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Synthetic Metals (v.161, #21-22)

Editorial Board (pp. iii).

A novel route for designing C60 derivatives with large first hyperpolarizability: Cage-opened cases by Liang Zhao; Min Zhang; Lili Shi; Shiling Sun; Shuixing Wu; Chunguang Liu; Zhongmin Su (pp. 2185-2191).
► Open-cage oxo-fullerene derivatives are more stable than fullerene. ► The formation of C55O5 may be easier than that of C54O6. ► They show remarkable static first hyperpolarizability. ► New route to explore novel NLO materials based on fullerene derivatives.Systematic density functional investigations on the structural and electronic properties of C55O5 and C54O6, two open-cage oxo-fullerene derivatives, have been performed. Those formed from topmost pentagon and hexagon of C60 cleaved with oxygen atoms, have a large circular opening 4.92Å and 5.99Å, respectively. The size of the opening is large enough to allow guest atoms or small molecules penetrating, thus C55O5 and C54O6 may act as promising candidates for fuel storage. The calculations on their nonlinear optical (NLO) properties with ZINDO/SCI–SOS method show that the investigated compounds possess remarkably larger static first hyperpolarizability ( β) values amounting to −239.48 and −339.83×10−30esu for C55O5 and C54O6, respectively, which are comparable to the reported exohedral C60 derivatives. It opens a new route to explore new type of NLO materials based on C60 derivatives.

Keywords: Open-cage fullerene; C; 55; O; 5; C; 54; O; 6; NLO; First hyperpolarizability; Sum-over-state

Fabrication and absorbing property of microwave absorbers based on BaAl2Fe10O19 and poly( o-toluidine) by Keyu Chen; Liangchao Li; Guoxiu Tong; Ru Qiao; Bin Hao; Xiaoxi Liang (pp. 2192-2198).
► BFA is coated effectively by conducting polymer POT. ► The M s of composites increases with increasing of BFA content. ► The BFA/POT composite have better microwave absorbing than their single component.BaFe10Al2O19/poly( o-toluidine) (BFA/POT) composite were synthesized by in situ polymerization of o-toluidine in the presence of BaFe10Al2O19 particles. The structure, composition and morphology of the obtained samples were characterized by using XRD, FT-IR, UV–vis spectroscopy, SEM, and TEM techniques. Their electrical conductivity, magnetic property and microwave absorbing property were measured by the four-probe meter, the vibrating sample magnetometer and the vector network analyzer, respectively. The results indicated that BFA particles were coated effectively by POT polymer chains and some interaction between POT chains and BFA particles were existed in the composite. The conductivity and saturation magnetization of BFA/POT composite were smaller than those of pure polymer and pure BFA, respectively. The constitution and film thickness of absorbent had a great effect on its microwave absorbing property. The microwave absorbing properties of the BFA/POT composite were better than those of pure BFA and POT. When optimizing the mass rate of BFA to OT up to 0.3, the composite with the thickness of 2mm had the minimum reflection loss of −29.16dB at approximately 14.06GHz, and the maximum available bandwidth of 9.3GHz, respectively. The results are shown that these composite could be used as advancing absorption and shielding materials due to their favorable microwave absorbing properties.

Keywords: Composite; In situ polymerization; Microwave absorbing property

Fabrication of TiO2-coated magnetic nanoparticles on functionalized multi-walled carbon nanotubes and their photocatalytic activity by Hongfu Zhou; Chen Zhang; Xiangdong Wang; Hangquan Li; Zhongjie Du (pp. 2199-2205).
Display Omitted► The photocatalyst possessed a novel sandwich nanostructure of MWCNTs–Fe3O4–TiO2 layer. ► The photocatalyst had a high catalytic activity for phenol degradation. ► The photocatalyst could be separated with magnets after the reaction was terminated. ► The photocatalyst could be re-calcined and used anew.A novel magnetic photocatalyst with a hybrid nanostructure consisting of multi-walled carbon nanotubes (MWCNTs), Fe3O4 nanoparticles and a TiO2 layer was prepared. First of all, poly(acrylic acid) (PAA) was grafted onto the surface of MWCNTs by in situ polymerization. Fe3O4 nanoparticles were then anchored on PAA chains through amidation reaction between the amino groups on the surface of the Fe3O4 nanoparticles and the carboxyl groups of PAA. Finally, a TiO2 layer was coated onto the surface of the modified MWCNTs through hydrogen bonding interactions between the hydroxyl groups on the surface of titanium dioxide and the carboxyl groups of PAA or the amino groups of Fe3O4. The morphology and structure of the intermediate and final hybrids were investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The magnetism of the product was characterized using a vibrating sample magnetometer. It was shown that the TiO2 decoration shifts the absorbance spectrum of the hybrid to the entire UV–vis region. The photo-catalytic function of the MWCNT/Fe3O4/TiO2 hybrids was validated for phenol degradation under irradiation of UV–vis light.

Keywords: Carbon nanotubes; Poly(acrylic acid); Fe; 3; O; 4; TiO; 2; Photocatalytic activity

Facile synthesis of polyaniline micro-rods with high yield by Youyi Sun; Guizhen Guo; Binghua Yang; Ye Tian; Minghong He; Yaqing Liu; Guizhe Zhao (pp. 2206-2210).
► Polyaniline (PAn) micro-rods was prepared in dimethyl fomamide (DMF) solution by one-step method. ► This present method shows an easy processing and does not need soft and hard template to attain final PAn micro-rods. ► The high yield of the PAn rods can be obtained by present method.A facile method to prepare polyaniline (PAn) micro-rods in dimethyl fomamide (DMF) solution was developed. The structure of the polyaniline micro-rods was determined by the Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray diffraction patterns (XRD), FT-IR and UV–vis spectroscopy. They showed that the average length and diameter of the polyaniline micro-rods were about 15μm and 6μm, respectively. At the same time, the effect of reaction solution and polystyrene (PS) concentration on the formation and morphology of the polyaniline micro-rods was further investigated in detail. The result showed that the reaction solution DMF was the key factor for the formation of polyaniline micro-rods and the morphology of polyaniline micro-rods could be controlled by PS concentration. Moreover, the electrical and microwave absorption properties of rod-like products were also investigated. And the result showed that the short micro-rod products had higher electrical and microwave absorption properties compared with long micro-rod products.

Keywords: Synthesized; Rod; Polyaniline; Electrical; Microwave absorption

High contrast green OLEDs using inorganic metal multi layer by You Hyun Kim; Sang Youn Lee; Wook Song; Mei Meng; Zheng Hong Lu; Woo Young Kim (pp. 2211-2214).
Green organic light-emitting diode (OLED) was fabricated using metal–inorganic–metal multi layer composed of thin Al, KCl and thick Al for achieving high contrast without polarizer. The ambient light reflection of OLED using inorganic metal multi layer, polarizer and conventional metal layer are 28.8, 26.9, and 82.1%, respectively. However, OLED with inorganic metal multi layer has high luminescence of 7367cd/m2, luminous efficiency of 1.81cd/A at 8V, and power efficiency of 0.91lm/W at 5.5V whereas OLED with polarizer has 6919cd/m2, 1.03cd/A at 8V, and 0.56lm/W at 5.5V each. The optical interference effect of inorganic metal multi layer showed possibility of replacing current polarizer to obtain higher contrast ratio in OLED.

Keywords: OLED; IMML; High contrast; Ambient light cancelation; Non-polarizer

Preparation and characterization of electromagnetic polyaniline/nickel plating graphite nanosheets composites through ultrasonic irradiation by Xinming Wu; Shuhua Qi; Guocheng Duan (pp. 2215-2219).
► The nickel-plated graphite nanosheets prepared by electroless plating. ► The PANI/Ni-NanoG composites synthesized successfully. ► The highest electrical loss of composites reached 4.3 at 10.7GHz. ► The highest magnetic loss was 4.4 at 9.3GHz.With excellent electromagnetic properties of polyaniline/nickel plating graphite nanosheets (PANI/Ni-NanoG) composites have been synthesized through ultrasonic irradiation. A uniform nickel film was obtained on graphite nanosheets surface via electroless plating method. Then PANI/Ni-NanoG composites were fabricated via in situ polymerization of aniline monomer in the presence of nickel coated graphite nanosheet through using ultrasonic technique. The resultant PANI/Ni-NanoG composites were characterized by using different analyses like X-ray diffraction techniques (XRD), Fourier transform infrared (FT-IR) and electromagnetic analysis. The FT-IR analysis revealed there was strong interaction between PANI and Ni-NanoG. XRD clearly indicates the typical graphite and the sharp nickel peaks. The electromagnetic analysis exhibited an unusual electromagnetic loss at the microwave frequency ( f=8.2–12.4GHz). Scanning electron microscopy (SEM) of the composites showed that Ni-NanoG dispersed in the PANI uniformly. According to the electrically test, the conductivity of the PANI/Ni-NanoG composites was dramatically increased compared with pure PANI. Thermogravimetric analysis (TGA) revealed that the composites have a higher degradation temperature than PANI alone.

Keywords: Polyaniline; Graphite nanosheets; Electroless plating nickel; Characterization; Electromagnetic properties

A study of polymers obtained by oxidative coupling of furan monomers by T. Tibaoui; B. Zaidi; M. Bouachrine; M. Paris; K. Alimi (pp. 2220-2225).
► Synthesis of modified PFu using FeCl3 and TiCl4 as oxidants. ► Use of vibrational and optical analysis to differentiate between the two compounds. ► Use of ESR to elucidate the nature of the formed radical centers.Via the procedure of oxidative coupling of furan monomers using either titanium tetrachloride (TiCl4) or ferric chloride (FeCl3) as oxidants, two different compounds are obtained. Different experimental analyses including infrared, Raman, optical absorption and ESR techniques are combined and completed by density functional theory to differentiate between both resulting compounds. It is found that both oxidants induce cleavage of aromatic rings. The rates of the resulting aliphatic sequences in each compound are different. Then, to elucidate the effect of oxidant on the electronic properties of the resulting compounds, an ESR dependant temperature study is done. We show that the compound obtained by using FeCl3 contains ionic structure. The effect of temperature on the dynamics of these electronic species is also studied.

Keywords: Furan; Oxidative polymerization; Conjugation length; ESR

Controlling charge injection by self-assembled monolayers in bottom-gate and top-gate organic field-effect transistors by Fatemeh Gholamrezaie; Kamal Asadi; Romero A.H.J. Kicken; Bea M.W. Langeveld-Voss; Dago M. de Leeuw; Paul W.M. Blom (pp. 2226-2229).
► We investigate the modulation of the charge injection in organic field-effect transistors with self-assembled monolayers using both a bottom-gate and a top-gate geometry. ► Current modulation by using SAMs in the top-gate geometry is more pronounced. ► We modified silver electrodes with a perfluorinated SAM which has injection barrier as high as 1.6eV into poly(9,9-dioctylfluorene). ► Saturated field-effect mobility is of 6×10−5cm2V−1s−1.We investigate the modulation of the charge injection in organic field-effect transistors with self-assembled monolayers (SAMs) using both a bottom-gate and a top-gate geometry. The current modulation by using SAMs is more pronounced in the top-gate geometry due to the better defined upper surface of the bottom source and drain electrodes. By modifying Ag electrodes with a perfluorinated monolayer an injection barrier as high as 1.6eV into poly(9,9-dioctylfluorene) can be surmounted, enabling the measurement of the saturated field-effect mobility of 6×10−5cm2V−1s−1.

Keywords: Charge injection; Self-assembled monolayer; Organic field-effect transistor

Synthesis, structure of 3D lanthanide (La(III), Pr(III)) nanoporous coordination polymers containing 1D channels as selective luminescent probes of Pb2+, Ca2+ and Cd2+ ions by Li-rong Yang; Shuang Song; Huai-min Zhang; Wu Zhang; Zhan-wei Bu; Tie-gang Ren (pp. 2230-2240).
► Two kinds of coordination polymersI andII based on the building blocks of La8C2O10 and La4C2O6 or Pr4C4O8 motifs have been synthesized and characterized. ►Two types of 1D nanochannels tier up alternatively in parallel manner in the polymerI. ►The luminescent experiments show that complexesI andII present particular selectivity toward Pb2+ and Ca2+ or Cd2+ ions.Two kinds of 3D coordination polymers, namely, {[La2(PDA)3(H2O)4]·H2O} (I) and {[Pr2(PDA)3(H2O)3]·H2O} (II) have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. In complexI, La(III) ions are nine-coordinated and ten-coordinated and have N1O8 or N1O9 polyhedral units connecting to the PDA2− anions forming tricapped trigonal prism and double-capped cubic antiprism geometries, respectively. Two types of ring motifs as building blocks constructed by La8C2O10 (20-membered ring) and La4C2O6 (12-membered ring) are connected alternately into a highly ordered 2D sheet and further assembled into a nanoporous 3D coordination polymer with parallel channels. In complexII, Pr(III) ions are eight-coordinated and nine-coordinated and have N1O7 or N2O7 polyhedral units connecting to the PDA2− anions forming trigonal dodecahedron and tricapped trigonal prism configurations, respectively. The tetranuclear homometallic motifs formed by Pr4C4O8 unit (16-membered ring), acting as the building blocks, are constructed into a 3D coordination polymer. Luminescent emissions of the lanthanide-based MOF of complexesI andII have been measured in the solution of DMF at room temperature, which reveal that they presenting ion-selective characters toward certain metals, such as Pb2+, Ca2+ and Cu2+ or Cd2+ ions.

Keywords: Synthesis; Structure; Nanoporous coordination polymers; Luminescent probes

ESR and LESR X-band study of morphology and charge carrier interaction in blended P3HT–SWCNT and P3HT–PCBM–SWCNT solid thin films by A. Konkin; C. Bounioux; U. Ritter; P. Scharff; E.A. Katz; A. Aganov; G. Gobsch; H. Hoppe; G. Ecke; H.-K. Roth (pp. 2241-2248).
► An electron exchange between SWCNT conductive electrons and P3HT polarons. ► The exchange rate of ∼0.02μs is comparable with the T2 of the P3HT polaron at 77K. ► The P3HT aromatic ring is parallel to the film plain in the metallic SWCNT:P3HT film.An electron spin resonance (ESR) X-band study of regio-regular poly(3-hexylthiophene) (RR-P3HT) and RR-P3HT/PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) composites blended with a low concentration (∼0.1–1%) of single wall carbon nanotubes (SWCNT) is presented. The substantial line-width broadening of polaron and PCBM anion radical ESR spectra was registered after SWCNT incorporation. The possibility of an electron spin exchange interaction between SWCNT conductive electrons and polymer polarons in the RR-P3HT:SWCNT blend without light illumination and between SWCNT conductive electrons and polymer polarons and PCBM anion radical electrons in the RR-P3HT:PCBM:SWCNT blend under light illumination is discussed. In addition, the unusually significant RR-P3HT film morphology (dominant crystalline phase orientation) is substantially altered, in particular a rotation of up to 90° of the P3HT crystalline phase relative to the film plane, due to SWCNT annexation in the polymer, is registered by the ESR spectra external magnetic field angular dependences.

Keywords: ESR; LESR; SWCNT; P3HT

Field effect in chemical vapour deposited graphene incorporating a polymeric gate dielectric by Y.Y. Tan; L.W. Tan; K.D.G.I. Jayawardena; J.V. Anguita; J.D. Carey; S.R.P. Silva (pp. 2249-2252).
We have investigated the room temperature long channel field effect characteristics of a single graphene layer transistor incorporating a poly-4-vinyl-phenol (PVP) organic insulating layer, as an alternative to conventional oxide gate dielectric materials. High purity copper foils were used in the chemical vapour growth of the graphene layer and visible Raman analysis confirmed the presence of a high quality mono-layer carbon film. Using a channel length of 50μm, a field effect hole mobility of 37cm2/Vs was calculated, which demonstrates the possibility of an all carbon graphene based large area transistor with carrier mobilities above those found in conventional long channel all organic electronic transistors.

Keywords: Chemical vapour deposition; Graphene; Transistor; Polymeric gate

Electrical and photovoltaic properties of FeTPPCl/p-Si heterojunction by M.M. El-Nahass; H.S. Metwally; H.E.A. El-Sayed; A.M. Hassanien (pp. 2253-2258).
► A junction of FeTPPCl/p-Si is fabricated using a thermal evaporation technique. ► The junction parameters are investigated by using ( IV) and ( CV) measurements. ► Also, the photovoltaic properties of this junction are investigated.Hybrid heterojunction cell based on thermally evaporated 5,10,15,20-tetraphenyl-21H, 23H-porphine iron (III) chloride (FeTPPCl) as the organic semiconductor and p-Si wafer as the inorganic semiconductor have been investigated. This device showed rectification behaviour like diode. The conduction mechanisms and the diode parameters have been studied using current–voltage ( IV) characteristics in the temperature range (298–373K) and capacitance–voltage ( CV) characteristics at room temperature. This cell exhibited photovoltaic characteristics with a short-circuit current ( I sc) of 2.8mA, an open-circuit voltage ( V oc) of 0.475V, a fill factor FF=32%.

Keywords: FeTPPCl; Organic/inorganic heterojunction; Hybrid heterojunction; Photovoltaic

Mechanical characterizations of cast Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)/Polyvinyl Alcohol thin films by Chang-hsiu Chen; Anna Torrents; Lawrence Kulinsky; Richard D. Nelson; Marc J. Madou; Lorenzo Valdevit; John C. LaRue (pp. 2259-2267).
► Cast films of the blend of PEDOT:PSS and PVA were prepared and measured uniaxially tensile test. ► High PEDOT:PSS wt% in PEDOT:PSS/PVA results higher Young's modulus, higher tensile strength and lower elongation % at break. ► SEM and XRD show the microstructures morphology of PEDOT:PSS/PVA. ► With electrical properties, idea trade-off wt% of PEDOT:PSS/PVA was determined.The polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate), hereafter referred to as PEDOT:PSS, has electrical properties superior to those of most conducting polymers, but it is too brittle to be employed in many applications. Blending PEDOT:PSS with other polymers is a promising route to reach a good trade-off between electrical and mechanical properties. This paper describes the mechanical characterization of PEDOT:PSS/PVA (Polyvinyl Alcohol) blends. The PEDOT:PSS/PVA films used in this study are produced by casting, and uniaxial tensile tests are performed to characterize the Young's modulus, fracture strain, tensile strength, and plastic deformation behavior of the blends as a function of the weight fraction of the components. For pure PVA, the Young's modulus, fracture strain and tensile strength are found to be, respectively, 41.3MPa, 111% and 41.3MPa. The strength exhibits a nearly perfect bimodal behavior, suddenly increasing by a factor 2 at a PEDOT:PSS content of 30%. Importantly, the ductility remains extremely high (∼94%, only 20% lower than pure PVA) up to PEDOT:PSS fractions of ∼50%. The Young's modulus monotonically increases with PEDOT:PSS content, reaching 1.63GPa at 50%. SEM imaging and XRD analysis allows correlation of these evolutions to substantial morphological changes in the PEDOT:PSS/PVA microstructure. When combined with a previously published electrical characterization study, the current work suggests that a PEDOT:PSS/PVA polymer blend with 30–40wt% of PEDOT:PSS provides the best trade-off of conductivity and ductility. For non free-standing films, higher PEDOT:PSS fractions (70%) might be preferable.

Keywords: PEDOT; PEDT; PVA; Polyvinyl Alcohol; Conducting polymers; Young's modulus; Mechanical properties

New naphthalene diimide-based compounds containing triarylamine units and imine linkages: Thermal, optical and electrochemical properties by Ewa Schab-Balcerzak; Marzena Grucela-Zajac; Michal Krompiec; Henryk Janeczek; Mariola Siwy; Danuta Sek (pp. 2268-2279).
► We obtained compounds consist of naphthalenediimide and triphenylamine diimine units. ► We analysed the thermal degradation kinetics of the synthesized compounds by TGA. ► We examined their photoluminescence and electrochemical properties. ► They exhibited low electrochemical band gap being promising for optoelectronics.Two novel poly(azomethinenaphthaleneimide)s ( poly(AZ-NI)s) and azomethine-naphthalene diimide (AZ-NI) consisting of electron-donating triarylamine with imine linkages and electron-accepting naphthalene diimide moieties were prepared via condensation of N,N′-bis(4-amino-2,3,5,6-tetramethylphenyl)naphthalene-1,4,5,8-dicarboxyimide (DANDI) with 4-formyltriphenylamine, 4,4′-diformyltriphenylamine and 4,4′,4″-triformyltriphenylamine. The thermal degradation kinetics of obtained compounds was studied by TGA. The activation energy ( E a) of thermal decomposition process was estimated by the first order Coats–Redfern equation and was in the range 115.1–266.7kJ/mol. Poly(AZ-NI)s and AZ-NI exhibited useful levels of thermal stability, their 5% weight-loss temperatures were above 350°C. Optical properties of the prepared compounds were investigated by UV–vis and photoluminescence (PL) measurements. The obtained alternating donor–acceptor compounds emitted mainly blue light. The electrochemical behavior of poly(AZ-NI)s, AZ-NI and DANDI was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). As calculated from CV, the electrochemical energy band gap ( Eg) of the linear polymer was equal to 1.15eV, but the Eg of the branched one was lower: 1.06eV, whereas the Eg of AZ-NI and DANDI was 1.32 and 0.47eV, respectively. For the first time, to the best of our knowledge, polynaphthaleneimides with triphenylamine units and azomethine linkages have been described in this article.

Keywords: Polyimides; Polynaphthaleneimides; Azomethines; Electrochemistry; Photoluminescence

Solid state dye-sensitized solar cells prepared by infiltrating a molten hole conductor into a mesoporous film at a temperature below 150°C by Kristofer Fredin; Erik M.J. Johansson; Maria Hahlin; Rebecka Schölin; Stefan Plogmaker; Erik Gabrielsson; Licheng Sun; Håkan Rensmo (pp. 2280-2283).
► We infiltrate a hole conductor in its molten form. ► Low melting point suggests reduced dye degradation. ► Electrodes were used for solar cells. ► Key efficiency limiting factor is rapid recombination.Infiltration of a molten hole conductor in a mesoporous film at an elevated temperature exhibits good wetting performance and the procedure is therefore suitable as part of the preparation method for solid state dye-sensitized solar cells. Herein, we present a system prepared by infiltrating 4-(diethyl-amino)benzaldehyde-1,1)-diphenyl-hydrazone in its molten form at a temperature below 150°C. The system displays a maximum photon-to-current conversion efficiency of about 35%, a value corresponding to an increase of about 5 times in comparison with a previously published system prepared by infiltrating a molten hole-conductor at a temperature exceeding 250°C. By means of comparing charge transport and recombination with the results measured for a liquid analogue, we conclude that whereas the transport rates are similar, recombination is significantly more rapid in the solid-state device.

Keywords: Dye; Solar cell; Solid-state; Transport; Recombination; Infiltration; Hole conductor

Exciton peak redshifting and broadening in polyaniline chains during ion-induced hydrophobic collapse and aggregation by Louis R. Nemzer; Arthur J. Epstein (pp. 2284-2288).
► Adding monovalent cosolutes to polyaniline suspensions causes the chains to collapse. ► The forced planarization of the polymer leads to a redshifting and broadening of the exciton absorption peak. ► Urea decreases the hydrophobic interaction and therefore has the opposite effect. ► Divalent coions cause redshifting at low concentrations, then a hypsochromic reversal. ► We preformed a quantitative spectral analysis to study the magnitude of these changes.The ion-induced reprecipitation of the emeraldine base form of polyaniline from an aqueous-organic binary solution is a facile method for obtaining polymer nanoparticles and microscale clusters. The hydrophobic collapse and aggregation that accompanies the addition of various cosolutes induces changes in the peak wavelength and linewidth of the main exciton absorption. In particular, we find that the addition of ionic cosoutes leads to a redshifting and broadening of this spectroscopic feature, with divalent coions exhibiting an additional hypsochromic reversal at high concentrations. The denaturant urea, in contrast, causes a blueshift and line-narrowing at all concentrations. Using a quantitative Lorentz fit, we show how the redshifting and broadening of this spectral feature can be attributed, at least in part, to the forced planarization of the polymer chains in the collapsed state.

Keywords: Polyaniline; Exciton; Spectroscopy; Polymer aggregation; Hydrophobic collapse

Optical properties and electronic structure of terminal group-perturbed ethynyl-linked dendrimers by Peng Zhang; Wenting Xue; Pei Liu; Lihua Gan (pp. 2289-2294).
► We experimentally and theoretically investigate electronic structures which reflect the emitting principle. ► Electronic structures and photophysical properties are tuned by terminal group as donor. ► We reveal their emitting mechanism, π–π* transition, intramolecular charge transfer and both interaction.Three ethynyl-linked dendrimers with terminal carbazole, namely the electronic donor–acceptor compounds1–3, the symmetric compound 9-(3-(2-(1-(2-(3-(9Hcarbazol-9-yl)-9-p-tolyl-9H-carbazol-6-yl)ethynyl)pyren-6-yl)ethynyl)-9-p-tolyl-9H-carbazol-6-yl)-9H-carbazole (1), the unsymmetric compounds 6-pyren-1-ylethynyl-9- p-tolyl-9 H-[3,9′]bicarbazolyl (2) and 3,6-di- tert-butyl-9-(4-pyren-1-ylethynyl-phenyl)- 9H-carbazole (3), respectively, were well investigated by experimental and theoretic methods. Good reversible oxidation and reduction processes of these compounds were observed, and the corresponding HOMO and LUMO levels could be well tuned by the different terminal group, which was proved by the theoretical calculation. In addition, they showed bright blue-green emission in dichloromethane solution and in the solid state, and exhibited efficient solvatochromism, suggesting that their electron transition may be considered as π–π* transition, charge–transfer transition and the coeffect of the former two, respectively.

Keywords: Ethynyl-linked dendrimers; Carbazole; Optical properties; Electronic structure; Intramolecular charge–transfer

Study of synthesis and fluorescence of europium complex/copolymer composite optical resins by in situ preparation by Dongmei Wang; Fuxiang Wang; Weixian Peng (pp. 2295-2300).
The in situ preparation and the photo-physical properties of optical resins containing lanthanide complexes have been investigated. Composite resins with narrow bandwidth and intense fluorescence were obtained through a free radical copolymerization of methacrylic acid (MA), styrene (St), EuCl3·6H2O, and organic ligands, in which the binary or ternary Eu3+ lanthanide ion complexes were synthesized in situ by a copolymerization process. The molecular structure, the dispersed morphology of the lanthanide complexes, and the luminescence properties of the optical resins were characterized. The relationships between the fluorescence properties of the optical resins and the types of organic ligands, and the relative molar ratio between the organic ligands and the lanthanides ion were investigated. Transmission electron microscopy (TEM) results showed that the lanthanide complexes, with a mean diameter below 20nm, were homogeneously dispersed in the optical resins. This in situ composite resin showed stronger luminescence intensity and a longer luminescence lifetime than that made by the doping method at the same concentration.Display Omitted► Novel transparent resins containing europium complex by an in situ composite method. ► The europium complexes and polymer were synthesized at the same time. ► The in situ method is conventional chemistry method (one pot method). ► The problem to obtain uniformly dispersed resins containing lanthanide complexes is solved. ► The resin by the in situ showed stronger emission intensities and longer lifetimes.The in situ preparation and the photo-physical properties of optical resins containing lanthanide complexes have been investigated. Composite resins with narrow bandwidth and intense fluorescence were obtained through a free radical copolymerization of methacrylic acid (MA), styrene (St), EuCl3·6H2O, and organic ligands, in which the binary or ternary Eu3+ lanthanide ion complexes were synthesized in situ by a copolymerization process. The molecular structure, the dispersed morphology of the lanthanide complexes, and the luminescence properties of the optical resins were characterized. The relationships between the fluorescence properties of the optical resins and the types of organic ligands, and the relative molar ratio between the organic ligands and the lanthanides ion were investigated. Transmission electron microscopy (TEM) results showed that the lanthanide complexes, with a mean diameter below 20nm, were homogeneously dispersed in the optical resins. This in situ composite resin showed stronger luminescence intensity and a longer luminescence lifetime than that made by the doping method at the same concentration.

Keywords: In situ; preparation method; Lanthanide complexes; Optical resins; Luminescence properties

Electropolymerization of m-aminophenol on expanded graphite and its electrochemical properties by Yong Kong; Yongsheng Zhou; Xueling Shan; Yunyang Jiang; Chao Yao (pp. 2301-2305).
During the polymerization, the peak currents increase with increase in the number of potential cycles. The autocatalytic polymerization is attributable to the –OH groups on the surface of expanded graphite.Display Omitted► Expanded graphite plays an important role in the polymerization of m-aminophenol. ► The electrochemical activity of PmAP decreases with increasing pH values. ► According to the FT-IR spectrum, the chemical structure of PmAP is proposed.The electrochemical polymerization of m-aminophenol on expanded graphite has been carried out in acidic solution using repeated potential cycling between −0.4 and 1.6V (vs. SCE). The electrolytic solution consisted of 0.01M m-aminophenol and 0.3M H2SO4. A blue film, i.e. poly ( m-aminophenol) (PmAP) was formed on the expanded graphite, and it has good electrochemical activity in solution with low pH value. The polymerization behavior of m-aminophenol on the expanded graphite electrode is quite different from that of m-aminophenol on metal or glassy carbon electrodes, and the functional groups on the surface of the expanded graphite play an important role in the autocatalytic polymerization of m-aminophenol. The synthesized PmAP was characterized by electrochemical impedance spectroscopy (EIS), FT-IR and scanning electron microscopy (SEM). Based on FT-IR, the structure of PmAP is proposed in this paper.

Keywords: m; -Aminophenol; Electrochemical polymerization; Expanded graphite; FTIR spectra; Electrochemical impedance spectroscopy

Polyaniline/CoFe2O4 nanocomposites: A novel synthesis, characterization and magnetic properties by G.D. Prasanna; H.S. Jayanna; A.R. Lamani; S. Dash (pp. 2306-2311).
The M( H) loops obtained for CoFe2O4 and PANI/CoFe2O4 nanocomposites at temperature 200K. The variation in the MS, MR and HC found to be affected dramatically with CoFe2O4 addition.Display Omitted► CoFe2O4 nanoparticles were prepared via a simple one step citrate–nitrate method. ► PANI/CoFe2O4 nanocomposites were synthesized by in situ polymerization technique. ► The structural, morphology characterization was by XRD, FTIR, TGA and SEM. ► The magnetic properties were measured in the temperature range 300–10K up to 30kOe. ► The variation in the MS, MR and HC found to be depending on CoFe2O4 addition.A conducting polymer, polyaniline (PANI)/CoFe2O4 nanocomposites were synthesized by facial in situ polymerization of aniline monomer with CoFe2O4 nanoparticles, where CoFe2O4 nanoparticles were prepared via a simple one step citrate–nitrate method. The structural, morphology and magnetic properties of the resulting nanocomposites were investigated in detail by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and magnetic measurements. The average particle size of the CoFe2O4 nanoparticles was measured to be 19nm. The magnetic properties of all the composites were measured using vibrating sample magnetometer (VSM) in the temperature range 300–10K up to 30kOe magnetic field. The magnetic properties of PANI/CoFe2O4 nanocomposites were improved by adding the CoFe2O4 nanoparticles, the variation in the saturation of magnetization ( MS), remanent magnetization ( MR) and coercivity ( HC) for PANI/CoFe2O4 nanocomposites facilitated the production of composite materials with considerable properties and found to be affected dramatically with cobalt ferrite addition.

Keywords: Conducting polymers; CoFe; 2; O; 4; Nanocomposites; Structural characterization; Magnetic properties

Role of dissolved oxygen diffusion in coating defect protection by emeraldine base by Yingping Li; Hongming Zhang; Xianhong Wang; Ji Li; Fosong Wang (pp. 2312-2317).
► EB coating protected exposed bare steel at coating defect well in 1wt% NaCl solution. ► A dense metal oxide film was observed on the steel surface under EB coating. ► No metal oxide film was detected on the surface of exposed steel. ► A new protection model was proposed to explain the protection behavior of EB coating. ► The protection was further verified by corresponding electrochemical measurements.The corrosion protection of emeraldine base (EB) on mild steel in the artificial defect exposed to 1wt% NaCl solution was studied using in situ optical microscope and scanning electron microscopy (SEM). The EB coating displayed good corrosion protection on the exposed bare steel, which was difficult to understand by traditional anodic protection mechanism or inhibitory protection mechanism, or cathodic protection mechanism, since steel usually cannot be passivated in brine, and EB coating cannot release inhibitory anions to protect exposed bare steel, and further, the galvanic coupling measurement demonstrates that EB cannot provide cathodic protection to exposed bare steel. The importance of dissolved oxygen diffusion caused by EB in corrosion protection was disclosed in this paper, a related protection model was therefore proposed, which was qualitatively verified by corresponding electrochemical measurements.

Keywords: Polyaniline emeraldine base; Mild steel; Corrosion protection

Flexible organic light-emitting diode with a conductive polymer electrode by Mansu Kim; Yoo Sung Lee; Young Chul Kim; Myung Soo Choi; Jun Young Lee (pp. 2318-2322).
► Conductive and transparent PEDOT:FTS film fabrication. ► Optical and electrical properties enhancement by introducing DMAc. ► Fabrication of standard Alq3 based double layer FOLEDs on the PEDOT:FTS anodes. ► Largely enhanced performance of the FOLED using DMAc-PEDO:FTS.We report on a flexible organic light-emitting diode (FOLED) prepared by using a poly(3,4-ethylenedioxythiophene) (PEDOT) anode formed via in-situ polymerization of ethylenedioxythiophene (EDOT) on a polyethersulfone (PES) substrate. Ferric p-toluene sulfonate (FTS) was used as a dopant, and N, N-dimethylacetamide (DMAc) was added to enhance the anode properties. The PEDOT:FTS film polymerized in the presence of DMAc (DMAc-PEDOT:FTS) exhibited better performance than those polymerized without DMAc (Normal-PEDOT:FTS) in terms of both optical transmittance and surface resistance, and the DMAc-PEDOT:FTS film gave a work function of 4.67eV which is 0.3eV higher than that of the Normal-PEDOT:FTS film. Optical transmittance and surface resistance of the DMAc-PEDOT:FTS films could be controlled to be 52–87% and 130–390Ω/sq, respectively. When an optimized DMAc-PEDOT:FTS film was employed as an anode, the Alq3 [(8-hydroxy-quinolinato)-aluminium] based FOLED device exhibited 30% higher luminous efficiency and more than 20 times higher max luminance than the device with the Normal-PEDOT:FTS anode.

Keywords: PEDOT:FTS anode; In-situ; polymerization; DMAc effect; Flexible organic light-emitting diode

Multifunctional electroluminescent material based on dimesitylboron and α-naphthylamino fluorene bridge by Wenguan Zhang; Zhiqun He; Yongsheng Wang; Shengmin Zhao (pp. 2323-2328).
► 2-Dimesitylboron-7-( N-phenyl-α-naphthylamino)-9,9-diethylfluorene (BNPEF). ► Multifunctional BNPEF as a blue emitter, hole- or electron-transporting materials. ► Light-emitting devices with single or multilayer of ITO/NPB/BNPEF/BCP/Alq3/LiF/Al. ► Devices A, B, C, D, E and F emitted at 456, 512, 488, 484, 520 and 528nm. ► Devices B, C, D, E and F showed efficiencies of 0.67, 2.92, 5.03, 4.03 and 2.35cd/A.By introducing a triarylamino and three-coordinate boron groups into a fluorene bridge, an asymmetric and bipolar compound, 2-dimesitylboron-7-( N-phenyl-α-naphthyl-amino)-9,9-diethylfluorene (BNPEF), was prepared. Light emissions of BNPEF were different in solvents of different polarities. A series of electroluminescent devices was fabricated. Device A ITO/BNPEF/LiF/Al, Device B ITO/NPB/BNPEF/LiF/Al, Devices C and D ITO/NPB/BNPEF/BCP/AlQ3/LiF/Al, Device E ITO/BNPEF/AlQ3/LiF/Al and Device F ITO/NPB/BNPEF/AlQ3/LiF/Al, were fabricated. Device A exhibited a blue emission at 456nm. Device B showed a green emission at 512nm with current efficiency of 0.67cd/A. The blue EL peaks of Devices C and D were at 488 and 484nm with current efficiencies of 2.92 and 5.03cd/A, respectively. Devices E and F emitted green lights at 520 and 528nm with current efficiencies of 4.03 and 2.35cd/A, respectively. The characteristics of the devices demonstrated that BNPEF was a multifunctional molecule acting as a blue emitting, or hole- or electron-transporting materials.

Keywords: Multicolor emission; Naphthylamino; Dimesitylboron; Fluorene bridge; Multifunctional; Electroluminescent device

Ionically conducting DNA-based membranes for eletrochromic devices by Agnieszka Pawlicka; Franciani Sentanin; Alessandra Firmino; James G. Grote; François Kajzar; Ileana Rau (pp. 2329-2334).
► Novel DNA-based free standing membranes with ionic conductivity properties. ► Blends of biopolymers with conducting polymers. ► Application in electrochromic devices. ► Environmentaly friendly materials.Ionically conductive membranes based on plasticized DNA with glycerol and containing conducting polymers such as: either PEDOT:PSS (poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)), POEA (poly (o-ethoxyaniline)) or electrochromic dye Prussian Blue (PB) were prepared, characterized and applied in electrochromic devices. The results of ionic conductivity measurements for the studied membranes varied, depending on the added polymer or dye, from 3×10−5S/cm for the pure DNA-based samples to 5.1×10−4S/cm for the samples containing PEDOT:PSS or PB, at room temperature. The samples exhibit a good thermal stability up to 170°C, with variable transparency range, depending on the added molecule. Moreover, the samples exhibit also a semicrystalline structure and in the case of pure DNA- and DNA–PB-based compounds two glass transition temperatures of −75°C and 60°C were observed. The membranes were applied in small electrochromic devices and have shown an up to 15% transmission change from colored to bleached states. The inserted/extracted charges were 0.7–3.0mC/cm2 after 15s of applied potential of −2.5V for membranes with thickness of 72–80μm. All obtained results indicate that DNA-based gel-polymer electrolytes (GPEs) are good candidates to be used in electrochemical devices.

Keywords: DNA; Gel electrolyte; Conducting polymers; Ionic conductivity; Electrochromic devices

Oligo(benzo[c]thiophene-2-oxide) a poly(isothianaphthene) derivative with good photovoltaic properties by C.O. Sánchez; J.C. Bernede; L. Cattin; F.R. Díaz (pp. 2335-2338).
► We have synthesized a new polymer, the poly(benzo[c]thiophene-2-oxide). ► We have probed this new polymer in organic solar cells as electron donor. ► We show that after sublimation this polymer can be used as efficient electron donor in organic solar cells.To improve the performances of organic solar cells, many efforts have been devoted to the synthesis of new compounds whose absorption spectra allow a better matching with that of the solar spectrum. To that respect, a new poly(isothianaphthene) derivative, with a low band gap, called, poly(benzo[c]thiophene-2-oxide), was synthesized and characterized by elemental analysis, UV–vis, FT-IR,1H NMR and XPS spectroscopy.The polymer synthesis was performed from 1,3-dihydrobenzo[c]thiophene-2-oxide by oxidative coupling using sulphuric acid in methanol as oxidizing agent in the presence of air. Oligomers have an optical band gap of 1.8eV. The oligomeric film prepared under high vacuum was probed in photovoltaic devices as an electron donor. Photovoltaic devices based on Glass/ITO/MoO3(3nm)/poly(benzo[c]thiophene-2-oxide) (15nm)/fullerene-C60(40nm)/Bathocuproine (BCP) (9nm)/Aluminium have been probed. The active area of the cells was 0.16cm2. These cells showed a power conversion efficiency of 1.24% under the illumination of AM 1.5 at 100mW/cm2, which shows that this family of poly(isothianaphthene) oligomers have promising properties for photovoltaic applications.

Keywords: Photovoltaic properties; Oligo(isothianaphthene) derivative; Band-gap; Synthesis; Characterization

A new BEDT-TTF-based organic metal with an anionic weak acceptor 2-sulfo-1,4-benzoquinone by Hiroki Akutsu; Yuka Maruyama; Jun-ichi Yamada; Shin’ichi Nakatsuji; Scott S. Turner (pp. 2339-2343).
Display Omitted► We prepared a weak anionic acceptor 2-sulfo-1,4-benzoquinone. ► The anion provides a dual-layered organic metal, α‴-β″-(BEDT-TTF)2(C6H3O2SO3)·H2O. ► The salt shows a metal-insulator transition at 90K.An anionic weak acceptor, 2-sulfo-1,4-benzoquinone, has provided a new BEDT-TTF (bis(ethylenedithio)tetrathiafulvalene) salt (BEDT-TTF)2(2-sulfo-1,4-benzoquinone)·H2O. Single crystal X-ray analysis indicates that the unit cell has two crystallographically independent donor layers, one of which has a β″-type packing motif and the other being disordered. Population analysis and SQUID magnetometry suggests that non-β″-layer has an α‴-type packing motif. The dual-layered salt shows metallic behavior with a metal–insulator transition at 90K.

Keywords: Organic conductors; BEDT-TTF; Electron acceptors

One-dimensional composites based on single walled carbon nanotubes and poly(o-phenylenediamine) by M. Baibarac; I. Baltog; M. Scocioreanu; B. Ballesteros; J.Y. Mevellec; S. Lefrant (pp. 2344-2354).
Display Omitted► One-dimensional composites based on SWCNTs and POPD are synthesized. ► SEM studies show an incorporation of SWCNTs in POPD fibers mass. ► The adsorption of POPD and SWNTs on Au support are investigated by SEIRA spectroscopy. ► Using SERS spectroscopy a functionalization of SWCNTs with POPD is demonstrated.The direct mixing of aqueous ferric chloride and o-phenylenediamine (OPD) solution at room temperature in the absence and presence of carbon nanotubes (CNTs) has been used to prepare poly(o-phenylenediamine) (POPD) micro-fibers and composites of the type CNTs/POPD having nanotubes incorporated in polymer fiber mass. Using surface enhanced infrared absorption (SEIRA) spectroscopy significant modifications in the low frequency range of the polymer spectrum are revealed when Au is used as metallic support. Similar variations are reported for the POPD samples prepared by the electropolymerization of OPD onto rough Au electrode. A covalent functionalization of CNTs with POPD and a doping process of POPD with radical anions of CNTs is proved by surface enhanced resonant Raman scattering and SEIRA spectroscopy. The X-ray diffraction (XRD) studies indicate a high crystallinity both for POPD and CNTs/POPD composites prepared by chemical or electrochemical methods.

Keywords: Polymer; Carbon nanotubes; Raman scattering; Infrared spectroscopy

Photoconducting and electrical properties of Al/TIPS-pentacene/ p-Si/Al hybrid diode for optical sensor applications by R.K. Gupta; M.E. Aydın; F. Yakuphanoglu (pp. 2355-2360).
► Al/TIPS-pentacene/ p-Si/Al Schottky diode was fabricated using spin coating. ► The ideality factor was calculated to be 1.97. ► Transient photoconductance measurements show that the diode is sensitive to light. ► The fabricated diode could be used as an optical sensor.Schottky diode based on 6,13 bis (triisopropylsilylethynyle) (TIPS) pentacene was fabricated using spin coating. The junction properties and photoconductivity of the Al/TIPS-pentacene/ p-Si/Al diode were studied. The ideality factor and barrier height of the diode were calculated using IV characteristics and obtained to be 1.97 and 0.65eV, respectively. The photocurrent of the diode depends on the illumination intensity and increases with increasing photo-illumination intensity. The transient photocurrent results indicate that photocurrent under illumination is higher than the dark current and increases with increase in light intensity. The capacitance of the diode decreases with increasing frequency due to a continuous distribution of the interface states. The linear dependence of the double log plot of photocurrent and light intensity suggests that the Al/TIPS-pentacene/ p-Si/Al diode could be used as an optical sensor.

Keywords: TIPS-pentacene; Photodiode; Schottky diode; Current–voltage; Capacitance–voltage

Synthesis and characterization of the novel shape-persistent nanosized cavity macrocycle by Qinggang Kong; Haiyan Qian; Hongzhong Bo; Chaozhi Zhang; Kai Liu; Xiangyu Zhang; Jianke Wang; Jun Li; Guizhi Gao (pp. 2361-2367).
Display Omitted► Friedel–Crafts reaction was employed to prepare the new shape-persistent macrocycle (TPAP)3. ► The yield of (TPAP)3 is up to 34%. ► (TPAP)3 possesses about Φ10×8.4Å molecular inner cavity. ► The macrocycle is a big electron-rich donor. ► It could form 1:1 π-donor–π-acceptor (D–A) complexes with C60.The Friedel–Crafts reaction was employed to prepare the shape-persistent macrocycle (TPAP)3 with direct cyclization from three monomers of 2-(4′-(Phenyl(4″-methylphenyl)amino) phenyl)-propan-2-ol (TPAP), which contains two reactive groups of the t-hydroxyl and the p-proton on the triphenylamine. Under a very low monomer concentration (ca. 1%), the yield of the shape-persistent macrocycle (TPAP)3 is up to 34%. FT-IR, NMR, MALDI-TOF and MS were applied to determine the structure of macrocycle. It can be a good candidate as the hole-transporting layer because its photoluminescent spectrum appears no emission peaks in the range of 400–600nm. The geometry of (TPAP)3, optimized by the density functional theory (DFT) calculations using Gaussian03 software at the B3LYP/6-31G(d) level, showed that (TPAP)3 possesses an approximately 10Å diameter and 8.4Å depth molecular inner cavity. Owing to three nitrogenous lone electron pairs and six conjugated large π bonds of the macrocyclic electron-excessive phenylene almost directing into the cavity, the macrocycle is a big electron-rich donor which may be favorable for selective extraction of special diameter metal ions, high effective and selective catalysis and the formation of 1:1 π-donor–π-acceptor (C60) complexes through the host–guest interactions.

Keywords: Friedel–Crafts reaction; Synthesis; Nanosized cavity macrocycle; Characterization

Synthesis and characterization of conductive polyimide/carbon composites with Pt surface deposits by John M. Kinyanjui; David W. Hatchett; Gina Castruita; Asanga D. Ranasinghe; Lothar Weinhardt; Timo Hofmann; Clemens Heske (pp. 2368-2377).
Display Omitted► Conductive polyimide/carbon composites were produced using a binary solvent system to maximize carbon dispersion. ► Percolation thresholds were achieved at carbon loadings between 2.5–5% for the polyimide/carbon composites. ► Electrochemical deposition of Pt was achieved at free-standing conductive polyimide/carbon electrodes. ► Pt catalysis and surface reactivity was examined using the methanol oxidation reaction.The preparation of free-standing polyimide/carbon (PI/Carbon) substrates and the electrochemical deposition of Pt to produce PI/Carbon/Pt electrodes are demonstrated to provide thermally stable and conductive PI composites. The conductivity of polyimide (PI)/Carbon composites is evaluated as a function of composition of a binary solvent involving DMSO (dimethyl sulfoxide) and highly volatile acetone, which enhances carbon dispersion (PI/Carbon) in the polymer precursor. The solution conditions have been optimized to provide the highest conductivity for the lowest relative carbon loading. The deposition of Pt metal on PI/Carbon composite electrodes is demonstrated using cyclic voltammetry. The conductivity of the PI/Carbon composite is sufficient that the metal precursor PtCl42− is fully reduced and deposited without the need for additional chemical reduction processes. Thermal gravimetric analysis (TGA) shows that the thermal stability of PI is maintained with carbon incorporation and platinum deposition. Scanning electron microscopy (SEM) analysis shows that carbon aggregation at the PI surface is minimized and that Pt deposits are well dispersed. X-ray photoelectron spectroscopy (XPS) results indicate that the electrochemical reduction of PtCl42− produces metallic Pt deposits on the PI/Carbon composite. Four-point probe measurements are utilized to assess the conductivity of the materials and highlight the influence of C and Pt on the electronic properties of modified PI. Finally, the electrochemical reactivity of PI/Carbon/Pt composite is examined using the redox properties for ferricyanide and the catalytic oxidation of methanol in acidic solution. The electrochemical experiments demonstrate that the free-standing PI/Carbon composites are sufficiently conductive to observe the electrodeposition of Pt metal that is stable and reactive on the organic substrate.

Keywords: Composite; Polyimide; Carbon; Platinum; Methanol oxidation

Star-shaped dendritic molecules based on carboxylated carbazole and pyrrole as peripheral oxidizable units by Jean-Paul Lellouche; Zvika Pomerantz; Rachel Persky; Hugo E. Gottlieb; Subrata Ghosh (pp. 2378-2383).
Display Omitted► Polycarboxylated carbazole- and pyrrole-based dendritic monomers. ► Carboxylated peripheral building blocks were synthesized in one step. ► Pyrrole-/carbazole-based dendritic monomers were synthesized in three steps. ► Electropolymerization of polycarboxylated monomers was investigated. ► The carbazole-based monomers produced stable functionalized conducting polymer film.The synthesis and spectroscopic characterization of three tricarboxylated pyrrole (Pyr)- and carbazole (Cbz)-containing star-shaped dendritic molecules13 have been described here. Clauson–Kaas, amide coupling and debenzylation reactions have been used as key chemical tools. Electropolymerization of these oxidizable molecules has been investigated. The carboxylated Cbz-based molecules upon oxidative electropolymerization produced stable electroactive polyCOOH polyCbz films.

Keywords: Polycarbazole; Polypyrrole; Dendrimers; Elctropolymerization; Conducting polymers

Electrical characterization of heterojunction between polyaniline titanium dioxide tetradecyltrimethylammonium bromide and n-silicon by H. Çetin; B. Boyarbay; A. Akkaya; A. Uygun; E. Ayyildiz (pp. 2384-2389).
► The organic/inorganic semiconductor heterojunction has been fabricated by thin film formed on n-Si semiconductor substrate using spin coating technique from the solution of polyaniline titanium dioxide composite. ► The forward I–V characteristics of the device have been analyzed on the basis of the standard thermionic emission theory. ► The temperature-dependent I–V characteristics of the PANI TiO2 TTAB/n-Si heterojunction have revealed a double Gaussian distribution. ► PANI TiO2 TTAB has been characterized by using Fourier Transform Infrared, Ultraviolet–visible spectra and X-ray diffraction analysis.The organic/inorganic semiconductor heterojunction has been fabricated by thin film formed on n-Si semiconductor substrate using spin coating technique from the solution of polyaniline (PANI) titanium dioxide (TiO2) composite chemically synthesized in the presence of the cationic surfactant, tetradecyltrimethylammonium bromide (TTAB). The thickness of the polymeric film coated on the n-Si substrate has been found to be 110nm by using the profilometer. The current–voltage ( IV) characteristics of the PANI TiO2 TTAB/n-Si heterojunction have been measured in the temperature of 178–238K. The IV characteristics of the PANI TiO2 TTAB/n-Si heterojunction have shown the rectifying behavior. The forward IV characteristics of the device have been analyzed on the basis of the standard thermionic emission (TE) theory. An abnormal increase in the barrier height and decrease in the ideality factor with increasing temperatures has been shown. This behavior has been interpreted assuming inhomogeneity of barrier formed at the interface. The temperature-dependent IV characteristics of the PANI TiO2 TTAB/n-Si heterojunction have revealed a double Gaussian distribution giving mean barrier heights of 0.916eV and 1.164eV and standard deviations of 0.114eV and 0.131eV, respectively. Furthermore, the PANI TiO2 TTAB has been characterized by using Fourier Transform Infrared (FTIR), Ultraviolet–visible (UV–vis) spectra and X-ray diffraction analysis (XRD).

Keywords: PACS; 82.35.Cd; 79.40.+z; 73.30.+y; 85.30.Hi; 79.60.Jv; 73.40.EiConducting polymers; Thermionic emission; Schottky barrier diodes; Heterojunctions; I; –; V; characteristics

Rectifying behavior of [60]fullerene charge transfer complexes: A theoretical study by Manuel García; Patricia Guadarrama; Estrella Ramos; Serguei Fomine (pp. 2390-2396).
► We modeled rectifying properties of [60]fullerene complexes with organic donors. ► All complexes were able to rectify electric current. ► Maximum rectification ratio was found to be 73 at 0.3V. ► Rectification ratio depends on the separation distance between donor and acceptor.New type of molecular diodes based on charge transfer complexes of fullerene[60] with organic donors has been proposed and studied theoretically. Current–voltage curves and the rectification ratios (RR) for three different molecular diodes were calculated using direct ab initio method at M06/LACVP(d) level of theory in the range from −2 to +2V. The highest RR of 73.6 was determined for the complex of C60 with cyclic oligothiophene at 0.3V (C60–CT8–Au). Other molecular diodes show lower RR, however, all complexes show RR higher than 1 at all voltages. The asymmetric evolutions and alignment of the molecular orbitals with the applied bias were found to be essential in generating the molecular diode rectification behavior. It seems that large donor–acceptor distance in C60–CT8 complex is crucial for the high RR in C60–CT8–Au compared to other complexes.

Keywords: Molecular diode; [60]Fullerene; DFT; Polythiophene

Modification of ITO surface using aromatic small molecules with carboxylic acid groups for OLED applications by Ali Kemal Havare; Mustafa Can; Serafettin Demic; Salih Okur; Mahmut Kus; Hasan Aydın; Nesli Yagmurcukardes; Suleyman Tari (pp. 2397-2404).
Display Omitted► Two different OLED structures with SAM and without SAM were fabricated. ► The SAM layer enhances the luminous and quantum efficiency. ► The SAM layer improves the turn-on voltage and diode current of OLED devices.4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) was synthesized in order to facilitate the hole-injection in Organic Light Emitting Diodes (OLED). MPPBA was applied to form self-assembled monolayer (SAM) on indium tin oxide (ITO) anode to align energy-level at the interface between organic semiconductor material (TPD) and inorganic anode (ITO) in OLED devices. The modified surface was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). KPFM was used to measure the surface potential and work function between the tip and the ITO surface modified by SAM technique using MPPBA. The OLED devices (ITO/MPPBA/TPD/Alq3/Al) fabricated with SAM-modified ITO substrates showed lower turn-on voltages and enhanced diode current compare to the OLED devices fabricated with bare ITO substrates.

Keywords: Self-assembled; OLED; Hole injection

Synthesis and characterization of graphene-supported metal nanoparticles by impregnation method with heat treatment in H2 atmosphere by Sung Mook Choi; Min Ho Seo; Hyung Ju Kim; Won Bae Kim (pp. 2405-2411).
► Synthesis of graphene-supported Pt, Pd, Rh, Ru, Sn, and Ni nanoparticles. ► Material preparation via impregnation method with subsequent heat treatment. ► Investigation of structural and electronic properties of the graphene-supported nanoparticles. ► The small particle sizes and fine dispersion of metal nanoparticles on graphene. ► Influence of heat treatment to structural properties.Graphene as a support for various metal nanoparticles was synthesized through a wet-chemical method combined with thermal exfoliation of graphite. The 60wt% metals (Pt, Pd, Rh, Ru, Sn, and Ni) supported on the graphene materials were prepared by impregnation method with a subsequent heat treatment in H2 atmosphere. Physicochemical analyses such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were employed to investigate the structural and electronic properties of the deposited metals on the graphene material. The metal nanoparticles were finely dispersed on the graphene support. The graphene-supported Pt, Pd, Rh, and Ru materials appeared to be metallic phase, however, the Sn phase showed an oxide state. The graphene-supported Ni revealed a core/shell-like structure of oxide and metallic phases at the surface and core part, respectively. The graphene-supported Pt and Ni were further heat-treated to investigate structural change of the supported nanoparticles, in which the particle size became larger and their crystallinity of the Pt and Ni was enhanced with increasing treatment temperatures.

Keywords: Graphene support; Metal nanoparticles; Impregnation; Heat treatment

Performance of OPVs cells with the eutectic alloy Wood's metal used as cathode and P3HT:PC61BM blend as active layer by Cristina Salto; José-Francisco Salinas; José-Luis Maldonado; Gabriel Ramos-Ortíz; Mario Rodríguez; Marco-Antonio Meneses-Nava; Oracio Barbosa-García; José-Alfredo Del Oso; Mauricio Ortíz-Gutiérrez (pp. 2412-2416).
► OPVs cells based on P3HT:PC61BM are fabricated with Wood's metal as cathode. ► Wood's metal is a eutectic alloy of Pb/Bi/Cd/Sn that melts at 75°C. ► It could make suitable the easy and fast test of mass production for solar panels.OPVs cells based on the well known photoconductor polymer blends of P3HT:PC61BM were fabricated by using Wood's metal as cathode under a vacuum free process. Wood's metal is a eutectic alloy of Pb/Bi/Cd/Sn (25%, 50%, 12.5% and 12.5%, respectively) that melts at 75°C, and permits an easy and quick device implementation. As anode, the commercial and transparent indium tin oxide (ITO) deposited on glass slides was used. The photovoltaic performance of these OPVs cells is compared to other results reported recently in the literature, where most of the OPVs devices were fabricated by using standard methods. Our OPVs cells electrical conversion parameters: Voc=528mV, Jsc=7.35mA/cm2, FF=0.45 and η=1.8% are very acceptable. The metal alloy used here could make suitable the easy and fast test of mass production for solar panels.

Keywords: Organic photovoltaics; Organic semiconductors; Bulk heterojunction; Wood's metal cathode

Optimization of yellow phosphorescent organic light-emitting devices based on triplet exciton diffusion length by Juan Zhao; Junsheng Yu; Zhu Ma; Lu Li; Yadong Jiang (pp. 2417-2421).
► Diffusion of triplet excitons from light emitting layer is studied. ► A non-doped red phosphorescent ultra-thin layer is used as exciton-sensing layer. ► A diffusion length of triplet exciton between 3nm and 5nm is inferred. ► Further device optimization is obtained by introducing 5nm exciton blocking layer.Study on the diffusion of triplet excitons from light emitting layer (EML) in organic light-emitting devices doped with yellow phosphorescent material to the adjacent hole transporting layer (HTL) is carried out, in which a non-doped red phosphorescent ultra-thin layer as an exciton-sensing layer is set in various position of HTL. A diffusion length of triplet exciton between 3nm and 5nm is inferred from the observed and disappeared red light emission in electroluminescent spectra. For further device optimization, either 5nm 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA) or 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) as a exciton blocking layer is introduced to block the exciton diffusion. The maximum current efficiency and power efficiency of the optimized device are reached to 24.6cd/A and 16.3lm/W, respectively. The high performance is ascribed to confined diffusion of triplet excitons from light-emitting zone and higher radiation efficiency of the triplet exciton.

Keywords: Organic light-emitting devices; Yellow phosphorescent; Triplet exciton diffusion length; Exciton-sensing layer

Organic field effect transistors fabricated using a composite of poly(9-vinylcarbazole) and pentacene precursor by Dong-Su Kim; Jae Ho Kwon; Song Yun Cho; Changjin Lee; Kwang-Sup Lee; Tae-Dong Kim (pp. 2422-2426).
► A solution-processable pentacene precursor was synthesized by Diels–Alder reaction. ► A composite system of the pentacene with PVK was investigated for OFET device. ► A hole mobility of 2.2×10−2cm2V−1s−1 was achieved with a threshold voltage of −4V.Organic field effect transistors (OFETs) were fabricated using a solution processable composite of a pentacene precursor and poly(9-vinylcarbazole) (PVK) used for the combinatorial properties of its small molecules and polymers. The pentacene precursor was synthesized by a Diels–Alder reaction from pentacene with N-sulfinylbutylcarbamate in the presence of a catalytic amount of a palladium compound. A composite system of the pentacene precursor with PVK was investigated for OFET device performance. The photophysical and thermal properties of the blending system were characterized, and the film morphology was investigated by using atomic force microscopy (AFM). A maximum hole mobility of 2.2×10−2cm2V−1s−1 was achieved with a threshold voltage of −4V and on/off current ratio of 1.8×106.

Keywords: Organic field-effect transistors; Pentacene precursor; Poly(9-vinylcarbazole); Hole mobility; Solution processing

A highly sensitive non-enzymatic ascorbate sensor based on copper nanoparticles bound to multi walled carbon nanotubes and polyaniline composite by Nidhi Chauhan; Jagriti Narang; Rachna Rawal; C.S. Pundir (pp. 2427-2433).
Steps involved in the preparation of CuNPs/c-MWCNT/PANI modified Au electrode.Display Omitted► Constructed a non-enzymatic ascorbate sensor (CuNP/c-MWCNT/PANI/Au electrode) by single-step electrodeposition method. ► The sensor showed optimum response within 2s at +0.4V. ► The response was linear up to 600μM ascorbic acid concentration with a detection limit of 1.0μM (at signal/noise=3). ► A number of serum substances had practically no effect on sensor response. ► The half life of electrode was 4 months.A novel, stable and highly sensitive non-enzymatic ascorbic acid sensor was developed using copper nanoparticles (CuNPs), carboxylated multi-walled carbon nanotubes (MWCNTs) and polyaniline (PANI) composite electrodeposited on gold electrode. The modified Au electrode was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry and impedance spectroscopy. The linear sweep voltammetry peak current showed a linear dependence on the ascorbic acid concentration and a linear calibration curve was obtained in the range, 5–600μM of ascorbic acid with a correlation coefficient ( r) of 0.998. The sensors response time was less than 2s and detection limit was 1.0μM (at signal/noise=3). When tested with serum, fruits and vegetables, the sensor exhibited high electrocatalytic activity, fast response and good selectivity against common interfering species, suggesting its potential to be developed as a non-enzymatic ascorbic acid sensor.

Keywords: Non enzymatic; Ascorbic acid; Multiwalled carbon nanotubes; Polyaniline; Copper nanoparticles; Amperometric biosensor

Synthesis and photovoltaic property of donor–acceptor type conjugated polymer containing carbazole and 4,7-dithiazolylbenzothiadiazole moiety utilized as a promising electron withdrawing unit by Jang Yong Lee; Kwan Wook Song; Ho Jun Song; Doo Kyung Moon (pp. 2434-2440).
Display Omitted► A DA-type photovoltaic material (PCDTzBT) with a 4,7-dithienylbenzothiadiazole (DTBT) moiety as electron-withdrawing units. ► It exhibited a band gap as low as 1.85eV and well balanced HOMO and LUMO energy levels. ► Photovoltaic cells with various active layer forming conditions were fabricated. ► PDBTTPT exhibited the best power conversion efficiency (PCE) of 0.448%.A donor–acceptor type low band gap conjugated polymer that was composed of carbazole and 4,7-dithiazolylbenzothiadiazole (DTzBT), i.e. Poly [N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thiazol-2′,1′,3′-benzothiadiazole)] (PCDTzBT), was synthesized through the Suzuki coupling polymerization for organic photovoltaics. According to the simulated electronic properties, the synthesized polymer exhibited a better balanced energy level than the polymer that included the 4,7-dithienylbenzothiadiazole (DTBT) moiety. In optical and electrochemical experiments, it exhibited a band gap as low as 1.85eV and well balanced HOMO and LUMO energy levels of −5.54 and −3.65eV, respectively. A PCE of 0.448% was observed in the device that used the PCDTzBT/PC71BM blend film as the active layer. In spite of the well-balanced energy level and low band gap, it is believed that the low PCE value depended on the low molecular weight.

Keywords: Organic photovoltaics; Electron withdrawing material; Conjugated polymers; Copolymerization

Third-order nonlinear optical properties of P3DDT–CdS nanocomposites by Yanmao Dong; Jianmei Lu; Shunjun Ji; Caijian Lu (pp. 2441-2445).
► Poly(3-dodecylthiophene)–CdS as third-order nonlinear optical material. ► Nonlinear optical properties of P3DDT–CdS is enhanced by CdS and P3DDT. ► Coherent oscillation of the conduction band electrons in the nanocomposites. ► The valence band offset of P3DDT–CdS is higher than conduction band offset. ► Electron-hole recombination in the P3DDT for the P3DDT–CdS.A novel inorganic–organic photoluminescent (PL) and nonlinear optical (NLO) poly(3-dodecylthiophene)–CdS (P3DDT–CdS) with different molar ratios of CdS to P3DDT were synthesized via a oxidation coupling polymerization reaction and chemically hybridized approach, respectively. The P3DDT matrix possesses a highest-occupied molecular orbital value of about −5.87eV determined from cyclic voltammetry. The third-order nonlinear optical susceptibility of P3DDT–CdS (−4.41×10−12esu) is higher than that of P3DDT and CdS, respectively. The coherent oscillation of the conduction band electrons in the nanocomposites is responsible for excellent NLO properties of P3DDT–CdS. The CdS particles as electron transport layer and photosensitizers had a nanoscale size in P3DDT adopting transmission electron microscopy. PL results show that, the electron-hole recombination occurred in the P3DDT is dominant, due to the valence band offset of P3DDT–CdS is higher than conduction band offset. The figures of merit of P3DDT and P3DDT–CdS are of −4.25 and −0.99, respectively. So, the P3DDT–CdS shows a potential application in the all-optical switching materials.

Keywords: Poly(3-dodecylthiophene); CdS; Nonlinear optics; Photoluminescence

Effect of monomer concentration on interfacial synthesis of platinum loaded polyaniline nanocomplex using poly(styrene sulfonic acid) by Wonbin Cho; Soo-Jin Park; Seok Kim (pp. 2446-2450).
To find an optimal synthesis condition and confirm electrochemical properties of PANI–PSS–Pt composite for electrode material, we performed this work by changing synthesis condition such as mole ratio of ANI and Pt precursor. It was found that the composites could be successfully prepared by using interfacial polymerization method. In graph b (mole ratio of Pt/ANI was 1:10), the composite electrode showed high specific current density meaning an improved electroactivity in comparison to graph a (1:4) or graph c (1:40).Display Omitted► PANI composites were prepared by using an interfacial polymerization. ► Monomer content influenced the morphological and electrochemical properties. ► Synthesis condition was studied by changing mole ratio of ANI and Pt precursor. ► Electrochemical performance was related with the cluster size of Pt particles.Polyaniline–poly(styrene sulfate)–platinum (PANI–PSS–Pt) composites were prepared via interfacial synthesis. Polymerization of aniline and an incorporation of platinum (Pt) in polyaniline (PANI) were carried out simultaneously by using H2PtCl6 as an oxidizing agent in poly(styrene sulfonic acid) solution. To find an optimal synthesis condition, PANI–PSS–Pt composites were prepared with different mole ratio of aniline monomer and platinum precursor concentration. Resulting composites were compared with PANI–Pt–PSS composites prepared by using non-interfacial synthesis method.Doping degree and electronic structure of PANI–PSS–Pt composites were characterized by UV–Vis absorption spectroscopy. The morphological structures of PANI–PSS–Pt were evaluated by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behaviors of PANI–PSS–Pt were investigated according to their characteristic current–voltage curves. PANI–PSS–Pt composite synthesized in 0.05M monomer concentration showed smaller cluster size of composites and the highest current density value of 0.45mA/mg.

Keywords: Polyaniline; Platinum; Interfacial synthesis; Doping acid; Composite electrode

The synthesis and electroluminescent properties of dithienylquinacridone-based copolymers for white light-emitting diodes by Ho Jun Song; Seung Min Lee; Jang Yong Lee; Byung Hyun Choi; Doo Kyung Moon (pp. 2451-2459).
Display Omitted► We synthesized the dithienylquinacridone derivative as an orange dopant. ► The synthesized PFTQ polymer series showed good solubility and thermal stability. ► Charge trapping was more effective in DTquinacridone compared to quinacridone. ► Polymers of PFTQ3, PFoxdTQ3 and PFoxdCzTQ3 showed white color emission.The dithienylquinacridone derivative that produces orange emission in fluorene, a representative blue light-emitting material, was added in a small quantity as a dopant to synthesize poly[fluorene-co-DTQuinacridone] (PFTQ) using the Suzuki coupling reaction. The copolymer was synthesized at various mole ratios and was soluble in organic solvents. The luminous efficiency of PFTQ3 was 0.50cd/A, the power efficiency was 0.24lm/W, and the maximum brightness was 1450cd/m2. In addition, the device made from PFTQ3 emitted white light with the CIE coordinates of (0.31, 0.35). After thermal treatment, its luminous efficiency, power efficiency and maximum brightness were 0.71cd/A, 0.34lm/W, and 3905cd/m2, respectively, corresponding to an improvement of about 1.4 times of the sample prior to thermal treatment.

Keywords: Conjugated polymers; PLED; Dithienylquinacridone; Fluorene

Porous graphene/carbon nanotube composite cathode for proton exchange membrane fuel cell by Young Soo Yun; Doyoung Kim; Yongsug Tak; Hyoung-Joon Jin (pp. 2460-2465).
► We made porous Pt-graphene/MWCNT composite cathodes for PEMFCs. ► Graphene sheets were coated uniformly with the Pt nano-particles of 2–3nm at a high loading of 50wt%. ► Pt-graphene was bound homogeneously to MWCNTs, which induced a porous network structure. ► These porous electrodes could provide an efficient electrical pathway for the redox reaction.Porous Pt-graphene/multiwalled carbon nanotube (MWCNT) composite cathodes were fabricated for proton exchange membrane fuel cells and their electro-chemical performances were examined. Rod-like MWCNTs with a high aspect ratio induced a porous network structure and Pt-graphene was bound homogeneously to the porous network structure of MWCNTs in the form of a very rough surface, which facilitated simultaneous access between the Pt electro-catalyst and reactant. In addition, the porous MWCNT network enabled the Pt-graphene electrode to overcome the deficiency induced by high electrical resistance by providing an electrical pathway for the oxygen reduction reaction (ORR). Therefore, the ORR charge transfer resistance of the Pt-graphene/MWCNT composite cathode was much smaller than that of the Pt-graphene cathode, and the maximum power density of the Pt-graphene/MWCNT composite cathode was four times higher than that of the Pt-graphene cathode.

Keywords: Cathodes; Carbon nanotubes; Graphenes; Proton exchange Membrane fuel cell

Aryl substituted 9-(2,2-diphenylvinyl)carbazoles as efficient materials for hole transporting layers of OLEDs by R. Griniene; J.V. Grazulevicius; K.Y. Tseng; W.B. Wang; J.H. Jou; S. Grigalevicius (pp. 2466-2470).
► Aryl substituted 9-(2,2-diphenylvinyl)carbazoles were synthesized. ► These derivatives used as hole transporting materials in OLEDs. ► Efficiency of 4.8cd/A and brightness exceeding 13,000cd/m2 were obtained.Phenyl or naphthyl substituted 9-(2,2-diphenylvinyl)carbazoles were synthesized by the multi-step synthetic route. The materials were examined by various techniques including thermogravimetry, differential scanning calorimetry, and electron photoemission technique. These derivatives were also tested as hole-transporting materials in bilayer OLEDs with Alq3 as the emitter. The devices exhibited promising overall performance with a turn-on voltage of 3.2V, a maximal photometric efficiency of about 4.8cd/A and maximum brightness of 12,400–13,100cd/m2.

Keywords: Carbazole derivatives; Amorphous material; Ionization potential; Light emitting diode

Two novel 2D and 3D coordination polymers constructed from pyrazine-2,3-dicarboxylic acid and chloride bridged secondary building units by Güneş Günay; Okan Zafer Yeşilel; Mustafa Serkan Soylu; Seda Keskin; Hakan Dal (pp. 2471-2480).
Display Omitted► Two novel 3D and 2D MOF architectures of Cu(II) and Cd(II)-hydrogenpirazine-2,3-dicarboxylate complexes have synthesized and characterized. ► The Hpzdc ligand acts as a bridging ligand with two different bridging modes and it exhibits a new coordination mode. ► 1D hybrid water–chloride anionic [(H2O)8Cl2] n cluster has been identified. ► The complex2 shows strong peaks with the emission at 540 and 595nm.The synthesis, spectroscopic properties and crystal structures of {[Cu2(μ-Cl)23-Hpzdc)(Cl)(H2O)2]·1.5H2O} n (1) and {[Cd(μ-Cl)(μ-Hpzdc)]·H2O} n (2) complexes were reported (H2pzdc=pyrazine-2,3-dicarboxylic acid). H2pzdc is singly deprotonated in both complexes and the coordination mode of Hpzdc ligand in1 has been first reported in this presentation. The complex1, which has a 3D framework structure, was formed with double μ-chloride and μ3-Hpzdc bridges. In1, water molecules occupy in the 1D channel as guest molecules. Furthermore, unprecedented 1D hybrid water–chloride anionic [(H2O)8Cl2] n cluster has been structurally identified. In the complex2, the Cd(II) atom is seven-coordinated by two hydrogen pyrazine-2,3-dicarboxylate, two chloride and one aqua ligands in a distorted monocapped octahedral coordination geometry. The Cd(II) atoms are bridged by the bis(bidentate) Hpzdc ligands, forming 1D polymer chain. The adjacent 1D chains are linked each other through the double chloride bridges to form 2D layer. The layers are connected together through O–H⋯O interactions resulting in a three-dimensional framework. The mechanisms for these compounds were validated by density functional theory (DFT) calculations on the experimental geometries. The photoluminescent property of2 was investigated in the solid state at room temperature. Moreover, in order to assess the potentials of1 and2 in gas storage applications, we performed atomically detailed simulations.

Keywords: Pyrazine-2,3-dicarboxylic acid; Pyrazine-2,3-dicarboxylate complexes; Metal-organic framework; Water–chloride clusters

Unsymmetrical squarylium dyes with π-extended heterocyclic components and their application to organic dye-sensitized solar cells by Takeshi Maeda; Naoki Shima; Tatsuya Tsukamoto; Shigeyuki Yagi; Hiroyuki Nakazumi (pp. 2481-2487).
► Four unsymmetrical squarylium dyes with π-extended heterocycles were synthesized. ► π-Extended heterocyclic components lead to red-shifted absorption of the dyes. ► The squarylium dyes achieved acceptable performance in the NIR region ( η<1.6%). ► The photovoltaic performances depended on the structure of heterocyclic components.Novel π-extended squarylium dyes have been synthesized as sensitizers for use in dye-sensitized solar cells (DSSCs). Four quaternary salts with extended π-systems, quinolinium, benz[c,d]indolium, benzopyrylium, and benzo-1-thiopyrylium, were selected as electron-rich heterocyclic components and condensed with indole-based semisquarylium bearing a carboxyl group as an anchor for their immobilization on TiO2 to obtain four unsymmetrical squarylium dyes (SQ1–4). They exhibited intense absorption in the near-infrared region in solution and on the TiO2 surface (absorption edge: approximately 900nm). Investigation of their electrochemical properties revealed that electron injection from the excited dyes to the TiO2 conduction band was thermodynamically permitted. A molecular-orbital calculation indicated that the electron distribution moved from the cyclobutene core to the heterocyclic components bearing the carboxyl group by photoexcitation ofSQ1–4. The photovoltaic performances of DSSCs based on the squarylium dyes significantly depended on the structure of heterocyclic components. Among the series of squarylium dyes,SQ2–4 achieved comparatively high performance in metal-free NIR sensitizers ( η=1.1–1.6%), in accordance with the calculation results. These results suggest that the structure of heterocyclic components strongly affects not only the absorption properties of the dyes but also the photovoltaic performances of DSSCs based on these dyes.

Keywords: Squarylium dye; Near-infrared; Dye-sensitized solar cells; Nanocrystalline TiO; 2

The interfacial electronic structure between pentacene and multilayer graphene by Sang Wan Cho; Yeonjin Yi; Seong Jun Kang (pp. 2488-2491).
► The electronic structure at the interface region between pentacene and multilayer graphene. ► The hole and electron injection barrier from multilayer graphene to the pentacene layer. ► The complete interfacial energy level band diagram of pentacene/multilayer graphene.The electronic structure at the interface region between pentacene and multilayer graphene (MLG) was investigated by in situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The secondary electron cutoffs, highest occupied molecular orbital (HOMO), and core-level changes were measured after deposition of pentacene on MLG to investigate the electronic structure at the interface. From the results, it was confirmed that there was neither band bending nor an interface dipole at the pentacene/MLG interface, even though a vacuum level shift was observed due to the three-dimensional growth of pentacene. In addition, there was no chemical reaction observed at the interface. The complete interfacial energy level band diagram of pentacene/MLG was also obtained to confirm the hole and electron injection barriers.

Keywords: PACS; 72.80.Le; 73.20.−r; 73.20.At; 85.30.TvGraphene; Pentacene; Photoelectron spectroscopy; Electronic structure; Band diagram

Theoretical studies on structures and spectroscopic properties of highly efficient phosphorescent iridium(III) complexes with pyrazine and pyrimidine ligands by Jian-Po Zhang; Li Jin; Hong-Xing Zhang; Fu-Quan Bai (pp. 2492-2497).
A series of iridium(III) complexes (C^N)2Ir(acac) (C^N=mppz (1), fmppz (2), ppm (3), and fppm (4); acac=acetoylacetonate, mppz=2-methyl-3-phenylpyrazine, fmppz=2-(2,4-difluorophenyl)-3-methylpyrazine, ppm=2-phenylpyrimidine, and fppm=2-(2,4-difluorophenyl)-pyrimidine) have been investigated theoretically to explore their electronic structures and spectroscopic properties. The structures in the ground and excited states have been optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. The calculated bond lengths of Ir–N, Ir–C, and Ir–O in the ground state agree well with the corresponding experimental results. Upon excitation, the bond lengths of Ir–N and Ir–C lengthen by 0.03Å and that of Ir–O shortens by 0.02Å compared with those in the X1A ground states. At the TD-DFT and PCM levels,14 give rise to absorptions at 499, 457, 460, and 427nm and phosphorescent emissions at 549, 519, 505, and 465nm, respectively. The HOMOs of14 are mainly localized on the metal atom and C^N ligands, while the LUMOs are the π*(C^N) type orbital. Therefore, the transitions of14 are all attributed to {[d(Ir)+π(C^N)]→[π*(C^N)]} charge transfer. It is shown that the emissions are significantly dominated by the metal participating in the frontier molecular orbitals and affected by the C^N ligands but are hardly perturbed by the acac ligand.

Keywords: Cyclometalated iridium(III) complexes; Electronic structures; Spectroscopic properties; TD-DFT calculations; OLED

Characterization of the surface properties of polypyrrole films: Influence of electrodeposition parameters by Tilia Patois; Boris Lakard; Sandrine Monney; Xavier Roizard; Patrick Fievet (pp. 2498-2505).
► Electrochemical polymerization of polypyrrole films on fluorine tin oxide. ► Influence of deposition parameters on their electrical and structural properties. ► Characterization of polymers (Van der Pauw, optical profilometry, SEM, AFM).Polypyrrole films were electrosynthesized on conductive tin oxide substrates by potentiostatic deposition in various aqueous electrolyte solutions including p-toluenesulfonate, naphthalenesulfate, nitrate, tetrafluoroborate, and perchlorate anions. Electrical and structural characteristics (morphology, roughness and thickness) were determined using Van der Pauw method, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Optical Profilometry (OP). Experimental parameters including the electrolyte, applied electrodeposition potential, and pyrrole concentration were shown to affect the morphologies and conductivities of so-prepared polypyrrole films. The p-toluenesulfonate doped polypyrrole film showed the highest conductivity whereas the perchlorate doped one showed the lowest conductivity of all the films. On the contrary, the film thickness did not affect the electrical conductivity. Concerning the morphology, globular-shaped topographic structures were obtained for nearly all the polymer films, but with different sizes of globules and aggregates. Both roughness and morphological features were also proved to be very dependent from the electropolymerization parameters.

Keywords: Conducting polymer; Polypyrrole; Electrodeposition parameters; Structural properties; Morphology

Synthesis of hollow microspheres poly(o-phenylenediamine)/iron oxide composites and application of fluorescence probe in yeast RNA detection by Zhoufeng Wang; Fang Liao (pp. 2506-2509).
In this communication, we demonstrated that chemical oxidation polymerization of o-phenylenediamine (oPD) by Fe2(SO4)3 at room temperature results in the formation of hollow microspherical PoPD/Fe2O3 composites, which were self-assembled from 2D nanosheets. PoPD/Fe2O3 composites could be used for rapid determination of yeast RNA as a fluorescence probe, based on the fluorescence enhancement of composites in the presence of yeast RNA. The novel morphology of PoPD/Fe2O3 composites synthesized in the research can be used as a new fluorescence probe for sensitive determination of DNA or RNA.

Keywords: Polymers; Composite materials; o-Phenylenediamine; Fluorescence probe; Yeast RNA

New insight into the redox behavior of polyaniline by Natalia Gospodinova; Veronica Muşat; Hristo Kolev; Julia Romanova (pp. 2510-2513).
► Mesoporous thin polyaniline films formed by highly crystalline fibrils. ► Propagation of polyaniline reduction in acidic medium. ► Water penetration in the films is crucial for the propagation of the reduction. ► Presence of highly hydrated ions favors the water penetration.Polyaniline is one the most promising conducting polymers due to its ability to respond to environmental modifications by change in the properties. Here, we report an unprecedented redox behavior of polyaniline. Namely, propagation of reduction in thin highly organized polyaniline films immersed in acid aqueous medium (see ). The films represent a homogeneous interpenetrating network of nano-sized polyaniline fibrils and water molecules. It is found that the presence of highly hydrated anions like HCOO favors both short- and long-range ordering, as well as the propagation of reduction in the polymer.

Keywords: Polyaniline; Highly organized films; Redox behavior; Conducting polymers

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