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Synthetic Metals (v.161, #13-14)

Editorial Board (pp. iii).

Non-volatile organic memory based on CdSe nano-particle/PMMA blend as a tunneling layer by Jung-Min Kim; Dong-Hoon Lee; Jun-Ho Jeun; Tae-Sik Yoon; Hyun Ho Lee; Jong-Wook Lee; Yong-Sang Kim (pp. 1155-1158).
► In this work we demonstrated the NPs floating gate memory with CdSe NPs. ► The NPs could be easily fabricated using blended solution of CdSe NPS in PMMA. ► We have observed the memory effect of NPs, using CV and IV measurement. ► The devices had a large memory window of 15V. ► The device showed long charge retention ability of over 10,000s.The use of nano-particle/polymer blend as the tunneling layer for non-volatile organic memory is an alternative to change and improve the device characteristics and performances. A non-volatile organic memory based on the pentacene semiconductor/polymethylmethacrylate (PMMA)+CdSe nano-particle blend tunneling insulator/PMMA gate insulator, is demonstrated by a simple fabrication process. We have observed the charging and discharging effect of CdSe NPs, using capacitance–voltage and current–voltage measurement. The capacitance and current change were observed by a charge transport between the pentacene semiconductor and the CdSe nano-particles. In addition, good reliability was confirmed by the retention characteristics.

Keywords: CdSe nano-particles; Non-volatile organic memory; Nano-particle/polymer blend

Vapor phase polymerization of poly (3,4-ethylenedioxythiophene) on flexible substrates for enhanced transparent electrodes by Christopher M. Madl; Peter N. Kariuki; Jessica Gendron; Louis F.J. Piper; Wayne E. Jones Jr. (pp. 1159-1165).
Display Omitted► PEDOT thin films were deposited on flexible substrates by vapor phase polymerization. ► VPP PEDOT exhibited improved electrode behavior over current deposition methods. ► VPP PEDOT provides a highly ordered polymer network. ► PEDOT thin films remained stable upon exposure to ambient conditions. ► Our results show promise for the future industrial production of PEDOT electrodes.Recently, conducting polymer thin films have been investigated as transparent electrodes in photovoltaic devices and organic light emitting diodes. Due to its relatively high conductivity and excellent transmission in the visible region, poly (3, 4-ethyelenedioxythiophene) (PEDOT) has been shown to be a viable option for such applications. Herein described is a method for the vapor phase polymerization (VPP) of transparent PEDOT thin film electrodes on flexible polyethylene naphthalate (PEN) substrates and the comparison of this VPP method with two current approaches to PEDOT deposition: solution-based in situ polymerization and spin coating a dispersion of PEDOT:PSS. Electrical conductivities and UV–vis transmittances were measured for films produced by each of these methods, with VPP PEDOT showing both the highest conductivity (approx. 600S/cm) and transmittance (>94% at 550nm). The surface morphologies of the films were compared using AFM and SEM imaging. The stability of these PEDOT films, stored under ambient conditions, was investigated by monitoring the conductivity and transmittance of the thin films over time.

Keywords: PEDOT; Conducting thin film; Flexible electrode; Vapor phase polymerization

Nanofibers doped with a phosphorescent iridium complex: Synthesis, characterization, and photophysical property study by Junfeng Zhang; Yigui Li; Chun Hui; Jun Zhu (pp. 1166-1171).
Display Omitted► An Ir(III) complex is synthesized and doped into polymer matrix. ► The crystal structure and electronic nature are studied. ► Photophysical properties of composite fiber are better than those of pure complex. ► Polymer matrix provides a rigid framework for the emitter.In this article, we report a novel Ir(III) complex of Ir(acac)(F-BT)2 (acac=pentane-2,4-dione, and F-BT=2-(2-fluorophenyl)benzo[d]thiazole), including its synthesis, characterization, crystal structure, and electronic nature. Data suggest that Ir(acac)(F-BT)2 molecules crystallize in monoclinic system with double molecules per unit cell, and the onset electronic transition is assigned as a character of metal-to-ligand-charge-transfer. By doping Ir(acac)(F-BT)2 into a polymer matrix of poly(vinylpyrrolidone) (PVP), we investigate the morphology, emissive character, excited state lifetime, and photostability of the resulting composite nanofibers, as well as those of pure sample. Data comparison suggests that the emission of the composite nanofibers shows a blue shift tendency, the excited state lifetime and photostability of the composite nanofibers become longer and better than those of pure Ir(acac)(F-BT)2. The rigid framework provided by PVP matrix is responsible for above improvements.

Keywords: Iridium complex; Photoluminescence; Nanofiber; Crystal

Improved light extraction efficiency with angle independent electroluminescence spectrum in nano-phosphor coated white organic light emitting diodes by Arunandan Kumar; Ritu Srivastava; Priyanka Tyagi; D.S. Mehta; M.N. Kamalasanan (pp. 1172-1176).
Display Omitted► In this paper WOLED has been fabricated using a down conversion layer. ► Down conversion layer was deposited by using a low cost spin coating technique. ► Extraction efficiency has been enhanced by 1.6 times. ► Electroluminescence spectrum has been found to be independent of angle. ► Color co-ordinates remain invariant with time.We have fabricated down converted white organic light emitting diodes (WOLEDs) by using cerium doped YAG nano-phosphor after mixing them in binder poly venyle acetate (PVAc) polymer matrix by changing the concentration of nano-phosphor. Down conversion layer was deposited by using a low cost spin coating technique. The enhancement in extraction efficiency by a factor of about 1.6 was found comparable to other expansive techniques for the fabrication of down conversion layer. We have characterized WOLEDs for angle dependency of electroluminescence spectrum. The electroluminescence spectra at viewing angles from normal to the substrates up to 75° off normal remain almost unchanged and does not show the angle dependence observed for other extraction efficiency enhancement techniques. The emission spectrum was also found to be stable with time, which is a common problem with multilayer WOLED. The spectral uniformity with angle and time with enhanced extraction efficiency and cheap deposition technique could be of great interest for the application of down converted WOLED.

Keywords: WOLED; Nano-phosphor; Light extraction; Angle independent emission

Synthesis of the hole-transporting molecular glasses possessing pendant 3,6-dibromocarbazolyl moieties by Daiva Tomkute-Luksiene; Tadas Malinauskas; Maryte Daskeviciene; Valentas Gaidelis; Robertas Maldzius; Jonas Sidaravicius; Vytautas Getautis (pp. 1177-1185).
Display Omitted► 3,6-Dibromocarbazolyl-containing molecular glasses have been synthesized from glycidyl ethers. ► Electrophotographic parameters of molecular glasses doped with sensitizers have been studied. ► Nature of the linking fragments has a significant influence on photosensitivity. ► Nature of the linking fragments affects the Tg, allowing for more precise control over it.Synthesis and properties of the well-defined 3,6-dibromocarbazolyl-containing molecular glasses are reported. They were prepared by the nucleophilic opening of the oxirane ring of 1,3-di(3,6-dibromocarbazol-9-yl)-2-propanol glycidyl ether with aniline, 4-fluoro-, 4-bromoanilines, 2,5-dimercapto-1,3,4-thiadiazole or glycidyl ether of 1,3-di(carbazol-9-yl)-2-propanol with 4,4′-thiobisbenzenethiol and 1,9-nonanedithiol followed by bromination. The obtained materials were examined by various techniques including differential scanning calorimetry, NMR, MS, UV, PL spectrometry. The electrophotographic parameters of the molecular glasses doped with difluoroboron-1,3-bis(4-metoxyphenyl)-1,3-propanedionate have been studied. The electrochemical properties and ionization potentials, measured by electron photoemission method in air, were investigated.

Keywords: 3,6-Dibromocarbazole; Molecular glass; Ionization potential; Photosensitivity; Electrophotography

Increasing of stability depended on the position of alkoxy group in PPV by Suhee Song; Sung Heum Park; Jaeyeon Jung; Il Kim; Kwanghee Lee; Youngeup Jin; Hongsuk Suh (pp. 1186-1193).
► The stability is attributed to the electron-withdrawing effect of the fluoro groups. ► The PPDFV derivatives with difluoro groups on the vinylene unit were synthesized. ► The PL spectra of p-EHOPh-PPDFV with para-alkoxy phenyl group are very stable.In order to prevent the photo oxidation of the vinylene group of poly( p-phenylenevinylene) (PPV) series, the poly( p-phenylenedifluorovinylene) (PPDFV) derivatives with difluoro groups on vinylene unit were synthesized by Gilch polymerization using potassium tertbutoxide. The stability of the PPDFV backbone is attributed to the electron-withdrawing effect of the fluoro groups which prohibit the initial step of [2+2] cycloaddition for the oxidation of the vinylene unit. In photo-degradation experiments with white light, the PL spectra of m-EHOPh-PPDFV film is blue shifted about 19nm and the optical density of the side peak at 380nm is increased to 0.5 atomic unit. In case of p-EHOPh-PPDFV, the PL spectra show almost same maxima peaks at 448–450nm after irradiation from 1h to 5h. p-EHOPh-PPDFV with para-alkoxy phenyl group shows very stable PL spectra against photo oxidation as compared to the case of m-EHOPh-PPDFV with meta-alkoxy phenyl group.

Keywords: PLED; Color stability; PPVs; Fluoro

The two-photon absorption property of stilbazolium derivative with A–π–D–π–A structure: Influence by counter-anion and aggregation by Jun Hou; Xue Wu (pp. 1194-1198).
► We report two stilbazolium derivatives with differdent counter-anion (Br and OH). ► The two stilbazolium derivatives have a quadrupoles (A–π–D–π–A) structure. ► Different counter-anion causes different TPA cross-sections value. ► The two stilbazolium derivatives could aggregate in solution. ► The TPA cross sections show some enhancement in the aggregated state.This paper reported two stilbazolium derivatives with differdent counter-anion (OPVBr and OPVOH). The two stilbazolium derivatives have a quadrupoles (A–π–D–π–A) structure, in which pyridinium cation was used as electron-accept group and dibutoxy benzene as electron-donor group. Their linear optical properties were investigated through UV–vis and fluorescence spectral analysis. Two-photon laser induced fluorescence measurements have shown that OPVOH have a small TPA cross section (35GM), while OPVBr have a large TPA cross section (904GM). The TPA cross-sections value of OPVBr is increased with the concentration increasing due to the enhancement of intermolecular π–π stacking interaction.

Keywords: Two photons absorption; Stilbazolium derivative; Anion; Aggregation

Synthesis and photovoltaic properties of heteroaromatic low-band gap oligomers for bulk heterojunction solar cells by Vellaiappillai Tamilavan; Myungkwan Song; Sung-Ho Jin; Myung Ho Hyun (pp. 1199-1206).
Heteroaromatic low-band gap oligomers utilizing electron rich thiophene-pyrrol-thiophene unit and electron deficient bis-thiophenyl-thiadiazoloquinoxaline unit were prepared and applied to bulk heterojunction solar cells.Display Omitted► Two heteroaromatic low-band gap oligomers were prepared. ► The absorption of the oligomers was in the range of 300–1200nm in film. ► The optical bad gaps of the oligomers were 1.08eV and 1.10eV, respectively. ► The oligomers were applied to bulk heterojunction solar cells.Two new low band gap oligomers, TPyTDzQ-P1 and TPyTDzQ-P2, comprised of electron rich 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole or 1-(p-octylphenyl)-2,5-di(2-thienyl)pyrrole (TPyT) and electron deficient 6,7-di-2-methylpropane-4,9-bis-(thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline (DzQ) units were synthesized using the Suzuki polycondensation reaction. The oligomers were found to harvest the solar flux from the ultraviolet (300nm) to near infrared (1200nm) regions. The optical bad gaps of the two oligomers were calculated to be 1.08eV and 1.10eV, respectively, while the electrochemical band gaps were calculated to be 1.17eV and 1.19eV, respectively. The two oligomers were used as electron donor materials in bulk heterojunction (BHJ) solar cells. The solution processable bulk heterojunction solar cells with ITO/PEDOT:PSS/TPyTDzQ-P1 or TPyTDzQ-P2:PC70BM/TiO x/Al configuration showed a maximum power conversion efficiency (PCE) of 0.43% with a short-circuit current density ( Jsc) of 3.41mA/cm2, open-circuit voltage ( Voc) of 0.39V and fill factor (FF) of 32%.

Keywords: Bulk heterojunction solar cells; 1-Aryl-2,5-di(2-thienyl)pyrrole; Oligomers; Solar cells; Thiadiazoloquinoxaline

Fabrication and thermal degradation behavior of polystyrene nanoparticles coated with smooth polyaniline by Behzad Davodi; Mohammad Soleimani Lashkenari; Hossein Eisazadeh (pp. 1207-1210).
► Synthesize uniform core–shell PAn/PS nanoparticle in simple polymerization method. ► Increasing thin PAn layer will increase thermal stability of PS matrix. ► When HPC used as stabilizer Tg is 83.6°C and with DBSNa is 70.3°C. ► Activation energy of PAn/PS particle is larger than PS particle. ► Variety of surfactant does not significantly enhance Tonset of nanocomposite.Electrically conductive core–shell polyaniline/polystyrene (PAn/PS) nanoparticles were synthesized in the presence of different surfactants. PS core particles were prepared in microemulsion system and further coated with PAn by using in situ polymerization method. The core–shell structure of PAn/PS nanocomposite was determined by scanning electron microscopy (SEM) and FTIR measurement. Differential scanning calorimetry (DSC) and thermo gravimetric analyzer (TGA) were used to investigate the thermal stability and thermal degradation behavior of PS and PAn-coated PS particles. Both DSC and TGA curves revealed that the coating of a thin PAn layer on the surface of PS can drastically increase the thermal stability of PS matrix. TGA isothermal degradation data illustrate that the activation energy of the PAn/PS particle is larger than PS particle.

Keywords: Polyaniline; Core/shell structure; Thermal degradation; Activation energy

Supercapacitor performance of porous carbon nanofiber composites prepared by electrospinning polymethylhydrosiloxane (PMHS)/polyacrylonitrile (PAN) blend solutions by Bo-Hye Kim; Kap Seung Yang; Hee-Gweon Woo; Kyoichi Oshida (pp. 1211-1216).
Porous carbon nanofiber composites (NFCs) were prepared by electrospinning blended solutions of polyacrylonitrile (PAN) and polymethylhydrosiloxane (PMHS) in N,N-dimethylformamide (DMF). A PMHS concentration of 5wt% was regarded as the optimum concentration to obtain fibers of a uniform size with a homogeneous dispersion of silica, the maximum specific surface area and the highest conductivity (4.91Scm−1) after heat treatment at 800°C. The supercapacitor electrode prepared with 5wt% PMHS had the highest specific capacitance, 126.86F/g, and the highest energy density, 17.0–10.0Wh/kg, in the range of 400–20,000W/kg in a 6M KOH aqueous solution.

Keywords: Porous carbon nanofiber composites; Electrospinning; Polymethylhydrosiloxane; Silica; Supercapacitor

Polyaniline synthesis with iron(III) chloride–hydrogen peroxide catalyst system: Reaction course and polymer structure study by Michal Bláha; Martina Riesová; Jiří Zedník; Alojz Anžlovar; Majda Žigon; Jiří Vohlídal (pp. 1217-1225).
► FeCl3/H2O2 system gives nearly standard polyaniline if H2O2 concentration is kept low. ► Catalytic decomposition of H2O2 with Fe ions induces significant side reactions. ► Increasing H2O2 concentration causes or enhances partial self-doping of polyaniline. ► Self-doping was proved by UV/vis and resonance Raman but not by IR and NMR spectra. ► Phenolic groups are supposed to be acidic groups responsible for self-doping.We report on the catalytic polymerization of aniline (ANI) with FeCl3/H2O2 system, which can considerably lower contamination of neat polyanilines (PANIs) by side-products characteristic of stoichiometric polymerization. However, catalytically prepared PANIs exhibit reduced conductivity related most probably to side reactions involving radicals generated as integral components of the FeCl3/H2O2 system. Catalytic polymerization of ANI with FeCl3/H2O2 system was found to be the reaction of approximately 2nd order with respect to ANI and gives PANIs of a good quality only when [H2O2] in the reaction mixture was kept low, i.e., at under-stoichiometric ratios [H2O2]/[ANI]. At over-stoichiometric ratio [H2O2]/[ANI], PANIs of lowered conductivity, worse spectroscopic characteristics and increased size of PANI nanostructures were obtained; nevertheless, these PANIs were not over-oxidized to pernigraniline state. The reaction-time profiles of the open-circuit potential of reaction mixtures exhibited an inflection related to the H2O2 depletion from the system. Total consumption of H2O2 exceeded its consumption necessary on ANI polymerization, which proves partial decomposition of H2O2 by Fe ions. UV/vis and resonance Raman spectra indicate incomplete deprotonization of PANIs prepared with FeCl3/H2O2 system and subsequently treated with aqueous ammonia, which proves partial self-doping of these PANIs. However, IR and NMR spectra indicate rather low extent of self-doping. It has been proposed that self-doping of PANI involves phenolic OH groups originated from side reactions involving radical species formed from H2O2.

Keywords: Catalytic oxidative polymerization; Conducting polymer; Hydrogen peroxide; Iron(III) chloride; Polyaniline

Prediction of wear properties in A356 matrix composite reinforced with B4C particulates by Mohsen Ostad Shabani; Ali Mazahery (pp. 1226-1231).
In the present study, wear properties of A356 unreinforced alloy and composites with different vol.% of boron carbide particles were investigated. It is noted that composites exhibit better wear resistance compared to unreinforced alloy. According to the differences in wear rates of the composites, two separate wear rate were identified as low and high wear rate regimes. A combination of artificial neural network (ANN) and finite element technique (FEM) was implemented in order to predict the composites wear behavior. The FEM method is used for discretization and to calculate the transient temperature field of quenching. It is observed that predictions of ANN are consistent with experimental measurements for A356 composite and considerable savings in terms of cost and time could be obtained by using neural network model.

Keywords: Metal matrix composites (MMCs); Wear resistance; ANN; FEM

Factors affecting the radical scavenging activity of polyaniline by Ashveen V. Nand; Sudip Ray; Allan J. Easteal; Geoffrey I.N. Waterhouse; Marija Gizdavic-Nikolaidis; Ralph P. Cooney; Jadranka Travas-Sejdic; Paul A. Kilmartin (pp. 1232-1237).
Display Omitted► Polyaniline nanorods formed under falling pH conditions are superior radical scavengers to granular polyaniline. ► Polymer oxidation state determines radical scavenging capacity ahead of surface area or conductivity. ► Granular polyaniline has a higher BET surface area than polyaniline nanorods.Polyaniline was chemically synthesized by oxidizing aniline with ammonium persulfate with and without hydrochloric acid (G-PANI and NR-PANI, respectively). NR-PANI and G-PANI were dedoped with ammonium hydroxide to yield NR-PANIdd and G-PANIdd. SEM images revealed a typical granular morphology for G-PANI and G-PANIdd, while NR-PANI, formed using a ‘falling pH method’, and NR-PANIdd, consisted of micro/nanorods and flakes. The samples were characterized using FTIR and the level of oxidation was determined by X-ray photoelectron spectroscopy (XPS). The surface area of the samples was measured by the BET method. The free radical scavenging activity, using the DPPH assay, showed the following ranking: NR-PANI>G-PANI≈NR-PANIdd>G-PANIdd. The radical scavenging activity of the polyanilines did not correlate with conductivity or surface area measurements, but was critically dependent upon the level of oxidation, and higher activity was obtained with the more reduced polyaniline samples.

Keywords: Polyaniline; Nanorods; DPPH; Surface area; Radical scavenging

Low band gap copolymer containing naphthalene-1,4,5,8-tetracarboxylic bisimide: Synthesis, properties and organic solar cell applications by Phimwipha Piyakulawat; Anusit Keawprajak; Jörg Wlosnewski; Michael Forster; Udom Asawapirom (pp. 1238-1244).
Display Omitted► Novel copolymers based on fluorene, naphthalene bisimide, and dithienylbenzothiadiazole. ► Incorporation of dithienylbenzothiadiazole increase the LUMO and the charge transfer. ► Copolymer exhibits two broad absorption bands in the range of 300–750nm. ► PFTBTN shows small optical band gap with 1.69eV.A new alternating donor–acceptor copolymer, poly{[2,7-(9,9′-dioctylfluorene)- alt-5,5′-(bis(2,2′-thiophene)-4,7-(2,1,3-benzothiadiazole)]- co-[2,7-(9,9′-dioctylfluorene)- alt-5,5′-(bis(2,2′-thiophene)-2,6-naphthalene-1,4,5,8-tetracarboxylic- N, N′-di(2-ethylhexyl)imide]} (PFTBTN), was synthesized for the use of photovoltaic cells. The copolymer containing fluorene, as the donor segment and naphthalene bisimide, dithienylbenzothiadiazole, as the acceptor segment was polymerized via Suzuki couplings to achieve a polymer with a narrow band gap. The band gap values of the copolymer film determined from optical and electrochemical measurements were 1.69 and 2.06eV, respectively. The optical absorption spectrum revealed two broad bands in the range of 300–750nm. Electrochemical studies indicate sufficiently deep HOMO/LUMO levels that enable a high open-circuit voltage when fullerene derivative ([6,6]-phenyl-C61 butyric acid methyl ester) was used as an electron acceptor. Bulk heterojunction photovoltaic cells were fabricated in the device configuration of ITO/PEDOT:PSS/PFTBTN:PCBM/TiO x/Al. Open-circuit voltage reached 0.74V with the maximum energy conversion efficiency of 0.40% under the illumination of AM 1.5 (100mW/cm2).

Keywords: Naphthalene bisimide; Low band gap copolymer; Photovoltaic cell; Bulk heterojunction

Synthesis and electrochemical, electrochromic and electrical properties of novel s-triazine bridged trinuclear Zn(II), Cu(II) and Lu(III) and a tris double-decker Lu(III) phthalocyanines by Pınar Şen; Fatih Dumludağ; Bekir Salih; Ali Rıza Özkaya; Özer Bekaroğlu (pp. 1245-1254).
Novel trinuclear zinc, copper and lutetium phthalocyanines and a tris double-decker lutetium phthalocyanine have been prepared and characterized. Electrical properties of all trinuclear complexes and electrochemical, in situ spectroelectrochemical and electrochromic properties of the tris double-decker lutetium phthalocyanine were also investigated.Display Omitted► The new s-triazine-bridged trinuclear Zn(II), Cu(II) and Lu(III) phthalocyanines, and a tris double-decker Lu(III) phthalocyanine have been synthesized and characterized. ► The d.c. and a.c. conductivities of the phthalocyanine compounds were measured as a function of temperature. ► The temperature dependence of the frequency exponent showed that the conduction in these compounds is due to hopping of charge carriers. ► The tris double-decker phthalocyanine complex showed well-defined electrochromic behaviour with green-blue and blue-purple colour transitions.The new s-triazine-bridged trinuclear Zn(II) and Cu(II) phthalocyanines have been synthesized from the reaction of corresponding anhydrous metal salts, Zn(OAc)2 and CuCl with 4,5-bis(hexylthio)-phthalonitrile and 2,4,6-tris(2-thiophthalonitrile)-s-triazine. The tris phthalonitrile derivative of s-triazine was prepared from the reaction of 4-nitrophthalonitrile and thiocyanuric acid in dry dimethylformamide as solvent using K2CO3 as the base. The same route was applied to prepare the trinuclear Lu(III) phthalocyanine analogue. The conversion of tris phthalonitrile into its isoindoline derivative was accomplished by bubbling ammonia gas through a solution in methanol in the presence of sodium methoxide. The cyclization of two different isoindoline derivatives and 4,5-bis(hexylhthio)-1,2-diiminoisoindoline, with lutetium (III) acetate in dimethylformamide gave trinuclear Lu(III) phthalocyanine. The reaction of this complex with octakis-hexylthio phthalocyanine led to the isolation of tris double-decker Lu(III) phthalocyanine. The structures of the target compounds were confirmed by elemental analysis, UV–vis, IR and MALDI-TOF mass spectroscopies. The d.c. and a.c. conductivities of the phthalocyanine compounds were measured as a function of temperature. The small value of pre-exponential factor suggested the conduction by localized states in the band tails and by localized states near the Fermi level. The temperature dependence of the frequency exponent showed that the conduction in these compounds is due to hopping of charge carriers. The tris double-decker phthalocyanine complex showed well-defined electrochromic behaviour with green-blue and blue-purple colour transitions.

Keywords: Trinuclear phthalocyanines; Tris double-decker; A.c. conductivity; Impedance spectra; Electrochemistry; Electrochromism

Preparation of porous nanorod polyaniline film and its high electrochemical capacitance performance by Jiguo Tu; Jungang Hou; Wei Wang; Shuqiang Jiao; Hongmin Zhu (pp. 1255-1258).
► Porous nanorod polyaniline films were electrochemically polymerized. ► The highest specific discharge capacitance was 569.1Fg−1. ► The discharge capacitance retained 97.7% over 1000 cycles.Nano-sized polyaniline (PANI) films were electrochemically deposited onto an ITO substrate by a pulse galvanostatic method (PGM) in an aqueous solution. The morphology of the as-prepared PANI film was characterized using a field emission scanning electron microscope (FESEM). It was observed that the as-prepared PANI films were highly porous, and showed a nano-sized rod-like or coralline-like morphology depending on the charge loading performed in the electropolymerization process. Furthermore, the PANI films were electrochemically measured by the galvanostatic charge–discharge (GCD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests in 1molL−1 HClO4 solution. The results showed that such PANI films had a favorable electrochemical activity and an excellent capacitance. The rod-like PANI film prepared with the charge loading of 1000mC showed the highest discharge capacitance of 569.1Fg−1 at a low current density of 1Ag−1. The discharge capacitance retained 97.7% after 1000 cycles at a large current density of 10Ag−1.

Keywords: Polyaniline; Electropolymerization; Nano-sized; Supercapacitor

Long aging time thermal degradation of the ac conductivity and complex permittivity of conducting polypyrrole by I. Sakellis; A.N. Papathanassiou; J. Grammatikakis (pp. 1259-1263).
► The dispersive region of the dc conductivity of conducting polypyrrole is practically invariant to one year thermal ageing. ► Cross-over frequency links to the dc conductivity. ► Dielectric loss peak splits into two components within two years thermal ageing.The modification of the ac conductivity and the complex permittivity of conducting polypyrrole was monitored throughout a two years thermal aging at 343K. Reduction of the cross-over frequency is correlated with the degradation of dc-conductivity, while the ac conductivity region corresponding to the so-called ‘universal’ dielectric relaxation remains practically insensitive during the first year of ageing, which implies a collective co-operativity among multiple degradation processes that yield a practically time-independent effective disordered environment. A broad dielectric loss peak recorded in fresh specimens splits into two distinct relaxations for intermediate stages of the annealing process. The aging-time evolution of the dc component and the relaxations are qualitatively analysed and time constants are determined.

Keywords: PACS; 72.80.Le; 77.22.Gm; 71.20.RvPolypyrrole; Conducting polymers; Thermal aging; ac-conductivity; Dielectric loss

1-(3-Methoxycarbonyl)propyl-2-selenyl-[6,6]-methanofullerene as a n-Type Material for Organic Solar Cells by Shih-Ching Chuang; Chih-Wei Chiu; Shang-Chieh Chien; Chih-Wei Chu; Fang-Chung Chen (pp. 1264-1269).
Display Omitted► We synthesized 1-(3-methoxycarbonyl)propyl-2-selenyl-[6,6]-methanofullerene (SeCBM) as a n-Type Material for Organic Solar Cells. ►SeCBM displays similar UV–Vis absorption pattern as that ofThCBM and show hypsochromic shifts as compared to that ofPCBM in the visible region. ►SeCBM exhibits similar LUMO energy level as its sulfur analogueThCBM and lower energy level than that ofPCBM. ► Thin film consisting ofSeCBM/P3HT exhibited an average power conversion efficiency of 3.26% and a champion efficiency as high as 3.81% under AM 1.5G irradiation.Demand for green and renewable energy is stimulating research into future materials for energy production. Thin films of materials possessing both electron accepting and donating functions play a unique role in solar energy technology because of their light weight, flexibility, and economical, low-temperature, and large-area fabrication. A [60]fullerene derivative, [6,6]-2-selenyl-C61-butyric acid methyl ester (SeCBM), has been synthesized in three steps, namely through Friedel–Crafts acylation of selenophene, hydrazone formation and Bamford-Steven reaction. Organic photovoltaic device incorporating SeCBM and the conducting polymer P3HT exhibited an average power conversion efficiency of 3.26% and a champion efficiency as high as 3.81% under AM 1.5G irradiation.

Keywords: [60]Fullerene; Photovoltaic; Device; Organic solar cell; P3HT

Colored nanoparticles dispersions as electronic inks for electrophoretic display by Da Li; Yuan Le; Xin-Yan Hou; Jian-Feng Chen; Zhi-Gang Shen (pp. 1270-1275).
► Phthalocyanine green (CuPcCl) nanoparticles with a mean size of 120nm was prepared by anti-solvent recrystallization method and combined with in situ modification to improve the electrophoretic properties and dispersion ability in organic medium. ► Stable TiO2/C2Cl4 dispersion was prepared by coated TiO2 surface with trimethoxyoctylsilane. ► The green CuPcCl and white TiO2 dispersions were suitable as electronic ink and showed potential value in the application of electrophoretic display.Phthalocyanine green (CuPcCl) nanoparticles was successfully prepared by anti-solvent recrystallization method and combined with in situ modification to improve the electrophoretic properties and dispersion ability in organic medium. The produced particles were characterized by SEM, FT-IR and ζ-potential test. It was found that the particles exhibited 120nm with spherical shape and narrow size distribution when the modifier was mixture of CTAB and PVP. Sedimentation ratio of the prepared CuPcCl particles in tetrachloroethylene was nearly down to zero within 30 days and the ζ-potential was 26.8mV. In addition, stable TiO2/C2Cl4 dispersion was prepared by coated TiO2 surface with trimethoxyoctylsilane. The sedimentation ratio of the modified TiO2 was nearly 7.6% within 30 days, and the ζ-potential value was −28.9mV. The particle size was about 300nm with spherical morphology. The results demonstrated that green CuPcCl and white TiO2 dispersions were suitable as electronic ink and showed potential value in the application of electrophoretic display.

Keywords: Phthalocyanine green; Titanium dioxide; Nanoparticle dispersions; Modification; Electrophoretic display

Diamine ligands with multiple coplanar conjugation rings and their phosphorescent copper complexes: Synthesis, characterization, crystal structures, and photophysical property by Jijun Xu; Dong Yun; Bin Lin (pp. 1276-1283).
Display Omitted► Cu(I) complexes with multiple coplanar conjugation rings are synthesized. ► Their crystal structures and photophysical properties are investigated in detail. ► The free rotation of conjugation rings may compromise the conjugation. ► Excess coplanar conjugation moiety is harmful for emissive state.In this paper, we report a series of diamine ligands with multiple coplanar conjugation rings and their corresponding phosphorescent Cu(I) complexes, including their synthesis, crystal structures, photophysical properties, and electronic nature. Geometric parameters suggest that the Cu(I) center localizes at a distorted tetrahedral geometry within the Cu(I) complexes. Theoretical calculation reveals that all emissions originate from triplet metal-to-ligand-charge-transfer excited state. It is found that the free rotation of conjugation rings may compromise the coplanar plane and thus has little effect on the photophysical property of their corresponding Cu(I) complexes. But excess coplanar conjugation moiety is harmful for emissive state. The detailed quenching mechanism is investigated.

Keywords: Cu(I) complexes; Single crystal; Coplanar conjugation; Luminescence quenching

CNT/PEDOT core/shell nanostructures as a counter electrode for dye-sensitized solar cells by Hyun-Jun Shin; Sang Soo Jeon; Seung Soon Im (pp. 1284-1288).
► CNT/PEDOT core/shell nanostructures, with PEDOT shell thickness of 2–5 nm, were fabricated by chemical oxidative polymerization using anionic surfactant dodecylbenzene sulfonic acid. ► CNT/PEDOT exhibited improved electrical conductivity as well as higher polymerization yield than those of pure PEDOT. ► The dye-sensitized solar cell using CNT/PEDOT counter electrode with the lowest surface resistivity showed enhanced conversion efficiency (4.62%) than CNT (3.88%) and PEDOT (4.32%).CNT/PEDOT nanostructures composed of carbon nanotube (CNT) cores and poly(3,4-ethylenedioxythiophene) (PEDOT) shells were synthesized by chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) using FeCl3 and dodecylbenzene sulfonic acid (DBSA) as the oxidant and surfactant, respectively. The resulting CNT/PEDOT nanostructures had a PEDOT layer thickness of 2–5nm that exhibited not only higher polymerization yield but also enhanced thermal stability and electrical conductivity relative to pure PEDOT. N-Methyl-2-pyrrolidone (NMP)-based CNT/PEDOT paste containing polyvinylidene fluoride (PVDF) as a binder was painted directly onto fluorine-doped tin oxide (FTO) glass for use as a counter electrode (CE) material in dye-sensitized solar cells (DSSCs). While DSSCs made of pure CNT and PEDOT CE exhibited power conversion efficiencies of ∼3.88% and 4.32% under standard AM 1.5 sunlight illumination, respectively, the cell efficiency was enhanced to ∼4.62% with the CNT/PEDOT CE. This enhancement was due to the improved fill factor of the CNT/PEDOT-based DSSC realized by the increased electrical conductivity of the CNT/PEDOT composite.

Keywords: Dye-sensitized solar cell; Counter electrode; Poly(3,4-ethylenedioxythiophene); Carbon nanotube

Synthesis and photovoltaic application of donor–acceptor type copolymers containing 9-cyanomethylenefluorene derivatives with chemically tunable electronic properties by Shigeyoshi Sato; Kazuhito Hashimoto; Keisuke Tajima (pp. 1289-1298).
Display Omitted► New electron-deficient building blocks for semiconducting copolymers are synthesized. ► Substituents strongly affect the electron withdrawing ability of the blocks. ► LUMO energy levels of the polymers can be tuned. ► Performance of photovoltaic devices shows the importance of LUMO level alignments.Four 9-cyanomethylenefluorene derivatives were synthesized as a new class of electron-deficient building blocks for donor–acceptor (D–A) type alternating copolymers. UV–vis absorption spectroscopy, cyclic voltammetry and density functional theory calculations show that the substituent X at the cyanomethylene unit, depending on its electron-withdrawing ability (X=–H, –CONMe2, –COO iBu and –CN), can continuously control the LUMO energy level of the monomer. D–A type copolymers were synthesized using the derivatives and an oligothiophene as the electron-donating block. The photovoltaic performance of D–A copolymer:PCBM bulk heterojunction devices shows the importance of LUMO level alignment to achieve efficient charge separation at the donor/acceptor interface. After optimization, the power conversion efficiency of the device with X=–H reached 1.14% with VOC of 0.61V, JSC of 3.24mAcm−2 and FF of 0.58 under the irradiation of AM1.5 simulated solar light. The electronic properties of the copolymers correlated well with the electron-withdrawing ability of the monomers while the structure of the π-conjugated backbone was preserved, demonstrating the advantage of the chemically tunable monomer design.

Keywords: Conjugated polymers; Thin films; Copolymerization; Energy levels; Polymer solar cells

Photovoltaic and impedance spectroscopy analysis of p–n like junction for dye sensitized solar cell by I.S. Yahia; Hoda S. Hafez; F. Yakuphanoglu; B. Filiz Senkal; M.S.A. Abdel Mottaleb (pp. 1299-1305).
► A dye-sensitized solar cell based on nanostructure TiO2 coated with PCBM:P3HT blends was fabricated. ► The photovoltaic properties at different illumination intensities were measured and analyzed. Also, the photovoltaic parameters were extracted. ► Impedance spectroscopy including capacitance–voltage, the conductance–voltage, the series resistances–voltage characteristics of the DSSC solar cell were measured in a wide range of frequency for the first time. ► Negative capacitance was found in the studied cell and was intercepted based on the DSSC structure for the first time. ► The photovoltaic performance of the dye-sensitized solar cell can be improved using various organic semiconductors.A dye-sensitized solar cell based on nanostructure TiO2 and PCBM:P3HT blend was fabricated and the photovoltaic and impedance spectroscopy properties of the solar cell were investigated. The solar cell gives a short circuit current density of 0.75mA/cm2 and an open circuit voltage of 0.60V under AM1.5. The photovoltage of the solar cell was greatly enhanced by PCBM:P3HT blend. The capacitance–voltage, the conductance–voltage, the series resistances–voltage characteristics of the solar cell were measured in a wide range of frequency for the first time for DSSC applications. The capacitance–voltage shows a behavior from the positive to negative capacitance due to injection of electrons from the FTO electrode into TiO2. It is evaluated that the photovoltaic performance of the dye-sensitized solar cell can be improved using various organic semiconductors.

Keywords: TiO; 2; nanostructure; PCBM:P3HT; Photovoltaic properties; Impedance spectroscopy; Positive and negative capacitance

Synthesis of poly(aniline- co-5-aminosalicylic acid) and its properties by Shaolin Mu (pp. 1306-1312).
The copolymerization of aniline and 5-aminosalicylic acid (ASA) in H2SO4 solution was first carried out on a glassy carbon electrode using cyclic voltammetry. The spectra of IR and1H NMR demonstrated the presence of –OH group, –COOH group, and free radical in the polymer, indicating that the copolymerization of aniline and ASA took place under the electrolysis to form poly(aniline- co-5-aminosalicylic acid) (PAASA). The electric properties of PAASA are strongly dependent on the monomer concentration ratio in a reaction mixture and the upper switching potential used for the synthesis of the copolymer and the electrode materials. PAASA synthesized under the optimal conditions has a good redox activity from pH<1 to pH 12.0; and in particular, only a 37.6% decay of the redox activity was observed after consecutive cycles from pH 4.0 to 12.0 based on cyclic voltammograms. The spectra of1H NMR revealed some unexpectedly magnetic properties of the deprotonated PAASA. This would be the primary cause why PAASA still holds a high redox activity at pH 12.0. The conductivity of PAASA is 0.58Scm−1 that is lower than that of polyaniline.

Keywords: Aniline and 5-aminosalicylic acid; Electrochemical copolymerization; Redox activity; Spectra of IR and NMR; Morphology

Electrochemical synthesis and corrosion behavior of polyaniline-benzoate coating on copper by Milica M. Gvozdenović; Branimir Z. Jugović; Jasmina S. Stevanović; Branimir Grgur; Tomislav Lj. Trišović; Zvonimir S. Jugović (pp. 1313-1318).
Electrochemical polymerization of polyaniline (PANI) coating on copper electrode was performed galvanostatically in the current density range between 0.50 and 1.25mAcm−2, from aqueous solution of 0.3moldm−3 sodium benzoate and 0.2moldm−3 aniline. The corrosion behavior of PANI coated copper and copper electrode exposed to 0.5moldm−3 sodium chloride solution was investigated by potentiodynamic and electrochemical impedance spectroscopy techniques. It was observed that thin PANI (5μm) coating had provided efficient protection (∼96%) to copper in 0.5moldm−3 sodium chloride solution. Unusual initial impedance behavior to that normally observed with conventional organic coatings was attributed to dedoping of benzoate anions from the polymer coating.

Keywords: Electrochemical polymerization; Sodium benzoate; Polyaniline; Copper

Synthesis, electrochemical and spectroelectrochemical properties of highly soluble tetra substituted phthalocyanines with [4-(thiophen-3-yl)-phenoxy] by Ali Erdoğmuş; Atıf Koca; Ahmet Lütfi Uğur; İbrahim Erden (pp. 1319-1329).
► Zinc, oxo-titanium, cobalt, and manganese phthalocyanine derivatives substituted with nonperipheral 3-( tetra[4-(thiophen-3-yl)-phenoxy] moieties have been synthesized and characterized. ► The introduction of [4-(thiophen-3-yl)-phenoxy] on the ring results in precludes aggregation. ► Incorporation redox active metal centers, CoII, TiIVO and MnIIIOAc into the phthalocyanine core extend the redox richness of the Pc ring. ► Quantification of xyz color coordinates of the each electrogenerated anionic and cationic redox species indicates possible polyelectrochromic applications.Zinc, oxo-titanium, cobalt, and manganese phthalocyanine derivatives substituted with nonperipheral 3-( tetra[4-(thiophen-3-yl)-phenoxy] moieties have been synthesized and characterized by elemental analysis, IR,1H NMR spectroscopy, electronic spectroscopy, and mass spectra. The compounds have good solubility in various polar and nonpolar organic solvents and not aggregated (in the same solvents) within a wide concentration range. Electrochemical and spectroelectrochemical measurements exhibit that incorporation redox active metal centers, CoII, TiIVO and MnIIIOAc into the phthalocyanine core extend the redox richness of the Pc ring with the reversible metal-based reduction and oxidation couples of the metal centers in addition to the common Pc ring-based electron transfer processes.

Keywords: Oxotitanium; Cobalt; Manganese; Phthalocyanines; Electrochemistry; Spectroelectrochemistry

Synthesis and characterization of a novel fullerene derivative containing carbazole group for use in organic solar cells by Dongbo Mi; Ji-Hoon Kim; Sung Cheol Yoon; Changjin Lee; Jin-Kyun Lee; Do-Hoon Hwang (pp. 1330-1335).
► We synthesized a novel carbazole-group-containing fullerene derivative. ► The solubility of the new derivative in common organic solvents was found to be high. ► Bulk hetero-junction photovoltaic devices with the new fullerene derivative as the electron acceptor and P3HT as the electron donor were fabricated and characterized.A novel carbazole-group-containing fullerene derivative (CBZ-C60) with good solubility in common organic solvents was synthesized. This derivative was analyzed by using many techniques such as NMR, FAB-MS, FTIR and UV–vis absorption spectroscopy. Further, bulk heterojunction photovoltaic devices were fabricated. Since the LUMO energy level of CBZ-C60 was higher than that of fullerene, the open-circuit voltage ( Voc) of devices based on CBZ-C60 was higher than that of devices based on fullerene. The power-conversion efficiency was highest for devices with composite thin films that have P3HT/CBZ-C60 composition ratios of 1:1 and were annealed at 150°C for 10min. The maximum Voc, short-circuit current density, and PCE of the best device were 0.64V, 2.32mA/cm2, and 0.48%, respectively.

Keywords: Fullerene derivatives; Carbazole; Organic solar cell

Syntheses and characterization of new low-band gap polymers containing 4 H-cyclopenta[ def]phenanthrene unit and 4,7-di(thien-2-yl)-2 H-benzimidazole-2-spirocyclohexane for photovoltaic device by Jaehong Kim; Sung Heum Park; Jinwoo Kim; Shinuk Cho; Il Kim; Kwanghee Lee; Hongsuk Suh (pp. 1336-1342).
Display Omitted► Synthetic trials for new low-band gap polymers for solar cell. ► Synthetic trials to decrease the band gap of copolymers are successful. ► Synthetic trial to increase solubility on the electron-deficient moiety is successful. ► We show the possibility to find highly soluble new electron-deficient moiety.Two new low-band gap polymers, poly[(2,6-(4,4-bis(2′-ethylhexyl)-4 H-cyclopenta[ def]phenanthrene))- alt-(5,5-(4′,7′-di(thien-2-yl)-2 H-benzimidazole-2′-spirocyclohexane))] (PCPP-DTCHBI) and poly[(2,6-(4,4-bis(4-((2-ethylhexyl)oxy)phenyl)-4 H-cyclopenta[ def]phenanthrene))- alt-(5,5-(4′,7′-di(thien-2-yl)-2 H-benzimidazole-2′-spirocyclohexane))] (PBEHPCPP-DTCHBI), were synthesized and characterized for the photovoltaics. These polymers showed typical characteristics of low-band gap polymers through the internal charge transfer (ICT) between 4 H-cyclopenta[ def]phenanthrene as the electron-rich unit and di(thien-2-yl)-2 H-benzimidazole-2′-spirocyclohexane as the electron-deficient unit. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels are −5.52 and −3.82eV for PCPP-DTCHBI, and −5.36 and −3.76eV for PBEHPCPP-DTCHBI, respectively. Optical band gaps of PCPP-DTCHBI and PBEHPCPP-DTCHBI are 1.70 and 1.60eV, respectively. As compared to the case of poly[(2,6-(4,4-bis(2′-ethylhexyl)-4 H-cyclopenta[ def]phenanthrene))- alt-(5,5-(4′,7′-di(thien-2-yl)-2,1,3-benzothiadiazole))] (PCPP-DTBT), PCPP-DTCHBI shows deeper HOMO energy levels by 0.12eV and lower band gap by 0.3eV. The FET mobilities of PCPP-DTCHBI and PBEHPCPP-DTCHBI are 1.19×10−4 and 5.11×10−5cm2/Vs, respectively, and the power conversion efficiencies of the solar cell devices of the PCPP-DTCHBI and PBEHPCPP-DTCHBI blended with [6,6]phenyl-C71-butyric acid methyl ester (PC71BM) are 1.01% and 0.53%, respectively. The newly designed DTCHBI unit can be used as the electron-deficient moiety inducing efficient ICT for low band gap generation while keeping deep HOMO energy level of the polymer.

Keywords: Cyclopentaphenanthrene; 2; H; -Benzimidazole; Polymer solar cell; Internal charge transfer; Low-band gap

3,6-Di(9-carbazolyl)-9-(2-ethylhexyl)carbazole based single-layer blue organic light emitting diodes by V.V. Cherpak; P.Y. Stakhira; D.Yu. Volynyuk; J. Simokaitiene; A. Tomkeviciene; J.V. Grazulevicius; A. Bucinskas; V.M. Yashchuk; A.V. Kukhta; I.N. Kukhta; V.V. Kosach; Z.Yu. Hotra (pp. 1343-1346).
► The blue OLED based on non-doped film of TCz1 was fabricated. ► Electroluminescence spectrum is similar to photoluminescence spectrum. ► Device exhibit high current efficiency of 11.5cd/A and EQE of 1.72%.The electroluminescent device ITO/CuI/3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole(TCz1)/Ca/Al in which TCz1 for the first time was used as the emitting layer, was fabricated by means of vacuum deposition. The device emits blue light with a peaks at 388 and 406nm at 4.5V, with high current efficiency values (11.5cd/A) and external quantum efficiency (1.72%).

Keywords: Organic light emitting devices; Carbazole derivates; Blue emitting

Effects of iron(III) p-toluenesulfonate hexahydrate oxidant on the growth of conductive poly(3,4-ethylenedioxythiophene) (PEDOT) nanofilms by vapor phase polymerization by Mohammad Amdad Ali; Hyunho Kim; Chiyoung Lee; Hoseok Nam; Jaegab Lee (pp. 1347-1352).
Display Omitted► Final thickness of poly(3,4-ethylenedioxythiophene) (PEDOT) films found that the polymerization was chemical reaction limited, and that the final film thickness was linearly dependent on oxidant concentration. ► The influence of spin-coated iron(III) p-toluenesulfonate hexahydrate (Fe(PTS)3) oxidant solution on the polymerization and resulting PEDOT structures was also investigated. ► The formation of a surface organic layer, as a result of spinning, promoted uniform and smooth PEDOT films.Study of the effects of evaporation time and oxidant concentration on the polymerization rate and final thickness of poly(3,4-ethylenedioxythiophene) (PEDOT) films found that the polymerization was chemical reaction limited, and that the final film thickness was linearly dependent on oxidant concentration. The influence of spin-coated iron(III) p-toluenesulfonate hexahydrate (Fe(PTS)3) oxidant solution on the polymerization and resulting PEDOT structures was also investigated. Spin-coated low-density (1.35g/cm3) Fe(PTS)3 oxidant solution, consisting of highly anisotropic paracystalline structures, provided open frameworks for the growth of conducting polymers, leading to a-axis oriented paracrystalline PEDOT films. Polymerization proceeded through the oxidant framework, increasing the density of PEDOT-filled oxidant solution to 2.01g/cm3 with negligible change of thickness. Furthermore, the formation of a surface organic layer, as a result of spinning, promoted uniform and smooth PEDOT films.

Keywords: PEDOT; Vapor phase polymerization; Fe(PTS); 3; Conducting polymer

Solid-state oxidation of aniline hydrochloride with various oxidants by Ivana Šeděnková; Elena N. Konyushenko; Jaroslav Stejskal; Miroslava Trchová; Jan Prokeš (pp. 1353-1360).
Display Omitted► Aniline hydrochloride was oxidized in the solid state with three different oxidants: ammonium peroxydisulfate, iron(III) chloride, and silver nitrate. ► Solid-state reaction with APS leads to a conducting product with conductivity of 0.21Scm−1. ► Non-conducting material was obtained after reaction with iron(III) chloride. ► The oxidation with silver nitrate yields a composite material, polyaniline salt and silver particles, with conductivity 1.5×10−3Scm−1.Aniline hydrochloride was oxidized in the solid state with three different oxidants: ammonium peroxydisulfate, iron(III) chloride, and silver nitrate. Polyaniline salt was obtained after a few hours when ammonium peroxydisulfate was used as an oxidant. The polymerization of aniline hydrochloride with silver nitrate leads to polyaniline only after several days; in the case of iron(III) chloride, aniline oligomers were obtained. The conductivity of the polyaniline was 0.21Scm−1 when ammonium peroxydisulfate was applied; it is comparable with the conductivity of a ‘standard’ polyaniline. The oxidation with silver nitrate yields a composite material, polyaniline salt and silver particles, with conductivity 1.5×10−3Scm−1. Photoacoustic spectroscopy was employed to study the kinetics of the oxidation reaction. Infrared and UV–vis spectra were efficient tools to characterize the final products, and to compare their molecular structure with that of the polyaniline prepared under ‘standard’ conditions in aqueous medium.

Keywords: Conducting polymer; Polyaniline; Solid-state polymerization; Photoacoustic spectroscopy; Silver; Mechanochemical route

The effect of different hard segments in polyurethane on the electrical conductivity of polyurethane grafted multi-walled carbon nanotube/polyurethane nanocomposites by Sungjin Yun; Hyungu Im; Jooheon Kim (pp. 1361-1367).
► Polyurethane (PU) was grafted on the surface of multi-walled carbon nanotubes. ► PU/PU-g-MWNTs film was obtained using a simple blending method. ► HDI-based PU film demonstrated homogeneously dispersed MWNTs in the matrix. ► The critical exponent of HDI film calculated based on fitted data was 2.43. ► HDI film led to enhanced electro-conductivity compared to the MDI film.Polyurethane (PU) grafted multi-walled carbon nanotubes (MWNTs) (PU-g-MWNTs) containing different hard segments (hexamethylene diisocyanate, HDI, and methylenediphnyl 4,4′-diisocyanate, MDI) were synthesized to fabricate an electro-conducting nanocomposite. The PU conducting nanocomposites were obtained using a simple blending method. PU-g-MWNTs can improve the interfacial compatibility between the MWNTs and PU matrix. The HDI-based PU nanocomposite showed enhanced dispersibility of the functionalized MWNTs than the MDI-based nanocomposite. The difference in dispersity was related to its electrical conductivity. The critical concentration of the MDI-based nanocomposite was lower than the HDI-based nanocomposite because less dispersed and more aggregated MWNTs partially formed a conducting path at a lower concentration. The critical exponent of the HDI-based nanocomposite revealed that the better dispersed MWNTs exhibited enhanced electrical conductivity, compared to the MDI-based nanocomposite, as the filler concentration was increased.

Keywords: Polymer-matrix composites; Carobn nanotube; Polyurethane; Electro-conductivity; Percolation threshold

Electropolymerization of PANI coating in nitric acid for corrosion protection of 430 SS by Hongbin Lu; Youzhen Zhou; Sascha Vongehr; Kun Hu; Xiangkang Meng (pp. 1368-1376).
► A smooth and adherent PANI coating was electropolymerized on SS via HNO3 solution. ► The PANI coating provides a strong and steady corrosion protection for the SS. ► The corrosion inhibition is mainly attributed to the oxide layers under the PANI. ► The oxide layers under PANI are thinner and denser than those formed on bare SS.A smooth and adherent polyaniline (PANI) coating was electropolymerized in HNO3 solution by cyclic voltammetry in order to protect the ferritic and economic 430 stainless steel (SS) from corrosion. The corrosion resistance was evaluated in 3.5wt.% NaCl solution by anodic polarization, potentiodynamic polarization, and electrochemical impedance spectroscopy. The PANI coating shifts the corrosion potential of SS to the passive region and provides a strong and steady corrosion resistance. A low growth rate leads to a compact PANI coating that acts as a good physical barrier. However, the strong corrosion inhibition is mainly attributed to the dense oxide layers formed by the catalytic effect of PANI at the polymer/metal interface. The composition of the oxide layers was analyzed via depth profiling using X-ray photoelectron spectroscopy alternating with sputtering. Compared with layers formed on uncoated SS, the iron and chromium oxide layers under the PANI are thinner and denser, absorbing less oxygen, and providing a stronger corrosion inhibition.

Keywords: PANI coating; Electropolymerization; Nitric acid; 430 SS; Corrosion; Oxide layers

Mesoporous silica doped with a chemosensor based on phosphorescent copper(I) complex: Synthesis, characterization, photophysical property, and sensing behavior towards molecular oxygen by Jiusi Jia; Yu Tian; Zhi Li (pp. 1377-1382).
► A phosphorescent Cu(I) complex is synthesized and doped into MCM-41 matrix. ► Its crystal structure and photophysical property are studied. ► The yellow emission is sensitive towards molecular oxygen. ► A maximum sensitivity of 4.48 with short response time is realized.In this paper, we report the synthesis, crystal structure, photophysical properties, and electronic nature of a phosphorescent Cu(I) complex of [Cu(OP)(PPh3)2]BF4, where OP and PPh3 stand for 2-(5-phenyl-[1,3,4]oxadiazol-2-yl)-pyridine and triphenylphosphine, respectively. [Cu(OP)(PPh3)2]BF4 is a yellow-emitting complex with a phosphorescence peaking at 552nm and a long excited state lifetime of 83.5μs under N2 atmosphere. Density functional calculation reveals that the emission comes from a triplet metal-to-ligand-charge-transfer excited state. We dope [Cu(OP)(PPh3)2]BF4 into a mesoporous silica matrix of MCM-41, hoping to explore the possibility of using the doped silica as an oxygen sensing material. The resulted samples exhibit a maximum sensitivity of 4.48 towards oxygen with short response time due to the large surface-area-to-volume ratio of MCM-41 matrix, and no photobleaching is detected in these samples.

Keywords: Cu(I) complex; Oxygen sensor; Single crystal; Luminescence; Mesoporous silica

Effect of acceptor substituents on photophysical and photovoltaic properties of triphenylamine–carbazole alternating copolymers by Zhi-Guo Zhang; Yang Yang; Siyuan Zhang; Jie Min; Jing Zhang; Maojie Zhang; Xia Guo; Yongfang Li (pp. 1383-1389).
Three alternative copolymers of carbazole and triphenylamine with different substituents were designed and synthesized. The substituent effect on absorption, morphology, and photovoltaic property of copolymers was fully investigated.Display Omitted► We synthesized 3 copolymers of carbazole and triphenylamine pending acceptor groups. ► The pendant cyano groups lead to red-shifted absorption of the polymers. ► Polymer solar cell based on PCzTPA-CN demonstrates a high Voc of 0.93V.Three alternative copolymers of carbazole (Cz) and triphenylamine (TPA) with substituent containing acceptor group of aldehyde (PCzTPA-CHO), mono-cyano (PCzTPA-CN) or di-cyano (PCzTPA-DCN), were designed and synthesized. Through manipulating the acceptor group attached to TPA unit, the electronic properties and energy levels of the copolymers were effectively tuned. The presence of pendant cyano groups leads to a decrease in the LUMO levels, but influences the HOMO levels very little, so that results in a lower bandgap and red-shift of its absorption spectrum. These results suggest a simple and effective approach for tuning the bandgap in a conjugated polymer through modification of the pendant acceptor groups. Their optoelectronic properties are largely determined by the nature of pendant substituent. Polymer solar cell based on PCzTPA-CN as donor and PC70BM as acceptor demonstrates a power conversion efficiency of 0.81% with a high Voc of 0.93V.

Keywords: Carbazole–triphenylamine copolymers; Acceptor side chains; Conjugated polymers; Polymer solar cells

Indication of formation of charge density waves in silver nanoparticles dispersed poly(methyl methacrylate) thin films by Manisree Majumder; Aloke Kumar Chakraborty; Bipul Biswas; Avijit Chowdhury; Biswanath Mallik (pp. 1390-1399).
► Thin films of silver nanoparticles–poly(methyl methacrylate) (PMMA) nanocomposites. ► Non-linearity in dark current vs. time profiles and thermal hysteresis of current. ► Electric field induced manipulation of silver nanoparticles in PMMA matrix. ► Structural reorientation of PMMA. ► Indication of charge density waves.Silver nanoparticles of various sizes have been prepared through the chemical synthesis and dispersed into poly(methyl methacrylate) (PMMA) matrix resulting in solution cast nanocomposite thin films. For characterization of the films, UV–vis absorption spectroscopy and FESEM were used. Observed blue shift of the surface plasmon absorption band position of the nanocomposite films is an indication of gradually smaller size of the silver nanoparticles that have been dispersed into the PMMA matrix. Dark current ( I d) vs. time profiles and the fluctuations in current–voltage characteristics for the PMMA films with dispersed silver nanoparticles were found to depend on the position of surface plasmon absorption band. Results of electrical studies have been found to be temperature- and voltage-dependent manifesting nonlinear nature of the I d which may be an indication of formation of charge density waves in the silver nanoparticles–PMMA nanocomposite films. The increase in the standard deviation in I d (calculated from the I d vs. time profiles) for the silver nanoparticles–PMMA nanocomposite films may be due to the increase in the plasmon oscillations. Thermal hysteresis has been observed in the PMMA films and in the silver nanoparticles–PMMA nanocomposite films. Results on the observed electrical properties have been discussed in the light of interaction of silver nanoparticles with PMMA matrix, structural reorientation of PMMA, role of electric field in the manipulation of silver nanoparticles in the polymer matrix etc.

Keywords: Polymer; Silver nanoparticle; Charge density wave; Surface plasmon absorption band; Hysteresis in current

Microstructure, dielectric response and electrical properties of polypyrrole modified (poly N-vinyl carbazole–Fe3O4) nanocomposites by Ipsita Haldar; Mukul Biswas; Arabinda Nayak (pp. 1400-1407).
► PNVC–Fe3O4 nanocomposites are prepared by in situ solid state polymerization. ► Encapsulated nanocomposite with polypyrrole shows enhanced dielectric constants. ► Fe3O4 nanoparticles are fairly well-dispersed in the composite matrix. ► Grain boundary contribution of dielectric properties is dominant in nanocomposite.N-vinyl carbazole (NVC) was polymerized in the presence of nanodimensional Fe3O4 in solid state at ∼65°C and a nanocomposite of poly N-vinyl carbazole with Fe3O4 (PNVC–Fe3O4) was isolated. This composite was further modified by encapsulation with polypyrrole (PPY) via oxidative polymerization of pyrrole in an aqueous dispersion of the PNVC–Fe3O4 composite in the presence of potassium persulfate (KPS). The presence of PNVC and of PPY in the PPY–PNVC–Fe3O4 composite was confirmed by FTIR spectroscopic analyses. TGA and DTA analyses showed the overall thermal stability trend as: Fe3O4>PNVC–Fe3O4>PPY–(PNVC–Fe3O4)>PNVC. HRTEM images revealed that the PPY–(PNVC–Fe3O4) nanocomposites have an average grain size of ≈37nm in good agreement with the values estimated from XRD data. SEM analysis indicated the preponderance of spherical particles embedded in the matrix. The dielectric constants of PNVC–Fe3O4 and the PPY–Fe3O4 systems were low (110–400) whereas the PPY encapsulated PNVC–Fe3O4 nanocomposites showed significantly higher values of dielectric constant (>1000), suggested that the interfaces between grain and grain boundary of the composite play a dominant role for enhancing dielectric properties of the system. Relaxation behaviors for the nanocomposite system were explained considering Maxwell–Wagner two-layered dielectric models. The ac conductivity was found to be independent on frequency in the range 102–103Hz for all the nanocomposites implying contribution of free charges and rise thereafter appreciably in the frequency range of 1–25kHz due to trapped charges in the grain boundary.

Keywords: Nanocomposites; Polymerization; Dielectric constant; Impedance spectra; ac conductivity

Gold nanoparticles–polyaniline composite material: Synthesis, structure and electrical properties by Tatiana Berzina; Andrea Pucci; Giacomo Ruggeri; Victor Erokhin; Marco P. Fontana (pp. 1408-1413).
Display Omitted► The new material supplying a network with elements functioning as synapses and neurons. ► Organic memristors operate as synapses, gold nanoparticles represent the threshold elements. ► The synthesis, morphology and electrical properties of composite materials. ► New materials for bio-inspired information processing.Gold nanoparticles–polyaniline composite materials were synthesised and their structure and electrical properties were analised. Different stabilizing agents were used resulting in the formation of nanoparticles with sizes within 5–10nm. The best results were obtained when the composite material was obtained during the polymerization of the anilinium salt in the presence of the mixture composed by dodecyl benzene sulfonic acid and 2-mercaptoethanesulfonic acid stabilized gold nanoparticles. Electrical properties of this composite material demonstrated the formation of Schottky barriers between polyaniline and gold particles, an essential property for its use in bio-inspired complex information handling materials.

Keywords: Polyaniline; Gold nanoparticles; Schottky barrier

A new approach for the synthesis of polyaniline microstructures with a unique tetragonal star-like morphology by Seyed Jamal Tabatabaei Rezaei; Yasamin Bide; Mohammad Reza Nabid (pp. 1414-1419).
Display Omitted► Shape-controllable polyaniline (PANI) microstructures with a unique tetragonal star-like morphology were synthesized by a rapid initiated strategy with glycine (Gly) as dopant. ► The molar ratios of aniline to glycine play an important role in the formation of the tetragonal star-like polyaniline microstructures. ► It was proposed that the self-assembly of nanoplates is driven by the hydrogen bonding between the polymer chains and carboxyl group of glycine.Shape-controllable polyaniline (PANI) microstructures with a unique tetragonal star-like morphology were synthesized by a rapid initiated strategy with glycine (Gly) as dopant. The results demonstrate that the morphology of PANI microstructures is significantly influenced by the molar ratio of aniline to glycine. The PANI prepared in this study exhibits nanofiber-like morphology with exceptionally high crystallinity. These nanofibers can self-assemble into tetragonal star-like microstructures with a unique alignment. The chemistry, morphology, and crystal structure of glycine doped star-like microstructures were studied using SEM, UV–vis, FT-IR, XRD and cyclic voltammetry (CV).

Keywords: Microstructure; Nanofiber; Polyaniline; Rapid initiated polymerization; Self-assembly

Photoinduced protonation of polyaniline assisted by hydrogen-bonding materials by Zheng Shi; Valentine K. Johns; Candace Alber; Yi Liao (pp. 1420-1423).
► Photo-induced conductivity of polyaniline/photo-acid generator composites was investigated. ► Addition of polyvinyl alcohol to the composites increased the photo-induced conductivity. ► A hydrogen-bonding photo-acid generator increased the conductivity from 10−5Scm−1 to 10−1Scm−1. ► Hydrogen bonding assists proton transfer in the irradiated composites.Composites of the emeraldine base form of polyaniline (PANI-EB) and photo-acid generators (PAGs) increase their conductivities upon photo-irradiation due to protonation of PANI-EB. Such materials may be utilized to fabricate conducting patterns by photo-irradiation. However, the conductivity obtained by direct irradiation of PANI-EB/PAG composites was normally quite low, and conductivity above 10−3Scm−1 often required post-treatment with HCl. In this work, poly(vinyl alcohol) (PVA), which can form a hydrogen bonding network, was added to PANI-EB/PAG. Results showed that PVA enhanced film quality, conductivity and reproducibility. Photo-induced conductivity of 10−2Scm−1 was obtained when the ratio of PANI-EB/PVA/PAG was 1:1:0.6. A novel PAG, bis(p-hydroxyphenyl)phenylsulfoniumtriflate [(PhOH)2PhS+ OTf], which can form hydrogen bonds with PANI was synthesized and mixed with PANI-EB. A composite of PANI-EB and the PAG with a ratio of 1:0.5 achieved a conductivity of 10−1Scm−1 after irradiation. However, the initial conductivity before irradiation was as high as 10−5Scm−1 due to relatively high acidity of the PAG.

Keywords: Polyaniline; Hydrogen bonding; Poly(vinyl alcohol); Photo-acid generator; Conductivity

A novel Re(I) complex with oxdiazole moiety: Synthesis, characterization, photo- and electro-luminescence properties by Li Yingkui (pp. 1424-1429).
Display Omitted► A novel phosphorescent Re(I) complex is synthesized. ► Photophysical, electronic, electrochemical, and thermal properties are studied. ► Yellow emission peaking at 545nm is realized. ► A maximum current efficiency of 11.3cd/A is achieved.In this paper, we report a novel phosphorescent Re(I) complex of Re(CO)3(OP)Br, where OP=2-(5-phenyl-[1,3,4]oxadiazol-2-yl)-pyridine, including its photophysical properties, geometric/electronic structures, electrochemical and thermal properties. Experimental data suggest that Re(CO)3(OP)Br is a promising yellow emitter peaking at 545nm with short excited state lifetime of ∼0.06μs. The Re(I) center localizes in a distorted octahedral field in Re(CO)3(OP)Br and the emissive state of Re(CO)3(OP)Br has metal-to-ligand-charge-transfer character, leading to the room-temperature phosphorescence. Further analysis reveals that Re(CO)3(OP)Br has HOMO and LUMO energy levels at −5.90V and −3.57V respectively, as well as its high thermal decomposition temperature of 380°C. Using Re(CO)3(OP)Br as a dopant, an electroluminescence peaking at 560nm is realized, with a maximum luminance of 4300cd/m2 and a maximum current efficiency of 11.3cd/A.

Keywords: Re(I) complex; Single crystal; Electroluminescence; Photophysical properties; Luminescence

Application of polyaniline nanocomposite coated on rice husk ash for removal of Hg(II) from aqueous media by Mohsen Ghorbani; Mohammad Soleimani Lashkenari; Hossein Eisazadeh (pp. 1430-1433).
► Synthesize of polyaniline and its nanocomposites containing rice husk ash. ► Optimum conditions for Hg(II) removal is pH 9 and adsorbent dosage of 10g/L. ► Adsorption of Hg(II) is fast and equilibrium is achieved by 20min of contact time. ► Removal efficiency of PAn/RHA is higher than PAn and RHA in all experiments.In this study, preparation of polyaniline (PAn) and its nanocomposite containing rice husk ash (RHA) was discussed, and their capability to removal of Hg(II) from aqueous solution was studied. Polyaniline (PAn) synthesized chemically in the presence of potassium iodate as an oxidant, coated on rice husk ash via cast method. The removal of Hg(II) was investigated using polyaniline, rice husk ash and polyaniline/rice husk ash nanocomposite, respectively. The products were investigated in terms of morphology and chemical structure with scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), respectively. Batch studies were performed to evaluate the influence of various experimental parameters like pH, adsorbent dosage, contact time and the rotating speed. Optimum conditions for mercury removal were found to be pH 9, adsorbent dosage of 10g/L, equilibrium time 20min and rotating time 400rpm.

Keywords: Nanocomposite; Rice husk ash; Polyaniline; Mercury; Removal

Electrical characterization of Au/Pd/n-GaN/Pd/Au device structure in the radio frequency range by simulation study by A. Sertap Kavasoglu; Nese Kavasoglu; Gorkem Oylumluoglu (pp. 1434-1440).
► Au/Pd/n-GaN/Pd/Au device structure have been studied by simulation software. The software has been developed by our group. ► The anomalous peaks in the C–V curves are observed. ► Nyquist plots are shown that two barrier height can be clearly observed.GaN based devices are highly promising optoelectronic devices for many years due to their useful applications in photovoltaic energy conversation, fiber optic communication and atmosphere monitoring. GaN based devices such as Schottky barrier, metal–semiconductor–metal and p-i-n structure have been fabricated and characterized so far. A proper understanding of the impedance or admittance spectroscopy result is crucial since it is a powerful tool to calculate the physical and electronic parameters of a device. In this study, temperature dependent dark current–voltage ( IV) and dark impedance spectra of n type GaN based metal–semiconductor–metal device have been studied with current–voltage and impedance spectra by simulation. All current–voltage characteristics exhibited good rectification behavior. The forward and reverse bias capacitance–voltage ( CV) characteristics of the Au/Pd/n-GaN/Pd/Au device were simulated at 2MHz probing frequency. Nyquist plots of simulated device at 295K are shown that two-barrier heights can be observable above critical threshold bias point. Frequency depended inverse dielectric loss tangent spectra of Au/Pd/n-GaN/Pd/Au device at different DC bias voltages also shows significant two peaks. This indicates that our simulation is extremely useful for determination of potential barrier numbers.

Keywords: PACS; 73.40.Sx; 73.40.Qv; 73.30.+y; 73.40.Ns; 84.37.+q; 61.80.−xSchottky barrier; C; –; V; and; G; –; V; characteristics; Interface states; Capacitance anomaly

Excitons in organic semiconductors by Ahmed Dkhissi (pp. 1441-1443).
The exciton binding energy ( E b) is one of the heavily debated issues in conjugated polymer literature. Most of the experimental studies suggest values around 0.3–0.4eV for PPV. On the other hand, binding energies ranging from 0.06eV to more than 1eV have been reported as well. Time Dependent Density Functional Theory (TDDFT) is employed to calculate E b for PPV and polythiophenes and their derivatives in order to (i) to clarify the controversial debate of the magnitude of the exciton in PPV and (ii) to study the influence of the substituents on the exciton binding energy of conjugated polymers.

Keywords: The exciton binding energy; Organic semiconductors; TDDFT

Synthesis of selenopheno[3,2- c]thiophene derivatives and (opto)electrochemical properties of new low bandgap conjugated polymers by Yu-Ra Jo; Soo-Hyoung Lee; Youn-Sik Lee; Yun-Hwa Hwang; Myoungho Pyo; Kyukwan Zong (pp. 1444-1447).
► π-Conjugated polymers consisting of fused rings of selepheno[3,2- c]thiophene derivatives are synthesized. ► Polymers show low bandgap in a range of 0.91 and 1.06eV. ► Polymers possess higher HOMO levels by 0.2eV than corresponding thienothiophenes. ► These polymers can be utilized for a efficient hole transport material in polymer solar cells.Various selenopheno[3,2- c]thiophene (STh) derivatives functionalized by 4- n-butylphenyl, 4- n-pentylphenyl, 4- tert-butylphenyl, and n-octyl were newly synthesized in a concise and efficient way. Electrochemical and optical properties of polymers were examined by cyclic voltammetry and visible-near infrared (Vis-NIR) spectrophotometry. When compared with polymers of thieno[3,4- b]thiophene, poly(selenopheno[3,2- c]thiophene) (PSTh) was more easily oxidized by ca. 0.2V (higher HOMO). On the other hand, the bandgap of electrochemically prepared PSTh varied with substituents, but showed similar values to those of poly(thieno[3,4- b]thiophene). While the resonance effect of phenyl substituents slightly lowered HOMO, the combination of resonance and inductive effects decreased LUMO more effectively, resulting in the lowest bandgap of 0.91eV for 4- tert-butylphenyl functionalized PSTh.

Keywords: Selenopheno[3,2-; c; ]thiophene; Bandgap; Conjugated polymer; NIR; HOMO

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