Synthetic Metals (v.161, #11-12)

Synthesis, structure and luminescent properties of two-dimensional lanthanum(III) porous coordination polymer based on pyridine-2,6-dicarboxylic acid by Li-Rong Yang; Shuang Song; Cai-yun Shao; Wu Zhang; Huai-Min Zhang; Zhan-Wei Bu; Tie-gang Ren (925-930).
The novel porous coordination polymer {[La4(PDA)10(H2O)8]·2H2O} n with two-dimensional framework has been prepared by hydrothermal synthesis of pyridine-2,6-dicarboxylic acid (H2PDA) and lanthanum nitrate under mild conditions and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. The complex crystallizes in triclinic system, space group P-1. La(III) ions in the coordination polymer are nine-coordinated and have N1O8 or N2O7 polyhedral units connected to the PDA2− anions forming tricapped trigonal prism geometries. The H2PDA ligands coordinate to the central La(III) ions in bridging tetradentate and pentadentate modes. The thermal decomposition of the complex has been predicted with the help of thermal analyses (TG and DTG). The complex exhibits luminescent property in the near-UV at room temperature in the solution of DMSO due to the π *  →  n or π *  →  π transitions of PDA2− anions.
Keywords: Synthesis; Structure; Luminescent properties; Coordination polymer; Pyridine-2,6-dicarboxylic acid;

Characterization of the field-effect conductivity distribution in pentacene thin-film transistors by a near-field scanning microwave microscope by Arsen Babajanyan; Harutyun Melikyan; Jerome Carnis; Youngwoon Yoon; Hanju Lee; Hyung Keun Yoo; Kiejin Lee; Barry Friedman (931-936).
► We visualized the conductivity profiles in the active layer of a pentacene FET by a NSMM. ► The 3D image of microwave reflection coefficient clearly distinguishes the conductivity profiles caused by holes and electrons, though motion of electrons from the drain generates the same trace of transient current as that of holes moving from source to drain. ► The electric field profiles, the complementary image of conductivity profiles, which are visualized by using an optical second harmonic generation method, support the results.Direct probing of the conductivity distribution in organic materials is motivated by the need to obtain a deeper understanding of carrier behavior in organic thin-film transistors (OTFT), organic electro-luminescent devices, organic photoconductors, and organic biosensors. Here we used a near-field scanning microwave microscope to visualize conductivity profiles in OTFT channel. Applying this technique to pentacene field-effect transistors has revealed changes of the conductivity distribution in the channel arising from the development and exhaustion of an accumulated charge region. The electric field profiles, the complementary image of conductivity profiles, which are visualized by using an optical second harmonic generation method, support the results. We anticipate that direct observation by this microwave method will find wide application in measurement of carrier conductivity in organic and nonorganic materials.
Keywords: Pentacene; Field-effect transistor; Conductivity distribution; Microwave microscope;

High conductivity and supermagnetism of polyaniline (PANI)-coated multi-walled carbon nanotube (MWCNT) composites containing monodispersed 6 nm iron oxide (Fe3O4) nanoparticles has been successfully synthesized by in situ chemical oxidative polymerization using anionic surfactant dodecylbenzenesulfonic acid sodium salt. Hydrophilic 6 nm spherical Fe3O4 nanoparticles fabricated by the thermal decomposition process were chemically modified using 11-aminoundecanoic acid tetramethylammonium salt. The modified nanoparticles were further mixed with carboxylic acid containing multi-walled carbon nanotubes (c-MWCNTs) in an aqueous solution to form one-dimensional Fe3O4 coated c-MWCNT template and PANI/c-MWCNT nanocomposite were then synthesized via in situ chemical oxidative polymerization in HCl solution. Structural and morphological analysis using FESEM, HRTEM and XRD showed that the fabricated Fe3O4 coated c-MWCNT/PANI nanocomposites are one-dimensional core (Fe3O4 coated c-MWCNT)–shell (PANI) structures. The electrical conductivity of 1 wt% Fe3O4 coated c-MWCNT/PANI nanocomposites at room temperature is 37.7 S/cm, which is decreased to 28.6 S/cm with the loading of 5 wt% Fe3O4 nanoparticles. The magnetic properties of Fe3O4 coated c-MWCNT/PANI nanocomposites exhibit supermagnetism with saturation magnetization in the range of 0.04–0.15 emu/g, which increases as the amount of Fe3O4 nanoparticles increases.
Keywords: Polyaniline; Carbon nanotubes; Magnetite; Electrical properties; Magnetic properties;

The synthesis, characterization of newly synthesized metal-free 2 and metallophthalocyanine complexes 35 (MPcs, M = Ni, Co, Cu) and quaternized metallophthalocyanine derivatives 3a, 5a (MPcs, M = Ni, Cu) containing 4,5-bis(quinolin-6-yloxy) substituents have been presented in this work. The new compounds have been characterized by using elemental analysis, UV–vis, IR, 1H NMR, 13C NMR and MS spectroscopic data. Also, aggregation properties of Pcs were investigated at different concentrations in chloroform, dimethylformamide and water. The effect of the concentration on the aggregation properties of complexes 25 was studied in chloroform. No aggregation was demonstrated in chloroform from concentration between 1 × 10−5 and 0.4 × 10−5  M.
Keywords: Synthesis; Microwave; Aggregation; Quaternization; Cobalt; Phthalocyanine;

► Characterization of the series resistance time evolution of organic solar cell. ► Lambert W function provides a quick tool for the aging study. ► The method enables to discriminate if the one diode model can be applied to a device. ► Good fit to experimental data is possible without using complex numerical algorithms. ► Other commonly used methods (i. e. the JV gradient method) give unreliable results.The time evolution of the series resistance of bulk heterojunction solar cells realized and stored in inert atmosphere as well as in air has been monitored by fitting the experimental current v s . voltage characteristic to the analytical solution of the real diode equation obtained by means of the Lambert W function. The method allows to determine if and at what extent the standard one diode model can be used to acceptably describe the organic device in the field of a preliminary simple and fast evaluation of the series resistance evolution with time, without the need of complex and time consuming numerical fitting algorithms.
Keywords: Organic photovoltaic; Lambert W function; Aging; Modeling; Bulk heterojunction;

Polyaniline (Pani) has been electrochemically polymerized on conducting fabrics of polyester covered with polypyrrole/PW12O40 3−, obtaining a double conducting polymer layer. Electrochemical synthesis was performed by potentiostatic synthesis at 1 V. The chemical characterization of the material before and after Pani polymerization was performed by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). The morphology of the coatings was observed employing scanning electron microscopy (SEM). The electrochemical characterization was performed by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). It has been demonstrated that scan rate is an important parameter that influences the response obtained when characterizing conducting fabrics by CV. High scan rates do not allow the observation of redox peaks. However if lower scan rates are employed its apparition has been reported. The electrochemical deposit of polyaniline enhances the electroactivity of the material as it has been demonstrated by CV. SECM measurements showed local response with positive feedback (electroactive material) for the samples in open circuit conditions. XPS analysis also showed a higher doping level (N+/N), consistent with higher material electroactivity.
Keywords: Polyaniline; Polypyrrole; Conducting fabrics; Cyclic voltammetry; SECM;

Eu-β-diketonate complex OLED as UV portable dosimeter by W. Quirino; R. Reyes; C. Legnani; P.C. Nóbrega; P.A. Santa-Cruz; M. Cremona (964-968).
The fabrication and the characterization results of a triple-layer organic light emitting diode (OLED) using a fluorinated Eu3+-β-diketone complex particularly sensitive to UV radiation are presented. The electroluminescence spectra of the devices, fabricated by thermo evaporation carried out in a high vacuum environment, present narrow emission bands characteristics of the Eu3+ ion. The intensity of these peaks decrease as a function of the UV radiation impinging on the device, and is strongly dependent from the UV radiation cumulative dose. The results show that measuring the main Eu3+ emission intensity it is possible to fabricate a portable UV personal dosimeter using this kind of complexes as emitting layer in an OLED device. The OLED emission will be inversely proportional to the UV irradiation exposure.
Keywords: OLED; UV dosimeter; Europium complexes; Electroluminescence; Photo-degradation;

A study of optical properties and annealing effect on the absorption edge of pristine- and iodine-doped polyazomethine thin films by Bozena Jarzabek; Jan Weszka; Barbara Hajduk; Jan Jurusik; Marian Domanski; Jan Cisowski (969-975).
Aromatic polyazomethine (PPI) thin film have been obtained by chemical vapor deposition (CVD) method, via polycondensation process and characterized by X-ray diffraction, AFM, FTIR and detailed UV–Vis–NIR studies. Optical transmission and fundamental reflectivity spectra of the film have been examined within the spectral range 200–2500 nm. The refractive index (n), film thickness (d) and parameters of the absorption edge i.e. the optical gap (E G) and the Urbach energy (E U) have been found for the PPI film before and after iodine (I2) doping. Then the annealing effect (from 25 °C every 25 °C up to 225 °C) on the absorption edge have been investigated during “in situ” spectral measurements. Amorphous character of the films allowed us to obtain the E G and E U values, in the way typical for amorphous semiconductors. As a result of iodine doping, the energy gap of the PPI film (2.19 eV) distinctly reduces to 1.73 eV, due to the polaron states and, simultaneously, the Urbach energy decreases. Thermal stability of the pure PPI film, being the typical feature of polyazomethines, was confirmed, while after iodine doping the film turned out to be thermo-stable only below 100 °C; then the distinct changes of the optical gap and the Urbach energy, connected with the iodine releasing process, have been presented and discussed.
Keywords: Polyazomethine; Thin films; Doping; Thermal annealing; Optical absorption edge;

In this paper we investigate the influence of the substrate material and film thickness on the Peierls transition temperature in tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) thin films, grown by physical vapor deposition. Our analysis shows that the substrate material and the growth conditions strongly influence the film morphology. In particular, we demonstrate that the Peierls transition temperature in thin films is lower than in TTF–TCNQ single crystals. We argue that this effect arises due to defects, which emerge in TTF–TCNQ thin films during the growth process.
Keywords: Organic thin films; Peierls transition; TTF–TCNQ; One-dimensional metal;

The effect of polypyrrole coatings on the adhesion and structure properties of UHMWPE fiber by Xin Jin; Wenyu Wang; Lina Bian; Changfa Xiao; Guo Zheng; Cun Zhou (984-989).
To improve the adhesion between ultrahigh molecular weight polyethylene (UHMWPE) fiber and polymer matrix, pyrrole is oxidatively polymerized on the UHMWPE fiber surface continuously. The micro-composite of polypyrrole (PPy)-coated fiber/epoxy was prepared and the fiber was studied by interfacial shear strength (IFSS) through a single fiber pull-out method. Compared with the UHMWPE fiber as-received, the mean value of IFSS between PPy-coated UHMWPE and epoxy increased from 1.06 MPa to 5.72 MPa. In addition, the surface morphology and structure of PPy-coated UHMWPE fiber were studied by SEM, FT-IR, DSC and DMA. The results showed that PPy-coated UHMWPE fiber surface was observed with some particles attached. Although there is no chemical interaction between PPy and UHMWPE chains, PPy has some interaction with UHMWPE molecular chains according to the results of DMA. The PPy coatings have an effect on the adhesion may be associated with the roughened surface of the fiber and upon intermolecular interaction.
Keywords: Polypyrrole; UHMWPE fiber; Chemical oxidation polymerization; Single fiber pull-out test; Interfacial shear strength;

Preparation and characterization of PAn/NiO nanocomposite using various surfactants by Mahdi Aleahmad; Hamidreza Ghafouri Taleghani; Hossein Eisazadeh (990-995).
Conducting nanocomposite of NiO–PAn has been prepared in the aqueous medium using polyvinyl alcohol and hydroxypropylcellulose as a surfactant. The conductivity of the composites was measured as a function of the NiO concentration in reaction solution. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and electrical resistivity proved that NiO affect the properties of composite.
Keywords: Nanocomposite; Polyaniline; Surfactant; Morphology; Conductivity;

Solvent-drop assisted mechanochemical synthesis of the black and green polymorphs of the tetrathiafulvalene–chloranil charge transfer salt by Shermane Benjamin; Silvina Pagola; Zachary Huba; Everett Carpenter; Tarek Abdel-Fattah (996-1000).
► The green and black polymorphs of TTF–CA were synthesized by mechanochemistry. ► We report the lattice parameters of the TTF–CA black polymorph. ► Both TTF–CA polymorphs undergo chemical decomposition upon heating under air.This work describes the synthesis of the green and black polymorphic forms of the tetrathiafulvalene–chloranil (TTF–CA) charge transfer salt as pure phases, by solvent-assisted mechanochemistry. Both materials were characterized using laboratory and high-resolution X-ray powder diffraction (XRPD), elemental analysis and scanning electron microscopy (SEM). The high-resolution XRPD pattern of the TTF–CA black polymorph was indexed with a triclinic lattice a  = 10.756(5) Å, b  = 11.057(4) Å, c  = 6.614(2) Å, α  = 101.36(2)°, β  = 93.69(3)°, γ  = 89.37(3)°, V  = 769.6(5) Å3. The chemical stability of these phases upon heating was investigated using thermogravimetric analysis (TGA), elemental analysis and X-ray powder diffraction (XRPD), indicating that both polymorphs undergo chemical decomposition, and ruling out the transition to an air-stable high temperature polymorph.
Keywords: Charge transfer salt; Molecular conductors; Tetrathiafulvalene–chloranil; Polymorphism; Mechanochemistry; X-ray powder diffraction;

Tetrathiafulvalenium–bromide systems as nanosticks and nanoparticles stabilized by PEDOT by Matthieu Souque; Dominique de Caro; Lydie Valade (1001-1004).
In this communication, we describe the first PEDOT-stabilized TTF-based nanoobjects (PEDOT: poly(3,4-ethylenedioxythiophene)). Two tetrathiafulvalenium–bromide systems, namely TTFBr0.59 and TTFBr, have been processed as nanosticks and well-dispersed nanoparticles in PEDOT, acting as a stabilizing agent. Nanopowders are studied by various techniques including infrared, Raman, X-ray diffraction, transmission electron microscopy, and transport measurements.
Keywords: Tetrathiafulvalene; Conducting polymers; PEDOT; Nanoparticles; Nanosticks;

A new donor–acceptor carbazole derivative containing N-2-(2-ethylhexyl)-1,8-napthalimide as acceptor pendant was synthesized at three steps and directly coated on to ITO glass surface by using electrochemical process. Subsequently, electrochemical co-polymerization of this monomer was carried out by using 3,4-ethylenedioxythiophene (EDOT) as co-monomer to give electrochromic polymer film. Spectro-electrochemical studies indicated that co-polymer films exhibit relatively lower band gap than that of homo-polymer. Consequently, photo-induced energy and charge transfer properties from the donor-carbazole to naphthalimide-acceptor were studied by using cyclic voltammetry, UV–vis absorption and emission spectroscopy.
Keywords: Carbazole; 1,8-Naphthalimide; Donor–acceptor polymer; Electrochromic polymer; Charge transfer properties;

Developing perylene diimide based acceptor polymers for organic photovoltaics by Ziqi Liang; Russell A. Cormier; Alexandre M. Nardes; Brian A. Gregg (1014-1021).
Perylene diimides are known as promising n-type semiconductor building blocks. Here we report the synthesis and characterization of a set of three soluble poly(perylene diimide)s and their preliminary characterization in organic photovoltaic cells. These polymers are made through the polycondensation of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) with a variety of poly(ethylene glycol) (PEG)- or poly(propylene glycol) (PPG)-based diamine comonomers. The flexible spacer offers increased solubility in organic solvents and allows the perylene core to assume a conformation that promotes favorable cofacial π–π interactions. Mixtures of these polymers with the hole-transporting polymer, poly(3-hexylthiophene) (P3HT) result in significant fluorescence quenching. However, the phase separation occurs on a scale too large for a bulk heterojunction solar cell. The PPGylated poly(perylene diimide) shows an unusually low free electron concentration (∼1.0 × 1012  cm−3) and therefore makes an excellent model system for future doping studies. These new polymers may have promise as stable electron-conductive layers with large light-absorptivities in solution-processable applications of organic electronics.
Keywords: Perylene diimides; n-Type organic semiconductors; Electron acceptor; Solution processable; Organic photovoltaics;

In this paper, four water soluble rare-earth(III) fluorescent chemosensors, Na3RE(PDA)3 (PDA = pyridine-2,6-dicarboxylic acid, and RE = Sm, Eu, Tb, Dy), are synthesized and characterized. Their excitation and emission spectra, fluorescence responses towards Cr(III), quenching mechanism, oxygen and thermal sensitivity of the complexes are systemically studied. The emission intensity and the excited state lifetimes of the four complexes decrease with increasing concentration of trivalent chromium (Cr(III)). Their sensing behavior towards Cr(III) is investigated by fluorescence spectroscopy. Results suggest that Na3Dy(PDA)3 exhibits highest sensitivity and linear spectral response towards Cr(III) (Stern–Volmer constant = 0.461 × 107  L/mol, linearity = 0.996). It is note worthy that oxygen has little effect on the emission of Na3RE(PDA)3 complexes. These important advantages make themselves promising candidates to be utilized in actual applications.
Keywords: Cr(III); Optical sensors; Rare earth; Water soluble;

For the first time, processible polyaniline salt was prepared by inverted emulsion polymerization pathway without using any emulsifier. Aniline oxidation with benzoyl peroxide, in the presence of formic acid, yields novel polyaniline-formate salt containing free formic acid (PANI salt), the latter being trapped due to agglomeration and the presence of cohesive forces between the acid molecules and polyaniline chains. The synthetic procedure, outlined above, constituted the basis for the preparation of PANI salt containing free formic acid. PANI salt was studied by complementary characterization methods: conductivity, FT-IR, XRD, XPS & TGA. PANI salt containing free formic acid turned out to be especially well suited for the fabrication of blends with poly(vinyl alcohol), showing a very low percolation threshold. This lowering of the percolation threshold was attributed to the plasticizing effect of polyvinyl alcohol molecules present in the polymer matrix.
Keywords: Conducting polymers; Emulsion polymerization; X-ray; ESCA; Films;

The present study compares two biphasic blends constituted by immiscible thermoplastics: polypropylene (PP)/polycaprolactone (PCL) and polyamide 12 (PA12)/PCL, both filled with carbon nanotubes (CNT). The experimentations, led with the aim to point up the differences between the two blends, were carried out on the rod formed samples (diameter 1.5 mm) just after extrusion or pelletization. During this process, CNT are first introduced in PCL and then mixed with PP or PA12. These two blends can comprise different kinds of morphologies depending on components weight fractions. The electrical conductivity is affected by the blend morphology on one hand and by the localization of CNT on the other hand. Even with a similar mixing sequence, CNT localization is different between the two blends. CNT migration from PCL to PA12 was highlighted in the PA12/PCL blend, in comparison with the PP/PCL blend where CNT stay in PCL.. Different experimental techniques such as selective phase extraction, microscopy analyses (SEM and TEM), rheology measurements and interfacial energy calculations based on surface tension measurements, can explain the different behaviours of each blend. A correlation between the observed morphology and the wetting coefficient calculated with experimental measurements of surface tensions allowed to predict CNT localization.
Keywords: Nanocomposite; Carbon nanotubes; Interfacial energy; Polymer blend; Biphasic blend;

Synthesis, photo- and electroluminescent properties of norbornene based platinum-containing copolymers by Yulya E. Begantsova; Leonid N. Bochkarev; Irina P. Malysheva; Natalia E. Stolyarova; Yurii A. Kurskii; Mikhail A. Lopatin; Evgenii V. Baranov; Vasilii A. Ilichev; Gleb A. Abakumov; Mikhail N. Bochkarev (1043-1050).
► Pt-containing copolymers were synthesized by ROMP of norbornene based monomers. ► Photo- and electroluminescence properties of the copolymers were investigated. ► The max electroluminance of 260 cd/m2 at 21 V was achieved.Norbornene based monomers containing the 2-phenylpyridinato–N,C2′ platinum(II) complex bonded by acetylacetonate or pyrazolonate anchor groups were synthesized and copolymerized with a carbazole-containing norbornene comonomer by ring-opening metathesis polymerization (ROMP). The photo- and electroluminescence spectra of the resulting Pt-copolymers are similar. They consist of broad bands with maxima at 495, 530 and 565 nm which arise from the mixed ligand centered (LC) and metal to ligand charge transfer (MLCT) transitions. The copolymer with the cyclometalated platinum(II) complex bonded to the polymer chain via the pyrazolonate anchor group revealed the highest brightness of electroluminescence (260 cd/m2 at 21 V).
Keywords: Platinum; Copolymer; ROMP; Electroluminescence; Photoluminescence;

Ablation of PEDOT/PSS with excimer lasers for micro structuring of organic electronic devices by Moritz Schaefer; Jens Holtkamp; Arnold Gillner (1051-1057).
In this paper we present a potentially fast method for high resolution micro structuring of organic electronics via laser patterning. An investigation of the absorption spectrum in the UV/VIS regime of poly (3,4-ethylene dioxythiophene) poly (styrene-sulfonate) (PEDOT/PSS) has shown that UV-laser radiation should be used for optimal laser ablation of the material. Hence, the ablation characteristics of PEDOT/PSS with two different excimer lasers are compared with each other. The optimal fluence for the ablation of the material has been determined. The lasers used in this study are ArF (λ  = 193 nm) and KrF (λ  = 248 nm) excimer lasers.
Keywords: PEDOT/PSS; Excimer laser; Laser ablation; Micro patterning;

The effects of local dipole on the chiroptical properties of chiral conjugated oligomers were investigated by comparative studies on two analogous chiral oligo(phenyleneethynylene)s: Myr-OPE-Br and Myr-OPE. Myr-OPE-Br carries local dipoles introduced by electron-accepting Br-groups and electron-donating chiral alkoxy-groups, while Myr-OPE only carries chiral alkoxy groups. The DSC thermogram of Myr-OPE-Br showed a glass transition at ∼80 °C and a cold crystallization centered at 120 °C, while Myr-OPE only showed a glass transition at ∼90 °C. Thermal annealing treatment showed significant effects on the absorption and CD spectra of spin-coated film of Myr-OPE-Br: with annealing above 100 °C, the absorption maximum exhibited an obvious red shift; the absorption bands displayed well-resolved vibronic structures; the CD spectrum was inversed compared to those with no annealing or annealing at 80 °C; and the g abs value of the annealed film increased with increasing annealing temperature and time. After annealing at 140 °C for 1 h, a maximum g abs value above 0.117 was observed for Myr-OPE-Br film. While for Myr-OPE, the thermal annealing treatment showed no obvious effect on both the absorption and CD spectra. The CD spectra of both the as-coated film and annealed film of Myr-OPE showed no obvious Cotton effect. The observed large g values as well as the thermochromic changes in the absorption and CD spectra of annealed Myr-OPE-Br films were attributed to the presence of local dipoles.
Keywords: Chiral; Oligo(phenyleneethynylene); Local dipole; Thermal annealing; Optical activity;

Acylpyrazolonate-based lanthanide complexes: Synthesis, crystal structures and photoluminescence properties by Xi-Li Li; Xiaoxia Niu; Lai-Fu He; Xiang-Li Feng; Shao-Ming Fang; Li-Feng Han; Li-Ming Zhou; Hong-Ping Xiao (1063-1067).
Display Omitted► There are two crystallographically independent molecules with different geometries in Tb(III) and Eu(III) structural unit, respectively. ► Acylpyrazolonate-based Tb(III) complex displays intensely green luminescence both in solid state and in solution. ► Hpmap is a good sensitizer for Tb(III) emitting.Two new acylpyrazolonate-based lanthanide complexes of formula [Ln(pmap)3(H2O)2]·CH3COOC2H5 (Ln = Tb 1, Eu 2 and pmap = 1-phenyl-3-methyl-4-acetyl-5-pyrazolonate) have been prepared and characterized by X-ray single crystal determination and spectroscopic methods. The crystal structure analysis reveals that 1 and 2 are isostructural and crystallize in the triclinic space group P 1 ¯ with two independent, but structurally similar molecules in the structural unit, which are exceptionally rare in acylpyrazolonate-based mononuclear lanthanide complexes. In CH3CN solution, the photoluminescence investigation demonstrates that 1 displays intensely green emission of Tb(III)-centered, while Eu(III)-complex does not emit characteristically red luminescence. The results are elucidated in terms of the energy gap ΔE(3ππ*–5D4 or 5D0) between Hpmap ligand and resonance levels of Tb(III) or Eu(III) ion.
Keywords: Acylpyrazolonate; Photoluminescence; Lanthanide complex; Crystal structure;

TiO2/carbon nanofiber (CNF) composites containing Ag nanoparticles (Ag–TiO2/CNF) were prepared and their photocatalytic degradation ability upon visible light irradiation assessed. The reduction of methylene blue (MB) adsorption in an aqueous solution by the photocatalysts occurred due to the combined effects of MB adsorption in the pores of CNFs and decomposition by the photocatalysts throughout the process. The Ag–TiO2/CNF photocatalyst degraded MB 17 times faster than the TiO2/CNF composites with no Ag nanoparticles after 3 h under visible light illuminations.
Keywords: Carbon nanofiber; TiO2; Ag nanoparticles; Photocatalyst; Visible light;

Display Omitted► The effect of multiple intermolecular interactions on charge transfer was studied. ► The band structure shows that dispersion is proportional to the π-stacking area. ► The hydrogen bonding interactions have a great influence on the dispersion of VB. ► The dispersion of CB is enhanced and VB is restrained when the interactions coexist. ► When the type of weak interactions increases, the dispersions will be enlarged.To get insights of the effect of multiple intermolecular interactions on the charge transport ability of polymorphs, we systematically investigated nine crystals in two kinds of polymorphs within the framework of band model, in which the type and strength of the weak interactions are different. The results show that: (i) the dispersions are relative to the π-stacking area. The bigger area the is, the larger dispersion the is. Thus, it can enhance the charge transport ability. (ii) Hydrogen bonding interactions have a great influence on the dispersion of valence band (VB) rather than conduction band (CB). (iii) When π-stacking and hydrogen bonding interactions coexist in the polymorphs, they enhance the dispersions of CB and restrain that of VB. (iv) When the type of weak interactions increases, the dispersions will be enlarged. Understanding the effect of multiple weak interactions on the polymorphs is a theoretical guide to design novel organic semiconductors with efficient charge transport ability.
Keywords: 3(5)-(9-anthryl)pyrazole; Polymorphs; Intermolecular interactions; Charge transport; Band model;

► Thin film of P3OT was successfully prepared using dip coating technique. ► Both capacitance and conductance characteristics are quite sensitive to the applied frequency. ► Non-ideal forward bias J–V characteristics of the Al/P3OT/ITO Schottky diode were observed. ► The energy distribution of the interface state density Dit was determined. ► Values of the interface and the series resistance are responsible for the non-ideal behavior of J–V and C–V characteristics.Thin film of poly(3-octylthiophene) (P3OT) was successfully prepared using dip coating technique. The morphology and the crystal structure of the prepared thin film were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. A study on interface states density distribution and characteristic parameters of the Al/P3OT/ITO device capacitor have been made. The diode parameters such as ideality factor, series resistance and barrier height were extracted from the forward biasing JV characteristics. The energy distribution of the interface state density D it was determined from the forward bias JV characteristics by taking into account the bias dependence of the effective barrier height. The CV and G/ωV characteristics were measured in the frequency range from 10 kHz to 1 MHz and dc biasing voltage swept from −4 V to +4 V at room temperature (300 K). The non-ideal behavior of JV and CV characteristics can be attributed to the presence of the interface and the series resistance.
Keywords: P3OT; Al/P3OT/ITO organic Schottky diodes; XRD and SEM; JV and CV characteristics; Series resistance; Interface state density;

Fabrication and optical characterization of electrospun poly(3-buthylthiophene) nanofibers by Soung Kyu Park; Krishna P. Dhakal; Jeongyong Kim; Jin Heung Kim; Heesuk Rho (1088-1091).
Light-emitting poly(3-buthylthiophene) (P3BT) nanofibers were fabricated via an electrospinning method. Ten weight percent poly(ethylene oxide) (PEO) was included in a P3BT spinning solution to maintain the required viscosity for electrospinning. The formation of P3BT nanofibers was confirmed through high-resolution confocal photoluminescence imaging and spectroscopy and micro-Raman measurements performed on single strands of P3BT nanofibers. Our results show that P3BT nanofibers can be fabricated using the electrospinning method that can produce abundant continuous nanofibers.
Keywords: Electrospinning; Polymer nanofiber; Poly(3-buthylthiophene); P3BT; Raman scattering; Confocal microscope;

Preparation and electrochemical properties of LiNi1/3Co1/3Mn1/3O2–PPy composites cathode materials for lithium-ion battery by Peixin Zhang; Li Zhang; Xiangzhong Ren; Qiuhua Yuan; Jianhong Liu; Qianling Zhang (1092-1097).
Layered LiNi1/3Co1/3Mn1/3O2 was synthesized by co-precipitation method, and a series of polypyrrole–LiNi1/3Co1/3Mn1/3O2 composites were then prepared by polymerizing pyrrole monomers on the surface of LiNi1/3Co1/3Mn1/3O2. The bare sample and composites were subjected to analysis and characterization by the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the composites were investigated with galvanostatic charge–discharge test and AC impedance measurements, which show that the formed coats of polypyrrole (PPy) significantly decrease the charge-transfer resistance of LiNi1/3Co1/3Mn1/3O2. And the composite containing 2.0 wt% PPy exhibits a good electrochemical performance, its specific discharge capacity is 182 mAh g−1 at 0.1C rate and voltage limits of 2.8–4.6 V, while the capacity of the bare sample is only 134 mAh g−1.
Keywords: Polypyrrole; LiNi1/3Co1/3Mn1/3O2; Cathode materials; Lithium-ion batteries;

Polypyridyl Ru(II)-sensitizers with extended π-system enhances the performance of dye sensitized solar cells by Malapaka Chandrasekharam; Ganugula Rajkumar; Chikkam Srinivasa Rao; Thogiti Suresh; Marri Anil Reddy; Paidi Yella Reddy; Yarasi Soujanya; B. Takeru; Yum Jun-Ho; Mahammad Khaja Nazeeruddin; Michael Graetzel (1098-1104).
New polypyridyl ruthenium(II) complexes “cis-Ru(4,4′-dimesityl-2,2′-bipyridine) (Ln) (NCS)2 H102” and “cis-Ru(4,4′-bis(2,3,6-tri-isopropylphenyl)-2,2′-bipyridine) (Ln) (NCS)2 H105”, where Ln  = 4,4′-dicarboxylic acid-2,2′-bipyridine; were synthesized and successfully applied to sensitization of nano-crystalline TiO2 based solar cells (DSSCs). The DSSCs of H102 and H105 fabricated from 0.16 cm2 TiO2 electrodes exhibited broader comparable photocurrent action spectra with almost identical solar-to-electrical energy conversion efficiency (η) as compared to N719 sensitizer. The incident photon-to-current conversion efficiency (IPCE) values of 98% and 95% were obtained for H102 and H105 sensitizers respectively. Under 1 sun condition, η-values of 8.39% (short-circuit photocurrent (J SC) = 16.4 mA/cm2, open-circuit photo voltage (V OC) = 692 mV, fill factor = 0.734), 8.76% (J SC  = 16.3 mA/cm2, V OC  = 735 mV, fill factor = 0.734) and 9.12% (J SC  = 16.1 mA/cm2, V OC  = 745 mV, fill factor = 0.753) were obtained for H102, H105 and N719 sensitizers respectively.
Keywords: Dye sensitized solar cells; Extended π-system; Polypyridyl Ru(II)-sensitizers;

Limitations of dual and complementary inorganic–organic electrochromic device for smart window application and its colorimetric analysis by S.S. Kalagi; S.S. Mali; D.S. Dalavi; A.I. Inamdar; Hyunsik Im; P.S. Patil (1105-1112).
Display Omitted► We investigated WO3 and PANI dual and complementary device for smart window application. ► We studied its limitations in terms of inorganic–organic electrochromic. ► The change in transmittance of WO3 film was found to be 63.92%. PANI film showed an optical attenuation of 50.69% while the transmission change through the IOECD was equal to 57%. ► Also noted that even though the coloration efficiency increases with respect to the working electrode, it decreases with reference to the counter electrode. ► Charge unbalanced of dual complementary device, the coloration efficiency is always less than that of one of the constituent electrodes.Inorganic tungsten oxide (WO3) and organic polyaniline (PANI) films were used as the cathodic and anodic electrodes of an inorganic–organic electrochromic device (IOECD). WO3 was deposited by sputtering while PANI films were electrodeposited on transparent Indium doped Tin Oxide (ITO) glass substrates, respectively. Optical and electrochemical studies were performed to find the optical attenuation, coloration efficiencies, reversibility and response time separately for the individual films as well as for the assembled IOECD. The change in transmittance of WO3 film was found to be 63.92%. PANI film showed an optical attenuation of 50.69% while the transmission change through the IOECD was equal to 57%. Colorimetric analysis was done to define the colors in the bleached and colored states in terms of L*ab values and xy chromaticity diagram. Factors limiting the performance of an IOECD were analyzed. It was found that in a charge unbalanced dual complementary IOECD, the coloration efficiency is always less than that of one of the constituent electrodes.
Keywords: WO3; PANI; IOECD; Thin films; Colorimetric; Limitations;

Cyclometalated iridium(III) complexes with 5-acetyl-2-phenypyridine derived ligands for red phosphorescent OLEDs by Kum Hee Lee; Hyun Ju Kang; Seok Jae Lee; Ji Hyun Seo; Young Kwan Kim; Seung Soo Yoon (1113-1121).
Display Omitted► We develop six Ir(III) complexes with 5-acetyl-2-phenylpyridine derivatives as ligands. ► We examine changes in increase of π-conjugation in the phenyl moiety. ► Increasing π-conjugation will improve color purity. ► These new Ir(III) complexes (1–6) possess highly efficient electroluminescent properties.A series of new iridium complexes with 5-acetyl-2-phenylpyridine derivatives as ligands was developed. The complexes exhibited high EL performance when applied to OLEDs. These materials showed red emission with a peak at 575–636 nm. In particular, one of the devices in this study showed a maximum luminous efficiency, maximum power efficiency, external quantum efficiency and CIE coordinates of 29.0 cd/A, 6.13 lm/W, 8.86% at 20 mA/cm2 and (0.57, 0.43) at 10 V, respectively. In addition, a deep red OLED with CIE coordinates of (0.67, 0.32) at 10 V exhibited a maximum luminous efficiency, maximum power efficiency and external quantum efficiency of 5.61 cd/A, 1.02 lm/W and 5.35% at 20 mA/cm2, respectively.
Keywords: Orange–red Ir(III) complexes; 5-Acetyl-2-phenypyridine; PHOLEDs;

The carbonization of granular polyaniline to produce nitrogen-containing carbon by Zuzana Rozlívková; Miroslava Trchová; Milena Exnerová; Jaroslav Stejskal (1122-1129).
Display Omitted► A new nitrogen-containing carbon material has been obtained. ► Molecular structure corresponds to carbon material containing nitrogen atoms. ► The granular morphology of polyaniline was retained. ► The residue of the sample after carbonization is close to 60 wt.%. ► Content of nitrogen is above 15 wt.%, which is interesting for applications.Polyaniline (PANI) was prepared by the oxidative polymerization of aniline. The deprotonated product, a PANI base, was carbonized in an inert atmosphere at temperatures up to 800 °C for various times. The mass decreased to 40–50 wt.% at temperatures above 600 °C. The progress of molecular structure during carbonization was followed by infrared and Raman spectroscopies. The carbonization at 650 °C for 1 h is suggested for the optimum conversion of PANI to carbon. The product retained the original globular structure of PANI. The conductivity of the carbonized material was low for carbonizations below 600 °C, <10−10  S cm−1, and increased to 10−4  S cm−1 after treatment at 800 °C. The content of nitrogen, ∼10 wt.%, was not affected appreciably by the carbonization.
Keywords: Polyaniline; Conducting polymer; Carbon; FTIR spectroscopy; Raman spectroscopy; Conductivity;

A flexible capacitor based on conducting polymer electrodes by B.C. Kim; C.O. Too; J.S. Kwon; J.M. Ko; G.G. Wallace (1130-1132).
Flexible electrodes for supercapacitors have been prepared by depositing polypyrrole (PPy) on to a gold-coated PVDF membrane. Specific capacitance values of the order of 380 F g−1 for PPy/Nafion and 420 F g−1 for PPy/p-toluenesulfonate were obtained. For the PPy/Nafion electrode, an energy density of 56 Wh kg−1 and a power density of 15.50 kW kg−1 were available after 5000 cycles.Using a self-contained fully flexible device comprising polypyrrole as both electrodes and a PVDF membrane as separator, a capacitance of 30 F g−1 was observed after 5000 cycles.
Keywords: Polypyrrole; Flexible electrode; Nafion; Supercapacitor;

Enhanced color stability and improved performance in white organic light-emitting devices by utilizing a double-graded structure by Hua-Ping Lin; Fan Zhou; Xiao-Wen Zhang; Dong-Bin Yu; Jun Li; Liang Zhang; Xue-Yin Jiang; Zhi-Lin Zhang (1133-1136).
High efficiency fluorescent white organic light-emitting device (WOLEDs) was investigated by using a double-graded (DG) structure. This strategy can greatly improve the device performances such as better color stability, higher luminance and enhanced efficiency. The optimized WOLED gives the Commission Internationale de L’Eclairage (CIE) color coordinates of (0.324, 0.341) at 20 mA/cm2, a negligible color shift of Δ x, y  = ±[0.000.001] from 4 to 200 mA/cm2, a maximum brightness of 39,740 cd/m2 at 17 V and a maximum luminance efficiency of 11.5 cd/A at 16 V. In addition, current-induced fluorescence quenching is mostly controlled.
Keywords: White OLED; Double-graded; Color stability; High current efficiency;

A cyclopentadithiophene/thienopyrroledione-based donor–acceptor copolymer for organic solar cells by Christopher M. MacNeill; Eric D. Peterson; Ronald E. Noftle; David L. Carroll; Robert C. Coffin (1137-1140).
A new cyclopentadithiophene/thienopyrroledione-based donor–acceptor copolymer (P1) was synthesized using a microwave-assisted Stille coupling procedure and was compared to a known benzodithiophene-based copolymer using the same thienopyrroledione acceptor monomer (PBDTTPD). Cyclopentadithiophene-based copolymers have been known to exhibit lower band gaps than their corresponding benzodithiophene-based counterparts. The polymer showed excellent solubility at room temperature in chlorinated solvents. The absorption onset for P1 is close to 740 nm as compared with ∼685 nm for PBDTTPD, corresponding to an optical band gap of 1.67 eV, which is 0.15 eV lower than PBDTTPD. The photovoltaic characteristics of the polymer were determined under AM1.5 illumination. The P1:PCBM BHJ device showed a high V oc (0.92 V) and J sc (8.02 mA/cm2) as well as a good PCE (2.43%), while the best device with 2% solvent additive gave a PCE of 3.47%.
Keywords: Organic photovoltaics; Cyclopentadithiophene; Thienopyrroledione; Solar cell;

Toward a high specific power and high stability polypyrrole supercapacitors by Jingping Wang; Youlong Xu; Jie Wang; Xianfeng Du (1141-1144).
Polypyrrole (PPy) films doped by p-toluenesulfonic (PTS) are prepared by pulse current polymerization (PCP PPy) in aqueous solutions. Cations (H+, Li+, Na+, and K+ ions) in working electrolyte solutions have a great influence on the electrochemical properties of PCP PPy films for supercapacitors. In 3 M aqueous chloride solutions, the smaller cations lead to the better electrochemical properties of PCP PPy films. PCP PPy films show ideally capacitive characteristics with a very high specific power of 110.9 kW kg−1 in 3 M HCl when its specific energy reaches 18.4 Wh kg−1. PCP PPy films are very stable in 3 M HCl, showing less than 4% decay over 160,000 and 20,000 charge/discharge cycles at current density of 40 A g−1 within voltage range of 0–0.4 V and 0–0.8 V, respectively. The results of SEM show that many pits and grooves appear on the surface of PPy anode in 3 M KCl after 30,000 cycles, which should be main reason of rapid decay of PPy capacitance in 3 M KCl.
Keywords: Polypyrrole; Supercapacitors; High stability; High specific power;

Zinc quinolates through styryl substitution in 2-position via acetoxy exchange reaction by Liuqing Chen; Peng Tao; Chunyan Sun; Xuguang Liu; Bingshe Xu (1145-1149).
2-Methyl-8-quinolinol reacted with salicylaldehyde to give the corresponding substituted 2-styryl-8-quinolinol. Two schemes were adopted in order to prepare zinc quinolates complex through styryl substitution in 2-position. In , four steps were used including hydrolysis of acetoxy, and single crystal of product of this step was acquired. For , acetoxy exchange reaction was directly used to give Zn complex from the styryl derivative a and Zn(OAc)2 in the presence of ethanol and triethylamine, which is a more facile synthesis method of zinc quinolates through styryl substitution in 2-position. The spectroscopic, thermal and optical properties of Zn complex were investigated. The thermal stability of Zn complex was higher than that of styryl derivative a. The residue yield at 800 °C in N2 for Zn complex was 64.3% whereas that for styryl derivative a was almost zero. Solutions of Zn complex in THF emitted yellow light with photoluminescence (PL) maximum at 551 nm, which is considerably red-shifted relative to Znq2 (535 nm) and Zn(2-Meq)2 (515 nm). The ground- and excited-state geometries, charge distributions, and excitation energies of Zn complex were evaluated by ab initio calculations.
Keywords: Acetoxy exchange reaction; Styryl quinolate; Zinc complex;

The photoelectrochemical properties of poly(3-hexylthiophene) (P3HT) and poly(2,3-diethylquinoxaline-5,8-diyl) (PDEQx) thin films on ITO (indium-tin oxide) electrodes were investigated in aqueous media. Photoirradiation of the P3HT-coated electrode resulted in cathodic photocurrents in the presence of methyl benzoylformate, whereas the PDEQx-coated electrode generated stable anodic photocurrents in the presence of 2-mercaptoethanol. The action spectra indicate that photoexcitations of the polymers cause photoelectrochemical reactions. The films of P3HT and PDEQx exhibit a typical photochemical response of p- and n-type semiconducting materials, respectively.
Keywords: Conjugated polymers; Photoelectrochemistry; Organic semiconductors;