Synthetic Metals (v.158, #21-24)

Photoreactive hole-transporting polymer bearing oxetane moieties and its application to green polymer light-emitting diodes by Min Ju Cho; Myung Hee Kim; Kyu Nam Kim; Jung-Il Jin; Young Min Kim; Young Wook Park; Byeong-Kwon Ju; Dong Hoon Choi (785-789).
A new hole-transporting polymer was prepared by the copolymerization of 9-(4-vinyl-benzyl)-9H-carbazole and 3-methyl-3-(4-vinyl-benzyloxymethyl)-oxetane in the presence of α,α′-azobisisobutyronitrile (AIBN). The latter contains an oxetane unit that is cationically photopolymerizable. It was characterized by NMR, GPC, IR spectroscopy, TGA, and differential scanning calorimetry (DSC). Multilayer polymer light-emitting diodes (PLEDs) were fabricated layer by layer by using the spin-coating method with an organic solution of a photoreactive copolymer. Organic soluble poly[2-(carbazol-9-yl)-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (CzEh-PPV) that carries hole-transporting carbazole pendants was also synthesized and employed as a green-emitting material in PLEDs. After UV illumination for photoreaction in the new photoreactive oxetane-based copolymer (VCz-Ox), we could spin coat the CzEh-PPV solution for the next layer. The hole-transport capability of the copolymer was evaluated in multilayer PLEDs that were fabricated to test the device performances.
Keywords: Photoreactive; Carbazole; Hole-transport materials; Cationic photopolymerization;

Synthesis of a fluoresceine-derivatized fluorene and its electrogenerated copolymers with fluorene: New pH indicators by Rimane Aoun; Ali Yassin; Mouhieddine El Jamal; Ali Kanj; Joëlle Rault-Berthelot; Cyril Poriel (790-795).
The synthesis of a fluorene derivative bearing a fluorescein moiety is described together with its anodic electropolymerization in presence of various amount of fluorene. Both polymers and monomers can be used as pH indicators in water and other medium. The fluorescence and absorption properties in function of the pH are presented and compared with those of fluorescein. In the excited state, the Fluorescein–fluorene monomer appears to be a stronger acid than fluorescein.
Keywords: Fluorescein; Anodic copolymerization; Fluorene; pH sensor; Fluorescence;

Design and electropolymerization of a new optically active iron tetraspirobifluorenyl porphyrin by Cyril Poriel; Yann Ferrand; Paul Le Maux; Joëlle Rault-Berthelot; Gérard Simonneaux (796-801).
The synthesis of optically active iron tetraspirobifluorenyl porphyrin is described. Organic conducting polymers have been prepared by anodic oxidation of these building blocks. Preliminary tests of asymmetric alkene epoxidation have been performed giving only moderate yields.
Keywords: Anodic polymerization; Chiral polymetalloporphyrins; Spirobifluorene; Iron-porphyrin; Tetraarylporphyrin;

Organic white light-emitting diodes using a new DCM derivative as an orange-red doping molecule by Do-Hoon Hwang; Jong-Don Lee; Hoon-Je Cho; Nam Sung Cho; Sang Kyu Lee; Moo-Jin Park; Hong-Ku Shim; Changhee Lee (802-809).
A new DCM derivative containing a phenothiazine moiety, 4-(dicyanomethylene)-2-t-butyl-6-(9-ethylphenothiazine-2-enyl)-4H-pyran (DCPTZ), has been synthesized for use as an orange-red fluorescent dye molecule in organic light-emitting diodes (OLEDs). EL devices with the structure ITO/PEDOT-PSS/α-NPD/Alq3:DCPTZ/Alq3/LiF/Al were fabricated with various DCPTZ doping concentrations. The maxima in the EL spectra of the devices varied from 580 to 620 nm depending on the doping concentration of the dye molecule. An EL device with 0.5% dopant concentration was found to exhibit a maximum brightness of 81,500 cd/m2 at 13.3 V and a power efficiency of 4.1 lm/W with CIE coordinates (0.51, 0.47) at a luminance of 100 cd/m2. White light-emitting devices with the structure ITO/PEDOT-PSS/α-NPD/α-NPD:DCPTZ/DPVBi/Alq3/LiF/Al were also fabricated. The thickness of the blue light-emitting 1,4-bis(2,2-diphenylvinyl)benzene (DPVBi) layer was varied to obtain white light emission. White light emission from the device was observed when the thickness of the DPVBi layer was greater than 10 nm. The maximum brightness and power efficiency of the device with a 20-nm DPVBi layer were found to be 30,300 cd/m2 and 2.0 lm/W, respectively, with CIE coordinates (0.33, 0.36). In addition, the white EL device exhibits a relatively high color rendering index (CRI) of about 83.
Keywords: Organic white light-emitting diode; DCM derivative; Organic semiconductor;

Organic light-emitting diodes based on new n-doped electron transport layer by J.W. Ma; Wei Xu; X.Y. Jiang; Z.L. Zhang (810-814).
Organic light-emitting diodes with 8-hydroxy-quinolinato lithium doped 4′7-diphyenyl-1, 10-phenanthroline as electron transport layer (ETL), and etrafluro-tetracyano-quinodimethane doped 4,4′,4″-tris(3-methylphenylphenylamono) triphenylamine as hole transport layer (HTL) are demonstrated. The conductivity of carrier transport layers with different doping concentration is examined by hole-only and electron-only devices. Compared with the referenced device (without doping), the current efficiency and power efficiency of the p–i–n device are enhanced by approximately 51% and 89%, respectively. This improvement is attributed to the improved conductivity of the transport layers and the efficient charge balance in the emission zone.
Keywords: Organic light-emitting diodes; Doping concentration; Carrier transport; Conductivity;

Diphenylamine-4-sulfonic acid and aniline were copolymerized by cyclic scanning of the potential in 1 M HCl solutions on platinum substrates. The inversion potential was shifted from values where diphenylamine-4-sulfonic acid is the only monomer oxidized to higher values where the oxidation of aniline is significant. FTIR-ATR spectroscopy and XPS results revealed the role played by the inversion potential on the preferential incorporation of each monomer. As a result, the sulfonation degree of the copolymers shows an interesting influence of the upper potential limit employed.
Keywords: Diphenylamine-4-sulfonic acid; Aniline; Electropolymerization; FTIR-ATR spectroscopy; XPS;

The charge transport properties of polyaniline including boron (PANI-B)/p-type silicon diode have been investigated. The current–voltage characteristics of the device have been investigated under white and ultraviolet light illuminations. Electronic parameters such as the barrier height, diode ideality factor and series resistance, were determined from the current–voltage (IV) characteristics in the dark of the device and were found to be 0.81 eV, 3.58 and 1.67 × 106  Ω, respectively. The photocurrent for the device was found to be 0.857 μA. The open circuit voltage (V oc  = 119.6 mV) under UV illumination is higher than that of the open circuit voltage under (V oc  = 57.6 mV) white light illumination, although the intensity of the UV light has lower value. The obtained photovoltaic results suggest that the polyaniline including boron/p-type silicon device can be used as a sensor in optical applications.
Keywords: Diode; Organic layer; Photovoltaic properties;

Epoxy-carbazole compositions by Piotr Czub; Wojciech Mazela; Jan Pielichowski (826-830).
The method of receiving mixed epoxy-carbazole compositions which, for the fact of its photoluminescence ability, may be used for production of LEDs diodes, has been elaborated. Mechanical, thermal and optical properties of low-molecular-weight epoxy resin Ruetapox 0162 of different content of 5-(9-carbazolyl)methyl-1,3-oxothiolane-2-thione has been examined. It has been also confirmed that in the reaction of co-cross-linking of resin and carbazole derivatives; materials of typical for epoxy resin: high mechanical strength, thermal stability, low water absorption, and low flammability, have been obtained. Radiation absorption spectrums in UV range and photoluminescence of maximum of respectively 328 and 342 nm and also 348 and 365 nm are characteristic for isolated carbazole molecules, which proves that epoxy resin may well perform a function of scattering matrix for carbazolyl substituents. The compositions of 5 wt.% is characterized by the best mechanical features and the highest photoluminescence intensity.
Keywords: Epoxy resins; 5-(9-Carbazolyl)methyl-1,3-oxothiolane-2-thione; Photoluminescence properties;

Synthesis and electropolymerization of 3,5-dithienylpyridines, their complexes and N-methylpyridinium cations by Michał Krompiec; Stanisław Krompiec; Hanna Ignasiak; Mieczysław Łapkowski; Piotr Kuś; Łukasz Stanek; Robert Penczek; Stefan Lis; Krzysztof Staniński; Mieczysław Sajewicz; Katarzyna Gębarowska (831-838).
A new, convenient and highly active catalytic system for coupling of thienylstannanes (3,4-ethylenedioxy-2-tributylstannylthiophene and 5-tributylstannyl-2,2′-bithiophene) with 3,5-dibromopyridine has been developed. The reaction was carried out at 140 °C, in xylene, the catalytic system was generated in situ from [Pd(acac)2] and P(o-tol)3 (0.25 mol.% Pd). Products of the coupling, i.e. 3,5-bis(3,4-ethyledioxy-2-thienyl)pyridine and 3,5-bis(2,2′-bithiophen-5-yl)pyridine) were subjected to reaction with methyl triflate in CH2Cl2 solution yielding the respective N-methylpyridinium salts. Electrochemical properties of the four new compounds have been studied. New, electrochromic polymers have been obtained from 3,5-bis(2,2′-bithiophen-5-yl)pyridine and from its complexes with BF3 and Sc3+ as well as from its N-methyl pyridinium triflate. All the new polymers, except the one obtained from unmodified 3,5-bis(2,2′-bithiophen-5-yl)pyridine are electrochemically stable. Therefore, it is suggested that the prerequisite of obtaining stable copolymers of thiophene and pyridine by electropolymerization is blocking of the pyridine nitrogen atom by alkylation or complexation.
Keywords: Polythiophene; Pyridine; Thienylpyridine; Electropolymerization; Boron trifluoride etherate; Stille coupling;

Synthesis, photophysical and photochemical studies on long chain zinc phthalocyanine derivatives by Abimbola Ogunsipe; Mahmut Durmuş; Devrim Atilla; Ayşe Gül Gürek; Vefa Ahsen; Tebello Nyokong (839-847).
The synthesis and characterization of 2,9,16,23-chloro-3,10,17,24-triethyleneoxysulphanylphthalocyaninato zinc(II) (CTESZnPc) is described. The photophysics and photochemistry of CTESZnPc and those of tetrakis(triethyleneoxysulphanyl)zinc phthalocyanine (TTESZnPc) and octakis(triethyleneoxysulphanyl)zinc phthalocyanine (OTESZnPc), are presented and compared with those of unsubstituted zinc phthalocyanine (ZnPc). The presence of triethyleneoxysulphanyl substituents on the ZnPc ring gave rise to higher values of singlet oxygen (Φ Δ) and photodegradation (Φ Pd) quantum yields in DMF. However, TTESZnPc, OTESZnPc and CTESZnPc are less fluorescent than ZnPc, judging from their fluorescence quantum yield (Φ F) values. Fluorescence was lower in toluene than in DMF due to aggregation in the former solvent. Triplet quantum yield (Φ T) values were found to increase with the presence of substituents on the ZnPc ring, while triplet lifetimes (τ T) were found to vary linearly with the logarithms of solvent viscosities. The fluorescences of the substituted ZnPc complexes were effectively quenched by benzoquinone (BQ), and the quenching data analyzed by the Stern–Volmer equation. The Stern–Volmer constants and the diffusion-controlled bimolecular rate constants were calculated.
Keywords: Phthalocyanine; Quantum yields; Singlet oxygen; Photodynamic therapy; Benzoquinone; Quenching;

Pulsed sonoelectrochemical synthesis of polyaniline nanoparticles and their capacitance properties by Raman Ganesan; Sangaraju Shanmugam; Aharon Gedanken (848-853).
Polyaniline nanoparticles with sizes of 20–40 nm were prepared by the pulsed sonoelectrochemical method. These nanoparticles are characterized by IR, UV–vis, HRSEM and TEM analysis. IR and UV–vis confirm the formation of polyaniline nanostructures. The capacitance of these materials was studied by cyclic voltammetry in 1 M H2SO4. The PANI nanoparticles prepared at 1 V show a higher capacitance value than PANI prepared at 0.9 V and polyaniline prepared by pulsed electrochemical deposition.
Keywords: Polyaniline; Sonoelectrochemistry; Electrodeposition; Cyclic voltammetry; Supercapacitor; Nanoparticles;

Three new trimers PV, FV and CV were synthesized by Heck coupling of 4(4-bromophenyl)-2,6-diphenylpyridine with substituted divinylbenzene, divinylfluorene and divinylcarbazole, respectively. They were very soluble in chloroform, dichloromethane, tetrahydrofuran and toluene. FV and CV were more thermally stable and showed higher glass transition temperature than PV. Their absorption maximum was located at 327–397 nm with optical band gap of 2.53–2.73 eV. FV and CV emitted blue-green light with emission maximum at 455–489 nm while PV emitted green-yellow light with emission maximum at 496–530 nm. Upon protonation, the trimer thin films displayed red-shifts of the emission maximum. The electrochemical and electroluminescent properties of the trimers were studied. Light-emitting diodes (LEDs) based on these trimers were fabricated. These LEDs showed bright blue light for FV, CV and bluish-green light for PV which are in line with their photoluminescence spectra. The maximum brightness was reached approximate 1000 cd/m2 for PV, 380 for FV, and 400 for CV, at current density of 200 mA/cm2.
Keywords: Divinylene molecules; Heck coupling; Photophysics; Fluorene; Carbazole; Pyridine; Light-emitting diodes; Electroluminescence;

Correlation of memory characteristics of polymer bistable memory devices with metal deposition process by Sung Hyun Kim; Kyoung Soo Yook; Jyongsik Jang; Jun Yeob Lee (861-864).
Origin of bistability in organic bistable memory devices (OBDs) was investigated by using two metal deposition processes of electron beam deposition and thermal deposition. Thermal deposition of Al was more effective than electron beam deposition to get high on/off ratio and stable operation of OBDs and metal nanoparticle formation during metal deposition was found to be critical to bistability of polymer OBDs.
Keywords: Bistability; Organic memory; Metal deposition process;

Poly(3,4-ethylenedioxythiophene)/copper (PEDOT/Cu) composites were prepared by an in situ redox reaction of 3,4-ethylenedioxythiophene (EDOT) and copper(II) chloride. During the reaction, EDOT was oxidatively polymerized by Cu(II) chloride, while the Cu(II) ions were reduced to produce Cu metal particles. PEDOT/Cu composite films were also successfully prepared on CuCl2-coated poly(ethylene terephthalate) (PET) films by the vapor phase polymerization of EDOT. PEDOT/Cu films were characterized using UV–vis spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to confirm the formation of PEDOT, and the presence of metallic Cu particles.
Keywords: Copper; PEDOT; Composites; In situ vapor polymerization;

Blue organic electroluminescent devices based on the spiro[fluorene-7,9′-benzofluorene] derivatives as host and dopant materials by Kyu-Sung Kim; Young-Min Jeon; Hyun-Seok Lee; Joon-Woo Kim; Chil-Won Lee; Ji-Geun Jang; Myoung-Seon Gong (870-875).
The novel spiro[fluorene-7,9′-benzofluorene]-based blue host material, 2-(10-phenylanthracene)-spiro[fluorene-7,9′-benzofluorene] (BH-3P), was successfully prepared by reacting 2-bromo-9,11-spiro[benzofluorene-fluorene] (3) with 9-phenylanthracene-10-boronic acid through the Suzuki reaction. Diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)-phenyl]-amine (BD-1), 2-[4′-(phenyl-4-vinylbenzeneamine)phenyl-spiro[fluorene-7,9′-benzofluorene] (BH-3BD) and 4-[2-naphthyl-4′ (phenyl-4-vinylbenzeneamine)]phenyl (BD-1N) were used as dopant materials. Blue OLEDs with the configuration of ITO/DNTPD/α-NPD/BH-3P:5% dopant/Alq3/Al–LiF were prepared from the BH-3P host and BD-1, BD-1N and BH-3BD dopants and they showed blue EL spectra at around 452 nm at 7 V and luminance efficiencies of 1.9–3.3 cd/A.
Keywords: Blue OLED; Host; Dopant; Spiro[fluorene-7,9′-benzofluorene]; Color purity;

Enhanced quantum efficiency in polymer light-emitting diode with water soluble non-conjugated polymer by A.R. Chun; S.H. Kim; M.S. Kim; C.G. Kim; S.J. Lee; T.W. Kwon; D.K. Park; S.J. Cho; J.G. Lee; S.H. Lee; Z.X. Guo; H.S. Woo (876-878).
We have fabricated highly efficient polymeric light-emitting diode (PLED) from water soluble non-conjugated polymer, polyurethane (PU), by using it as an ultra-thin insulating layer on the top of commercially available blue-emitting polymer, polyfluorene (PFO). The device with PU layer showed a maximum external quantum efficiency of 1.3% while the one without PU layer showed the efficiency of 0.6%. We propose that the better performance in PLED with PU layer was due to a well-balanced charge injection in emitting layer after the effective hole accumulation at the PFO/PU interface and thus increase in electron tunneling from cathode metal to emitting polymer.
Keywords: Polymeric light-emitting diode; External quantum efficiency; Hole accumulation;

In order to investigate semi-conductor nanocrystals in polymer light-emitting diodes (PLEDs), CdSe nanocrystals-conjugated polymer composite was used as the emitting material. High-quality CdSe were synthesized successfully by simple chemical colloid methods and doped into a green light-emitting polymer, PFBT8. As the concentration of CdSe in composite increases, the turn-on voltage of the device decreases, while EL intensity increases. The improvement is more remarkable when the concentration of CdSe increases in a certain range.
Keywords: Green light-emitting diodes; CdSe; Semi-conductor nanocrystals; Conjugated polymer;

Polyaniline (PANI) thin film on alumina was prepared by the chemical oxidation of aniline with ammonium peroxydisulphate in acidic aqueous medium. DC conductivity, microwave transmission and reflection, microwave conductivity, shielding effectiveness and microwave dielectric constant of the conducting PANI films are reported. DC conductivity was between 0.15 × 10−3 and 3.13 × 10−3  S/cm. Microwave conductivity was between 0.2 and 10 S/cm. The PANI films coated on alumina gave shielding effectiveness value of −1 to −4 db. The ɛ′ was between 2 and 350 whereas ɛ″ was between 437 and 60. Measurements have been carried over the frequency range of 8.2–18 GHz.
Keywords: Polyaniline; Microwave; Alumina; Conductivity; Shielding effectiveness; Dielectric constant;

Polypyrrole as a protective pigment in organic coatings by M. Selvaraj; S. Palraj; K. Maruthan; G. Rajagopal; G. Venkatachari (888-899).
This study deals with the preparation and characterization of polypyrrole (PPy) using ferric chloride and ammonium dichromate as oxidants and also with the addition of a common surfactant in aqueous solution. The combination of oxidant and surfactant in the preparation of PPy has shown that there is an enhancement in conductivity and also in the yield of the PPy. The deprotonated PPy exhibits a better stability with decreasing conductivity. Fourier transform infrared spectroscopy (FTIR) confirmed that the surfactant radical sulphoxide got incorporated into the PPy as a dopant and also the presence of chromate radical was indicated by the appearance of peak at 459 cm−1. Thermo Gravimetric Analysis (TGA) indicates that the weight losses for PPy-Cl and PPy-CrO4 are 97% and 35–50% at 1000 °C, respectively. X-ray diffraction (XRD) studies also give an idea about the size and shape of the polymer. The corrosion resistance property of PPy-incorporated coatings on mild steel substrate in sodium chloride solution indicates that the PPy-CrO4/epoxy-polyamide coating gives maximum duration of protection compared with other systems.
Keywords: Polypyrrole; Ammonium dichromate; Ferric chloride; Corrosion studies;

Encapsulation of multi-walled carbon nanotubes by poly(4-vinylpyridine) and its dispersion stability in various solvent media by Sanghyun Hong; Myunghun Kim; Chang Kook Hong; Dongsoo Jung; Sang Eun Shim (900-907).
MWNTs were effectively functionalized with KMnO4 in the presence of a phase transfer catalyst at room temperature. The hydroxyl functionalized MWNTs were reacted with a vinyl group-carrying silane-coupling agent and the terminal vinyl groups were used to fabricate poly(4-vinylpyridine) brushes by solution polymerization. Finally, P4VP-encapsulated MWNTs were obtained. The resulting materials were analyzed using TEM, TGA and their dispersion stability in various solvents was characterized by Turbiscan. It was found that the dispersion stability of P4VP-encapsulated MWNTs is dramatically improved in alcoholic medium due to the chemical affinity of P4VP with alcohol. This functionalization technique would provide a facile route to prepare various polymer brushes on the surface of MWNTs in order to improve the dispersion of MWNTs for potential applications.
Keywords: Carbon nanotubes; Phase transfer catalysis; Microencapsulation; Modification; Dispersion stability;

We have investigated the effects of thermal annealing before and after cathode deposition on poly(3-hexylthiophene) (P3HT)/[6,6]–phenyl C61-butyric acid methyl ester (PCBM) blend photovoltaic cells with different cathode buffer layers. The introduction of cathode buffer layer such as lithium fluoride (LiF) and calcium oxide (CaO) in pre-annealing cells can increase the open-circuit voltage (V oc) and the power conversion efficiency (PCE). Post thermal annealing after cathode deposition further enhanced the PCE of the cells with LiF/Al cathode, whereas the performance of the cell with CaO/Al cathode is decreased. It is found that the V oc and PCE can be largely enhanced when the post-annealed cell with Ca/Al cathode is exposed in air. This may attribute to the formation of CaO buffer layer, which favors increasing shunt resistance and V oc. Finally, a PCE of 4.60% is calculated under AM1.5G solar illumination at 100 mW/cm2.
Keywords: Photovoltaic cells; Conjugated polymer; Thermal annealing; Open-circuit voltage; Power conversion efficiency;

Synthesis and luminescent properties of Ir complexes with fluorine substituted phenylpyridine derivative ligands by Jiawei Hu; Guanghui Zhang; Hung-Hsin Shih; Peipei Sun; Chien-Hong Cheng (912-916).
Two phosphorescent iridium(III) complexes Ir(DFPP)2(acac) and Ir(DFPP)2(pic) (DFPP, 2-(2,4-difluorodephenyl)-3-phenylpyridine; acac, acetylacetone; pic, 2-picolinic acid) were synthesized. The complexes have strong phosphorescent characters. The organic light emitting devices (OLEDs) based on these complexes with the configuration of ITO/NPB (40 nm)/Ir complex: CBP (7%, 30 nm)/BCP (15 nm)/Alq (30 nm)/LiF (1 nm)/Al (100 nm) were fabricated. The device based on Ir(DFPP)2(acac) emits green color with a maximum external quantum efficiency of 4.14%, a brightness of 28,786 cd m−2; and the device based on Ir(DFPP)2(pic) emits cyan color with a maximum external quantum efficiency of 3.05%, a brightness of 24,220 cd m−2.
Keywords: Electrophosphorescence; Ir complex; Synthesis; OLED;

Ground state electronic absorption and photoluminescent properties of a series of porphyrin and phthalocyanine mixed rare earth triple- and double-decker complexes, namely [(TClPP)M(Pc)M(TClPP)] (a), [(TClPP)M(Pc)M(Pc)] (b) and [(TClPP)M(Pc)] (c) [Pc = phthalocyaninate; TClPP = eso-tetrakis(4-chlorophenyl)porphyrinate; M = Tb (1a1c), Eu (2a2c)] have been investigated comparatively. The optical properties analogous to each other for these sandwich compounds suggests that internal π–π interactions between each macrocycles within the compounds defining the electronic properties of the chromophores brought within van der Waals distance. Besides, the unexpected phosphorescence bands of the terbium containing double- and triple-deckers, arising from 3T(π, π*) state of the compounds indicates that rare earth metals chelated in the highly conjugated macrocyclic compounds play no direct role in the stable states, but determine the relaxation rates and pathways of the excited states following photoexcitation of sandwich-type tetrapyrrolic complexes.
Keywords: Porphyrin; Phthalocyane; Sandwich; Rare earth; Luminescence; Photophysics;

Polyaniline (PANI) and polyaniline/silver nanocomposites have been synthesized by sonochemical and ionizing radiation technique. These composite materials were obtained through sonication and γ irradiation of an aqueous solution of aniline and silver nitrate at room temperature. The suggested mechanisms to explain the formation of these products are based on the fact that both methods produce hydroxyl radical •OH and hydrogen radical •H, which acts as an oxidizing agent for the polymerization process of aniline monomer and as reducing agent for silver ions, respectively. Spectroscopic, X-ray and scanning electron microscope (SEM) measures showed that polyaniline and silver nanoparticles of 40 nm of average diameter are obtained when ultrasonic technique is used whereas silver nanoparticles of 60 nm average, and highly fibrillar polyaniline network with diameter of 60 nm is obtained when γ radiation is used.
Keywords: Conducting polymers; Sonochemistry; Ionizing radiation; Polyaniline;

Polymerization of aniline in ice by Elena N. Konyushenko; Jaroslav Stejskal; Miroslava Trchová; Natalia V. Blinova; Petr Holler (927-933).
It was observed that the oxidative polymerization of aniline proceeded well not only in the liquid mixtures at 20 °C or −5 °C but also in ice at −24 °C. The oxidative polymerization took place in the solutions of strong acid (0.1 M sulfuric acid) or weak acid (0.4 M acetic acid). It is proposed that the initially generated polyaniline participates in the further redox process, leading to new polyaniline formation. The molecules of the monomer (aniline) and oxidant (peroxydisulfate) thus react by transferring electrons through the conducting polyaniline, without the need to be in direct contact. The polymerization in the liquid phase or in the solid frozen state changes the morphology of the polyaniline. Polyaniline nanogranules or nanotubes are produced in the liquid state, while thin nanowires of 20 nm diameter connecting the submicrometre polyaniline particles have been observed when the polymerization took place in ice.
Keywords: Aniline; Polyaniline; Conducting polymer; Redox reaction; Nanotube; Nanowire; Electron transfer; Ice; Solid-state polymerization;

Electronic structure of frontier states in an evaporated thin film of a highly amphoteric and polar molecule by Jun’ya Tsutsumi; Daisuke Yamamoto; Hiroyuki Yoshida; Naoki Sato (934-938).
{4-[4,5-Bis(methylsulfanyl)-1,3-dithiol-2-ylidene]cyclohexa-2,5-dien-1-ylidene}malononitrile (BMDCM) is designed toward a highly amphoteric and polar molecule (HAPM). Its electron donating and accepting abilities in the solid state were examined from the measurements of its electronic structure using ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES): The threshold ionization energy I s th and electron affinity A s th in the solid state were determined to be 5.1 ± 0.15 and 3.5 ± 0.4 eV, respectively. These values turn out to be comparable to the corresponding values of typical donor or acceptor compounds, indicating high abilities in both electron donating and accepting nature of BMDCM. The origin of such a nature of BMDCM is discussed in terms of aromatic stabilization in its ionic states.
Keywords: Amphotericity; Narrow-gap organic semiconductor; Ultraviolet photoemission spectroscopy; Inverse photoemission spectroscopy;

Electronic properties and junction behaviour of micro- and nano-meter-sized polyanthranilic acid/metal contacts by Arun Kumar Singh; Rajiv Prakash; A.D.D. Dwivedi; P. Chakrabarti (939-945).
Self-doped conducting polymer, polyanthranilic acid (PANA) was synthesized and used for the first time for fabrication of contacts with the configurations (Al, Ti, Sn metal)/PANA/indium tin oxide (ITO) coated glass and Al/PANA/Pt-nano-probe using mico- and nano-meter thick PANA layers, respectively. The chemically synthesized PANA dissolved in methanol was deposited over the substrate (ITO coated glass plate/Al-flat electrode) using spin coating technique. The current–voltage (IV) characteristics and diode performance parameters of micro- and nano-meter sized devices were compared and contrasted by using micro- and nano-contact arrangements. The IV characteristics of the above two configurations exhibited a rectifying contact with Al and Ti metals and an ohmic contact with Sn. The morphology of polyanthranilic acid film was studied using atomic force microscope and UV–vis spectroscopic technique was used to obtain the optical bandgap of the polymer.
Keywords: Polyanthranilic acid; Conducting polymer; Schottky diode; Electronic and junction properties;

Scavenging of DPPH free radicals by polypyrrole powders of varying levels of overoxidation and/or reduction by Chyong Fang Hsu; Lijuan Zhang; Hui Peng; Jadranka Travas-Sejdic; Paul A. Kilmartin (946-952).
Polypyrrole (PPy) powders were synthesized chemically using the oxidant ammonium persulfate (APS). The free radical scavenging properties were evaluated using a form of the α,α-diphenyl-β-picrylhydrazyl (DPPH) assay adapted for use with 1.0 mg amounts of conducting polymer powders. A lower scavenging capacity was obtained when a higher ratio of APS to pyrrole was used in the chemical synthesis which also led to a decrease in polymer conductivity and doping level as determined by the amount of (bi)sulfate present given by elemental analyses. The occurrence of overoxidation of polypyrrole at a higher oxidant level was confirmed in FTIR spectra by the presence of a carbonyl group. PPy prepared at a lower APS/pyrrole ratio contained more bipolaron charge carriers, which were converted to polarons upon initial reduction with hydrazine. More complete reduction with hydrazine led to a loss of (bi)sulfate dopant, but to improved DPPH radical scavenging, confirming that the conducting polymer is acting as a reducing agent in scavenging DPPH radicals.
Keywords: Polymers; Radical reactions; Polypyrrole; DPPH; Overoxidation;

Surfactant-assisted polypyrrole/titanate composite nanofibers: Morphology, structure and electrical properties by Qilin Cheng; Ying He; Vladimir Pavlinek; Chunzhong Li; Petr Saha (953-957).
In this work, we demonstrate a simple route to the preparation of bulk quantities of polypyrrole/titanate (PPy/TN) composite nanofibers using cetyl trimethylammonium bromide (CTAB) as a structure-directing agent. Titanate (TN) nanowires and CTAB act as a template for fabrication of the composite nanofibers. The structural characterization shows that the resulting nanocomposite exhibits core-shell nanofiber networks and the average diameter of the nanofibers is around 50–90 nm. The electrical conductivity measurements reveal that the addition of TN nanowires slightly enhances the conductivity of the composite. The ac conductivity follows the power law, which varies with the mass ratio of pyrrole monomer to TN. A possible mechanism is also proposed to interpret the formation of the PPy/TN composite nanofiber networks.
Keywords: Polypyrrole; Titanate nanowires; Composite nanofibers; Electrical properties;

Oligothiophene based organic semiconductors with cross-linkable benzophenone moieties by Ajay Virkar; Mang-Mang Ling; Jason Locklin; Zhenan Bao (958-963).
Two oligothiophene based organic semiconductors with photo-cross-linkable benzophenone (BP) groups were synthesized and characterized. Solution cast and evaporated thin film transistors (TFTs) were created and field effect mobilities exceeding 10−3  cm2  V−1  s−1 were achieved. Upon film cross-linking the mobility increased nearly a factor of two suggesting some molecular reorganization. The stability and crosslinking of the semiconducting films were monitored by Fourier Transform Infrared Spectroscopy (FTIR). Preliminary work was also performed to study the potential of attaching analyte molecules to the semiconductor surface via photo-attachment to the BP groups for future sensor applications. The water contact angle of the semiconductor layer before and after the attachment of l-glutamic acid was measured. A drop of nearly 20 degrees suggests incorporation of the amino acid onto the surface of the semiconductor film after UV crosslinking.
Keywords: Oligothiophene; Polymerization; Photochemical;

Synthesis and nonlinear optical properties of two three-branched two-photon polymerization initiators by Xian Zhang; Xiaoqiang Yu; JinShui Yao; Minhua Jiang (964-968).
Two three-branched photopolymerization initiators, 1,3,5-tris[p-(4-N,N-dibutylamino)vinylbenzene]benzene (TBAVBB) and 1,3,5-tris[p-(4-N,N-diphenylamino)vinylbenzene]benzene (TPAVBB) have been synthesized with solid-phase Wittig reaction. The single-photon fluorescence, quantum yields, lifetimes and solvent effects of the initiators were studied in detail, and both compounds were found to exhibit good single-photon fluorescence emission. Two compounds are good two-photon absorptiontive chromophores and operative two-photon photopolymerization initiators. Two-photon absorption (TPA) cross-sections from 730 nm to 870 nm at intervals of 10 nm have been measured with the two-photon-induced fluorescence method, and the maximal TPA cross-sections of TBAVBB and TPAVBB are 432.7 GM and 546.2 GM (1 GM = 1 × 10−50  cm4  s photon−1  molecule−1) at 800 nm, respectively. We measured the quasi two-photon polymerization rates (R p) based on scanning speed and the width of the written protruding line. Polymerization rates of TBAVBB and TPAVBB were found to be 117.8 μm3  s−1 and 66.2 μm3  s−1 in the case of the laser power 0.3 W at 800 nm, respectively.
Keywords: Synthesize; Single-photon fluorescence; Two-photon absorbing; Photopolymerization initiators; TPA cross-section; Polymerization rate;

Electronic properties of organic–inorganic (OI) hybrid heterojunction fabricated by forming a thin macrocyclic diamagnetic and binuclear Cu(II) complex [Cu2(L)(ClO4)2][ClO4]2 (where L is C33H32N2O4) film on n-Si wafer have been studied. The Au/Cu(II) complex/n-Si contact has a rectifying behavior with the barrier height of 0.96 eV and the ideality factor of 2.96 determined from forward-bias current–voltage (IV) characteristics at room temperature. The energy distribution of the interface state density (N ss) in the semiconductor band gap at Cu(II) complex/n-Si interface obtained from IV characteristics ranges from 1.62 × 1013  cm−2  eV−1 at (E c  − 0.66) eV to 6.82 × 1012  cm−2  eV−1 at (E c  − 0.9) eV.
Keywords: Organic–inorganic semiconductor contact; Binuclear Cu(II) complex; Schottky diode;

Magnetic oscillations amplitude of a dirty quasi two-dimensional organic metal by David Vignolles; Alain Audouard; Vladimir N. Laukhin; Marc Nardone; Enric Canadell; Nataliya G. Spitsina; Eduard B. Yagubskii (973-976).
Magnetoresistance of dirty crystals of the organic metal (BEDO)5Ni(CN)4·3C2H4(OH)2 (where BEDO stands for the bis(ethylenedioxy)tetrathiafulvalene molecule) has been measured up to 54 T at liquid helium temperatures. Quantum oscillations are clearly observed in a large field range even though a Dingle temperature as high as about 13 K is deduced from the field dependence of the oscillations amplitude. This value corresponds to scattering time as low as τ D ∼ 0.1  ps, leading to ω c τ D values (where ω c is the cyclotron pulsation) smaller than 1. Possible origins of the observed low scattering time value are discussed.
Keywords: Organic metals; High magnetic fields; Quantum oscillations; Fermi surface;

Controllable functionalization of single-wall carbon nanotubes by in situ polymerization method for organic photovoltaic devices by Daqin Yun; Wei Feng; Hongcai Wu; Baoming Li; Xiaozheng Liu; Wenhui Yi; Junfen Qiang; Song Gao; Shaolin Yan (977-983).
Single-wall carbon nanotubes (SWNTs) have been covalently modified with poly[(2-methoxy,5-octoxy)1,4-phenylenevinylene] (MO-PPV) by in situ polymerization reaction to form a series of nanocomposites with well-controlled interfaces. The method provided a mean to disperse nanotubes uniformly and maximize the interfacial area at the same time. Absorption spectrum and electron microscopy imaging of the composite structure have been influenced by doped a small amount of functionalized SWNTs. Moreover, steady-state and time-resolved photoluminescence spectra quenched markedly by the introduction of internal polymer/nanotube junctions within the polymer matrix. Photovoltaic devices based on MO-PPV/SWNTs bulk heterojunctions showed much better in performance. The data suggested that such improvement was attributed to the bulk molecular heterojunctions intrinsic nanophase separation that resulted more efficient excitons separation, transportation and collection.
Keywords: MO-PPV/SWNTs nanocomposites; Absorption spectrum; Steady-state and time-resolved photoluminescence spectra; Photovoltaic devices;

Electronic structures of 8-hydroquinolatolithium on Au substrate: The organic electron injection layer having semiconducting properties by Kwanghee Cho; Sang Wan Cho; Pyung Eun Jeon; Hyunbok Lee; Chung-Nam Whang; Kwangho Jeong; Seong Jun Kang; Yeonjin Yi (984-987).
We studied the electronic structures of the 8-hydroquinolatolithium (Liq)/Au interface using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and theoretical calculation. It is revealed that Liq is an organic semiconducting material with electron and hole injection barriers of 1.28 and 1.32 eV in contact with Au, respectively. The theoretical calculations showed that the highest (lowest) occupied (unoccupied) molecular orbital [HOMO (LUMO)] of Liq mainly derive from the quinolate part of the molecule. The HOMO and LUMO levels are highly delocalized throughout the quinolate part, giving it good conducting properties unlike other insulating electron injection layers. Furthermore, the electronic structures of Liq are nearly identical to tris-(8-hydroquinoline) aluminum (Alq3), so that the energy level mismatching between the two molecules could be minimal. This explains why the Alq3 based device in combination with Liq shows good performance.
Keywords: OLEDs; Electronic structure; Injection barrier; Alq3; Liq; UPS; XPS;

Enhanced electroluminescent properties of triarylamine-endcapped X-branched oligofluorene by Fan Yang; Xiao Ling Zhang; Kang Sun; Mo Jun Xiong; Ping Fang Xia; Zi Jian Cao; Zhong Hui Li (988-992).
A facile approach for synthesis of the triarylamine-endcapped X-branched oligofluorene, X-OF(2)Ph-NPh and its corresponding linear oligofluorene, OF(2)Ph-NPh by Suzuki cross-coupling as a key reaction has been developed. This novel X-branched oligofluorene exhibits much higher thermal and electrochemical stabilities and enhanced electroluminescent properties as comparison to its corresponding linear counterpart. Using a simple two-layer OLED structure of ITO/oligofluorene (40 nm)/PBD (40 nm)/LiF (1 nm)/Al (150 nm), the luminance efficiency of X-OF(2)Ph-NPh-based OLED can also reach up to 2.8 cd/A with a maximum brightness of 1700 cd/m2 and remarkably better than 1.2 cd/A with a maximum brightness of 700 cd/m2 for its corresponding linear oligofluorene OF(2)Ph-NPh-based OLEDs.
Keywords: X-branched oligofluorene; Synthesis; Functional properties; Electroluminescent property; OLED;

Carbazole-based bis(enamines) as effective charge-transporting amorphous molecular materials by E. Puodziukynaite; E. Burbulis; J.V. Grazulevicius; V. Getautis; J. Jankauskas (993-998).
A series of carbazole-based bis(enamines) as glass-forming hole transport materials has been synthesized and characterized. The amorphous films of the reported compounds demonstrate extraordinarily high hole-drift mobilities reaching 5 × 10−2  cm2/V s at high electric fields. To our knowledge this is one of the highest values observed to date for amorphous molecular p-type semiconductors. The reported compounds constitute materials with high thermal stability with five percent weight loss temperatures exceeding 370 °C as characterised by thermogravimetric analysis. They form glasses with the glass transition temperatures ranging from 83 to 126 °C as established by differential scanning calorimetry. Photoelectric properties of the materials were examined by electron photoemission and time of flight technique. The electron photoemission spectra of the layers revealed the ionization potentials as low as 4.98–5.15 eV.
Keywords: Enamine; Molecular glass; Ionization potential; Charge transport;

Interpolymer complexation of water-soluble self-doped polyaniline by Olga A. Pyshkina; Byeongyeol Kim; Alexei N. Korovin; Alexander Zezin; Vladmir G. Sergeyev; Kalle Levon (999-1003).
Water-soluble polyaniline compounds are important for potential applications in organic electronics. The use of organic inks as an example require accurate control of the size and charge of the conducting particles, which both can be optimized with an additional complexation, charge neutralization. We report here the synthesis and characterization of internally doped highly sulfonated polyaniline with sulfur to nitrogen ratio S/N of ∼1. This electroactive polyelectrolyte, which has high water solubility in all pH regions, was complexed with oppositely charged poly-N-ethyl-4-vinylpyridinium bromide and the properties of such interpolymer complex were studied.
Keywords: Polyaniline; Interpolymer complex; Water soluble;

Polymer-dispersed liquid crystal based on E7: Morphology and characterization by P. Formentín; R. Palacios; J. Ferré-Borrull; J. Pallarés; L.F. Marsal (1004-1008).
Polymer-dispersed liquid crystals (PDLCs) are liquid crystal dispersions within a polymer matrix. PDLCs have attracted the interest of researchers for their applications as light shutters, smart windows, and active displays. Herein, we report on the preparation and characterization of PDLCs by a combination of two types of induced phase separation. Experimental results show the nucleation and growth of the E7 liquid crystal droplets from poly(styrene), poly(methylmethacrylate) or poly(dimethylsiloxane) which are used as a polymeric matrix. The time evolution of liquid crystal droplets in terms of liquid crystal domain diameter was quantified. PDLCs were characterized by Fourier transform infrared spectroscopy and Raman spectroscopy.
Keywords: Polymer-dispersed liquid crystal (PDLC); Phase separation; Fourier transform infrared spectroscopy;

We report on the synthesis of poly(3-octylthiophene)/γ-Fe2O3 nanocomposite by realizing the transfer of maghemite nanoparticles from aqueous solution to organic media. Monomer was polymerized in non-aqueous chloroform in the presence of the dispersed iron-oxide particles. The iron-oxide content of the composite was determined by atom absorption spectroscopy (ICP-AAS) and energy dispersive X-ray microanalysis technique (EDX). The molecular structure was characterized by UV–vis spectroscopy and photoacoustic Fourier transform infrared spectroscopy (PAS-FTIR). X-ray diffraction (XRD) was used to characterize the supramolecular structure. Morphology change could be followed by scanning electron microscopy (SEM) which shows that the presence of maghemite particles during the synthesis results in a more compact structure consisting of spherical particles. The effective chain-length did not alter in comparison with the net polymer, moreover the structural change can be well correlated with the conductivity and capacity increase, determined from AC impedance spectroscopy measurements. The successful synthesis of the new composite possessing conducting, superparamagnetic and thermoelectric properties, can lead to possible applications.
Keywords: Poly(3-octylthiophene); Maghemite; Nanocomposite; Superparamagnetic; Thermoelectric;

Four new molecular solids, [1-(2′-F-4′-R-benzyl)pyridinium][bis(maleonitrile dithiolato)nickel] (abbreviated as [RFBzPy][Ni(mnt)2], R = F (1), Cl (2), I (3), H (4)), have been prepared and characterized. The Ni(III) ions in 13 form a 1D zig-zag chain within a Ni(mnt)2 column. The chain is uniform in 2 and 3, while it is alternating in 1. The cations and Ni(mnt)2 ions of 4 stack in complicated way in which the stacking of Ni(III) ions shows an ACA-type repeat unit. Magnetic susceptibility measurements in the temperature range 1.8–300 K show that 1 and 4 are diamagnetic, whereas 2 and 3 exhibit ferromagnetic coupling behavior. The χ M T of 2 and 3 can be well reproduced by the Baker equation for a 1D S  = 1/2 magnetic chain with g  = 2.01, J  = 17.8 cm−1 for 2, and g  = 2.04, J  = 41.1 cm−1 for 3.
Keywords: Bis(maleonitriledithiolato)nickel(III) monoanion; Molecular solids; Substituted pyridinium; Crystal structures; Ferromagnetic coupling;

Synthesis, characterization and photoluminescence of poly(VK-(ppy)2Ir(N-phMA)) by Weijie Wang; Tuo Zhu; Guoqing Chen; Cheng Li; Hongbo Di; Chunxia Ren; Yuqiang Ding (1022-1027).
Reaction of N-phenyl methacrylamide (N-phMA) with (ppy)2Ir(μ-Cl)2Ir(ppy)2 (ppy = 2-phenylpyridine) in dichloromethane at the present of sodium methoxide at room temperature yields Iridium(III)-containing complex (ppy)2Ir(N-phMA) in which a N-substitued acrylamide was firstly applied as ancillary ligand. Complex (ppy)2Ir(N-phMA) can readily copolymerized with the commonly used N-vinyl carbazole (VK) for PLED materials in different feed ratios to generate a series of metal-containing polymers poly(VK-(ppy)2Ir(N-phMA))s whose chemical structures are well-defined. Investigations of thermal and photophysical properties indicate that these polymers are of interest materials for PLED.
Keywords: Light-emitting polymer; Luminescence; N-Phenyl methacrylamide; Metal complex; Iridium-containing polymer;

A luminescent polymer, poly{2-[10′-(2″-(4″′-oxyphenyl)-5″-phenyl-1″,3″,4″-oxadiazole)-decyloxy]-1,4-phenylenevinylene-alt-2,5-didodecyloxy-1,4-phenylenevinylene} (PPOXA), was synthesized. The electron withdrawing pendant, 2′-(4″-phenoxy)-5′-(4″′-phenyl)-1′,3′,4′-oxadiazole (OXD), is separated from the main chain via a linear 1,10-decamethylenedioxy chain. The band gap and photoluminescence (PL) maximum wavelength of PPOXA and HDO (poly(2-hexadecyloxy-1,4-phenylenevinylene-alt-2,5-didodecyloxy-1,4-phenylenevinylene)) exactly match each other (2.19 eV and 557 nm). In addition, the electroluminescence (EL) maximum wavelength of PPOXA is 559 nm, which is very close to that of HDO (557 nm). In the PL and EL spectra of film, the emission from conjugated 1,3,4-oxadiazole (OXD) unit was not observed and did not affect the EL and PL maxima of PPOXA. The HOMO and LUMO energy levels of the main chain figured out from the cyclic voltammogram and the UV–vis spectrum are −5.11 and −2.94 eV, respectively, which are very close to those of HDO (−5.13, −2.94 eV). The estimated HOMO and LUMO energy levels of the pendant are −6.54 and −2.84 eV, respectively. Single layer EL device based on PPOXA has a maximum external quantum efficiency of 0.23 cd/A, which is significantly higher than that of HDO (0.043 cd/A) measured under the same conditions. The energy levels figured out from optical and electrochemical data strongly support that the OXD pendants have hole blocking properties. Single layer structured EL device based on PPOXA (ITO/PPOXA/Al) shows the emission at the reverse bias with an efficiency of 0.043 cd/A, which is very comparable to that of ITO/HDO/Al under the forward bias.
Keywords: Poly(p-phenylenevinylene); Electroluminescence; Conjugated 1,3,4-oxadiazole; AC electroluminescent device;

Synthesis and electrochemical and optical characterization of poly(3-octadecylthiophene) by Hállen D.R. Calado; Tulio Matencio; Claudio L. Donnici; Luiz A. Cury; Jacques Rieumont; Jean-M. Pernaut (1037-1042).
The 3-octadecylthiophene has been synthesized and characterized by FTIR, UV–vis and 1H and 13C NMR. The correspondent polymer, the poly(3-octadecylthiophene) (PODT) has been chemically and electrochemically synthesized. The obtained polymer is soluble in common organic solvents, such as chloroform, tetrahydrofuran and toluene. IR and NMR spectra analysis confirm its regio-regularity. The electrochemical properties studied by cyclic voltametry of PODT electrochemically synthesized were characterized by a semi-reversible behavior with one anodic peak at 0.96 V and one cathodic peak at 0.77 V vs. Ag/AgNO3. Spectroelectrochemistry and optical properties, such as optical absorption and photoluminescence (PL) were studied at different temperatures for the PODT chemically synthesized. Spectroelectrochemical results clearly indicate the polaron formation. The results obtained from the analysis of the dependence on temperature of the optical properties of the PODT casting film corroborate the high regio-regular structure of the chains.
Keywords: Conjugated polymer; Poly(3-octadecylthiophene); Photoluminescence; Cyclic voltammetry; Coupling reactions;

Effect of magnetic field on electrochemical polymerization of EDOT by M.S. Cho; Y.Y. Yun; J.D. Nam; Y. Son; Y. Lee (1043-1046).
Poly(3,4-ethylenedioxythiophene) (PEDOT) films were synthesized by electropolymerization under an applied magnetic field on ITO glass. The effects of the magnetic field on the electrochemical polymerization of EDOT and the redox behavior were examined. The cyclic voltammetry (CV) result indicated that the applied magnetic field exceedingly accelerated the polymerization rate. The effect of the conformation of the PEDOT chains under applied magnetic field was studied by Raman spectroscopy. Scanning electron microscopy (SEM) showed the morphological changes of PEDOT film in the presence of the magnetic field. The parallel applied magnetic field induced the formation of more expanded chain structure as well as sharp crystalline morphology.
Keywords: Conducting polymer; PEDOT; Magnetic field; Cyclic voltammetry;

Electronic conduction mechanism in chitin–polyaniline blend by A.T. Ramaprasad; Vijayalakshmi Rao (1047-1053).
The electrical conductivity of chitin–polyaniline blend doped with HCl has been studied in the temperature range 323–373 K for various blend compositions. Conductivity of blends increases from less than ≈10−7  S/cm to 2.15 × 10−5  S/cm, depending on the percentage of polyaniline in the blend due to self-doping of LiCl. When these blends are doped with HCl conductivity raises to ≈9.68 × 10−2  S/cm. Current–voltage data is analyzed using various models available. The results suggest Schottky–Richardson and one-dimensional variable range hopping mechanisms for undoped blend and one-dimensional variable range hopping mechanism in the case of doped blend.
Keywords: Polyaniline; Chitin; Electrical properties; Conduction mechanism; Doping; Blending;

Synthesis of tetraarylsilanes and its usage as blue emitters in electroluminescence by Qun Shen; Shanghui Ye; Gui Yu; Ping Lu; Yunqi Liu (1054-1058).
A series of blue-emitting materials with sp3 Si cores were synthesized by Suzuki Coupling reaction and characterized by spectroscopy. Their usages as blue emitters in organic light-emitting diodes (OLEDs) were preliminary investigated. Blue emission with comparable brightness and efficiency were obtained with structure of ITO/NPB/tetraarylsilane/TPBi/LiF/Al. Moreover, these tetraarylsilane compounds exhibited high thermal decomposition temperatures (T ds) which indicated that these compounds might be explored for potential application in flat panel display.
Keywords: Tetraarylsilane; Photoluminescence; Electroluminescence;

Study on nonlinear optical properties of N+ ion implanted poly-o-toluidine films by Yan Shaolin; Wu Hongcai; Liu Xiaozeng; Gao Song; Li Baoming (1059-1061).
Poly-o-toluidine (POT) was synthesized chemically using (NH4)2S2O8 as oxidizing agent in acidic media. The POT films were prepared by spin-coating method with a thickness of about 300 nm and implanted by 35 keV N+ ions with the dose in the range of 6.3 × 1013 to 7.6 × 1016  ions/cm2. The POT films in pristine and implanted forms were characterized by visible absorption spectra, which showed that the optical absorption in the visible band was reinforced by ion implantation. The optical band gap (E g) of POT film derived from the visible absorption spectrum was decreased from 3.3 to 2.59 eV with the increase of ion dose. The effect of ion implantation on third-order nonlinear optical (NLO) susceptibility (χ (3)) was investigated carefully by degenerate four-wave mixing (DFWM) technique. The χ (3) value of pristine POT film was 3.27 × 10−10  esu and the maximum χ (3) value of implanted POT film was increased to 3.56 × 10−9  esu when the ion dose was 1.9 × 1016  ions/cm2.
Keywords: Ion implantation; Poly-o-toluidine; Degenerate four-wave mixing; Three-order nonlinear optical susceptibility;

We report the excitation spectrum of a ∼ 185 nm thick layer tris-(8-hydroxyquinolate)-aluminium, vapour deposited on a 100  μ m thick borosilicate microscopy cover glass, in the 1.9–2.4 eV range using a conventional cavity-ringdown spectrometer setup. The spectrum is collected at room temperature in an open cavity. It shows a broad loss structure with a maximum around 2.1 eV and a width of ∼ 0.2 eV. The spectrum is in conformity with literature phosphorescence spectra and with literature TDDFT computed T1← S0 transition energies. The observed loss structure can be attributed to the T1← S0 absorption band of tris-(8-hydroxyquinolate)-aluminium.
Keywords: OLED; Triplet; Absorption; Tris-(8-hydroxyquinolate)-aluminium; Cavity ringdown; Spectroscopy;

A new type of hybrid polymer electrolyte matrix based on benzidine impregnated polyepichlorohydrine (PEC) with TiO2 nanofiller was developed for dye-sensitized solar cells (DSSCs). The polymer electrolytes were characterized by scanning electron microscopy (SEM), TGA, XRD and FT-IR, and the assembled DSSCs by photocurrent density–voltage and energy conversion efficiency (η) measurements. The ionic conductivity and the interfacial contact with dye attached TiO2 particles were enhanced markedly by the addition of electrochrome impregnated polymer electrolyte, resulting in very high overall energy conversion efficiency.
Keywords: Dye-sensitized solar cells; Polymer electrolytes; Nanofillers; Benzidine;

Controlling the electrical properties of pentacene-based organic inverter by ultraviolet by Jeong-M. Choi; Wonjun Choi; Seungjun Lee; Seongil Im (1072-1076).
We report on the fabrication of pentacene-based organic inverter with two p-channel thin-film transistors (TFTs) on polymer/AlO x bilayer dielectric, which has been patterned by using high-energy ultraviolet (UV, 254 nm) illumination. After pentacene-channel growth on the dielectric, our inverter showed a high-voltage gain of ∼8 under −6 V supply voltage (V DD) but voltage transfer characteristics (VTC) curve is too marginal to guarantee a desirable inverter operation between 0 and −6 V. When low-energy UV (352 nm) was applied onto one of the two p-TFTs, which plays as a load in the inverter circuit, the VTC curve was adjusted to be more adequate for inverting operation due to the UV-induced modification on the threshold voltage and channel resistance of the load-TFT. Our UV-treated inverter also demonstrated much faster inverting dynamics than that of pristine inverter due to the lowered channel resistance of load-TFT.
Keywords: Pentacene; Inverters; Ultraviolet;