya Kubo; Akiko Nakao; Yasuyuki Ishii; Reizo Kato; Gen-etsu Matsubayashi (425-428).
Crystals of [Au(ppy)(S-S)]2[Q][Solvent]n [ppy  =  C-deprotonated-2-phenylpyridine(−); S-S = C8H4S8 2−: 2-{(4,5-ethylenedithio)-l,3- dithiole-2-ylidene}-l,3-dihtiole-4,5-dithiolate(2−), C8H4S6O2 2−: 2-{(4,5-ethylenedioxy)-l,3-dithiole-2-ylidene(-l,3-dihtiole-4,5-dithiolate (2−); Q  = PF6 , BF4 AsF6 and TaF6 ; solvent = PhCl and PhCN; n  = 0–0.5] type cation radical salts were prepared by constant current electrolysis of benzonitrile or chlorobenzene solutions of unsymmetrical [Au(ppy)(S-S)] type metal complexes with [Bun 4N][Q] as electrolyte. These salts exhibit two types of unique columnar structures. The one (S-S = C8H4S8 2−, Q = PF6 /S-S = C8H4S6O2 2−, Q = BF4 ) contains the two-fold head-to-head stacking of cation radicals while the other (S-S = C8H4S8 2−, Q  = AsF6 , TaF6 ) is based on the stacking of tetramers of cation radicals. [Au(ppy)(C8H4S8)]2[PF6] shows semiconductive behavior (E a  = 0.03 eV) under ambient pressure. Interestingly, it shows metallic behavior under high pressure (>0.8 GPa). To our knowledge, this is the first example of the metallic cation radical salt based on the unsymmetrical metal complex. Other radical cation salts show insulating or semiconducting behavior (E a  = 0.11–0.15 eV).
Keywords: Electrocrystallization; Single-crystal growth; Elemental analysis; X-ray diffraction; Organic conductors based on radical cation salts;

Synthesis and Properties of TTF Oligomers Possessing Electron-Withdrawing Groups in the Spacer by S. Matsumoto; W. Matsuda; H. Fueno; Y. Misaki; K. Tanaka (429-432).
Dimeric and trimeric tetrathiafulvalene (TTF) derivatives possessing carbonyl groups in the spacer (1, 2) and dimeric TTF derivatives and tetrathiapentalene (TTP) derivatives possessing ester groups in the spacer (3, 4) have been synthesized. Cyclic voltammogram of 13 exhibits two pairs of redox waves. No significant shift of redox potentials was observed as increase of the TTF units. Cyclic voltammogram of 4 shows four pairs of two-electron redox waves. The E 1 / 2 2 − E 1 / 2 1 value of 4 is larger than that of the corresponding monomer and the first redox wave is slightly broad, suggesting small intramolecular interaction between two TTP units in the oxidation states.
Keywords: UV-Vis-NIR absorption; Electrochemical methods; Ab initio quantum chemical methods and calculations;

Non-linear transport in the incommensurate SDW phase of (TMTTF)2Br under pressure by K. Nomura; K. Ishimura; N. Matsunaga; T. Nakamura; T. Takahashi; G. Saito (433-436).
The spin-density wave (SDW) phase with an incommensurate wave vector is induced as a ground state in the organic compound (TMTTF)2Br under the pressure above 0.5 GPa. We investigated the collective sliding motion of the SDW condensate with measuring the non-linear conductivity in this SDW phase. The measurement was done with dc and pulse methods. Below the SDW transition temperature T sDW, the sharp increase of conductivity from the ohmic one was observed with the clearly defined threshold electric field E T. This indicates the depinning of the SDW and the excess conductivity above E T is associated with the sliding motion of the SDW. The absolute value of E T is fairly larger than that observed in (TMTSF)2PF6, whose ground state is the incommensurate SDW at ambient pressure. With decreasing the temperature from T SDW, E T increases gradually and shows a relatively sharp drop after a peak around 03T SDW. This temperature is supposed to be connected with the sub-phase transition proposed from the temperature dependence of NMR relaxation rate. In addition, the excess conductivity normalized to the ohmic one, which corresponds to the current carried by the SDW condensate, shows a dip at 0.3T SDW with decreasing the temperature. In the dc I-V characteristics, the hysteretic behavior near E T appears only around 0.3T SDW. These behaviors suggest that the sliding mechanism of the SDW condensate varies across 0.3T SDW. We discuss the dynamics of the SDW in (TMTTF)2Br in comparison with that in (TMTSF)2X, considering the sub-phase transition.
Keywords: Transport measurements; Conductivity; Hall effect; Magnetotransport; Other phase transitions; Organic conductors based on radical cation and/or anion salts;

Pyrazino-fused organic conductors, CnDTP-TTF and CwDTP-STF (n = 5,6) by S. Kimura; K. Yamashita; H. Suzuki; S. Ichikawa; H. Mori; Y. Nishio; K. Kajita (437-440).
We have obtained several charge-transfer complexes of CnDTP-TTF (n  = 5,6). The C5DTP-TTF salts are the κ-type semiconductor with high room-temperature conductivities, whereas β′′-(C6DTP-TTF)2(GaCl4)0.66 shows the metallic behavior down to 40 K. In order to improve the conductivity by increasing the bandwidth, we have applied a pressure and synthesized a series of the selenium analogues, CnDTP-STF (n  = 5,6). In this report, crystal structures and conducting behaviors of CnDTP-TTF salts, and the attempt of increasing the bandwidths are described.
Keywords: Organic conductors based on radical cation and/or anion salts; Transport measurements; conductivity; Hall effect; magnetotransport; Metal-insulator phase transitions; X-ray emission; Diffraction and scattering;

Electrical Conduction in Divalent BEDT-TTF Salts by H. Ito; Y. Yokochi; H. Tanaka; S. Kuroda; R. Kanehama; M. Umemiya; H. Miyasaka; K. -i. Sugiura; M. Yamashita (441-444).
Transport and ESR measurements have been performed on organic semiconductors synthesized by the diffusion method. For (BEDT-TTF)Cu2Br4, a pressure of 1 GPa raises the conductivity by up to one order of magnitude, but does not alter the semiconducting nature. By the ESR measurements, we find no Cu2+ signals, indicating that the BEDT-TTF molecules are divalent. The Hall carrier concentration increases exponentially with temperature, approaching the spin concentration evaluated by the low-temperature ESR from π-electrons. Thermopower measurements also support the contribution of the thermally activated electronic carriers. For (BEDTTTF)2Cu3Br7(H2O), the conductivity increases twice by applying a pressure of 0.8 GPa.
Keywords: Organic conductors; Conductivity; Hall effect; Thermopower; Electron spin resonance;

Magnetism in BEDT-TTF materials by R.T. Clay; S. Mazumdar (445-448).
Strong commensurate antiferromagnetism proximate to superconductivity is found in some members of the κ-(ET) family, while a spin gap (SG) is found in the θ-(ET). Both κ- and θ-(ET) materials have frustrated triangular lattice structures. We show from calculations of spin-spin correlations within the effective half-filled band triangular lattice proposed for the κ-ET, as well as for the real lattice, that long range AFM order is not obtained as a consequence of this frustration. We argue that some other mechanism reduces the magnetic frustration in these systems. We show that the low temperature magnetic states in these materials can only be understood if the effects of the cooperative charge and bond ordering transitions occurring at higher temperatures in these systems are taken into account. In the κ-ET, this co-operative transition leads to unequal hole populations on the ET dimers that form the triangular lattice.
Keywords: Organic conductors based on radical cation and/or anion salts; Organic superconductors;

Angle-dependent magneto-transport measurements on κ- (BEDT-TTF)2Cu(NCS)2 under pressure by A.F. Bangura; P.A. Goddard; S. Tozer; A.I. Coldea; R.D. McDonald; J. Singleton; A. Ardavan; J. Schleuter (449-452).
Magnetotransport measurements have been performed on single crystals of κ-(BEDT-TTF) 2 CuNCS) 2 in fields of up to 33 T at temperatures between 500 mK and 4.2 K. Using a diamond anvil cell mounted on a goniometer, measurements of the angle and temperature dependence of the interlayer resistance, R ZZ under hydrostatic pressures between 1.1 kbar and 17.3 kbar were performed. For the first time we have been able to measure angle-dependent magnetoresistance oscillations under pressure due to both the ID and 2D Fermi surfaces in addition to Shubnikov de Haas oscillations. The results show that the shape of the elliptical quasi-2D Fermi-pocket is more elongated under a hydrostatic pressure of 9.8 kbar compared with ambient pressure. When the magnetic field B is close to parallel to the highly conductive plane, bc, a peak in R ZZ is observed with an angular width determined by the ratio of the maximum inter- and intra-layer Fermi velocities. The width of this peak is found to increase with pressure suggesting that the Fermi surface becomes more three-dimensional upon application of pressure.
Keywords: Magnetotransport; Organic superconductors;

Evidence of band-filling control of τ−type organic conductors by thermal treatment by H. Yoshino; T. Nakanishi; Lin Li; Keizo Murata; D. Graf; E.S. Choi; J.S. Brooks; Y. Nogami; G.C. Papavassiliou (453-456).
The two dimensional (2D) organic conductor τ-(EDO-S,S-DMEDT-TTF)2(AuBr2)1+y , (y  ≤ 0.875) is known to exhibit sample dependence of the electric resistivity. The present authors assumed that the possible difference in y is responsible for the sample dependence and the amount of y can be effectively controlled for each crystal by thermal treatment. If it is the case, the band filling of the present compound can be also controlled. To observe the change in the band filling directly, the magnetoresistance was measured up to 45 T at 0.5 K for the magnetic field perpendicular to the conducting ab plane of the samples from one single crystal, one of which had been heated up to 400 K. Both the samples showed the two series of Shubnikov-de Haas oscillations of the magnetoresistance as reported previously. We, however, found the remarkable difference in the frequency of the slower oscillations between the virgin and heated samples. The X-ray study revealed that the thermal treatment does not affect the crystal structure related to the 2D band structure. Thus the frequency change by the thermal treatment is caused by the change in the band filling and it is tuned by heating the crystal.
Keywords: Transport measurement; Magnetotransport; Organic conductors based on radical cation salts;

Preparation of 1,3,5-trithia-2,4,6-triazapentalenyl films on gold surfaces by K. Iketaki; K. Kanai; K. Tsuboi; W. Fujita; K. Awaga; M. Knupfer; Y. Ouchi; K. Seki (457-460).
Thin films of 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA) were prepared on gold surfaces by “dry” and “wet” processes and were investigated by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and surface plasmon resonance (SPR) spectroscopy. Vacuum deposition and self-assembly method were used as dry and wet processes, respectively. In the dry process, the S 2p XPS spectra show the formation of S―Au bond between TTTA molecules and gold surfaces. In addition, UPS measurements revealed that TTTA molecules are closely packed without decomposition. In the wet process, the adsorption kinetics monitored by SPR indicates that TTTA molecules are strongly bound to gold surfaces. The thickness of TTTA films from ethanol and hexane solutions was 1.3 nm and 1.8 nm, respectively, which suggests multilayer formation.
Keywords: Organic/inorganic interfaces; Photoelectron spectroscopy; Self-assembly using surface chemistry; Magnetic phase transitions;

The preparation, X-ray crystal structure, EPR and magnetic measurements of [CuII(hfac)2(TTF-py)2](BF4)2.2CH2Cl2, a new material where the conducting and the localized spin systems are covalently linked through conjugated bridges, are reported. This materials is in line with a previous compound [CuII(hfac)2(TTF-py)2](PF6).2CH2Cl2, despite the full oxidation of the TTF-type organic donor ligand, we observed the presence of dimerized TTF chains.
Keywords: Single-crystal growth; Electron spin resonance; Magnetic measurements; X-ray diffraction; Organic conductors based on radical cation;

For the first time, we have determined the crystal structure of CT complexes between M(isq)2 and CHL (isq = diiminobenzosemiquinonato; CHL =  p-chloranil; M=Ni, Pt). M(isq)2 and CHL formed segregated stacking and 1 -D uniformly spaced chain with face to face separations of 3.30–3.35 Å for M(isq)2 and 3.15 Å for CHL The M-M distances were 3.61 Å for Ni and 3.60 Å for Pt, and no M…M interaction was found. The geometries, IR, and UV spectra indicated ionic ground states of the CT complexes. The CT complexes exhibited semiconducting character with similar activation energy of ca 0.2 eV at 200–300 K. The reaction of Ni(isq)2 with 2,5-dichlorobenzoquinone gave not an expected CT complex but a salt with composition of [Ni(isq)2]3Cl2. X-ray structure analysis revealed separated monomer and dimer of Ni(isq)2. The weak Ni…Ni interaction of 2.804 Å was found in the dimer. The geometries suggested that monomeric Ni(isq)2 was nearly neutral and that the Ni(isq)2 in the dimer was ionic with the charge of +1. The salt also showed a semiconductive behavior with activation energy of 0.27 eV at 200–300 K.
Keywords: X-ray diffraction; Infrared spectroscopy; UV-Vis-NIR absorption; Conductivity; Organic semiconductors based on conjugated molecules;

Fabrication of an organic-inorganic hybrid LB film of a magnetic polyoxometalate by Hee Sang Kim; Burm-Jong Lee; Dong Ho Park; Young-Soo Kwon (469-472).
A paramagnetic organic-inorganic hybrid Langmuir-Blodgett (LB) film was produced through orientation-controlled stabilization of a Ni-containing magnetic polyoxometalate (((NBu4)3 [PW9NiO43(HOOCC2H4PO)2]): Ni-POM) monolayer by attaching electrostatically hydrophobic N,N-dimethyldodecyl amine (DMDA). Although the Ni-POM itself did not show any development of surface pressure upon monolayer spreading, the surface pressure-area isotherm showed the formation of very stable monolayer on the water subphase when the polyoxometalate was spread together with DMDA. The hybrid LB films transferred on solid substrates were characterized by XPS and XRD spectra. The XPS spectra indicated the presence of Ni-POM in the LB film. The AFM image of the LB film showed that the Ni-POM particles were totally spread to monolayer. The X-ray diffraction spectra showed POMs are positioned to two-dimensionally spread multiplayer film. The peaks due to (100) and (200) planes are interpreted as the hybrid multiplayer film is composed of multilayer monolayers. The Ni-POM showed characteristic paramagnetic susceptibility, which was monitored by a SQUID magnetometer.
Keywords: Langmuir-Blodgett technique; Atomic force microscopy; X-ray photoelectron spectroscopy; Magnetic measurement;

Ferromagnetism and its photo-induced effect in 2D iron mixed-valence complex coupled with photochromic spiropyran by I. Kashima; M. Okubo; Y. Ono; M. Itoi; N. Kida; M. Hikita; M. Enomoto; N. Kojima (473-476).
Iron mixed-valence complex, (n-C3H7)4N[FeIIFeIII(dto)3](dto = C2O2S2), shows a spin-entropy driven phase transition called charge transfer phase transition around 120 K and a ferromagnetic transition at 6.5 K. These phase transitions remarkably depend on the hexagonal ring size in two-dimensional honeycomb network structure of [FeIIFeIII (dto)3]. In order to control the magnetic properties and the electronic state in the dto-bridged iron mixed-valence system by means of photo-irradiation, we have synthesized a photo-sensitive organic-inorganic hybrid system, (SP)[FeIIFeIII(dto)3](SP = spiropyran), and investigated the photo-induced effect on the magnetic properties by the measurements of magnetic susceptibility, ESR, IR, UV-vis and 57Fe Mössbauer spectra. Upon UV irradiation at 337 nm, a broad absorption band between 500 nm and 600 nm appears and continuously increases with the photo-irradiation time, which implies that the UV irradiation changes the structure of spiropyran from closed form to open one in solid state. The photochromism in spiropyran changes the ferromagnetic transition temperature and the coercive force.
Keywords: Magnetic measurements; Magnetic phase transition;

Reactions of the [FeIII(CN)6]3− anion with the [CuII(tn)]2+ ion (tn = 1,3-diaminopropane) afford the compounds {[CuII(tn)]2[FeII(CN)6]}3·[Na3FeIII(CN)6]·12H2O (1) and {[Cun(tn)]2[FeII(CN)6]}·KCl·5H2O (2). Despite the differences concerning their asymmetric units, both structures present strong similar features: in both structures, the Cu(II) ion presents a square-base pyramidal CuN5 environment and each [FeII(CN)6]4− anion is linked to six Cu(II) ions through its six N atoms leading to infinite [CuII(tn)]2[FeII(CN)6] layers which can be viewed as 2-D layered arrangement generated by the defective cubane units Cu4Fe3 involving Fe-CN-Cu bridges. The most important differences between the two structures concern essentially the inter-layer arrangement which is occupied, in compound 1, by isolated paramagnetic [Fe(CN)6]3− anions and water molecules, while in compound 2, this interlayer space is occupied by K+, Cl ions and water molecules. Magnetic data indicate for 1 weak antiferromagnetic interactions and presence of magnetically isolated [FeIII(CN)6]3−anion and for 2 weak ferromagnetic interactions between the Cu(II) ions.
Keywords: Coordination polymer; Copper; Hexacyanometallates; Magnetic properties;

Reaction between CuCl2 and K2tcpd (tcpd2−  = {C[CN)2]3}2−  = 2-dicyanomethylenc-1,1,3,3-tetracyanopropanediide anion) in presence of the neutral ligand tn (1,3-diaminopropane) in aqueous solution yields the new compound [Cu(tn)(tcpd)] (1) which was characterized by X-ray crystallography. The crystal structure of 1 consists of one [Cu(tn)]2+ unit and one tcpd2− anion, both located on general positions. Each Cu atom presents an essentially octahedral coordination with four nitrogen atoms arising from four polynitrile ligands and two nitrogen atoms from the chelating tn ligand. Despite its six nitrile groups potentially bridging, the tcpd ligand acts with a μ4-bridging mode via four nitrogen atoms of two different C(CN)2 wings leading to a 3D structure. The magnetic behavior for compound 1 shows a very weak antiferromagnetic coupling of the Cu(II) ions through the NC―C―CN bridge that can be very well reproduced with a regular S  = 1/2 antiferromagnetic chain model with g  = 2.108 and J  = −0.042.
Keywords: Coordination polymer; Transition metal; Copper; N ligands; Magnetic properties;

A carborane derivative containing two nitronyl nitroxide moieties, OCB-BNN was successfully synthesized and characterized. On the ESR study in the benzene solution, nonet lines of the hyperfine structure owing to the equivalent four nitrogen nuclei were observed. An X-ray crystallographic analysis revealed that the crystal lattice has a one-dimensional cavity. The spin distribution and the singlet-triplet energy gap of OCB-BNN were evaluated by the DFT calculation (UB3LYP-6-31G*). The synthesis, structure, ESR measurement and DFT calculation will be discussed.
Keywords: Density functional calculations; Electron spin resonance; Magnetic measurements; X-ray diffraction;

Anisotropy of ESR parameters in organic ferromagnet TDAE-C60 by M. Fujiwara; T. Kambe; K. Oshima (489-492).
We study the anisotropy of ESR parameters using single crystal TDAE-C60, which has two polymorphisms: the one is ferromagnetic a-phase and the other is non-ferromagnetic α′-phase. In both α′- and α-phase, the line-widths and g-factors show anisotropic angular dependences at room temperature, such as ΔHpp b  > ΔHpp c  ∼ ΔHpp a and gc  > gb  = ga. The anisotropic behaviour of g-factors in both phases suggest the uniaxial rotation of Jahn-Teller distorted C60 molecules around the c-axis, which is the close-packing direction of C60 molecules. In the α′-phase the temperature dependence of g-factors has a clear anomaly around 160 K. Below this temperature, the observed g-factors are in-between the monovalent C60 and TDAE+, indicating the restoration of missing TDAE spins. In the α-phase, the g-factors continuously shift with decreasing temperature, become anisotropic below 230 K, and show no remarkable anomaly at the structural phase transition temperature. These results suggest that the difference exists in the mixing between the wave functions of C60 and TDAE, which is possibly developed by the structural difference between α′- and α-phases. This difference separates the magnetic peculiarities of two polymorphisms in TDAE-C60.
Keywords: Electron spin resonance; Magnetic phase transitions; Fullerenes and derivatives;

Interaction of Torsional Oscillations with Polarons and Bipolarons in Conjugated Polymer by Alexandre Naves de Brito; Geraldo Magela e Silva (493-496).
We propose a model for the electronic interaction associated with torsional and bond length vibrations in quasi one dimensional chains of conjugated polymers. The model admits conformational bond length objects like polarons and bipolarons and torsional modes of vibration. It is shown that the dynamics of these objects can be studied by numerically integrating the corresponding time-dependent equations of motion for the bond length, ring torsion angle and pi-electrons. An extension of the PPP and SSH models is numerically solved using the Time-Dependent Hartree-Fock approximation. An wide range of conducting polymers is simulated by varying the moment of inertia of the monomers (ranging from polypyrrole to poly(3-hexyl)thiophene). The stereometric interactions between chains are parametrically considered with different torsional potentials. The results show that polarons and bipolarons are trapped between the antinodes of torsional vibration modes with wave length larger than their width. This effect damps down their mobility. It is also found that torsional vibration modes with very long wave lengths or wave lengths shorter than the width of polarons and bipolarons produces almost no effect on their propagation.
Keywords: Molecular dynamics; Lattice dynamics; Computer simulations; Many body and quasiparticles theories; Polythiophen and derivatives;

Conductivity measurement of insulated molecular wire formed by molecular nanotube and polyaniline by T. Shimomura; T. Akai; M. Fujimori; S. Heike; T. Hashizume; K. Ito (497-500).
A new series of nanotubes synthesized from α-cyclodextrin (molecular nanotube) form an inclusion complex with polyaniline, a conducting polymer. This inclusion complex can be considered to be an insulated molecular wire (IMW). In this study, we investigated the conductivity of this insulated molecular wire by using narrow-gap (150 nm) electrodes fabricated by a scanning-probe nanofabrication technique. The IMW, on doping, showed nearly ohmic I-V characteristics, and the conductivity was estimated to be 4 × 10−2  S/cm.
Keywords: Self-organization in macromolecules; Polyaniline and derivatives; Conductivity; Atomic force microscopy;