Synthetic Metals (v.161, #1-2)

A series of low band gap, donor–acceptor polymers composed of regioregular 3-hexylthiophene segments and quinoxaline derivative units were synthesized by Stille coupling polymerization. The polymers had relatively low optical band gaps ranging from 1.61 to 1.83 eV. A bulk-heterojunction structure of glass/indium–tin oxide (ITO)/PEDOT:PSS/polymer-PCBM (1:3)/BaF2/Ba/Al was fabricated to examine the photovoltaic properties. 1-(3-Methoxycarbonyl)propyl-1-phenyl-[6,6]-C-71 (PC71BM) was used as the acceptor material owing to its increased absorption property in the visible region compared to 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-61 (PC61BM). Among these polymers, P1 showed the best device performance with a PCE of 0.88%. These results provided an effective strategy for the design and synthesis of low band gap conjugated polymers with a broad range of absorption.
Keywords: Organic photovoltaics; Charge transfer; Conjugated polymers; Copolymerization;

Indentation modulus and hardness of polyaniline thin films by atomic force microscopy by D. Passeri; A. Alippi; A. Bettucci; M. Rossi; E. Tamburri; M.L. Terranova (7-12).
▶ We deposited polyaniline thin films with different thickness on stiff substrates. ▶ We performed depth sensing indentation measurements using an atomic force microscope. ▶ Indentation modulus and hardness were measured at different penetration depths. ▶ Bulk values of indentation modulus and hardness of polyaniline were deduced.Polyaniline (PANI) thin films with different thicknesses have been deposited on indium tin oxide (ITO) coated glass substrates by electrochemical polymerization of the aniline monomer in H2SO4 aqueous solution. By using the tip of an atomic force microscopy (AFM) apparatus as an indenter, cantilever deflection versus sample vertical displacement curves have been acquired and analyzed for evaluating the contact stiffness, by using an approach analogous to that developed for standard depth sensing indentation (DSI) tests. After the calibration performed using a set of polymeric reference materials, indentation modulus and hardness of PANI films have been deduced as a function of the reached maximum penetration depth. By using a model originally proposed for the analysis of standard DSI measurements, indentation modulus and hardness values of only PANI are finally deduced from the corresponding apparent values measured for the film-substrate systems, although they have to be considered as semi-quantitative estimations, since the roughness of the films does not allow a certain determination of the local thickness in correspondence of the probed points.
Keywords: Atomic force microscopy; Elastic modulus; Hardness; Thin film;

A novel highly soluble coordination polymer, poly(3,4-HBA-Cr-FDA), containing Cr(III) ion in the backbone was synthesized. Monomeric model compounds (MC-1 and MC-2) were also synthesized as the comparison materials. The structures were characterized by FT-IR, UV–vis, 1H and 13C NMR, and size exclusion chromatography (SEC). SEC results showed that the novel polymer had 65–68 repeated units. ICP-AES was used to determine the chromium content of MC-2. Thermal data were obtained by TGA and DSC techniques showing that MC-2 and the novel polymer had high rate of hydrate water. Cyclic voltammetry (CV) measurements were carried out and the HOMO–LUMO energy levels and electrochemical band gaps ( E ′ g ) were calculated. Additionally, the optical band gaps (E g ) were determined using UV–vis spectra of the materials. Electrical conductivity measurements of the doped (with iodine) and undoped polymer related to temperature and doping time were carried out by four point probe technique using a Keithley 2400 electrometer. Measurements were made using the polymeric film deposited on ITO glass plate by dip-coating method. Also, absorption spectra of doped polymeric film were recorded by a single beam spectrophotometer showing that doping procedure causes peak growing in absorption spectra. Ability of processing of poly(3,4-HBA-Cr-FDA) in gas sensors was discussed. Fluorescence spectra of the polymer in a series of solvents were obtained and it was found that poly(3,4-HBA-Cr-FDA) had green–red emitting emission in different solvents.
Keywords: Chelate polymers; Conjugated polymers; Gas sensor; Optical and electrochemical band gaps; Fluorescence;

Polypyrrole films on Al alloys: The role of structural changes on protection performance by Mirko Rizzi; Monica Trueba; Stefano P. Trasatti (23-31).
Polypyrrole (PPy) films were electrochemically synthesized on AA6082, AA5083 and AA2024 Al alloys by a two-step galvanostatic procedure: (1) activation in nitric acid and (2) deposition in oxalic acid. PPy films were characterized by elemental analysis, cyclic voltammetry, SEM/EDX, RAIR, solid-state 13C NMR, and EPR. The corrosion behaviour of PPy-coated alloys was evaluated in near neutral NaCl solution by single-cycle anodic polarization and open circuit potential monitoring. Film adhesion and polymer structure are principally determined by the nature of the Al substrate. Good quality films are obtained on the most reactive AA5083 and AA2024, while highly degraded, partially saturated polymer is electrogenerated on AA6082. The performance of PPy films was observed to depend strongly on the electrochemical test used for corrosion protection evaluation. Accordingly, the rate at which structural changes are driven within the polymeric matrix is of paramount importance to understand the corrosion inhibition properties of conducting polymers.
Keywords: Aluminium alloys; Polypyrrole; Corrosion protection;

Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to study the structure characterization of the Rhodamine B (Rh.B). The thermal stability and the lattice parameters were calculated using TGA and XRD, respectively. Bulk Al/Rh.B Schottky barrier device was prepared and their properties have been investigated by current density–voltage JV and capacitance–voltage CV characteristics in the temperature range 300–400 K. The device parameters extracted from the JV and CV characteristics are strongly influenced by the effect of temperature. The device exhibits a strong rectification characteristic and shows a maximum rectification ratio at ≈0.15 V for all the studied temperature range. The results clearly demonstrate that the electron transport at the Al/Rh.B interface is significantly affected by low barrier patches. The discrepancy between Schottky barrier heights (SBHs) obtained from the temperature dependencies of both JV and CV measurements is explained by the introduction of a spatial distribution of BHs due to the barrier height inhomogeneities that prevail at the Al/Rh.B interface. The deviations of apparent BHs were investigated by considering the microstructure of the Al/Rh.B interface. Moreover, the distribution of carrier concentration through the width of the depletion region is nearly uniform.
Keywords: Organic Schottky diode; Rhodamine B; Schottky diode; Current–voltage; Capacitance–voltage; Barrier height inhomogeneity;

▶ This work reports low driving voltage in organic light-emitting diodes using organic interlayer. ▶ The driving voltage of phosphorescent organic light emitting diodes was reduced by the organic interlayer. ▶ A high power efficiency of 73.3 lm/W was achieved in the green phosphorescent organic light emitting diodes using the organic interlayer.The power efficiency of organic light-emitting diodes (OLEDs) was improved using hexaazatriphenylene-hexacarbonitrile (HAT) as the interlayer between hole injection layer and hole transport layer for efficient hole injection. The hole injection was enhanced and the driving voltage was lowered by the HAT interlayer. A high power efficiency of 73.3 lm/W was obtained from the green phosphorescent organic light-emitting diode with the HAT interlayer.
Keywords: Low driving voltage; Organic interlayer; Power efficiency;

SrFe12O19-MWCNTs composites with different MWCNTs content were synthesized by sol–gel method. The results of X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) analyses demonstrated that the SrFe12O19 nanoparticles were immobilized on the external surfaces of the CNTs. Vibration sample magnetometer (VSM) and Network vector analyzer measurements indicated that 6 wt.% SrFe12O19-MWCNTs composites possessed the best magnetic and wave absorbing properties.
Keywords: SrFe12O19-MWCNTs composite; Mechanism; Electromagnetic parameter; Magnetic property; Wave absorbing property;

The organic field-effect transistor having 2,3 benzanthracene as active layer grown on SiO2 dielectric layer was fabricated. AFM results indicate that 2,3 benzanthracene thin film is formed from homogeneous small crystal grains with an average diameter about 200 nm. The electrical parameters such as mobility, threshold voltage, I on/I off ratio and SS value were determined. The obtained I on/I off and S values increase with visible light illumination due to more photogenerated charges. The mobility and threshold values were changed by visible light illumination. The organic thin film transistor exhibits a photovoltaic effect in turn-on state. The control of the threshold voltage of 2,3 benzanthracene-based organic thin film transistor was achieved by visible light illumination. The change in the threshold voltage is enough for the electronic technology applications of organic thin film transistors.
Keywords: Organic thin film transistor; 2,3 Benzanthracene; Photovoltaic effect;

In this work, a new method for the synthesis of polyaniline (PANI) nanotubes was presented. Experimentally, Mn2O3 nanofibers prepared by electrospinning technique were used as the oxidant template to initiate the polymerization of aniline in acid solution. After reaction, polyaniline shells were formed on the Mn2O3 nanofiber surface, and the Mn2O3 nanofibers were spontaneously removed. As a result, PANI nanotubes were obtained. As-prepared PANI nanotubes show an average diameter of 80 nm and inner diameter of 38 nm. The final PANI nanotubes were characterized by SEM, EDX, TEM, FTIR and XRD. The gas sensing of as-obtained PANI nanotubes was also investigated. It was found that the PANI nanotube sensing device could detect as low as 25 ppb NH3 in air at room temperature with good reversibility.
Keywords: Electrospinning; Mn2O3 nanofibers; Polyaniline nanotubes;

Display Omitted▶ Coacervate gel as template for silver and polypyrrole nanorod synthesis. ▶ Nanorod formation of Ag begins from the first instant while that of PPy takes a longer time. ▶ Dc conductivity of PPy-Ag composite is seven orders higher than that of the PPy nanorods. ▶ PPy-Ag systems indicate Ohmic behavior while the PPy nanorods exhibit semi-conducting behavior. ▶ Increased gel concentration decreases the average diameter of PPy nanorod by 50% while that of Ag nanorod decreases only 12%.Polypyrrole (PPy) and silver (Ag) nanorods are synthesized in cetyl trimethylammonium bromide–lauric acid (CTAB–LA) complex coacervate gel template. When PPy–CTAB–LA system is polymerized with AgNO3, Ag nanorods are produced while use of ammonium persulphate (APS) as initiator yields PPy nanorods. Ag-nanorods are produced from the initial stage while PPy nanorods take a longer time. The average diameter of Ag nanorods varies from 60 to 145 nm by increasing AgNO3 concentration from 0.27 M to 1.08 M and that of PPy varies from 145 nm to 345 nm by changing pyrrole concentration from 1 × 10−4 to 2 × 10−4 M, respectively. Fourier transformed infrared (FTIR) spectra indicate stabilization of Ag nanorods through complexation of PPy with adsorbed Ag+ ions. PPy nanoparticles are stabilized by adsorbed sulphate ions and lauric acid, both are acting as dopant to it. FFT pattern and EDX spectra clearly indicate the presence of Ag nanocrystals and PPy on the surface of Ag nanorods, respectively. The mechanism of nanorod formation is attributed from UV–Vis spectra showing a red shift of surface plasmon band of Ag and π–π* transition band of PPy with time. The highest dc conductivity of PPy–Ag composite is found to be 414.2 S/cm, 7 orders higher than that of PPy nanorods (9.3 × 10−4  S/cm). PPy–Ag systems show Ohmic behavior while PPy nanorods exhibit semi-conducting behavior. The preferential formation of Ag nanorod in AgNO3 initiated polymerization is attributed to the higher cohesive force of Ag than that of PPy. With two times higher LA and CTAB concentration in the gel the Ag nanorod diameter decreases only 12% while that of PPy nanorod decreases by 50%. Possible reasons are discussed from the hard and soft nature of the two nanorods and from the elasticity of the gel template.
Keywords: Polypyrrole; Silver; Nanorod; Conductivity;

Synthesis and properties of phenothiazylene vinylene and bithiophene-based copolymers for organic thin film transistors by Jun-Ho Kim; Young-Hoon Seo; Woo-Hyung Lee; Yongtaek Hong; Sang Kyu Lee; Won-Suk Shin; Sang-Jin Moon; In-Nam Kang (72-78).
A series of new phenothiazylene vinylene and thiophene copolymers (P1, P2, and P3) have been synthesized via Yamamoto and Stille coupling reactions. The number-averaged molecular weights (M n) of P1, P2, and P3 were found to be 12,000, 10,000, and 8200, with polydispersity indices of 3.5, 1.4, and 1.6, respectively. The UV–visible absorption spectra of the polymers contain two strong absorption bands in the ranges 306–325 nm and 430–480 nm, which arise from the absorptions of the phenothiazine segments and the conjugated main chains respectively. Solution-processed field-effect transistors (FETs) fabricated with these polymers exhibit p-type organic thin film transistor characteristics. The field-effect mobilities for P1, P2, and P3 were measured to be 1.8 × 10−4, 5.7 × 10−4, and 2.5 × 10−7  cm2  V−1s−1, respectively, with the corresponding on/off ratios of 5 × 102, 1 × 104, and 5 × 102.
Keywords: Organic thin film transistor; Phenothiazine; Bithiophene; Semiconducting polymer; Conjugated polymer;

Azomethine-based phenol polymer: Synthesis, characterization and thermal study by Fatih Doğan; İsmet Kaya; Ali Bilici (79-86).
▶ In this paper a new polyphenol derivate, PAPIMP, was synthesized by an oxidative polymerization process in alkaline medium. ▶ The conductivity measurements show that polyphenol derivate are semiconductor. The undopped the conductivity values of PAIPMN were about 10−11  S/cm. ▶ The apparent activation energies for thermal decomposition of polyphenol derivate were also obtained by Tang, Flynn-Wall-Ozawa (FWO), Kissenger-Akahira-Sunose (KAS) and Coats-Redfern methods (CR) were 96.97, 105.33, 97.28 and 88.60 kJ mol−1, respectively. ▶ The most likely decomposition process of polyphenol derivate found to be a D n Deceleration type.Azomethine-based phenol polymer, poly-2-{[(6-aminopyridin-2-yl)imino]methyl}-phenol (PAPIMP), was synthesized through the combination of condensation reaction and oxidative polymerization. Polymer isolated from aqueous solution was characterized by UV–vis, FT-IR, NMR and TG, SEC analysis. According to the SEC chromatograms, the number-average molecular weight (M n), weight-average molecular weight (M w) and polydispersity index (PDI) values of PAPIMP were determined to be 33,550, 78,900 g mol−1 and 2.352, respectively. Also, optical band gaps (E g) of APIMP and PAPIMP calculated from cyclic voltammetry (CV) measurements. Also, electrical conductivities of each component measured with four-point probe technique. TG analysis showed that PAPIMP was stable up to 300 °C. The thermal decomposition kinetics of PAPIMP was investigated by means of thermogravimetric analysis in dynamic nitrogen atmosphere at four different heating rates: 5, 10, 15 and 20 °C min−1. The apparent activation energies for thermal decomposition of PAPIMP were obtained by Tang, Flynn–Wall–Ozawa (FWO), Kissenger–Akahira–Sunose (KAS) and Coats–Redfern methods (CR) were 96.97, 105.33, 97.28 and 88.60 kJ mol−1, respectively; the mechanism function and pre-exponential factor were determined by master plots method. The most likely decomposition process was a D n Deceleration type in terms of the Coats–Redfern and master plots results.
Keywords: Oxidative polymerization; Schiff base polymer; Kinetic parameter;

Laser irradiation effects on the optical properties of layer-by-layer PPV/Congo Red thin films by Edson Laureto; Marco Aurélio Toledo da Silva; Ricardo Vignoto Fernandes; José Leonil Duarte; Ivan Frederico Lupiano Dias; Henrique de Santana; Alexandre Marletta (87-91).
In this paper we investigate the optical properties of thin films produced through the layer-by-layer (LbL) technique with a poly (p-phenylene vinylene) (PPV) precursor and the Congo Red (CR) azodye. Some significant changes are observed when the PPV/CR film is irradiated with polarized laser. An increase of about 10 times in the PPV emission intensity was observed, with an irradiation time of 100 min. Photoinduced birefringence measurements revealed that a high birefringence was produced in the region of the film submitted to photo-irradiation, while a photobleaching phenomenon was observed in the same region. However, such phenomena were not detected in measurements performed at low temperatures. The results indicate that a degradation process of the CR molecules is occurring with photo-irradiation, and the changes observed in the photoluminescence spectra are correlated with the combined effects of degradation and energy transfer between the PPV light-emitting conjugated segments and CR azochromophores.
Keywords: Poly (p-phenylene vinylene); Congo Red azodye; Birefringence; Photobleaching; Degradation; Photoluminescence;

Diphenylsilanes containing electronically isolated carbazolyl fragments as host materials for light emitting diodes by R. Zostautiene; J.V. Grazulevicius; Y.M. Lai; W.B. Wang; J.H. Jou; S. Grigalevicius (92-95).
▶ Branched derivatives containing diphenylsilane core and pendent carbazolyl fragments were synthesized and characterized. ▶ The derivatives were tested as host materials in blue phosphorescent OLEDs. ▶ The best device demonstrated current efficiency of 16.4 cd/A and maximum brightness exceeding 200 cd/m2.Branched derivatives containing diphenylsilane core and pendent carbazol-9-yl fragments were synthesized and characterized. The compounds represent amorphous materials of high thermal stability with glass transition temperatures of 54–93 °C and thermal decomposition starting at temperatures above 391 °C. The electron photoemission spectra of layers of the synthesized compounds showed ionization potentials of ca 5.9 eV. The derivatives were tested as host materials in phosphorescent OLEDs with iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate as the guest. The device with the host derivative containing four isolated carbazolyl fragments exhibited the best overall performance with maximum current efficiency of 16.4 cd/A and maximum brightness exceeding 200 cd/m2 .
Keywords: Oxetane; Amorphous material; Ionization potential; Host; Light emitting diode;

D-π-A organic dyes with carbazole as donor for dye-sensitized solar cells by Kola Srinivas; Chitumalla Ramesh Kumar; Manda Ananth Reddy; Kotamarthi Bhanuprakash; Vaidya Jayathirtha Rao; Lingamallu Giribabu (96-105).
Two donor-π-acceptor (D-π-A) organic dyes with carbazole as donor, phenylethynyl, thienylethynyl as π-spacers and cyanoacrylic acid as acceptor, have been synthesized and characterized. These dyes exhibit charge transfer character in the ground and excited states as supported by the UV–vis and fluorescence studies. They also show interesting electrochemical properties. DFT and TDDFT studies reveal that large intramolecular charge transfer takes place from the HOMO to LUMO, though the donor carbazole is twisted (∼51°) with respect to the π-conjugated spacer and acceptors with an idea of testing the dyes as sensitizers for DSSC. The DSSC devices were fabricated with these dyes by using redox electrolyte in a nonvolatile methoxypropionitrile solvent. The efficiency of the cells, short circuit current density, J sc, and open circuit photovoltage, V oc, and fill factor, FF, has been obtained for the two molecules. Calculations based on DFT plane wave method reveal the strong binding of the dyes on the surface of TiO2 (1 0 1) surface. It is concluded that these dyes can play the role of sensitizers in DSSC.
Keywords: Carbazole; Donor-pi-acceptor dyes; DSSC; Charge transfer; TD-DFT; Periodic DFT;

Chemical in situ polymerization of polypyrrole on bacterial cellulose nanofibers by D. Müller; C.R. Rambo; D.O.S.Recouvreux; L.M. Porto; G.M.O. Barra (106-111).
Conducting porous nanofibrous composite membranes of bacterial cellulose (BC) and polypyrrole (PPy) were prepared through in situ oxidative chemical polymerization of pyrrole (Py) on the surface of synthetized BC nanofibers by using FeCl3 as oxidant agent. The influence of polymerization conditions on electrical conductivity, morphological and thermal stability of the BC/PPy composites was investigated. The amount of PPy deposited on the BC nanofibers increased with increasing the monomer concentration and reaction time while the electrical resistivity of the composites decreased due to the formation of a continuous layer that coated the nanofiber surface. Fourier transform infrared (attenuated total reflectance mode) spectroscopy (FTIR-ATR) of the composites revealed strong interaction between PPy and BC, as characterized by a blue-shift of C–N band of PPy towards pure PPy with increasing Py concentration. BC/PPy composites showed higher thermal stability than BC membrane due to the protective effect of the conducting polymer coating. Scanning electron microscopy (SEM) analysis of the composites revealed that PPy consisted of particles of mean size of 35 nm that form a continuous coating that fully encapsulates the BC nanofibers. The material properties obtained by the method described in this work for the BC/PPy composites open interesting possibilities for novel applications of electrically conducting bio-based composites, particularly those that may exploit the biocompatible nature of the BC/PPy membranous composite.
Keywords: Intrinsically conducting polymer; Polypyrrole; Bacterial cellulose; Nanofibers;

Novel metallophthalocyanines 48 (M = Zn, Ni, Co, Cu, Lu, respectively), metal free 9 and double decker Lu(III) phthalocyanine 10 with four peripheral 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenoxy groups were synthesized by cyclotetramerisation of the phthalonitrile. Their electrochemical, electrical and gas sensing properties were also investigated.Display Omitted▶ The CBH model is the dominant conduction mechanism for the films of compounds 410. ▶ The films of compounds 47 have reversible sensor response to toluene vapor. ▶ Unusual redox behaviour of double decker LuPc2 in comparison with the others. ▶ Impedance spectroscopy and dc conductivity measurements were performed.A new mono substituted phthalonitrile derivative 3 was prepared by a nucleophilic displacement reaction of 4-nitrophthalonitrile with 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol. Novel metallophthalocyanines 48 (M = Zn, Ni, Co, Cu, Lu, respectively), metal free 9 and double decker Lu(III) phthalocyanine 10 with four peripheral 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenoxy groups were synthesized by cyclotetramerisation of the phthalonitrile and characterized by elemental analyses, FTIR, 1H NMR, UV–vis and MALDI-TOF MS spectral data. Cyclic voltammetry, differential pulse voltammetry and in situ spectroelectrochemistry of the phthalocyanine compounds have been studied. This allowed us to identify and compare metal- and phthalocyanine ring-based redox processes of the complexes. Impedance spectroscopy (IS) and dc conductivity measurements were performed as a function of temperature (300–430 K) and frequency (40–105  Hz.). The sensing properties of the films for toluene were also investigated. The dc results showed an activated conductivity dependence on temperature for all films. While room temperature impedance spectra consist of a curved line, a transformation into a full semicircle with increasing temperature was observed. The analysis of ac conductivity data showed that the CBH model is the dominant conduction mechanism for the electron transport in the films. While exposure to toluene has no effect on the conductivity of the film of 810 completely reversible sensor response to toluene only were obtained for compounds 47. It was also observed that the operating temperature had a considerable effect on sensing characteristics of the films.
Keywords: Synthesis; Phthalocyanine; Lutetium double decker; Electrochemistry–spectroelectrochemistry; Conductivity; Gas sensing;

▶ An effective chemical plating of Ni–P alloy on wool fabrics is proposed. ▶ Chitosan (CTS) is used as a carrier agent to absorb catalyst PdCl2. ▶ Adsorption mechanism of Pd (II) ions on CTS is studied and kinetic curves nicely fitted to the pseudo-first-order equation. ▶ Conductive wool fabrics are also characterized and have a good ability of electromagnetic shielding.In this study, an effective deposition of Ni–P alloy on wool fabric is proposed by a chemical plating approach with PdCl2 solution and a carrier agent chitosan (CTS). CTS possesses strong ability to absorb metal ions through several mechanisms, such as electrostatic attraction and chelation, depending on the pH of the solution. The lowest surface resistance of the wool fabric is achieved when Pd (II) ions are absorbed in acid condition (around pH = 2.5). Sorption isotherms are obtained and modeled using Langmuir and Freundlich model and kinetic curves nicely fitted to the pseudo-first-order equation. Also, isotherms have been introduced to obtain the thermodynamic parameters, such as Gibbs free energy, enthalpy and entropy. The resulting positive value of the enthalpy indicates that the adsorption is an endothermic process. Conductive wool fabrics are characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy. Evidenced by SEM, CTS–Pd is found on the surface of fabrics and effectively activated the chemical plating. FT-IR shows the adsorption of Pd (II) ions on CTS is mainly controlled by physical adsorption. Mechanical and physical tests were investigated and the encouraging results show no significant modification and open new perspectives for future application of wool fabrics.
Keywords: Chitosan; Pd; Wool fabric; Chemical plating; Electromagnetic shielding fabric;

▶ Electrical characteristics of the pentacene transistor subjected to a UV light excitation at a wavelength of 365 nm were analyzed. ▶ A significant increase in the drain current of the pentacene thin film transistor under a UV excitation of 365 nm is observed with a maximum photosensitivity of 4.51 in the depletion regime. ▶ It is evaluated that the pentacene thin film transistor can be used in UV photo-detecting devices.The pentacene thin film transistor was fabricated on a SiO2/Si substrate by thermal evaporated method at room temperature. Electrical characteristics of the pentacene transistor subjected to a UV light excitation at a wavelength of 365 nm were analyzed. A significant increase in the drain current of the pentacene thin film transistor under a UV excitation of 365 nm is observed with a maximum photosensitivity of 4.51 in the depletion regime. It is concluded that the pentacene thin film transistor can be used in UV photo-detecting devices.
Keywords: Thin film transistor; Photoresponse; Field effect mobility;

Organic single crystalline micro- and nanowires field-effect transistors of a tetrathiafulvalene (TTF) derivative with strong π–π orbits and S⋯S interactions by Hui Jiang; Xianjin Yang; Erjing Wang; Yanyan Fu; Yaling Liu; Hongxiang Li; Zhenduo Cui; Yongchang Liu; Wenping Hu (136-142).
Tetrathiafulvalene (TTF) was one of the most widely studied heterocyclic systems. However, TTF itself was easily oxidized, which induced the low stability and limited its potential applications. Here, a TTF derivative, 2,3,6,7-tetrakis(2-cyanoethylthio)tetrathiafulvalene (TCE-TTF), was synthesized. It was found that single crystalline micro- and nanowires of TCE-TTF were easily obtained by simple casting due to the enhanced π–π overlapping and S⋯S interaction. The thermal and vacuum stability analyses revealed TCE-TTF was much better than TTF. Single crystalline micro- and nanowires field-effect transistors were also fabricated by in situ dropping method. The typical mobility and on/off ratio were ∼0.02 cm2/V s and ∼103, which predicted great potential applications of organic nanowires electronics.
Keywords: TCE-TTF; TTF; Organic single crystal; Micro/nanowires; Self-assembly; Stability; Mobility;

Flexible N-channel organic phototransistor on polyimide substrate by Jae-eun Park; Biswanath Mukherjee; Hyejin Cho; Sungyoung Kim; Seungmoon Pyo (143-147).
We report a flexible photoresponsive organic field-effect transistor, phototransistor (OPT), based on a fluorinated copperphthalocyanine (F16CuPc) and polymer gate dielectric on a flexible polyimide substrate. Under light illumination, the device exhibited a photoresponsivity of 2.15 mA/W at V GS  = 2 V and optical power of 5.66 mW/cm2. The current ratio (I photo /I dark ) of the light to dark states was calculated to be around 300 at V GS  = 2 V. Furthermore, the switching time of the phototransistor was found to be lower than 0.1 s. When the substrate was bent outward up to a bending radius of 4.4 mm, the device still showed photoresponsive field-effect characteristics. However, the photoresponsivity and I photo /I dark ratio decreased with decreasing bending radius. These results indicate that the present flexible OPT could potentially be used in optoelectronic device applications.
Keywords: Organic field-effect transistor; Phototransistor; Photoresponse; Gate dielectric; Organic semiconductor;

Highly efficient solution-processed red organic light-emitting diodes with long-side-chained triplet emitter by Yu-Chiang Chao; Sheng-Yang Huang; Chun-Yu Chen; Yu-Fan Chang; Hsin-Fei Meng; Feng-Wen Yen; I-Feng Lin; Hsiao-Wen Zan; Sheng-Fu Horng (148-152).
Newly synthesized red Ir complexes tris[2-(4-n-hexyl-phenyl)quinoline]iridium(III) and tris[(4-n-hexylphenyl)isoquinoline)]iridium(III) with long alkyl side chains are utilized to demonstrate the high efficiency multi-layer solution-processed red organic light-emitting diodes. Solubilities of these triplet emitters are high which enable them to be uniformly dispersed in the polymer host. Blade coating method is utilized to prepare organic multi-layers without mutual dissolution between different layers. 17 cd/A current efficiency, 10 lm/W power efficiency, and 8.8% external quantum efficiency can be achieved for the device with CsF/Al cathode. 10,000 cd/m2 is reached at 10 V. Similar quantum efficiency is also achieved with an electron-transport layer and LiF/Al cathode.
Keywords: Polymer light-emitting diodes; Ir complexes;

▶ Deposited nano-composite layers made of carbon nanotubes and poly(o-phenylenediamine) keep the stainless steel in a passive state in acidic solution. The oxide film underneath the nano-composite layer is chromium enrichment and has high corrosion resistance in concentrated chloride solutions. The CNTs indirectly assist the passivation of the stainless steel by catalyic oxygen reduction and polymer oxidation process.Electrodeposition of a nano-composite made of oxidized carbon nanotubes (CNTs) and a conductive polymer such as poly(o-phenylenediamine) (PoPD) on a stainless steel surface from aqueous solution was carried out by cyclic voltammetry. The presence of the CNTs enhanced the deposition of the PoPD and this enhancement was more significant in the presence of single walled carbon nanotubes (sCNT) by comparison to multi-walled carbon nanotubes (mCNT). Scanning electron microscope images indicated the incorporation of the CNTs in the PoPD layer. The nano-composite layer as well as the pure PoPD layer keeps the stainless steel in a passive state in acidic solution. The oxide film underneath the nano-composite layer is unique and showed high corrosion resistance in concentrated chloride solutions, which was confirmed by the presence of high contents of iron and chromium components. These findings suggest that the CNTs indirectly assist the passivation of the stainless steel by catalyic oxygen reduction and polymer oxidation process.
Keywords: Carbon nanotubes; Composite; Electrodeposition; Passivation; Poly(o-phenylenediamine);

▶ Boron doped C60 film is prepared by plasma assisted thermal evaporation technique. ▶ B:C60 film is used as a coating material for Si film anodes of lithium secondary batteries. ▶ The B:C60 coated Si anode exhibits a high reversible capacity of 1200 mAh g−1 after 50 cycles. ▶ The electronic conductivity and diffusion coefficients of Li-ion on the Si/electrolyte interface are increased due to the boron doping.In this work, boron doped fullerene (B:C60) films were prepared by the radio frequency plasma assisted thermal evaporation technique for use as a coating material for the silicon thin film anode in lithium secondary batteries. Raman and XPS analyses revealed that the boron atoms were well inserted into the fullerene film lattices. The effect of the B:C60 film on the electrochemical characteristics of the silicon thin film was studied by charge–discharge tests, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The B:C60 coated silicon film exhibited a high reversible capacity of more than 1200 mAh g−1 when cycled 50 times between 0 and 2 V at a current density of 1200 μA cm−2 (1.5 C). The film also showed good rate capacity at different current densities and a more improved coulombic efficiency of 87.7% in the first cycle in comparison with that of the C60 coated film electrode.
Keywords: Fullerenes; Thin films; Boron-doped; Anodes; Lithium secondary batteries;

Electrochemical synthesis of polypyrrole nanowires in the presence of gelatin by Dongtao Ge; Jing Mu; Sanqing Huang; Pengfei Liang; Oko Unathi Gcilitshana; Shan Ji; Vladimir Linkov; Wei Shi (166-172).
▶ Gelatin as biotemplate for the electrochemical synthesis of polypyrrole nanowires. ▶ Different kinds of electrodes lead to the nanowires with quite different morphologies. ▶ Nanowires with normal size are formed on ITO electrode and nickel electrode result in superlong nanowires.Biotemplating is an emerging, unique approach for the synthesis and organization of the organic or inorganic materials into well-defined nanostructures. In this article, conducting polymer polypyrrole (PPy) nanowires were electrochemically synthesized using a protein molecule, gelatin, as a template. The morphologies, microstructures, chemical compositions, and electrochemical performances of the obtained nanowires were investigated in detail. It was found that the gelatin played an important role in the formation of the PPy nanowires and the morphologies of the nanowires were closely related to the electrodes used. This work not only extended the application of gelatin to the synthesis of the conducting polymer nanowires, but also presented a simple and useful route to the fabrication of PPy nanowires with different length, from normal size to superlong size.
Keywords: Conducting polymers; Polypyrrole; Nanowires; Biotemplate; Electrochemistry;

X-ray irradiation: A non-conventional route for the synthesis of conducting polymers by J.F. Felix; R.A. Barros; W.M. de Azevedo; E.F. da Silva (173-176).
A non-conventional methodology for polyaniline (PANI) synthesis using X-ray irradiation is presented in this article, and shows the oxidants normally used in the (chemical or electrochemical) conventional synthesis of PANI are not necessary. The method uses only high energy photons to interact with nitrate ions (NO3 ) and aniline monomer in an aqueous solution. The polymerization mechanism has also been investigated using radical scavenger (DMSO), and the results suggest that the hydroxyl radical (OH) generated in situ during exposure to X-ray could be the main agent responsible for oxidation and subsequent polymerization of the aniline monomer. Characterization of the morphology of the polymer by scanning electron microscopy (SEM) reveals that the PANI obtained by X-ray presents a predominantly fibrillar morphology with an average fiber diameter of 90 nm. Additionally, thermogravimetric analysis (TGA), elemental analysis, gel permeation chromatography (GPC), conductivity measurements, and spectroscopic characterization in the UV–vis and IR regions, showed that the polymer obtained is the polyemeraldine salt (the conducting form of the polymer).
Keywords: Polyaniline; X-ray radiation; Ionizing radiation;

The effects of dopant on morphology formation in polyaniline graphite nanoplatelet composite by Ngo Trinh Tung; Tran Van Khai; Hoik Lee; Daewon Sohn (177-182).
Display Omitted▶ The type of dopants plays important role in morphology formation and phase interaction in PANi/graphite nanoplatelet composite. ▶ The morphology of PANi was changed in the composite when HCl was used as dopant and there is interaction between PANi and graphite nanoplatelet. ▶ These effects were not observed in case of selenious acid as dopant.In this study, a nanocomposite (SELA-PANi/GNP) consisting of selenious acid (SELA) doped polyaniline (PANi) and graphite nanoplatelet (GNP) was prepared, and its structure and properties – in particular, morphology formation, as well as interaction between the two phases – were investigated using scanning electron microscopy (SEM), UV–vis spectroscopy, FTIR spectroscopy, X-ray diffraction, and electrical conductivity measurement. A PANi/GNP nanocomposite prepared in aqueous HCl solution (HCl-PANi/GNP) was also prepared for comparison with SELA-PANi/GNP. The results reveal that the dopant plays an important role in morphology formation in PANi/GNP nanocomposites. When HCl was used as the dopant, PANi coated GNPs were formed and no phase separation between PANi and GNP was seen. In contrast, when SELA was used as the dopant, the morphology of PANi remained unchanged in the composite, owing to the formation of rod or sphere micelle PANi structure during in situ polymerization; no interaction was observed between the two phases. The crystalline structure of PANi was not affected by the incorporation of GNP. The electrical conductivity of PANi/GNP increased with increasing GNP content, because of the electrical bridge effect of GNP in the PANi matrix.
Keywords: Conducting polymer; Polyaniline; Graphite nanoplatelet; Conducting composite;

▶ 3,5-bis(4-methoxyphenyl)dithieno[3,2-b;2′,3′-d]thiophene electropolymerizes. ▶ Its device operates in the range of 0.0 and 0.2 Vs, between yellow and blue colors.Electropolymerization of 3,5-bis(4-methoxyphenyl)dithieno[3,2-b;2′,3′-d]thiophene BMPhDTT, having strong electron-donating methoxy groups, was performed, utilizing potentiodynamic method. The homopolymer was characterized by cyclic voltammetry (CV), Fourier transform infrared (FTIR) and UV–vis spectroscopy. Spectroelectrochemical and electrochromic properties of the homopolymer film were investigated and a PBMPhDTT/PEDOT device was constructed to understand its characteristics in detail. It was revealed that the potential range of 0.0–2.0 V is suitable for operating the device between yellow and blue colors. It indicated a good open circuit memory and stability.
Keywords: Electrochromic materials; Dithienothiophenes; P4S10;

Conducting polynaphthalenes from 1,1′-binaphthyl and 1,1′-bi-2-naphthol via electropolymerization by Baoyang Lu; Congcong Liu; Yuzhen Li; Jingkun Xu; Guodong Liu (188-195).
Polynaphthalene films with electrical conductivity of 10−3  S cm−1 were successfully electrosynthesized by direct anodic oxidation of 1,1′-binaphthyl (BN) and 1,1′-bi-2-naphthol (BNO) in CH2Cl2 containing additional boron trifluoride diethyl etherate (BFEE). The introduction of BFEE greatly lowered the onset oxidation potentials of the monomers compared with other supporting electrolytes. The resulting poly(1,1′-binaphthyl) (PBN) films exhibited good redox activity and stability in different monomer-free electrolytes. Moreover, FT-IR spectra and quantum chemistry calculation results proved that PBN and poly(1,1′-bi-2-naphthol) (PBNO) were both synthesized mainly through the coupling of the monomers at α-positions of the naphthalene ring. Fluorescence spectral determination showed that the polymers were typical blue light-emitters with solution quantum yields of 0.17 and 0.13, respectively. The substitution of hydroxyl and naphthyl groups did not change the emission wavelength of polynaphthalene (about 417 nm). Surface morphology determination revealed that regular particles with different sizes were orderly assembled on ITO electrode after electrochemical growth.
Keywords: Conducting polymers; Electrosynthesis; Polynaphthalenes; Fluorescence;

Enhanced electroluminescence from MEH-PPV-POSS:CuInS2 nanocomposite based organic light emitting diode by Gamze Saygili; Cihan Ozsoy; Ilker Oner; Ceylan Zafer; Canan Varlikli; Siddik Icli (196-202).
Polymer:quantum dot (QD) composites show enhanced optical and electronic properties. In this study, polymer light-emitting diodes (PLEDs) were fabricated and characterized using poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylenevinylene] end capped with polyhedral oligomeric silsesquioxanes (MEH-PPV-POSS) as a luminescent polymer host and copper indium disulfide (CuInS2) QDs as a dopant. The emitted light originates from MEH-PPV-POSS. Incorporation of CuInS2 QDs into polymer matrix until certain amounts improved the device performance in terms of electroluminescence (EL) intensity, luminance, current and power efficiency compared to that of the undopped device. The improvement is remarkable when the QD concentration is 0.3 wt% in the composite. We demonstrate that CuInS2 QDs provide a better balance of charge carriers and prevent the formation of polymeric aggregates.
Keywords: Quantum dot; Conjugated polymer; Electroluminescence; Light emitting diode;