Synthetic Metals (v.161, #3-4)

The effects of ultraviolet light and heat treatment at the condition of an inert gas environment on the performance of polymer photovoltaic cells (PVCs) with poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and its blend with [1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6)C61] (PCBM) are investigated. It is found that photo cross-linking between vinyl pieces in the polymer backbone is limited in a blend film even though it takes place in a pure polymer film. This makes the PVCs with the blend heterojunction structures show excellent UV and heat stability if the temperature is lower than 120 °C.
Keywords: Conjugated polymer; PPV; Photovoltaic; Solar cell; Photo-crosslinking;

Electroplating formation of Al–C covalent bonds on multiwalled carbon nanotubes by Kang Pyo So; Chandan Biswas; Seong Chu Lim; Kay Hyeok An; Young Hee Lee (208-212).
We focus on the formation of strong aluminum (Al)–carbon nanotube (CNT) covalent bonds on the CNT walls without deteriorating CNTs for mechanically strong composite. We propose a simple electroplating method to realize Al–CNT covalent bonds on the CNT wall. The CNT electrode was formed on the Cu collector as a cathode and separated from the anode by an organic separator in tetrahydrofuran (THF) under Ar atmosphere. The Al deposition started to increase rapidly at above Al reduction potential. The formation of Al–C covalent bonds was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Charge transfer from CNTs to Al and generation of D-bands in Raman spectroscopy further confirmed the formation of Al–C covalent bonds.
Keywords: Carbon nanotube; Aluminum; Covalent bond; Composite; Electroplating;

▶ A new series of red emitting phosphorescent Ir(III) complexes, were synthesized for phosphorescent organic light-emitting diodes (PhOLEDs). ▶ All of the Ir(III) complexes had high thermal stability and emitted deep-red light with an excellent color purity at CIE (Commission International de l’Eclairage) coordinates of (0.67, 0.30). ▶ The red emitting PhOLEDs based on ITO/PEDOT:PSS/TCTA:TPBI:TPD:Ir complex/cathode exhibit a maximum external quantum efficiency of 0.51% and luminance of 180 cd/m2, respectively.A new series of red emitting phosphorescent Ir(III) complexes, [10-hexyl-2-(4-phenylquinolin-2-yl)-10H-phenothiazine]Iridium acetylacetonate [(PQHPT)2Ir(acac)], [10-hexyl-2-(4-phenylquinolin-2-yl)-10H-phenothiazine]Iridium picolinic acid [(PQHPT)2Ir(pic)] and [10-hexyl-2-(4-phenylquinolin-2-yl)-10H-phenothiazine]Iridium picolinic acid N-oxide [(PQHPT)2Ir(pic-N-O)] based on 10-hexyl-2-(4-phenylquinolin-2-yl)-10H-phenothiazine (PQHPT) main ligand and acetylacetonate (acac), picolinic acid (pic) and picolinic acid N-oxide (pic-N-O) ancillary ligands were synthesized for phosphorescent organic light-emitting diodes (PhOLEDs). The photophysical, electrochemical and electroluminescent (EL) properties of Ir(III) complexes were investigated. All of the Ir(III) complexes had high thermal stability and emitted deep-red light with an excellent color purity at CIE (Commission International de l’Eclairage) coordinates of (0.67, 0.30). The red emitting PhOLEDs based on ITO/PEDOT:PSS/TCTA:TPBI:TPD:Ir complex/cathode exhibit a maximum external quantum efficiency of 0.51% and luminance of 180 cd/m2, respectively.
Keywords: Solution-processed; PhOLEDs; Iridium(III) complex; Deep-red;

Preparation and characterization of conductive fabrics coated uniformly with polypyrrole nanoparticles by Yoshihiro Egami; Kunio Suzuki; Takanori Tanaka; Tadashi Yasuhara; Eiji Higuchi; Hiroshi Inoue (219-224).
▶ Polypyrrole nanoparticles could be uniformly and closely deposited on fabrics. ▶ The resistivity can be arbitrarity varied from 1010  Ω cm level to 10 Ω cm level. ▶ The resultant conductive fabrics has high fastness to rubbing. ▶ And the conductive fabrics could be used ultra-clean and ultra-low dust conditions.We have successfully fabricated a conductive fabric coated densely and uniformly with polypyrrole nanoparticles that were less than 50 nm in size by exposing a fabric immersed in a solution containing an oxidizing agent and a dopant to pyrrole vapor after partially pressing excess solution from the fabric with a nip-roll apparatus. The resistivity and color of the resultant conductive fabric depended on the concentrations of the oxidizing agent and dopant. The resistivity arbitrarily varied from an antistatic level (1010  Ω cm) to a high conductivity level (10 Ω cm), which was attributed to differences in the size, compactness and adhesiveness of the polypyrrole nanoparticles forming the conducting network. High fastness to rubbing of the conductive fabric was maintained even though the electrical conductivity varied, suggesting that the fabric could be used in ultra-clean and ultra-low dust conditions.
Keywords: Polypyrrole; Nanoparticle; Conductive fabric; Color difference; Fastness to rubbing;

Field-effect hole mobility of poly(3-hexylthiophene-block-3-(2-ethylhexyl)thiophene)s by Yue Zhang; Keisuke Tajima; Kazuhito Hashimoto (225-228).
The field-effect hole mobility of a series of highly regioregular all-conjugated P(3HT-b-3EHT) diblock copolymers was investigated. Although disordered segments of P3EHT were introduced, thin films of P(3HT-b-3EHT)s with 83 mol% P3HT exhibited field-effect hole mobilities up to 0.14 cm2  V−1  s−1 without any thermal treatment. In contrast, the corresponding random copolymers P(3HT-ran-3EHT)s showed a monotonic decrease in mobility upon introduction of 3EHT monomer units, owing to the decrease in polymer crystallinity. Absorption spectra of the films suggest the formation of improved structural order induced by the P3EHT block, which contributed to improved carrier transport properties in P(3HT-b-3EHT)s.
Keywords: Field-effect hole mobility; Poly(3-alkylthiophene); Block copolymer; Structural order;

Electronic excitations of the fullerene–thiophene-derived dyads by Bolesław Barszcz; Barbara Laskowska; Andrzej Graja; Eun Young Park; Tae-Dong Kim; Kwang-Sup Lee (229-234).
▶ The set of five fullerene–thiophene–derived dyads have been investigated. ▶ UV–vis absorption spectroscopy and time dependent DFT calculations have been used. ▶ In four dyads the strongest electronic excitations are due to fullerene part. ▶ The strongest electronic excitations in 3T-F are due to oligothiophene part. ▶ The HOMO-LUMO gap in 3T-F is smaller than in the other dyads.The electronic absorption spectra of fullerene–thiophene-derived dyads in the UV–vis range have been investigated and discussed taking into account the results of time-dependent density functional theory (TD-DFT) calculations. It was found that the strongest excitations in the dyads are mainly related to the excitations of the fullerene part with some influences from the thiophene-derived part and intramolecular charge transfer processes. The 3T–F dyad significantly differs from the others — the calculated HOMO–LUMO gap in this molecule is significantly lower than in other dyads. This difference is caused by the length of the oligomer and probably by the electron delocalization connected with that length.
Keywords: Fullerene; Thiophene; TD-DFT; UV–vis spectra;

Reflective behavior of strong absorption metallic photonic crystals by Dengteng Ge; Lili Yang; Yao Li; Jiupeng Zhao; Xue Li; Huijie Zhao (235-240).
The growing interest in fabrication and investigation of metallic photonic crystals is determined by the potential for new properties and applications. In this work, reflective spectra of strong absorption metallic photonic crystals including metal/template composites and metalic inverse opals were systematically studied. Fe–Ni alloy were electrodeposited through self-assembly templates, and inverse opals were fabricated after removal of templates. For metal/template composites, enhanced stop gap is blue shifted due to strong absorption of metallic materials. An effective fraction of alloy is introduced for the first time to describe the alloy participating in the Bragg effect, which is mainly determined by metal. However, alloy inverse opals show greater blue shift of broaden gap to high frequency regions and metallic nature in low frequency regions due to the existence of windows. Scanning electronic micrographs results indicate that there is a critical thickness of wall materials where there are windows in inverse opals. It is proposed here that windows are formed due to the associated breaking of thin alloy walls with template.
Keywords: Metallic photonic crystals; Absorption; Effective fraction; Windows;

▶ Mercaptoquinoline cobalt phthalocyanines have been synthesised. ▶ Cyclic voltammetry shows both ring and metal based processes. ▶ Complexes were used to modify carbon or gold electrodes. ▶ Electrodes were used to electrocatalytically oxidize l-cysteine.This study investigates the synthesis and characterization new peripherally (β) tetra-substituted 4-(2-mercaptoquinoline phthalocyaninato) Co(II) (CoPcSHQn, 3), and 4-(2-phenoxy-4-trifluoromethylpyridine phthalocyaninato) Co(II) (CoPcOHPy, 4). These complexes were characterized by elemental analysis, IR, mass and electronic spectroscopies and electrochemical methods. Both complexes show well resolved redox peaks attributed to both ring and metal based processes. Spectroelectrochemistry was used to confirm the assignments of the redox processes. For CoPcSHQn (3): CoIPc−2/CoIPc−3 (E 1/2  = −1.25 V, I), CoIIPc−2/CoIPc−2 (E 1/2  = −0.57 V, II), CoIIIPc−2/CoIIPc−2 (E 1/2  = +0.45 V, IV) and an irreversible process at E p  = +1.05 V vs Ag|AgCl for CoIIIPc−1/CoIIIPc−2 (V). Redox couple III at E 1/2  = −0.15 V was ascribed to aggregation. In the case of CoPcOHPy (4): CoIPc−2/CoIPc−3 (E 1/2  = −1.13 V, I), CoIIPc−2/CoIPc−2 (E 1/2  = −0.45 V, II), CoIIIPc−2/CoIIPc−2 at E 1/2  = +0.21 V (IV), and CoIIIPc−1/CoIIIPc−2 (E 1/2  = +1.01 V vs Ag|AgCl, V). Again III is associated with the aggregated species. Both complexes were electrodeposited on a glassy carbon electrode (GCE). For complex 3 self-assembled monolayers was also formed. The modified (CoPc-GCE) electrodes electrocatalytically detected l-cysteine at E p  = 0.62 V (3-GCE) and 0.59 V (4-GCE) vs Ag|AgCl.
Keywords: Cobalt; 2-Mercaptoquinoline; 2-Hydroxy-pyridine-4-trifluoromethyl; Cyclic voltammetry; Spectroelectrochemistry; Electrodeposition;

Oriented growth of zinc(II) phthalocyanines on polycarbonate alignment substrates: Effect of substrate temperature on in-plane orientation by Christelle Vergnat; Sureeporn Uttiya; Sirapat Pratontep; Teerakiat Kerdcharoen; Jean-François Legrand; Martin Brinkmann (251-258).
▶ Phthalocyanines are widely used organic semi-conductors forming columnar phases. ▶ Phthalocyanines are highly oriented on polymer alignment layers of polycarbonate. ▶ Polycarbonate substrates are prepared by rubbing and solvent induced crystallization. ▶ Substrate temperature controls the phthalocyanine orientation and structure.Highly oriented films of zinc(II) tetra-tert-butyl-phthalocyanine (ttb-ZnPc) and zinc(II) phthalocyanine (ZnPc) have been deposited on oriented and nanostructured substrates of bisphenol A polycarbonate. The polycarbonate substrates were prepared by a simple method that combines (i) the mechanical rubbing of an amorphous PC film and (ii) the solvent induced crystallization generating oriented crystalline lamellae with a high in-plane orientation. The preparation conditions yielding alignment layers with high orienting capability and improved thermal stability have been optimized. The effects of the substrate temperature (T s) on the morphology, the in-plane orientation and the optical properties of the phthalocyanine films have been investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM) and polarized UV–vis absorption spectroscopy. For both phthalocyanines, the in-plane orientation is observed to increase with increasing T s in the range 100–170 °C as indicated by an increase of the dichroic ratio of the optical absorption with T s. However, contrary to ZnPc, the high in-plane orientation of ttb-ZnPc is not related to the growth of elongated nanocrystals but simply to the orientation of columnar stacks parallel to the PC lamellae with a rather short 0.33 nm intermolecular stacking period and an inter-stack period of 1.65 nm. For similar growth conditions, a better orientation of ttb-ZnPc is achieved on PC substrates as compared to substrates of friction transferred polytetrafluoroethylene (PTFE). These results show that PC alignment layers are an interesting alternative to substrates of oriented PTFE for a large range of substrate temperatures up to 170 °C.
Keywords: Thin films; Molecular semi-conductors; Transmission electron microscopy; Alignment layer;

Synthesis of a polymeric 2,5-di-t-butyl-1,4-dialkoxybenzene and its evaluation as a novel cathode material by Peter Nesvadba; Lucienne Bugnon Folger; Pascal Maire; Petr Novák (259-262).
▶ Redox shuttles are frequently used for overcharge protection of Li-ion batteries. ▶ A polymeric analogue of the redox shuttle 2,5-di-t-butyl-1,4-dimethoxybenzene has been prepared. ▶ The novel polymeric analogue of the redox shuttle is a promising prototype of a new class of organic cathode materials for Li-ion batteries.A novel crosslinked polymeric 2,5-di-t-butyl-1,4-dialkoxybenzene derivative bearing dialkoxyaryl redox centers has been prepared and evaluated as a cathode material in a Li-ion battery. The polymer is a macromolecular analogue of the well known redox shuttle 2,5-di-t-butyl-1,4-dimethoxybenzene. The high cell voltage of 4 V and stable cycling behavior make the novel polymer a promising prototype of a new class of cathode materials.
Keywords: Li-ion batteries; Cathode materials; Redox-active polymers; Redox shuttles;

Synthesis and characterization of fluorene based π-conjugated ter-copolymers by Shyambo Chatterjee; Susanta Banerjee; Pallab Banerji (263-270).
▶ π-Conjugated ter-copolymers. ▶ Photo luminescent spectroscopy. ▶ Cyclic voltammogram.Three conjugated ter-copolymers P1, P2 and P3 were prepared in which fluorene was a common unit and varying subunits were thiophene–pyridine, thiophene–anthracene and pyridine–anthracene, respectively. The number-average molecular weights (M n) of the copolymers named as P1, P2 and P3 were found to be 13,400, 14,200 and 15,800 g/mol, respectively. These copolymers were soluble in common organic solvents such as chloroform, chlorobenzene, toluene, etc. and their tendency to form aggregates has been observed by the atomic force microscopy (AFM). The copolymers were investigated for their thermal, optical, electrochemical and impedance properties. They showed high glass transition temperatures and improved thermal and spectral properties. The copolymer P2 (thiophene/fluorene/anthracene) showed lower LUMO energy level and significant redox stability in respect to pyridine containing copolymers P1 (thiophene/fluorene/pyridine) and P3 (pyridine/fluorene/anthracene). The remarkable n-dope ability and stability of these polymers were discussed in the light of cyclic voltammetric and electrochemical impedance spectroscopic studies.
Keywords: Ter-copymers; Fluorescence spectroscopy; Cyclic voltammetry;

Initial stage of crystalline rubrene thin film growth on mica (0 0 1) by H. Zaglmayr; L.D. Sun; G. Weidlinger; Sh.M. Abd Al-Baqi; H. Sitter; P. Zeppenfeld (271-274).
We have studied the morphology and the spatially resolved photoluminescence of rubrene thin films at the early stage of crystallization. The initial growth proceeds via the formation of a wetting layer and the nucleation of islands with an amorphous structure. Crystallization starts when the amorphous islands coalesce and needle like crystalline fibers are formed in the gap between islands. The crystalline fibers then grow on top and in between the original amorphous islands leading to an “open network” of islands. The latter acts as the basis for the growth of semi-crystalline spherulites.
Keywords: Organic thin films; Fluorescence spectroscopy; Fluorescence microscopy; Epitaxial growth; Rubrene;

Bismuth nitrate doped polyaniline – Characterization and properties for thermoelectric application by Krishanu Chatterjee; Saibal Ganguly; Kajari Kargupta; Dipali Banerjee (275-279).
▶ To the best of our knowledge it is for the first time that bismuth nitrate has been used as a dopant to attain the conducting state of polyaniline. ▶ Nano rods of polyaniline was obtained in the electrochemical deposition. ▶ Dopant concentration has significant effect on the electrical transport properties viz. electrical conductivity and thermoelectric power. ▶ As a result a sample (20:1::Bi(NO3)3:PANI) with highest power factor has been identified which exhibit an increase of power factor by two fold as compared to HCl doped polyaniline. ▶ The mechanism of charge transport is explained and the variation of thermoelectric power with temperature is well fitted with an equation based on these mechanisms.Samples of polyaniline (PANI) doped with different concentrations of Bi(NO3)3 were electrodeposited. The structural characterization showed that the samples were rod like nanostructure with diameter 20 nm. The effect of dopant concentration on the electrical transport properties in the temperature range 300–400 K was discussed. The variation suggests metallic type conduction with a hopping/tunneling mechanism of transport with charge carriers. Thermoelectric power (S) was correlated with temperature through an equation considering the mechanism of transport of carriers. The sign of the carriers were found to be negative. The sample with weight ratio 1:20::PANI:Bi(NO3)3 showed a higher power factor (P) at almost all temperatures.
Keywords: Polyaniline; Bismuth nitrate; Nanorods; Conductivity; Thermoelectric power; Power factor;

Polar solvent soluble and hydrogen absorbing polyaniline nanofibers by Abdelaziz Rahy; Touria Rguig; Sung June Cho; Christopher E. Bunker; Duck Joo Yang (280-284).
▶ We successfully synthesized polar solvent soluble polyaniline nanofibers using organic additive. ▶ These nanofibers are soluble in water and other polar organic solvents such as ethanol. ▶ We found that surprisingly the nanofibers have hydrogen absoption capability as high as 4.3% at 298 K and 20 atmospheric pressure. ▶ We propose a hypothesis about the role of additive and how hydrogen can be stored in the nanofibers.Polar solvent soluble polyaniline nanofibers were synthesized from aniline in the presence of organic additive such as sucrose, C12H22O11 or sucralose, C12H19Cl3O8, by oxidative polymerization. These nanofibers synthesized in the presence of the additive were soluble in water as well as in other polar organic solvents such as methanol, ethanol, DMF and DMSO. We found the nanofibers have hydrogen absorption capability as high as 4.3% at 298 K and 20 atm. The role of the sucrose why it makes the polyaniline nanofibers become soluble and absorb hydrogen is explained, and a hypothesis is proposed about the role of sucrose and how hydrogen can be stored.
Keywords: Polyaniline; Nanofibers; Hydrogen storage;

Polyaniline nanofibres as templates for the covalent immobilisation of biomolecules by Carol Crean (neé Lynam); Emer Lahiff; Niamh Gilmartin; Dermot Diamond; Richard O’Kennedy (285-292).
The attachment of antibodies onto polyaniline nanofibres using covalent chemistry was investigated for the first time. Polyaniline nanofibres were functionalised post-polymerisation to attach either amide or carboxylic acid side-groups. These templates could then be further modified to attach antibodies, specifically in this instance mouse immunoglobulin G (IgG). The resultant conjugates were characterised using a variety of techniques including infrared, UV–vis and Raman spectroscopy. Conjugates were then used to detect secondary antibodies (anti-IgG). Results from enzyme-linked immunoassay studies indicate successful binding of the antibody to the polyaniline nanofibres. Carboxyl functionalised polyaniline nanofibres are shown in particular to decrease non-specific binding in the immunoassay. Direct electrical communication between polyaniline nanofibres covalently linked to peroxidase-labelled antibodies was observed during cyclic voltammetry, which demonstrates their potential for further development as nano-dimensional immunosensors.
Keywords: Polyaniline nanofibres; Conducting polymer functionalisation; Antibody conjugation; Immunoassay;

Determination of Methamphetamine Hydrochloride by highly fluorescent polyfluorene with NH2-terminated side chains by Chao He; Qingguo He; Changmin Deng; Liqi Shi; Yanyan Fu; Huimin Cao; Jiangong Cheng (293-297).
Three different poly{9,9-bis[6′(–NHBoc, –NH3 + and –NH2)hexyl]fluorene}s (PF-NHBoc, PF-NH3 + and PF-NH2) have been synthesized and characterized. Both UV–Vis and fluorescence spectroscopic results supported the interaction between the polyfluorenes and Methamphetamine Hydrochloride (MAPA) was derived from the different terminals of hexyl side chains. Among the three polyfluorenes, PF-NH2 exhibited the best sensory response to Methamphetamine Hydrochloride (MAPA) in THF arising from its –NH2 terminals. The fluorescence of PF-NH2 was immediately quenched once the MAPA was added, and the detection limit of MAPA was determined to be ∼25 ng/mL. Fluorescence quenching experiments of PF-NH2 by NH4Cl and other metal ions confirmed that electrostatic interaction should make contributions to the quenching behavior, in addition, upward non-linear curvature and much higher quenching constant (K sv) in the Stern–Volmer plots for MAPA suggested some other interactions such as hydrophobic or/and hydrogen-bonding interactions dominated the analyte-induced aggregation, and such hydrophobic interaction was responsible for the sensitive selectivity. The fluorescent quenching experiments upon adding other drugs such as Pethidine Hydrochloride (PTD) and Ephedrine Hydrochloride (EPD) confirmed such selectivity, especially under the high concentration of the Stern–Volmer plots. The high sensitivity, selectivity, and its simple and fast character, made it a new and effective way for drug detection.
Keywords: Polyfluorene; Methamphetamine Hydrochloride; Analyte-induced aggregation;

Synthesis of polyaniline nanofibers and nanotubes via rhamnolipid biosurfactant templating by Panisara Worakitsiri; Orathai Pornsunthorntawee; Tuspon Thanpitcha; Sumaeth Chavadej; Christoph Weder; Ratana Rujiravanit (298-306).
Polyaniline (PANI) nanorods and nanotubes with average diameters in the range of 121 ± 12 nm to 152 ± 13 nm were synthesized by the oxidative polymerization of aniline using hydrochloric acid as a dopant, ammonium peroxodisulfate as an oxidant, and a rhamnolipid biosurfactant produced by Pseudomonas aeruginosa SP4 as a soft template. The reaction conditions were systematically varied with the objective to maximize the electrical conductivity and aspect ratio of the PANI nanofibers. Optimized conditions, which involved an acid concentration of 0.1 M, an ANI-to-biosurfactant weight ratio of 23:1, and a polymerization time of 6 h, afforded a material with an electrical conductivity of 25 ± 2 S/cm. This material also exhibited the highest degree of crystallinity of all studied samples and matched the electronic properties of a reference material made without the surfactant.
Keywords: Biosurfactants; Glycolipids; Rhamnolipids; Conductive polymers; Polyaniline; Nanoparticles;

Synthesis and characterization of 2H-benzimidazole- and terthiophene-based polymer for organic photovoltaics by Suhee Song; Sung Heum Park; Youngeup Jin; Jinwoo Kim; Joo Young Shim; Youngran Goo; Ok-Sang Jung; Il Kim; Heesoo Lee; Euh Duck Jeong; Jong Sung Jin; Kwanghee Lee; Hongsuk Suh (307-312).
▶ Polymer based on 2H-benzimidazole and terthiophene for OPVs.New semiconducting polymer with alkoxy substituted terthiophene, as the electron rich unit, and 2,2-(1,5-pentamethylene)-2H-benzimidazole (PMBI), as the electron deficient unit, was synthesized using Stille polymerization. The advantage of PMBI is higher solubility of the polymer while keeping the coplanarity of the backbone as compared to the benzothiadiazole moiety of PCDTBT. In PMBI, the sulfur at 2-position of BT unit was replaced with the carbon of cyclohexane to make a highly soluble electron deficient moiety while keeping the 1,2-quinoid form of BT unit. The polymer, PTBHOTPMBI, exhibits more red shifted absorption peak as compared to the polymers with benzothiadiazole unit. The PTBHOTPMBI thin film shows two broad absorption bands with peaks at 475 and 755 nm and an absorption onset at 943 nm, corresponding to a band gap of 1.32 eV. The device of PTBHOTPMBI with PC71BM showed an open-circuit voltage (V OC) of 0.25 V, a short-circuit current density (J SC) of 2.30 mA/cm2, and a fill factor (FF) of 0.30, giving a power conversion efficiency of 0.17%.
Keywords: Polymer; Photovoltaic cells; Thiophene; 2H-Benzimidazole;

Alkyd coatings containing polyanilines for corrosion protection of mild steel by G.S. Gonçalves; A.F. Baldissera; L.F. Rodrigues; E.M.A. Martini; C.A. Ferreira (313-323).
▶ Protective alkyd paints containing polyaniline. ▶ Anodic protection of steel using coatings containing electroactive polymers. ▶ Protection of steel by a metallic free paint coating.A study was carried out to investigate the performance of anti-corrosion coatings obtained from alkyd paints containing polyaniline and polyaniline derivatives applied on carbon steel. The polyaniline, the polyaniline derivates and the paints were characterized through FTIR and Raman spectroscopies and thermogravimetric analysis. Cyclic voltammetry studies showed that polyaniline and its derivates gave electroactive properties to the paints. Accelerated corrosion experiments (salt spray and humidity chamber) revealed a significant improvement in the performance of the coatings which contained the electroactive polymer compared to conventional coatings. These results were verified by evaluation of the electrical resistance and capacitance measurements of the films using electrochemical impedance spectroscopy. For some of the samples, the Raman spectra demonstrated the presence of an oxide layer at the coating/substrate interface composed basically of Fe2O3 and Fe3O4. The results of this study reinforce the possibility of protecting carbon steel against corrosion through the formation of a protective layer of oxides using coatings which contain electroactive polymers.
Keywords: Polyaniline; Coating; Electrochemical impedance spectroscopy; Corrosion; Paint;

▶ The p-Si/1,4-DAAQ hybrid diode exhibits a photovoltaic behavior with open circuit voltage, V oc  = 0.365 V and short circuit current, I sc  = 127 μA under AM1.5. ▶ The obtained results indicate that p-Si/1,4-DAAQ inorganic–organic diode can be used as a photosensor in optoelectronic applications.The electrical and photosensing properties of the p-Si/1,4-DAAQ inorganic–organic diode have been investigated. The diode exhibits a non-ideal behavior with ideality factor of 2.03 and barrier height of 0.85 eV. The photovoltaic parameters, open circuit voltage, V oc and short circuit current, I sc of Al/p-Si/1,4-DAAQ diode under AM1.5 were found to be V oc  = 0.365 V and I sc  = 127 μA, respectively. The interface state density of the diode can be controlled by the illumination. The ratio values of C photo/C dark under 10 kHz, 100 kHz and 500 kHz spot frequencies were found to be 3.73, 3.33, 1.70 and 1.02, respectively and the C photo/C dark values decrease with increasing frequency. The obtained results indicate that the photocapacitance properties of the Al/p-Si/1,4-DAAQ diode can be controlled by frequency. It is evaluated that this device can be used a photosensor controlled frequency.
Keywords: Organic semiconductor; Photodiode; Photovoltaic;

Display Omitted▶ A new carbazole dendrimer has been synthesized by click chemistry. ▶ The convergent strategy and orthogonal coupling method were highly efficient. ▶ The electro-phosphorescence device based on the dendrimer was also reported.A new solution processable dendrimer, with carbazole as a hole transporting unit, was efficiently synthesized based on convergent approach by alternation of Cu-catalyzed azide/alkyne cycloaddition (CuAAC) reaction and Williamson ether synthesis. The orthogonal chemistry completely avoided protection and activation of the focal points in the process of dendrimer synthesis. The dendrimer showed wide bandgap and has good thermal stability. The carbazole dendrimer was studied as electrophosphorescent host materials. Electrophosphorescent devices with the configuration of ITO/PEDOT:PSS/carbazole dendrimer:Ir(ppy)3/TPBI/LiF/Al were fabricated. The device showed turn-on voltage of 5.74 V, a maximum current efficiency of 13.7 cd/A, a power efficiency of 6.39 lm/W and an external quantum efficiency of 5.03%.
Keywords: Click chemistry; Convergent orthogonal strategy; Dendrimer; Light-emitting diodes;

Synthesis of polypyrrole–ferric oxide (Ppy–Fe2o3) composites and study of their structural and conducting properties by Farah Kanwal; Saadat Anwar Siddiqi; Aisha Batool; M. Imran; Waheed Mushtaq; Tahir Jamil (335-339).
▶ In this piece of research work, the synthesized samples of polypyrrole/α-ferric oxide composites have been characterized. ▶ The conductivity of polypropyrrole has been enhanced by the addition α-ferric oxide. ▶ There is a good correlation among the structural properties and conductivity.Conducting polypyrrole/α-ferric oxide (PPy–Fe2O3) composites have been prepared using chemical oxidative polymerization with different weight percentages of α-ferric oxide (10–30 wt.%) dispersed during polymerization of pyrrole. These composites were characterized by FT-IR, X-ray diffraction, conductivity and scanning electron microscopy. Four-probe method was used to study the effect of doping on DC-conductivity of the composites. The dispersion of α-Fe2O3 in these composite imparts good structural and electrical properties in PPy. The percolation threshold for conductivity was found to be 10% of α-Fe2O3 contents in PPy. It arises from an enhanced homogeneous morphology, increase in crystallinity, particle size and shortening of conjugation chain length as confirmed by the scanning electron microscopy, X-ray diffraction and FT-IR analysis.
Keywords: Polypyrrole; Composite; Conductivity; FT-IR; XRD; SEM;

Analysis of optical properties of poly(3-methylthiophene) (P3MT) electrochemically synthesized by G.A. dos Reis; I.F.L. Dias; H. de Santana; J.L. Duarte; E. Laureto; E. Di Mauro; M.A.T. da Silva (340-347).
▶ Formation of mixed chains (benzene and quinone) is detected. ▶ Chemical reduction is a more efficient dedoping process than the electrochemical. ▶ We consider two different recombination mechanisms in the PL emission.In this work the P3MT was synthesized electrochemically on transparent conductive substrates of fluorine tin oxide (FTO) using the electrolyte Et4NBF4 in acetonitrile. To dedope the material, the samples were reduced electrochemically and chemically (in NH4OH solution). The films were characterized by electron paramagnetic resonance spectroscopy (EPR) and infrared spectroscopy (FTIR) and their optical properties examined by ultraviolet–visible absorption spectroscopy (UV–vis) and photoluminescence (PL). The FTIR spectra show the characteristic features of P3MT and, together with the results of EPR, allowed to evaluate the charge carriers and to identify benzene and quinones in the formation of chains. The UV–vis absorption spectra helped to obtain the average gap energy of P3MT and presented the ππ* transition band and a bipolaron band. In the PL spectra, with variation of excitation power and temperature, studies were performed through the fit with Gaussian functions, given the strong probability of the existence of two distinct contributions in the formation of the emission spectra. These two contributions were assigned to the emission of mixed chains (Gaussian centered at higher energy) and emission of benzenoid chains (Gaussian of lower energy) in the formed polymeric material.
Keywords: Electrochemical synthesis; Photoluminescence; Poly(3-methylthiophene);

Structural and spectral investigations of anthracene doped polyaniline by Bhakti V. Raigaonkar; Lajna P. Vijayan; Santa Chawla; R.N. Dubey; M.S. Qureshi (348-353).
To couple the inherent conducting capability of polyaniline with the emissive properties of optically active organic dopant, we propose a novel polyaniline–anthracene co-polymer system. This paper presents structural and spectral investigations on anthracene doped polyaniline synthesized using emulsion polymerization technique. UV/vis absorption spectroscopy, photoluminescence (PL), fluorescence decay and FTIR spectroscopy measurements were performed to carry out the structural characterization. The absorption measurements indicate a change in the degree of oxidation of the polyaniline from 0.57 to 0.68 in the dopant concentration range 0.5–1.0 wt% (w/v). PL spectroscopy results revealed a multiplet emission characteristics located at 383 nm, 405 nm, 428 nm and 455 nm. Emission at 405 nm is ascribed to 0 ← 0 of 1La transition of anthracene and the intensity of this band was found to be dependent on dopant concentration. The emission at 383 nm quenched in doped compounds. The fluorescence decay lifetime of polyaniline increased with increasing dopant concentration. FTIR transmittance peaks observed at 1293.5 cm−1 and 1238.6 cm−1 due to the π electron delocalization and protonation of the polymer respectively, suggest that anthracene doping may be protonating the polymer. The change in degree of oxidation and probable protonation of polyaniline as a result of anthracene doping coupled with observed PL characteristics suggest a structural modification of polyaniline because of anthracene doping. The structural tunability of polyaniline combined with promising emissive property of anthracene makes the anthracene:polyaniline binary system a viable alternative for optoelectronic and sensing applications.
Keywords: Organic compounds; Photoemission; Fourier transform infrared spectroscopy (FTIR); Optical properties;

Synthesis and photophysical properties of a new two-photon absorbing chromophor containing imidazo[4,5-f][1,10]phenanthroline by Hai-Guang Zhang; Xu-Tang Tao; Kao-Shan Chen; Chun-Xue Yuan; Min-Hua Jiang (354-359).
A new two-photon absorption compound, 2-{4-[(dicyanomethylidene-5,5-dimethylcyclohexl)vinyl]phenyl}imidazo[4,5-f][1,10]phenanthroline (DDVPIP), was synthesized and characterized. Its two-photon absorption (TPA) cross-section is obtained as 62 GM (1 GM = 1 × 10−50  cm4  photon−1  molecule−1) with 200 fs laser pulses at 800 nm. The one-photon excited fluorescence (OPEF) and two-photon excited fluorescence (TPEF) of DDVPIP are sensitive to the acid/base of the solution, which are enhanced in the basic solution but weakened in acidic solution. Charge-transfer (CT) states of DDVPIP were calculated through theory methods to explain its acid–base-sensitive fluorescent properties.
Keywords: Imidazo[4,5-f][1,10]phenanthroline; Two-photon absorption; Two-photon fluorescent sensor;

Electrochemical polymerization and characterization of polypyrrole on Mg–Al alloy (AZ91D) by Metehan C. Turhan; M. Weiser; Manuela S. Killian; B. Leitner; S. Virtanen (360-364).
We report the formation of polypyrrole (PPy) coatings on Mg alloy AZ91D from aqueous solutions of a dicarboxylic organic acid salt by cyclic voltammetry (CV) method. The polymeric films of PPy are directly coated onto AZ91D substrates without any pretreatment or intermediate steps. The electrochemically formed PPy films were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). Electrochemical impedance spectroscopy (EIS) measurements demonstrate a good corrosion protection.
Keywords: Magnesium; Magnesium alloy; AZ91D; Conductive polymer; Corrosion; Biocoating; Salicylate; Cyclic voltammetry; FT-IR; XPS; ToF-SIMS;