Synthetic Metals (v.162, #7-8)

Display Omitted► Polyaniline/clay as electrically conductive nanofillers successfully dispersed in epoxy resins. ► Influence of filler morphology on composites conductivity demonstrated. ► Polyaniline with higher aspect ratio reduces the electrical percolation threshold of composites. ► Conductivity improved with polyaniline/clay fillers compared to a standard polyaniline. ► Impact of epoxy formulation and curing conditions on composites conductivity underlined.Electrically conductive composites based on epoxy resin, anhydride hardener and polyaniline (PANI) as conductive filler have been formulated and characterized. Standard PANI (Pani) and PANI/clay (PANICN) nanofillers were used to study the impact of filler morphology on the electrical properties of composites. Clay was used as a nanostructured template to increase the PANI aspect ratio (ratio of length to diameter or thickness). The use of PANICN reduces the electrical percolation threshold of composites from 4.5 vol.% to 1.3 vol.%. Moreover, the conductivity of composites containing PANICN is improved to values superior to 10−3  S/cm. The effects of reagents and curing conditions were also evaluated. It was demonstrated that a classical alkaline curing accelerator, such as imidazole, exhibits chemical incompatibilities with the PANI conductive form, resulting in less conductive composites. Substituting the classical alkaline curing accelerator with a cationic accelerator, such as a Lewis acid, is a promising alternative to obtain conductive epoxy composites with a low content of PANI.
Keywords: Epoxy; Polyaniline; Clay; Morphology; Electrical properties;

► A semiconductor–metal transition induced by pressure in the polymer was reported, the critical pressure was 5.69 GPa. ► The parameter V 2,0 in the Ginder–Epstein model was varied to stand for applied pressure. ► While increasing pressure up to 5.69 GPa, the soliton lattice distortion and the gap disappeared. ► Our critical value agrees with the saturated pressures in experimental observations for electrical conductivity of the polymer under pressures.An n-type soliton of the pernigraniline-base polymer under pressure was investigated in an extended Ginder–Epstein model. The results showed that: while increasing pressure up to 5.69 GPa, excitation energy for a soliton reduced from 10.02 to 3.64 eV, meanwhile the gap and the lattice distortion disappeared. Original band changed from style of a semiconductor to that of a metal. The results agree with the experimental observations that electrical conductivity is increasing with applied pressure until a saturated value. Our theory supports soliton-conduction mechanism for the polymer under pressures less than 5.69 GPa. Under higher pressure, carriers would be electrons as if in a metal.
Keywords: Polymer; Conductivity; Soliton; Pressure;

New polymer acceptor for solar cells application by Shyambo Chatterjee; Susanta Banerjee; Pallab Banerji (566-572).
Architecture of bilayer and bulk heterojunction photovoltaic devices.Display Omitted► Soluble fluorinated PPV derivative. ► New acceptor material. ► Electrochemical n-doping and dedoping stability. ► High V oc value (1.16 V) for BHJ solar cell.New photosensitive fluorine containing PPV derivative (DBTFM-PPV) has been synthesized as an acceptor material via Gilch polymerization reaction. The polymer was soluble in many of the common organic solvents. Optical, electrochemical and photovoltaic properties including hole and electron mobility of this polymer was investigated. Bilayer (ITO/PEDOT:PSS/MEH-PPV/DBTFM-PPV/Al) and bulk hetero junction (ITO/PEDOT:PSS/DBTFM-PPV:MEH-PPV/Al) solar cells were fabricated where DBTFM-PPV act as an acceptor material. Bulk hetero junction (BHJ) solar cell showed higher efficiency than bilayer device. The power conversion efficiency (PCE) of the BHJ solar cells based on DBTFM-PPV:MEH-PPV (2:1) was 0.49% with an open-circuit voltage (V oc) of 1.16 V, fill factor of 0.49%, and a short-circuit current (J sc) of 1.17 mA/cm2.
Keywords: Fluorinated PPV-derivative; Photoluminescence; Solar cell;

Display Omitted► Selected acenes, cyclacenes and zigzag (4,0) single wall carbon nanotubes (SWCNTs). ► OH― functionalized at one end optimized using B3LYP/6-31G*. ► The impact of model molecule size on 13C NMR chemical shifts. ► The harmonic frequency of Raman radial breathing mode (RBM). ► RBM in monohydroxylated cyclic acenes correlated with their diameter.Selected acenes, cyclic acenes and model zigzag (4,0) single wall carbon nanotubes (SWCNTs) with one hydroxylic group at the open end were fully optimized at the B3LYP/6-31G* level of theory. The impact of molecule size on the B3LYP/pcS-2 calculated 13C NMR chemical shifts was studied to characterize pristine and tip-monofunctionalized ultra narrow SWCNTs. The harmonic frequency of Raman radial breathing mode (RBM) was determined for monohydroxylated cyclic acenes and correlated with their diameter. A regular convergence of selected CC bond lengths, RBM frequency and carbon chemical shifts upon increasing the size of the systems was observed and fitted toward very large systems with two-parameter mathematical formula. The observed values of selected structural, Raman and 13C NMR chemical shifts in the studied models point out toward a feasibility of NMR technique as a tool for characterization of pristine and OH― functionalized SWCNT materials.
Keywords: Acenes; Model zigzag (4,0) SWCNT; OH functionalization; NMR; Raman RBM mode; DFT;

A battery composed of a polypyrrole cathode and a magnesium alloy anode—Toward a bioelectric battery by Yong Kong; Caiyun Wang; Yang Yang; Chee O. Too; Gordon G. Wallace (584-589).
► Biocompatible polypyrrole doped with an anti-coagulant was used as a cathode. ► Bioresorbable Mg alloy was used as anode. ► A biocompatible electrolyte phosphate buffer saline was employed. ► The energy density obtained would be sufficient to power some bionic devices.A bioelectric battery can be implanted into the human body and relies on oxygen in the internal body fluid to produce electrical energy. In this work, a battery that uses polypyrrole doped with a biological polyelectrolyte (dextran sulfate, an anti-coagulant) as the cathode and bioresorbable Mg alloy (AZ61) as the anode was developed. This battery exhibited a discharge capacity of 565 mA h g−1 in phosphate buffered saline (PBS, pH = 7.4), a commonly used electrolyte in biological research; offering a specific energy density of ∼790 W h kg−1. The electrochemical properties of the cathode, anode and battery itself were investigated in different aqueous electrolytes. Cyclic voltammetry, linear sweep voltammetry, AC impedance, galvanostatic charge/discharge, and field-emission scanning microscopy techniques were applied for characterization.
Keywords: Bioelectric battery; Conducting polymers; Polypyrrole; Magnesium alloy;

Synthesis and characterization of poly(1-vinyltriazole)-grafted superparamagnetic iron oxide nanoparticles by H. Deligöz; A. Baykal; M. Şenel; H. Sözeri; E. Karaoğlu; M.S. Toprak (590-597).
Synthesis scheme of poly(1-vinyltriazole)-grafted SPION.Display Omitted► Superparamagnetic iron oxide nanoparticles (SPION) were fabricated by gel-to-crystalline conversion method. ► Telomerization of poly(1-vinyltriazole) on iron oxide nanoparticles was achieved via silanization process. ► Silica was coated on Fe3O4 nanoparticles to avoid the aggregation of the particles.We reported on the synthesis and detailed physicochemical characterization of poly(1-vinyltriazole)-grafted iron oxide nanoparticles. Superparamagnetic iron oxide nanoparticles (SPION) were fabricated by gel-to-crystalline conversion method. Telomerization of poly(1-vinyltriazole) on iron oxide nanoparticles was achieved via silanization process. XRD analysis confirmed the crystalline phase as magnetite, and FT-IR analysis confirmed the presence of PVTri on nanoparticles. Particle morphology was observed to be polygonic, due to the synthesis process, while average size estimated from TEM micrographs is 7 nm. Agreement between crystallite size estimated from XRD and particle size from TEM affirms single crystalline character of these nanoparticles. Dependence of conductivity on temperature showed a strong evidence for thermally activated polarization mechanism. Temperature and frequency dependence of dielectric permittivity revealed interfacial polarization and temperature-assisted-reorganization effects. Magnetic evaluation showed non-saturation and superparamagnetic characteristics of nanoparticles as well as magnetic particles being single domains.
Keywords: SPION; Magnetic nanomaterials; Conductivity; Permittivity; Magnetization;

Effects of gate dielectric composition on the performance of organic thin-film devices by Sujoy Das; Junghyun Lee; Taehoon Lim; Youngill Choi; Yong Sun Park; Seungmoon Pyo (598-604).
► Gate dielectrics affected the growth of organic semiconductor and OFET performance. ► Devices’ characteristics were significantly affected by ―OH group in the gate dielectric. ► Use of the optimized gate dielectric resulted in a higher performing OFET and complementary inverter.Four poly(4-vinyl phenol) based gate dielectrics were tested to optimize the performance of pentacene organic field-effect transistors. The dielectrics’ surface tensions, Fourier transform infrared spectra, capacitances and leakage currents were measured. The optimal dielectric allowed the transistor to show negligible hysteresis with high performance even in ambient conditions. A complementary inverter was fabricated by integrating in single substrate pentacene (p-type) and F16CuPc (n-type) OFETs containing the optimized gate dielectric. Its voltage transfer curve showed almost symmetric noise margin; it showed a logic threshold of 22.5 V and a maximum voltage gain (δV outV in) of 6.2 at V in  = 22.5 V.
Keywords: Organic field-effect transistors; Polymer gate dielectrics; Cross-linking reaction; Organic semiconductors; Organic complementary inverter;

► Synthesis and characterization of water soluble zwitterionic zinc phthalocyanines. ► Photophysical and photochemical properties in DMSO and PBS solution. ► Investigation of bovine serum albumin binding properties. ► Singlet oxygen generation.The non-peripherally tetra-(1a), peripherally tetra-(2a) and peripherally octa-(3a) zwitterionic zinc(II) phthalocyanine complexes bearing 2-(N-propanesulfonic acid)mercaptopyridine groups have been synthesized for the first time. These novel complexes have been characterized by elemental analysis, UV–vis, IR and 1H NMR spectroscopy and mass spectra. These zwitterionic complexes show excellent solubility in water, which makes them candidate photosensitizers for use in photodynamic therapy (PDT) of cancer. The photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yields) properties of synthesized zwitterionic zinc(II) phthalocyanine complexes were investigated in DMSO and phosphate buffered solution (PBS). This study also presented the water soluble zwitterionic zinc(II) phthalocyanines strongly bind to blood plasma proteins such as bovine serum albumin (BSA).
Keywords: Phthalocyanine; Zinc; Zwitterionic; Water soluble; Photosensitizer;

Synthesis of spiro[fluorene-9,9′-xanthene] derivatives and their application as hole-transporting materials for organic light-emitting devices by Zengze Chu; Dan Wang; Chao Zhang; Fuzhi Wang; Hongwei Wu; Zhibin Lv; Shaocong Hou; Xing Fan; Dechun Zou (614-620).
Display Omitted► We have synthesized a series of hole-transporting materials based on spiro(fluorene-9,9′-xanthene). ► These compounds have very high-lying HOMO levels (∼5.0 eV). ► The EL device based on DPA-SFXBu exhibits the maximum power efficiency of 2.31 lm/W.A series of hole-transporting molecules based on spiro(fluorene-9,9′-xanthene) were designed and synthesized by a copper-catalyzed modified Ullmann reaction. These compounds have very high-lying HOMO levels (∼5.0 eV), which are beneficial for the hole-injection from ITO anode. The double-layer EL devices using DPA-SFXMe and DPA-SFXBu as hole-transporting layers exhibit lower turn-on voltage and higher efficiency compared with those of a typical NPB-based device. The DPA-SFXBu-based device exhibits high maximum luminescence of 21,712 cd/m2, and its power efficiency can reach a value of 2.31 lm/W, which is nearly 90% higher than that of a similar NPB-based device.
Keywords: Spiro(fluorene-9,9′-xanthene); Hole-transporting; Carbazole; Organic light-emitting diodes;

Highly efficient MEH-PPV-POSS based PLEDs through optimization of charge transport by Gamze Saygili; Canan Varlikli; Ceylan Zafer; Cihan Ozsoy (621-629).
► MEH-PPV-POSS based single and double layer devices optimization were investigated. ► CuInS2 or TPBi in the emissive layer reduces FWHM, enhances device efficiency. ► Optimum TPBi doping ratio in MEH-PPV-POSS for enhanced charge transport is 50 wt%. ► 40 nm Bphen between polymer:CuInS2 and cathode leads best charge carrier balance.We demonstrated highly efficient devices based on well-known poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] end capped with POSS (MEH-PPV-POSS) polymer by combining of two approaches: (i) inserting of electron transport material (ETM) either between the emissive layer and cathode or into the emissive polymer, and (ii) doping of polymer with quantum dots (QDs). In order to overcome some handicaps, such as interchain interaction and imbalanced charge carrier fluxes, copper indium disulfide (CuInS2) QDs were incorporated into the polymer matrix, while N-arylbenzimidazoles trimer (TPBi) and 4,7-dipheyl-1,10-phenanthroline (Bphen) were used as ETMs. The best charge carrier balance and color purity were achieved by inserting 0.3 wt% CuInS2 into the polymer and 40 nm Bphen between the polymer and cathode with a current efficiency of 5.1 cd/A and an external quantum efficiency of 1% which is above the average of literature.
Keywords: Quantum dot; Conjugated polymer; Electron transport material; Charge balance; Color purity; Electroluminescence; Polymeric light emitting diode;

Synthesis and photovoltaic properties of a solution-processable organic molecule containing dithienylbenzotriazole and triphenylamine by Bo Liu; Ying-ping Zou; Mengqiu Long; Yue-hui He; Hong Zhong; Yong-fang Li (630-635).
Display Omitted► A solution-processable organic small molecule, TPA–DTBTz–TPA, was synthesized by a Heck cross-coupling reaction and well characterized. ► TPA–DTBTz–TPA film exhibits an absorption band from 300 to 620 nm. ► The organic solar cells based on a blend of TPA–DTBTz–TPA and PC60BM (1:2, w/w) show a power conversion efficiency (PCE) of 0.93%.A new solution-processable organic small molecule, namely, TPA–DTBTz–TPA with triphenylamine (TPA) as electron donor and dithienylbenzotriazole (DTBTz) as electron acceptor was synthesized by a Heck cross-coupling reaction, and characterized by 1H NMR, TGA, UV–vis absorption, and cyclic voltammetry. The compound was found to be easily soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene with excellent film forming properties. TPA–DTBTz–TPA film exhibits an absorption band from 300 to 620 nm. The organic solar cells based on a blend of TPA–DTBTz–TPA and PC60BM (1:2, w/w) show a power conversion efficiency (PCE) of 0.93% with a short circuit current density of 4.43 mA/cm2 and an open circuit voltage of 0.74 V, under the illumination of AM 1.5, 100 mW/cm2.
Keywords: Organic solar cells; Solution processable; Dithienylbenzotriazole; Triphenylamine; Heck cross-coupling reaction; Power conversion efficiency;

► PANI deposited on porous 3C-SiC for hydrogen sensor. ► Hydrogen sensing properties are measured not only room temperature but also elevated temperature. ► High linear sensing performances are shown at 100 °C. ► PANI on porous SiC shows good adhesion compared with thin film SiC.This paper describes the fabrication and characterization of a hydrogen sensor that uses polyaniline (PANI) nanofiber/porous 3C-SiC (PSiC) heterojunctions. In this work, a PSiC with pore diameter of 50 nm was formed from polycrystalline N-type 3C-SiC thin films by electrochemical anodization. PANI nanofibers with an average diameter of 60 nm and length of 300 nm were synthesized in compressed liquid carbon dioxide on PSiC, using the 2-step spin coating method. The electrical characteristics of PANI on PSiC heterojunction diodes were evaluated with current voltage measurements, showing a P–N junction. Hydrogen sensing properties were investigated at various temperatures with H2 concentrations ranging from 30 ppm to 150 ppm. The response decreased as the temperature increased. However, a high linearity response was shown at 100 °C with H2 concentrations. The response and recovery time was decreased at temperatures below 125 °C and unstable sensing properties were shown at 150 °C. The best performance was observed at 100 °C, with fast response and fast recovery times of 10 and 6 s, respectively.
Keywords: Polyaniline; Porous 3C-SiC; Hydrogen sensor; High temperature;

Theoretical study of organic molecules containing N or S atoms as receptors for Hg(II) fluorescent sensors by Ming-Kuan Yan; Chao Zheng; Jun Yin; Zhong-Fu An; Run-Feng Chen; Xiao-Miao Feng; Juan Song; Qu-Li Fan; Wei Huang (641-649).
Display Omitted► Sixteen organic compounds containing N or S atoms were investigated theoretically as receptors for Hg2+ fluorescent sensors. ► N (or C) is the most stable binding site for Hg2+ although S is kinetically favored. ► Several rules for the molecular design of excellent Hg2+ receptors were suggested. ► Suitable fluorophore/receptor pairs for the fabrication of off/on Hg2+ fluorescent sensors were also presented.Sixteen organic compounds containing N or S atoms were carefully selected to investigate the binding site of the Hg2+ and their coordination behaviors for the development of high performance Hg2+ sensors via DFT calculations. The binding energies according to optimized structures of the organic–metal complexes and interaction energies based on hard and soft acids and bases theory (HSAB) have been calculated out and compared with each other. Discussions on the NBO charge, ligand-to-metal charge transfer and molecular orbital of the organic receptors were also presented for further understanding of the coordination. It was found that in heterocyclic compounds, the most stable binding site for Hg2+ is N atom instead of S atom, although the S atom may be kinetically favored due to the lower spatial hindrance, larger detection radius with longer Hg2+–S bond length, and closer softness between Hg2+ and S groups. Several rules for the molecular design of excellent Hg2+ receptors and the suitable fluorophore/receptor pair conditions were suggested for the fabrication of high performance off/on Hg2+ fluorescent sensors too.
Keywords: Hg receptors; Fluorescent sensor; Binding site; Binding ability; DFT;

Charge storage in carbon nanotube–TiO2 hybrid nanoparticles by B.C. Kim; S.J. Kim; J.K. Chung; J. Chen; S.Y. Park; G.G. Wallace (650-654).
► Preparation of novel MWNT/TiO2 hybrid nanoparticles by using chemical vapour deposition. ► Capacitance values as high as 146 F g−1 were obtained in 0.1 M Tetrabutylammonium perchlorate. ► Demonstates highly accessible surface area and high cyclability of MWCNT/Ni–TiO2.Multi-walled carbon nanotubes (MWNTs) were directly deposited onto Ni modified TiO2 particles using chemical vapour deposition (CVD). These novel hybrid nanostrucured MWNT/TiO2 composites were characterised by scanning electron microscopy (SEM), revealing a novel hybrid structure wherein the CNT growth sprouted from the TiO2 particles and thermogravimetric analysis (TGA) that revealed a carbon content of 8%. Electrochemical methods were used to determine capacitance values as high as 146 F g−1 using acetonitrile containing 0.1 M tetrabutylammonium perchlorate as electrolyte. An energy density and power density of 21 Wh kg−1 and 10 kW kg−1 respectively were obtained.
Keywords: TiO2; MWNTs; Chemical vapour deposition; Capacitor;

► Three typical PPy/G electrodes (PPy/G-Cl, PPy/G-p-TS and PPy/G-DBS) as anode of CDI cell respectively. ► Dopants control the morphology of the PPy/G electrodes. ► PPy/G electrodes have good conductivity and fast electrochemical reaction in CDI process. ► The adsorption capacities of the PPy/G electrodes vary with the type of dopants. ► Dopants with high exchange ability enhance the adsorption capacity of the PPy/G electrode.Polypyrrole/graphite electrodes (PPy/G-Cl, PPy/G-p-TS and PPy/G-DBS) were synthesized by electrochemical polymerization process. The three type of electrodes were then used as anode respectively to study the effect of dopants on the adsorbing performance of PPy/G electrodes in capacitive deionization process. The morphology, thickness, conductivity of PPy layers and the surface area of the PPy/G electrodes were characterized and tested respectively, all of which depend on the type of dopants. The electrochemical impedance spectroscopies infer that the adsorbing processes of the PPy/G electrodes are controlled by Warburg diffusion. Also, the PPy/G-Cl and PPy/G-p-TS electrodes show better conductivity than the PPy/G-DBS electrode in CDI cells. The ion exchange capability of the PPy layers was measured by an electrochemical quartz crystal microbalance (EQCM), which proves that the ion exchange capability of the PPy layers is in the order of: PPy-p-TS > PPy-Cl > PPy-DBS. The results of adsorbing experiments indicate that the specific adsorption capacities of PPy/G electrodes to Cl vary with the type of dopants and follow the order of: PPy/G-p-TS > PPy/G-Cl > PPy/G-DBS. Further, it can be obtained that dopants dominate the electrochemically switchable ion exchange (ESIE), and the specific adsorption capacities of the PPy/G electrodes are mainly determined by the ESIE.
Keywords: Dopants; Polypyrrole; Capacitive deionization; Adsorbing performance;

Cationic and free radical polymerization of N-vinyl-2,3-diphenylpyrrole by Inna V. Tatarinova; Marina V. Markova; Al’bina I. Mikhaleva; Lyudmila V. Morozova; Ol’ga V. Petrova; Lyubov’ N. Sobenina; Tamara I. Vakul'skaya; Spartak S. Khutsishvili; Galina F. Prozorova; Konstantin B. Petrushenko; Alexander V. Yakimansky; J.Sh. Ma; G. Yang; Boris A. Trofimov (662-669).
Display Omitted► Oligomers with alternating pyrrole and ethylydene units have been obtained. ► The oligomers possess semiconducting and paramagnetic properties and fluoresce. ► The oligomers may find application as active binders and modifying agents.Cationic polymerization of N-vinyl-2,3-diphenylpyrrole (FeCl3·6H2O, complex LiBF4–dimethoxyethane, WCl6, BF3·OEt2, Me3SiCl, 2 wt%, benzene, 20–80 °C, 24–48 h) affords oligomers with alternating pyrrole and ethylydene units in up to 61% yields (molecular weight 800–3100). Free radical polymerization of this monomer (AIBN, 0.5–5 wt%, benzene, 80 °C, 1–50 h) leads to oligomers having polyethylene backbone with pendant 2,3-diphenylpyrrole moieties (in up to 92% yield, molecular weight 2100–2500). The oligomers show semiconducting (σ  = 2.6 × 10−7–4.2 × 10−6  S/cm after doping with I2) and paramagnetic (N  = 1.2 × 1018–4.8 × 1019  spin/g) properties and fluoresce in the region 383–388 nm (solution in dioxane).
Keywords: N-vinyl-2,3-diphenylpyrrole; Cationic polymerization; Radical polymerization; Conducting oligomers; Fluorescent oligomers;

► The energy levels of occupied molecular orbitals could be raised orderly. ► The unoccupied molecular orbitals have little changes. ► The hole injection become harder while the electron injection become easier.Time-dependent density functional theory (TDDFT) method was used to investigate the effect of arylacetylide chain length on the geometrical structures, electronic properties, electroluminescent properties, absorption and emission spectra of four cyclometalated Pt(II) complexes [Pt(tBu)3(tpy){CC(C6H4CC) n−1}C6H5]+ (n  = 1–4). The ωB97XD functional which includes long range corrections and empirical dispersion proved to be suitable for calculating the characters of the lowest singlet excited state (S1) and the lowest triplet excited state (T1) in TDDFT calculations. With the arylacetylide chain increasing, the energy levels of the occupied molecular orbitals could be raised orderly, while the unoccupied molecular orbitals had little changes. Moreover, both the absorption and emission wavelengths were red-shifted with the arylacetylide introduction. The difficulties of hole and electron injection gradually decreased. When there were four arylacetylide ligand, the complex had the best performance for electron and hole transport.
Keywords: Time-dependent density functional theory; Arylacetylide; Chain length effect; Electroluminescent properties;

Synthesis and characterization of La/Nd-doped barium-ferrite/polypyrrole nanocomposites by Yu Xie; Xiaowei Hong; Yunhua Gao; Mingjun Li; Jinmei Liu; Juan Wang; Jing Lu (677-681).
► We firstly prepared the La/Nd-doped barium-ferrite/polypyrrole nanocomposites. ► There were interactions between ferrite particles and PPy. ► Nanocomposites presented the core–shell structure. ► Nanocomposites exhibited the hysteresis loops of the ferromagnetic behavior. ► M S and H c of nanocomposites varied with the content of ferrite particles.La/Nd-doped barium-ferrite/polypyrrole nanocomposites were synthesized by in situ chemical polymerization of pyrrole in the presence of La/Nd-doped barium-ferrite particles. Structural, morphological and electro-magnetic properties of the nanocomposites were performed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), four-probe conductivity tester and vibrating sample magnetometer (VSM). The results of XRD indicated that La3+ and Nd3+ had entered into the lattice of barium ferrite. FTIR spectra demonstrated that there were interactions between ferrite particles and PPy. The TEM and SEM studies showed that the composites presented the core–shell structure. Under applied magnetic field, nanocomposites exhibited the hysteresis loops of the ferromagnetic behavior. The saturation magnetization and coercivity of nanocomposites varied with the content of Ba(LaNd)0.09Fe11.82O19 particles.
Keywords: Barium-ferrite; La/Nd-doped; Polypyrrole; In situ chemical polymerization; Electro-magnetic nanocomposites;

High conductivity and solubility of polypyrrole/graphene composites has been successfully synthesized by in situ chemical oxidation polymerization using various concentrations of cationic polyelectrolyte poly(styrenesulfonate) (PSS). Conductivities of composites synthesized with PSS are about five times of magnitude higher than the composites without PSS.Display Omitted► High conductivity and solubility of polypyrrole/graphene composites was synthesized. ► Structural analysis showed that the fabricated composites are core-shell structure. ► Conductivities of composites synthesized with PSS are higher than that without PSS.High conductivity and solubility of polypyrrole (PPy)/graphene composites has been successfully synthesized by in situ chemical oxidation polymerization using various concentrations of cationic polyelectrolyte poly(styrenesulfonate) (PSS) and ammonium peroxodisulfate (APS). Raman spectroscopy, FTIR, Raman, EPR and FESEM were used to characterize their structure and morphology. These FESEM images show that the fabricated PPy/graphene composites are core-shell structure. The results of Raman spectrum, FTIR and UV-Vis indicate the synthesized PPy/graphene composites are in the doped state. The conductivities of PPy/graphene composites synthesized with the weight ratio of PSS/pyrrole monomer at 0.5 are about five times of magnitude higher than that of PPy/graphene composites without PSS. These results are perhaps due to the part of cationic electrolyte served as a dopant can be incorporated to the PPy structure to improve the conductivity of fabricated PPy/graphene composites.
Keywords: Polypyrrole; Graphene; Composite; Electrical properties;

► Pyrrole-PAMAM (PAMAM; Polyamidoamine) dendrimers film enable immobilization of enzyme. ► The biosensor seems to be fast to respond and sensitive. ► The conducting polymer film used in this study is an effective platform to produce reliable biosensors.Glucose oxidase (GOx) was covalently immobilised onto an electrochemically prepared co-polymer composed of amidoamine-pyrrole dendrimers, for the construction of an amperometric glucose biosensor. First, second, and third generation amidoamine-pyrrole dendrimers with branched amine periphery and focal pyrrole functionality were synthesised via divergent pathways. Dendronised polypyrrole was synthesised by electrochemical copolymerisation of the aminoamine-pyrrole dendrimers from pyrrole monomers. These copolymers have been utilised as conducting films for amperometric glucose sensing. GOx retains its bioactivity after covalent immobilisation onto dendronised pyrrole-copolymers. Amperometric response was measured as a function of glucose concentration, at a fixed potential of +0.7 V vs. Ag/AgCl in a phosphate buffered saline solution (pH 7.5). The effects of pH and temperature on storage and reusability of the amperometric glucose biosensor were investigated. Our results indicate efficient immobilisation of the enzyme onto a PAMAM type dendrimer modified surface containing a pyrrole monomer linked to a PAMAM dendron, with high enzyme loading, and increased electrode lifetime and stability.
Keywords: PAMAM; Pyrrole; Glucose oxidase; Biosensor; Covalent immobilization;

Polyaniline (PANI)/TiO2 composites were prepared by a chemical oxidation polymerization and their structural and electrochemical properties were analyzed. The composites were prepared with various amount of TiO2 powder to find the relationship between the properties of composites and PANI/TiO2 ratio. The polyaniline containing 7.3 wt.% of TiO2 (sample b) showed the largest capacitance of 784 F g−1.Display Omitted► Conducting polymer electrodes were prepared with a different content of TiO2. ► TiO2 influenced the structural, morphological, and electrochemical properties. ► The composites showed the higher capacitance than pristine sample. ► Improved capacitance was due to the core/shell-like structure by polyaniline and TiO2.Polyaniline (PANI)/titanium dioxide (TiO2) composites were prepared by a chemical oxidation polymerization. The composites were prepared with various amount of TiO2 to find a relation between electrochemical properties of composites and compositions of TiO2 and PANI in the composites. PANI/TiO2 composites which had PANI as a shell and TiO2 as a core part of the composites were successfully synthesized. Fiber-like PANI was also observed within the composites. The synthesis was explained as two stages of polymerization. First stage is a polymerization reaction occurred by a strong oxidative potential of TiO2. Second stage is started by adding ammonium peroxydisulfate in reaction solution. Diameters of aggregations of the composites increased with the added amounts of TiO2. The composite prepared with 10 wt.% of TiO2 per aniline monomer weight showed the highest capacitance of 784 F g−1 among the prepared composites. But the composites prepared with excess amounts of TiO2 showed lower capacitance than the highest one. The lower capacitances of the composites prepared with excess amounts of TiO2 was considered as related with the diameters of the aggregations. The composites prepared with excess amounts of TiO2 had large diameters for the aggregations. The TiO2 particles in the core of composites that had large diameter are hard to participate in electrochemical reaction due to a long pathway from electrolyte to TiO2 core and a blocking effect by outer TiO2 particles.
Keywords: Titanium dioxide; Polyaniline; Composite materials; Electrochemical properties;

► Charge transport in two dimensional hopping systems. ► Two dimensional mobility model based on percolation system. ► Bimolecular recombination in two dimensional system. ► Recombination coefficient cannot be simply described as obeying the power law relation.We propose a model of charge transport and recombination in two dimensional hopping systems. It is developed rigorously using variable range hopping transport, drift diffusion and percolation theories. Based on the proposed model, a variety of temperature and carrier concentration dependencies of the bimolecular recombination coefficient can be well described.
Keywords: Hopping transport; Bimolecular recombination; Solar cell;

Thermal and morphological characterization of conducting, polyaniline/polystyrene blends by Iran da Silva Guimarães; Angel Alberto Hidalgo; Helder Nunes da Cunha; Leandro de Miranda Santos; José Aroldo Viana dos Santos; José Ribeiro dos Santos Júnior (705-709).
Display Omitted► In this study was prepared the conductive blends polyaniline/polystyrene (PAni/PS) by casting method resulting in flexible films. ► The resulting film easily removable from the substrate is thin with a glossy aspect. ► Meanwhile the PS films presented as a fragile material, the blends are similar to conducting polymer. ► The thermogravimetric measurements (TGA) show that the blends have higher thermal stability.In this study the conductive blend polyaniline/polystyrene (PAni/PS) was prepared by casting method resulting in flexible films, it was doped with hydrochloric acid. We conducted a series of characterizations such as infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and impedance spectroscopy (AC). The infrared (FTIR) analysis was intended to identify the main stretching vibrations of organic groups for both the components. The thermogravimetric measurements (TGA) show that the blends have higher thermal stability than the polymers alone, since the mass losses were less pronounced. The PS presented itself as a fragile material; the blends are similar to conducting polymer. On the other hand, the electronic microscopy scans showed that the PAni film has tiny clusters, which indicates that the thermoplastic interacts with PAni, resulting in a conductive blend with low bias current.
Keywords: Polyaniline; Polystyrene; Thermal stability; Blends;

A graphene oxide oxygen barrier film deposited via a self-assembly coating method by Lan Yu; Yun-Soo Lim; Jong Hun Han; Kunnyun Kim; Jong Yun Kim; Sung-Yool Choi; Kwonwoo Shin (710-714).
Display Omitted► Graphene oxide (GO) films deposited by a self-assembly coating method. ► Oxygen transmittance rate (OTR) of GO films increased by post-treatment. ► OTR of GO film 30–40 nm thick indicated a value less than 0.05 cc/m2  day. ► Light transmittance of GO film 30–40 nm thick was 85.6%.This study characterized the properties of a transparent oxygen barrier film in which graphene oxide (GO) was used as the barrier material. GO was produced by oxidizing graphite via chemical methods. Alternating self-assembled solution-deposited GO layers and poly(ethylenimine) (PEI) layers were then deposited on a polyethylene-terephthalate (PET) film surface. The deposited film displayed excellent oxygen barrier properties, decreasing the oxygen transmittance rate (OTR) to 0.05 cc/m2  day, and its light transmittance was 85.6%. Increasing the number of deposition barrier layers on the PET film decreased the OTR and light transmittance, and the electric conductivity increased. The deposited film was post-treated to obtain modified film characteristics.
Keywords: Graphene oxide; Self-assembly; Transparent; Oxygen barrier film; Oxygen transmittance rate;

Display Omitted► We develop Ir complexes with 5-benzoyl-2-phenylpyridine derivatives as ligands. ► We examine changes in fluorine and methyl groups in the phenyl moiety. ► These fluorine and methyl groups allow tuning of the band gap of Ir complexes, leading to improved color purity.Red phosphorescent emitters for OLEDs were synthesized using Ir(III) complexes based on 5-benzoyl-2-phenylpyridine ligands with fluorine and methyl substitution. Their electroluminescence, when doped in the emitting layers of multilayer OLEDs, was sensitive to their structural features. In particular, a highly efficient orange-red OLED showed a maximum luminance of 18,740 cd/m2 at 11 V, with a luminous efficiency of 25.9 cd/A, power efficiency of 8.74 lm/W, external quantum efficiency of 9.25% at 20 mA/cm2, and CIE x,y coordinates of (0.53, 0.47) at 8.0 V, respectively. A red OLED with CIE x,y coordinates of (0.66, 0.34) at 8.0 V exhibited a luminous efficiency, power efficiency and external quantum efficiency of 5.98 cd/A, 2.06 lm/W and 5.77% at 20 mA/cm2, respectively.
Keywords: Red phosphorescent; OLEDs; Ir(III) complex; 5-Benzoyl-2-phenylpyridine ligands;

Biocompatibility of polyaniline by Petr Humpolicek; Vera Kasparkova; Petr Saha; Jaroslav Stejskal (722-727).
► Biocompatibility of polyaniline salt and base was investigated. ► Polyaniline does not provoke any sensitization and skin irritation either. ► It shows considerable cytotoxicity, higher for polyaniline salt compared to base. ► Cytotoxicity was considerably reduced through de/re-protonation procedures.Both the non-conducting polyaniline, emeraldine base, and its conducting form, polyaniline hydrochloride, were tested for their biocompatibility in terms of skin irritation, sensitization and cytotoxicity performed on human immortalized non-tumorigenic keratinocyte and human hepatocellular carcinoma cell lines. The testing was carried out on extracts of polyaniline powders in agreement with requirements of international standards applicable for testing of medical devices. The results can be hence generally employed in all types of materials and devices containing polyaniline in various concentrations. The study confirmed that polyaniline has not induced any sensitization and skin irritation either. In contrast, both polyaniline forms showed considerable cytotoxicity, which was higher for polyaniline hydrochloride compared to polyaniline base and was observed on both cell lines. Differences between cytotoxicity found on human immortalized non-tumorigenic keratinocyte cell line and human hepatocellular carcinoma cell line were attributed to variability in specific metabolic capabilities of the respective cell lines. Significant reduction of cytotoxicity was achieved through deprotonation and reprotonation procedure, used as an additional purification step after polymer synthesis. Accordingly, the cytotoxicity is thus caused rather by the reaction by-products and residues than by polyaniline itself.
Keywords: Conducting polymer; Polyaniline; Biocompatibility; Cytotoxicity; Skin irritation;

Electrosynthesises and characterizations of copolymers based on pyrrole and 3,4-ethylenedioxythiophene in aqueous micellar solution by Yi-jie Tao; Hai-feng Cheng; Wen-wei Zheng; Zhao-yang Zhang; Dong-qing Liu (728-734).
► We prepared copolymers based on pyrrole and EDOT in aqueous micellar solution. ► The onset oxidation potential of pyrrole increases with the concentrations of pyrrole decrease in aqueous micellar solution. ► The feed ratio of pyrrole/EDOT plays an important role on the electrochromic properties of the copolymers. ► The incorporation of EDOT units into the Poly(pyrrole) chain improves the electrochemical stability of copolymers.Copolymers based on pyrrole and 3,4-ethylenedioxythiophene (EDOT) are electrodeposited on indium tin oxide (ITO) electrode with various feed ratio of pyrrole/EDOT in aqueous micellar solution. The structures of the resultant copolymers are characterized via cycle voltammograms, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and spectroelectrochemical analysis. Different electrochromic properties can be achieved by the copolymers prepared with various pyrrole/EDOT ratios. The π-π* transition absorption peak (λ max) of the deposited copolymer with the pyrrole/EDOT ratio of 1/10 at the neutral state is located at 542 nm and the calculated energy gap (E g) is 1.82 eV. Moreover, successive CVs indicate the copolymer film has a better electrochemical stability, retaining 80% of the original electroactivity after 1000 cycles, which mainly results from the incorporation of EDOT units into the Ppy.
Keywords: Electropolymerization; Copolymers; Aqueous micellar solution; Electrochromism;

Effect of substituents on the orientation of octasubstituted copper(II) phthalocyanine thin films by Tamara V. Basova; Meryem Çamur; Aliye Aslı Esenpınar; Sinem Tuncel; Aseel Hassan; Alexey Alexeyev; Hikmat Banimuslem; Mahmut Durmuş; Ayşe Gül Gürek; Vefa Ahsen (735-742).
► Octasubstituted copper(II) phthalocyanines form columnar-hexagonal mesophase over a wide temperature range. ► Phthalocyanines form oriented films on the substrate surface. ► Substituents in the phthalocyanine molecule have a significant effect on the orientation and electrical properties.Octasubstituted copper(II) phthalocyanines containing alkylthio-, alkyloxy-, (trioxyethylene)thio- and (trioxyethylene)oxy- substituents in peripheral positions have been synthesized and characterized using UV–vis, IR, and mass spectroscopies. The mesogenic properties of the copper(II) phthalocyanines have been studied by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The effect of the nature of substituents in the phthalocyanine ring on the liquid crystalline properties and the orientation of the molecules in thin films have also been investigated using a range of spectral methods as well as by X-ray diffraction analysis. Visible absorption spectroscopy yielded an evidence of a thermally induced molecular reorganization in the films. Polarized Raman spectroscopy was used to study the preferential orientation of molecules relative to the substrate surface. Influence of the nature of substituents in the phthalocyanine molecule in the thin films conductivity was also investigated.
Keywords: Phthalocyanine; Thin films; Liquid crystals; Molecular alignment;