Synthetic Metals (v.161, #15-16)

A new one-dimensional silver(I) coordination polymer, [Ag(μ-bpfb)(NO3)] n (1); bpfb = N,N′-bis(4-pyridylformamide)-1,4-benzene, has been synthesized and characterized by IR, 1H NMR and 13C NMR spectroscopy. The single crystal X-ray data show that the silver(I) 1D coordination polymer grows into a three-dimensional network by hydrogen bonding and π–π stacking interactions. Compound 1 with nanorod morphology was also prepared by sonochemical method. The cetyltrimethylammonium bromide (CTAB) as a cationic surfactant was used in reverse micelles technique to obtain spongy silver(I) bromide nanoparticles from compound 1. Also, different silver nanoparticles have been prepared via direct calcination at 673 K and thermal decomposition in oleic acid from compound 1. The nanostructures of [Ag(μ-bpfb)(NO3)] n (1), silver and silver(I) bromide were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) analysis. Thermal stability of compound 1 in both bulk and nano-sized form was studied by thermal gravimetric (TG) and differential thermal (DT) analyses.
Keywords: Silver(I) coordination polymer; Bispyridylamide; Nano-structure;

Display Omitted► Carbon black/acrylic copolymer hybrid particles were prepared for electrophoretic display application. ► Acrylic copolymer can be anchored stably on CB surface by ultrasonication. ► Treated CB can suspend stably in tetrachloroethylene with the aid of acrylic copolymer with proper chain structure, e.g. P(HEA–LMA) and P(DMA–LMA). ► The CB/P(DMA–LMA) hybrid particles can be applied in the dual particle electrophoretic system.To prepare black electrophoretic particles with good suspension stability in the low dielectric medium for electrophoretic display application, four kinds of carbon black (CB)/acrylic copolymer hybrid particles, CB/poly(2-hydroxyethyl acrylate-co-lauryl methacrylate) (P(HEA–LMA)), CB/poly(2-hydroxyethyl acrylate-co-2-ethylhexyl acrylate) (P(HEA–EHA)), CB/poly(2-(dimethylamino)ethyl methacrylate-co-2-ethylhexyl acrylate) (P(DMA–EHA)) and CB/poly(2-(dimethylamino)ethyl methacrylate-co-lauryl methacrylate) (P(DMA–LMA)), were prepared via polar bonding, the interaction between the carboxyl groups on the surface of CB and the hydroxyl or amino group in copolymers. Structure, morphology as well as electrophoretic properties of the particles were examined. The particle size of the P(HEA–EHA) and P(DMA–EHA) treated CB increases with increasing the storage time. While the particle size of the P(HEA–LMA) and P(DMA–LMA) treated CB is time independent, which can be attributed to the better extension of P(LMA) segments in tetrachloroethylene than P(EHA) and the resulting more effective steric effect. When the feed ratio of DMA/LMA was 3:5 by volume, the maximum values of the electrophoretic mobility and Zeta potential reach 5.44 × 10−10  m2  V−1  s−1 and 32.5 mV, respectively. The P(DMA–LMA) anchored CB particles can be applied in the dual-particle electrophoretic dispersion together with negative charged TiO2 to show black and white images.
Keywords: Suspension stability; Electrophoretic mobility; Carbon black; Steric effect;

Synthesis and characterization of new electroluminescent poly(p-phenylene) derivative by Mejed Chemli; Ayoub Haj Saïd; Nejmeddine Jaballah; Jean-Louis Fave; Mustapha Majdoub (1463-1468).
Display Omitted► We synthesize an acyl-functionalized poly(p-phenylene) by Yamamoto reaction. ► We perform a chemical modification of the polymer by the Claisen Condensation. ► A green emission at 512 nm was observed in thin solid film. ► We construct a green light emitting multilayer device [ITO/PEDOT:PSS/Modified Polymer/BCP/Al].A new electroluminescent poly(p-phenylene) (PPP)-type polymer (CHALC-PPP) incorporating chalcone-type groups as side-chains has been synthesized via a chemical modification of a precursor acyl-functionalized polymer. The chemical structure of the polymer was characterized by 1H NMR, 13C NMR, and FT-IR spectroscopic analysis. CHALC-PPP contains a substitution ratio of 40% of vinylaryl groups. It is fully soluble in common organic solvents and has a number–average molecular weight of 3750 g/mol. CHALC-PPP thin solid film absorbs in UV and emits in the green region with a maximum at 512 nm. From the cyclic voltammetry analysis, the HOMO and LUMO energies levels values are −5.67 and −2.70 eV, respectively. A multilayer diode device with the configuration ITO/PEDOT:PSS/CHALC-PPP/BCP/Al emitting a green light has been fabricated.
Keywords: Electroluminescent polymers; Poly(p-phenylene); Photoluminescence; Polymer light-emitting diode;

Phenothiazine conjugated bipyridine as ancillary ligand in Ru(II)-complexes for application in dye sensitized solar cell by Malapaka Chandrasekharam; Ganugula Rajkumar; Chikkam Srinivasa Rao; Thogiti Suresh; Paidi Yella Reddy (1469-1476).
► Novel Ru(II) sensitizer for application in dye sensitised solar cells. ► Phenothiazine is an excellent electron donating chromophore. ► N-alkyl phenothiazine conjugated bipyridine, a new class of ancillary ligand for Ru(II) sensitizers. ► Multiple performance improving structural features incorporated for increased efficiency.A new high molar extinction coefficient ruthenium(II)-bipyridine complex “cis-Ru(4,4′-bis((E)-2-(10-decyl-10H-phenothiazin-3-yl)vinyl)-2,2′-bipyridine)(4,4′-dicarboxylic acid-2,2′-bipyridine)(NCS)2 PTZ1″ was synthesized through conjugation of phenothiazine unit with bipyridine and characterized by FT-IR, 1H-NMR and ESI-MASS spectroscopes. Absorption measurements and time dependent-density functional theory (TD-DFT) calculations show increased spectral response for the ancillary ligand and the corresponding complex. The dye upon anchoring onto mesoporous nanocrystalline TiO2 solar cells exhibited solar-to-electric energy conversion efficiency (η) of 3.77% short-circuit photocurrent density ( J SC) = 7.79 mA/cm2, open-circuit voltage ( V OC) = 640 mV, fill factor = 0.750) under air mass 1.5 sunlight, the reference Z907 and HRS1sensitized solar cells, fabricated and evaluated under identical conditions exhibited η-value of 7.02% ( J SC  = 15.25 mA/cm2, V OC  = 650 mV, fill factor = 0.705) and 3.05% ( J SC  = 8.20 mA/cm2, V OC  = 610 mV, fill factor = 0.620) respectively. The lower film absorption of PTZ1on TiO2 surface could be probably due to larger molecular diameter and planarity of phenothiazine prone to aggregate in solution as well as on TiO2 surface. The DFT calculations show that the first three HOMOs of PTZ1 have t2g character as observed in case of Z907, while HOMO-4 and HOMO-5 have π-orbitals with major component on phenothiazine moieties of L1.
Keywords: Dye sensitized solar cells; Phenothiazine conjugation; Ruthenium complex;

Display Omitted► The peripheral α-substituted-functional manganase phthalocyanine is an organic semiconductor with optical band gap of 2.98 eV. ► The ITO/MnPc/Al diode shows a rectifying behavior due to the formation of MnPc/Al interface with a rectification ratio of 29.4 at ±2 V. ► The MnPc organic semiconductor can be used in electronic device applications as an organic diode.The semiconducting and metal/organic semiconductor properties of the newly synthesized NIR absorbing α-substituted manganase phthalocyanine bearing functional 2,3-dihydroxypropylthio moieties {M[Pc(S–CH3CH2(OH)CH2(OH))]4X}(M = MnIII) have been investigated by electrical conductivity–temperature, optical absorption and current–voltage characteristics methods. The electrical conductivity increases with the temperature, suggesting that the peripheral α-substituted-functional manganase phthalocyanine is an organic semiconductor. The optical band gap and trap energy values were determined and were found to be 2.98 eV and 1.95 eV, respectively. The ITO/MnPc/Al diode shows a rectifying behavior due to the formation of MnPc/Al interface with a rectification ratio of 29.4 at ±2 V. The series resistance R s and ideality factor n values were found to be 102.6 kΩ and 8.89, respectively. The interface state density for the diode was of order of 2.73 × 1011  eV−1  cm−2 with the interface time constant of 1.93 × 10−5.It is evaluated that newly synthesized α-substituted manganase phthalocyanine bearing functional 2,3-dihydroxypropylthio moieties is an organic semiconductor and can be used in electronic device applications as an organic diode.
Keywords: Organic semiconductor; Organic diode; Interfacial state density; Manganase phthalocyanine;

Scheme of the proposed multiple-step mechanism of the poly(N-PhPy) film formation in acid aqueous micellar medium, showing the loss of a pyrrolyl group and the incorporation of one oxygen atom, in the case of a “modified” tetramer.Display Omitted► Electrosynthesis of poly-N-phenyl-pyrrole [poly(N-PhPy)] by anodic oxidation of N-PhPy on Pt. ► Acid aqueous micellar medium (0.1 M sodium dodecyl sulfate, SDS). ► Formation of electroactive poly(N-PhPy) films. ► Characterization of poly(N-PhPy) films (oligomers) by MALDI-TOF, FT-IR and XPS. ► Weak red-shifts of the poly(N-PhPy) UV–Vis absorption and fluorescence spectra maximums relative to N-PhPy.Poly-N-phenyl-pyrrole [poly(N-PhPy)] was electrosynthesized by anodic oxidation of N-PhPy on Pt electrode in acid aqueous micellar medium (0.1 M sodium dodecyl sulfate (SDS) + 1.93 M HClO4 in 84/16 water/butanol v/v), using cyclic voltammetry (CV), chronoamperometry and chronopotentiometry. Electroactive poly(N-PhPy) films were formed upon scanning the potential (E) between 0.0 and 1.4 V/SCE, under controlled potential (E  = 0.9–1.3 V/SCE) or controlled current density (J  = 0.125–2.0 mA/cm2). The poly-NPhPy films were characterized by CV, MALDI-TOF mass spectrometry, FT-IR and X-ray photoelectron spectra (XPS), and their morphology was studied by scanning electron microscopy (SEM). Their optical properties, including electronic absorption and fluorescence spectra, were also investigated. A multiple-step mechanism for the poly(N-PhPy) films formation in micellar medium, based on the MALDI-TOF, FT-IR and XPS results, was proposed.
Keywords: Poly-N-phenylpyrrole; Electropolymerization; Micellar media; Optical properties;

Temperature-dependent kinetics of printed polymer light-emitting electrochemical cells by K.O. Burnett; P.P. Crooker; N.M. Haegel; Y. Yoshioka; D. MacKenzie (1496-1499).
► Light-emitting electrochemical cells turn-on time. ► Thermal activation energy for ion hopping. ► Transient measurements of current and light.The thermal activation energy for ion transport and related junction formation in a polymer light-emitting electrochemical cell (LEC) has been determined by measuring the transient behavior of light emission as a function of temperature from 257 K to 297 K. We find the initial time derivative of the light intensity to have an Arrhenius temperature dependence, with an activation energy of 1.6 eV. Our devices utilize a flourene-based polymer emitter which fluoresces at red/near-infrared wavelengths. The polymer matrix includes phenyl alkoxy-substituted PPV and an electrolyte/dopant system based on both solid polymer and ionic liquid dopants. Transient measurements of current and light emission have been used to capture the kinetics of both junction formation and junction decay and to measure variations in optical external quantum efficiency during device turn-on.
Keywords: Light-emitting electrochemical cell; Polymer light-emitting diode; Transient response; Thermal activation;

► New coordination polymers {[Ln2(PDA)(HPDA) (H2O)4ClSO4]·2H2O} n (Ln = La(III) and Ce(III) have been synthesized. ► 3D framework possessing 1D nanosized cavities with guest water molecules embedded. ► Luminescent emission of complex I displays selectivity toward Ag+, Hg2+ and K+.Two novel coordination polymers, namely, {[Ln2(PDA)(HPDA) (H2O)4ClSO4]·2H2O} n (Ln = La(III) and Ce(III) for complexes I and II, respectively) were synthesized through the reaction between pyridine-2,6-dicarboxylic acid (H2PDA) and La(NO3)3·6H2O and Ce2(SO4)3·8H2O under hydrothermal conditions. Both of these polymers possess 1D infinite nanosized cavities embedding guest water molecules. The complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses and single crystal X-ray diffraction. Two compounds crystallize in orthorhombic system, space group Pna2(1). Both of the complexes exhibit 3D metal–organic framework structure, where SO4 2− anions play as the bridge between 1D wavelike chains and the adjacent parallel pyridine rings were arranged through π–π interactions. The bi-bidentate coordination mode of SO4 2− anion was observed. Luminescent emissions of complex I were measured in the solution of DMF at room temperature. In addition, the luminescent emissions of complex I showed certain selectivity among some metal ions.
Keywords: Synthesis; Structure; Luminescent properties; Lanthanide coordination polymers; Pyridine-2,6-dicarboxylic acid;

Physical properties of ultrasonic sprayed nanosized indium doped SnO2 films by C.E. Benouis; M. Benhaliliba; F. Yakuphanoglu; A. Tiburcio Silver; M.S. Aida; A. Sanchez Juarez (1509-1516).
Display Omitted► The structural, morphological (AFM and FESEM), optical and electrical properties of indium doped tin oxide (TO) properties are investigated. ► Influence of indium as dopant is studied with accuracy and details. ► The deposition of films was achieved by new technique and soft, low cost USPD. ► AFM parameters details, such as section analysis, grain size distribution histogram, power spectral density PSD are deduced from XEI version 1.7.1 data processing and analysis software.Here, we report on the preparation and characterization of nanosized indium doped tin oxide films (TO:In). The films are grown by ultrasonic spray pyrolysis deposition (USPD) onto glass. The structural, optical, electrical and morphological properties of SnO2 (TO) films are investigated. The as-deposited films SnO2 have preferred orientation along the (2 0 0) plane and are polycrystalline with a tetragonal crystal structure. Following this direction, the average grain size, obtained from XRD patterns, decreases with the rate doping. It ranges from 64 to 17 nm. In UV spectrum, the transmittance increases followed by a slight decay within visible range. Optical band gap, E g, is about 4.1 eV. The samples reveal a high resistivity which varies in the range 104–107  Ω cm. Activation energies of shallow levels, as obtained from Arrhenius plots, vary from 85 meV to 165 meV. SEM and AFM analysis demonstrate nanostructure morphology.
Keywords: Ultrasonic spray pyrolysis deposition; Growth of SnO2; Indium doping TO:In; High transparency; Nanosized morphology; AFM morphology; Power spectral density;

Spontaneous formation of highly dispersed spheroidal metallic silver nanoparticles in surfactant-free N,N-dimethylacetamide by Luiz Pereira da Costa; André Luiz Barboza Formiga; Italo Odone Mazali; Fernando Aparecido Sigoli (1517-1521).
► This work shows the preparation of highly dispersed spheroidal silver nanoparticles. ► The reaction was carried out in surfactant-free N,N-dimethylacetamide solution. The nanoparticles average size is smaller than that obtained in N,N-dimethyformamide. ► N,N-Dimethyformamide interacts more weakly with Ag(I) than does N,N-dimethylacetamide. ► The chemical interactions strengths have implications on nanoparticles stabilization.The present work describes a simple method for preparing highly dispersed spheroidal metallic silver nanoparticles in surfactant-free N,N-dimethylacetamide solution. The optical properties, shape and size of the metallic silver nanoparticles obtained in N,N-dimethylacetamide after different times of reaction were characterized using UV–vis absorption spectroscopy and transmission electron microscopy. The average size of the metallic silver nanoparticles is smaller than that obtained by the well established procedure using N,N-dimethyformamide. Using optimized geometries for N,N-dimethylacetamide and N,N-dimethyformamide, vertical ionization energies and electron affinities were calculated by means of the UHF/DFT calculations of cations and anions, respectively. The difference between ionization energies and electron affinities is higher for N,N-dimethyformamide indicating that it is a harder base than N,N-dimethylacetamide. Therefore, N,N-dimethyformamide probably interacts more weakly with Ag(I) ions than does N,N-dimethylacetamide. The strength of this chemical interaction has implications on the stabilization and dispersion of silver nanoparticles obtained in N,N-dimethylacetamide. The low cost, simple methodology may be used as a platform for further studies in surface-enhanced Raman spectroscopy as well as with other optical properties that depend on the surface plasmon resonance of metallic silver nanoparticles.
Keywords: Silver nanoparticles; Plasmon; N,N-Dimethylacetamide;

Enhanced microwave absorption behavior of polyaniline-CNT/polystyrene blend in 12.4–18.0 GHz range by Parveen Saini; Veena Choudhary; B.P. Singh; R.B. Mathur; S.K. Dhawan (1522-1526).
Blends of polystyrene with polyaniline (PANI) coated multiwalled carbon nanotubes (MWCNTs) were designed which inherit dielectric and magnetic attributes from PANI and MWCNT respectively. The high resolution transmission electron microscopy image shows the PANI coating over MWCNT containing entrapped Fe catalyst. These blends show absorption dominated total shielding effectiveness (SE T ) of −45.7 dB (>99.99% attenuation) in the 12.4–18.0 GHz range, suggesting their utility for making efficient microwave absorbers. The enhanced SE T was ascribed to optimization of conductivity, skin-depth, complex permittivity and permeability. A good agreement between theoretical and experimental shielding measurements was also observed.
Keywords: Conducting polymer polyaniline; Carbon nanotube (CNT); Microwave absorption; Electromagnetic interference (EMI) shielding effectiveness; High resolution transmission electron microscopy (HR-TEM); Electrical conductivity;

Polyimide/Ta2O5 nanocomposite gate insulators for enhanced organic thin-film transistor performance by Liang-Hsiang Chen; Pang Lin; Jia-Chong Ho; Cheng-Chung Lee; Choongik Kim; Ming-Chou Chen (1527-1531).
• In situ formation of Ta2O5 nanocomposite polyimide films as insulators was studied. • Films imidization degree was characterized as a function of Ta2O5 precursor contents. • Increase of dielectric constant of these Ta2O5/polyimide films was observed. • Improved pentacene mobility in OTFTs by a factor of 2–3 was achieved. • Good current on/off ratio (>105) and low threshold voltage (−1.5 V) was also obtained.This study reports the preparation and characterization of polyimide/Ta2O5 nanocomposite films as insulators for organic thin-film transistors (OTFTs). The degree of imidization, thermal, electrical, and surface properties of the nanocomposite films were characterized as a function of Ta2O5 precursor contents. The nanocomposite films, with controlled/comparable insulator electrical characteristics and surface properties, have been found to enhance dielectric constant compared to pristine polyimide films, which resulted in improved pentacene TFT performance by a factor of 2–3 with carrier mobility values as high as 0.38 cm2/V s.
Keywords: Organic thin-film transistors (OTFTs); Nanocomposite; Hybrid films; Gate insulator;

Chiral conducting surfaces based on the electropolymerization of 3,4-ethylenedioxythiophene by Christopher D. McTiernan; M’hamed Chahma (1532-1536).
Display Omitted► Electrochemical oxidation of d or l-proline functionalized monothiophenes in the presence of an EDOT monomer affords copolymers with specific chirality. ► The resulting electroactive copolymers display excellent stability in both doped and undoped states. ► EDOT moiety increases the stability of chiral conducting surfaces.The synthesis and electrochemical characterization of d- and l-proline functionalized monothiophenes are reported. Both monomers 2L and 2D showed anodic peak potentials of 1.86 V vs. Fc+/Fc and their electropolymerization affords polymers that exhibit poor stability on platinum electrodes. However, the electrochemical copolymerization using cyclic voltammetry of 2L or 2D in the presence of EDOT gives polymeric films at the surface of the electrode with specific chirality. The E 1/2 of the copolymers was found to be 0.38 V vs. Fc+/Fc. The copolymers display excellent electrochemical stability and adhesion properties on the surface of platinum and ITO electrodes. Moreover, the films also undergo a reversible color change between their doped (blue-green) and undoped (blue-brown) states. Incorporation of the chiral pendant group was confirmed through the appearance of characteristic C=O stretching absorptions in the IR spectra of the copolymers.
Keywords: Polythiophene; EDOT; Amino acids; Copolymerization;

The synthesis of novel, unsymmetrical, octasubstituted metal-free and metallophthalocyanines (zinc, cobalt) bearing one chlorine, one morpholine moieties and six 4-tert-butylphenoxy substituents was achieved by a statistical condensation reaction of two corresponding phthalonitriles. The new compounds have been characterized by using elemental analyses, UV–vis, IR, 1H NMR and mass spectroscopic data. Voltammetric and spectroelectrochemical studies are in harmony with the reported metallophthalocyanine complexes, which support the proposed structure of the complexes.
Keywords: Electrochemistry; Phthalocyanine; Spectroelectrochemistry; Unsymmetric; Zinc;

Display Omitted► We perform first-principles calculations of one-dimensional peanut-shaped fullerene polymers. ► According to our result, some of them exhibit metallic properties. ► Regular hexagons connected throughout the tube are required for metallic properties.Some kind of one-dimensional (1D) peanut-shaped fullerene polymers (PSFPs) exhibit metallic properties, but their occurrence conditions are not yet clarified. By using the VASP (Vienna ab-initio simulation package) with density functional theory (DFT) and projector augmented wave (PAW) method, we have performed first-principles electronic structure calculations of four basic 1D PSFPs, T1, T2, T6, and T7 (the name of T1–T6 is the same as that of Wang et al. ) and two associated 1D PSFPs, T1SW1 and T6SW that are created by generalized Stone–Wales transformation (GSW) from T1 and T6. We found that almost regular six-membered rings connected throughout the tube are necessary to get metallic properties for the 1D PSFPs, although there may be several other conditions to expect metallic properties.
Keywords: C60; Fullerene polymer; First-principles calculation; Density functional theory; Band structure;

► Ce(III) coordination polymer with chiral Schiff base was synthesized. ► The crystal structure of the coordination polymer was determined. ► The coordination polymer displays two-dimensional plane grid network structure. ► The anticancer activities of the ligand and its coordination polymer were studied.The chiral Schiff base coordination polymer [Ce(H2L)3(NO3)3Ce(H2L)3(NO3)3(H2O)] n [H2L: trans-N,N′-bis-(2-hydroxy-1-naphthalidehy-dene)-(1R,2R)-cyclohexanediamine] was synthesized and characterized by infrared spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis. X-ray crystallography shows that the Ce(III) coordinates with three neutral Schiff base ligands and three nitrates. One Ce(III) is nine-coordinated by three oxygen atoms from three different Schiff base ligands and six oxygen atoms from three nitrates, the other Ce(III) is ten-coordinated because of the coordination of an additional water molecule. Each Schiff base ligand serves as a bridging ligand to link Ce(III) ions through oxygen atoms, leading to a coordination polymer. The Ce(III) coordination polymer displays two dimensional plane grid network structure. The antiproliferation activities of the ligand H2L and its Ce(III) coordination polymer on MDA-MB-231 breast cancer cells were also studied by MTT (3-[4,5-dimethyltiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) method. The results indicate that H2L and [Ce(H2L)3(NO3)3Ce(H2L)3(NO3)3(H2O)] n can inhibit the cellularproliferation. Moreover, the coordination polymer had higher antiproliferative activity than that of the ligand.
Keywords: Chiral Schiff base; Cerium(III) coordination polymer; Crystal structure; Antiproliferation;

Efficient synthesis and magnetic properties of triphenylamine bearing three nitronylnitroxide radicals by Masahiro Takahashi; Yutaka Kimura; Mitsuki Hagiwara; Keiki Kishikawa; Shigeo Kohmoto (1557-1562).
► We synthesized a triradical and reinvestigated its magnetic properties. ► The triradical has a C3-symmetrical molecular shape. ► The triradical showed different physical properties from those of reported. ► Tree spins on the triradical interact antiferromagnetically each other. ► The magnetic behavior was interpreted as a spin frustration system.Improved synthesis and reinvestigation of the magnetic properties of triphenylamine bearing three nitronylnitroxide radicals (1) were carried out. Single crystal X-ray crystallographic analysis of 1 established that its molecular shape had a C 3-symmetry. Our newly prepared 1 showed different physical properties from those of reported. SQUID measurements of 1 showed that each of the three spins of 1 behaved independently at room temperature. In contrast, the three spins coupled antiferromagnetically at lower temperature as low as ca. 1.8 K. These spin behaviors can be explained by a regular triangular antiferromagnetic model (J/k B  = −3.3 K) and interpreted as a spin frustration system.
Keywords: Triradical; Triphenylamine; Nitronylnitroxide radical; Single crystal X-ray crystallography; Spin frustration system;

One-dimensional antiferromagnetic behavior of a chiral molecular crystal, α′-(S,S-DMBEDT-TTF)2PF6 by Sara J. Krivickas; Atsushi Ichikawa; Kazuyuki Takahashi; Hiroyuki Tajima; John D. Wallis; Hatsumi Mori (1563-1565).
► The synthesis, crystal and electronic structures, resistivity, magnetic susceptibility, and dielectric constant of the novel chiral crystal, α′-(S,S-DMBEDT-TTF)2PF6 are presented. ► The α′-type donor arrangement affords the one-dimensional antiferromagnetic behavior with J  = −40 K. ► The frequency-dependent dielectric constant suggests the charge disproportionation above 100 K. ► The non-centrosymmetric space group due to the composed chiral molecules affords the possibility of piezoelectricity.The synthesis, crystal and electronic structures, resistivity, magnetic susceptibility, and dielectric constant of the novel chiral crystal, α′-(S,S-DMBEDT-TTF)2PF6 [DMBEDT-TTF = dimethylbis(ethylenedithio)tetrathiafulvalene] are presented. The α′-type donor arrangement affords the one-dimensional antiferromagnetic behavior with J  = −40 K. The calculated band structure indicates the pseudo-one-dimensional interaction in the molecular side-by-side direction along the b-axis. The frequency-dependent dielectric constant suggests the charge disproportionation above 100 K. The non-centrosymmetric space group due to the composed chiral molecules affords the possibility of piezoelectricity.
Keywords: Chiral molecular crystal; S,S-DMBEDT-TTF; 1D antiferromagnetic interaction; Non-centrosymmetric space group;

The oligothiophene compounds T3–T7 inclusive have been synthesized by standard chemical procedures in order to measure the complex admittance versus frequency of their micro-crystalline powders as compressed into a co-axial tube capacitor. The results are compared to that obtained from commercially available polythiophene powder. Optical measurements of the UV–visible absorption and luminescence (fluorescence) spectra were also obtained for these compounds suspended in solutions of dimethylsulfoxide and dichloromethane as well as for compressed solid powders. The impedance spectra show a typical Jonscher model variation with a large jump in conductivity between T4 and T5 followed by more gradual increases. A semi-log plot of conductivity or susceptibility versus chain length at fixed frequency shows that polythiophene fits in at T9 or T10. The photoluminescence peaks expressed in energy units (eV) show a linear increase with inverse chain length and in this case polythiophene fits in at T6. The uniform increase of the absorption maximum or a photoluminescence peak with the inverse chain length of successive oligothiophenes can also be used to calculate the effective “chain length” or conjugation of the end substitution of various radical groups to these same oligothiophenes. This has been done using results from previous work.
Keywords: Oligothiophene; Polythiophene; Conductivity; Susceptibility; Photoluminescence; Fluorescence;

Structure–properties relationship of hydrazones containing methoxy-substituted triphenylamino groups by V. Mimaite; J. Ostrauskaite; D. Gudeika; J.V. Grazulevicius; V. Jankauskas (1575-1581).
► Hole-transporting dimethoxytriphenylamine-based hydrazones. ► Structure–properties relationship. ► Glass transition temperatures ranging from 32 to 64 °C. ► Ionization potentials of the solid samples from 5.18 to 5.27 eV. ► Non-dispersive charge transport. ► Time-of-flight hole mobilities of the solid solutions of the derivatives in bisphenol-Z polycarbonate (50%) approaching 10−4  cm2/(V s).We have synthesized a series of hole-transporting dimethoxytriphenylamine-based hydrazones and studied the influence of the position of methoxy groups on the thermal, optical, electrochemical, and photoelectrical properties of the materials. The synthesized compounds form glasses with glass transition temperatures ranging from 32 to 64 °C. Compounds having methoxy groups in the ortho positions of triphenylamino moiety show higher glass transition temperatures than the corresponding derivatives having methoxy substituents in meta or para positions. Ionization potentials of the solid samples of hydrazones range from 5.18 to 5.27 eV. Hydrazones having methoxy substituents in para positions of triphenylamino moiety show superior charge-transporting properties with respect to hydrazones containing methoxy substituents in ortho and meta positions respectively. Molecularly doped bisphenol Z polycarbonate containing 50 wt.% of hydrazones with methoxy substituents in para positions of triphenylamino moiety show time-of-flight hole-drift mobilities approaching 10−4  cm2/(V s) at high electric fields.
Keywords: Hydrazone; Triphenylamine; Methoxy group; Ionization potential; Charge mobility;

► Conjugated copolymer based on thiazolothiazole and didecyloxynaphthalene units was synthesized. ► Photovoltaic properties of the copolymer were investigated blended with electron acceptor, PC61BM. ► The optimized photovoltaic device shows a power conversion efficiency up to 0.99%.A new alternating donor–acceptor conjugated copolymer, poly{(2,5-bis(3-decylthiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl)-alt-(2,6-[(1,5-didecyloxy)naphthalene])} (PNTzTz) based on thiazolothiazole and didecyloxynaphthalene units was synthesized using a typical Suzuki coupling polymerization method and was explored as a donor polymer in bulk heterojunction (BHJ) solar cells. The copolymer was characterized using differential scanning calorimetry, thermogravimetric analysis, UV–Vis absorption and cyclic voltammetry. It possesses moderate molecular weights and excellent thermal properties with a 5% weight loss around 340 °C. It also exhibits good optical absorption with an absorption peak at 475 nm and an absorption onset at 560 nm in the film state. Photovoltaic properties of the copolymer were investigated blended with electron acceptor, [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). The optimized photovoltaic device with a device structure of ITO/PEDOT:PSS/PNTzTz:PC61BM (1:2, w/w)/LiF/Al shows a power conversion efficiency up to 0.99% with a short circuit current density of 3.3 mA cm−2, an open circuit voltage of 0.96 V and a fill factor of 0.33 under the illumination of AM 1.5, 100 mW cm−2.
Keywords: Donor–acceptor conjugated polymer; Bulk-heterojunction polymer solar cell; Thiazolothaizole;

Synthesis and conductivity measurement of carbon spheres by catalytic CVD using non-magnetic metal complexes by Chien-Ming Lei; Wei-Li Yuan; Hsin-Chen Huang; Shao-Wei Ho; Chi-Jung Su (1590-1595).
► Non-magnetic metal complexes of La, Nb, and Ti as catalyst. ► Catalytic chemical vapor deposition (CCVD). ► Micrometer-sized carbon spheres (CSs). ► CSs with good electrical and thermal conductivity comparable to commercial Vulcan XC72.Carbon spheres (CSs) have been an important subject of research in recent years. Catalytic chemical vapor deposition (CCVD) was carried out in this work to synthesize solid-core CSs at mild temperatures from 720 to 810 °C. Non-magnetic metal complexes of La, Nb, and Ti, dispersed on porous kaolin support, were tried out as catalyst. X-ray diffraction patterns revealed the graphitic structures of CSs. TEM analysis showed no encapsulated transition-metal nanoparticles inside the CSs. It was found by Raman spectra that the La catalyst resulted in CSs with higher graphitization. To examine the potential applications of CSs to the fields such as catalysis, electrochemistry, and electronic device, values of the thermal and electrical conductivity of the prepared CSs using different catalysts were measured and found to be comparable to those of the commercial carbon black.
Keywords: Carbon spheres; Catalytic chemical vapor deposition; Non-magnetic metal complexes; Conductivity;

Improvement of single-walled carbon nanotube transparent conductive films using substrate pretreatment by Kwonwoo Shin; Rak-Kyung Park; Lan Yu; Chong-Yun Park; Young Sil Lee; Yun-Soo Lim; Jong Hun Han (1596-1599).
Display Omitted► Surface pretreatment increased the electric conductivity of carbon nanotube layer. ► Plasma treatment increased surface energy of PET, which increased the conductivity. ► Polymer electrolyte modulates surface charges, which determines the conductivity. ► Surfce pretreatment increased the adsorption of carbon nanotube on PET surface.This study sought to improve the characteristics of single-walled carbon nanotube (SWCNT) transparent conductive films (TCFs), such as their sheet resistance and transparency, by applying pre-treatments to their PET substrates. Oxygen–argon plasma pretreatment was found to increase the surface energies of the PET substrates from 33.9 to 74.2 mJ/m2, which improves the electric conductivity of the SWCNT-TCFs and provides a lower sheet resistance at a given light transmittance. Polymer electrolyte solution pretreatment was used to vary the surface functionality and modulate the surface charges quantitatively, as confirmed by the measurement of the resulting substrate zeta potentials, which varied between −45.8 and 18.2 mV. When the surfaces became negatively charged through pretreatment, the electric conductivities of the SWCNT-TCFs were increased. Both pre-treatments also improve the adsorption of SWCNTs onto the PET substrates and reduce the loss of coating solution during the spray deposition of SWCNTs.
Keywords: Carbon nanotube; Conductivity; Pre-treatment; Plasma; Polymer electrolyte; Sheet resistance;

Arylene bisimides with triarylamine N-substituents as new solution processable organic semiconductors: Synthesis, spectroscopic, electrochemical and electronic properties by Renata Rybakiewicz; David Djurado; Hubert Cybulski; Ewelina Dobrzynska; Irena Kulszewicz-Bajer; Damien Boudinet; Jean-Marie Verilhac; Malgorzata Zagorska; Adam Pron (1600-1610).
Display Omitted► Arylene bisimides with triarylamine N-substituents as new organic semiconductors. ► Obtained compounds are solution processable. ► They undergo reversible electrochemical oxidation and reduction. ► They are suitable for fabrication of all organic, p-channel field effect transistor.New solution processable organic semiconductors, consisting of pyrromelitic, naphthalene or perylene bisimide core and triarylamine N-substituents, have been synthesized. All three compounds are electrochemically active and undergo quasi-reversible oxidation and reduction as evidenced by cyclic voltammetry investigations. The oxidation process involves the transformation of the triarylamine substituents into radical cations as proven spectroscopically and spectroelectrochemically. The reduction process occurs at the arylene bisimide core leading to the formation of a radical anion and eventually a dianion in the second step. These findings are in perfect agreement with the DFT calculations which show that in the synthesized molecules the HOMO orbital is located on the triarylamine moiety whereas the LUMO one on the bisimide core. In all molecules studied the electrochemically determined ionization potential (IP) is slightly higher than 5.0 eV whereas in naphthalene and perylene derivatives the electron affinity (EA) is close to −3.9 eV. These values fulfill the requirements for n-type (electron) semiconductors in air operating n-channel field effect transistors (FETs) as well as for p-type (hole) conductors in p-channel FETs. To verify whether the newly synthesized compounds exhibit the expected electrical transport properties all organic (CYTOP dielectric) test transistors were fabricated. All three semiconductors showed no field effect in the n-channel configuration. To the contrary, they could be used in p-channel FETs showing, in the saturation regime, the hole mobility approaching 10−4  cm2  V−1  s−1 – the value which slightly exceeds that measured for low molecular weight, amorphous triarylamine semiconductors.
Keywords: Arylene bisimides; Triarylamine derivatives; Low band semiconductors; Organic transistors; DFT calculations;

Synthesis of polypyrrole with fewer structural defects using enzyme catalysis by Ryan Bouldin; Sethumadhavan Ravichandran; Akshay Kokil; Rahul Garhwal; Subhalakshmi Nagarajan; Jayant Kumar; Ferdinando F. Bruno; Lynne A. Samuelson; Ramaswamy Nagarajan (1611-1617).
► Soybean peroxidase (SBP) facilitates the formation of a more linear and defect free conducting polypyrrole. ► Use of soybean peroxidase alleviates need for use of redox mediators. ► Conductivity improved over an order of magnitude with SBP compared to other enzymes. ► Polymer yield and conductivity improved dramatically at lower temperatures.Enzymatic polymerization is an environmentally friendly alternative route for the synthesis of advanced π-functional materials. Until recently, synthetic methods for production of polypyrrole (PPy) were confined to the use of chemical oxidants or electrochemical methods. Here, we report the low temperature, oxidative polymerization of pyrrole using soybean peroxidase as the catalyst in aqueous non-toxic media. In addition to the benefits of the mild synthetic conditions, enzyme catalysis also affords PPy with fewer structural defects. Poly(sodium 4-styrenesulfonate) (PSS) was used as a charge-balancing dopant and dispersant for PPy to monitor changes in the absorption spectra of the polymer over time. However, the polymerization methodology is amenable to other dopants, including small molecule dopants like 10-camphor sulfonic acid. Spectroscopic characterization indicated that the PPy was conductive, and was produced in higher yields and at faster rates at lower temperatures. Careful temperature control combined with the appropriate choice of dopant ensured production of more electrically conductive PPy with conductivities that exceeded 3 S/cm. UV–Vis spectroscopy was used to provide evidence of favorable interactions between pyrrole and the dopant that may have facilitated the reaction. These interactions, combined with a low synthesis temperature and controlled enzyme-catalyzed radical generation, synergistically favored the formation of PPy with fewer defects and a more linear structure.
Keywords: Conducting polymer; Polypyrrole; Enzymatic; Oxidoreductases; Soybean peroxidase;

Polymer infrared photo-detector with high sensitivity up to 1100 nm by En-Chen Chen; Shin-Rong Tseng; Yu-Chiang Chao; Hsin-Fei Meng; Chih-Feng Wang; Wen-Chang Chen; Chian-Shu Hsu; Sheng-Fu Horng (1618-1622).
► A low band-gap conjugated polymer was studied for the near infrared photo-detector application. ► Intense absorption in NIR wavelength (to 1000 nm) ► The estimated optical and electrochemical band-gaps are quite small around 1.15 eV and 1.08 eV, respectively. ► The photo-detector has the incident photon-to-electron conversion efficiency 28.9% at 1000 nm (−5 V) and 6.2% at 1100 nm (−5 V).We reported a low band-gap conjugated polymer, poly[2,3-bis(4-(2-ethylhexyloxy)phenyl)-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine] (PDTTP), was studied for the near infrared (NIR) photo-detector application. PDTTP shows intense absorption in NIR wavelength (to 1000 nm) and the estimated optical and electrochemical band-gaps of PDTTP are quite small around 1.15 eV and 1.08 eV, respectively. The low band-gap and the extended long wavelength absorption originates from the introduction of alternating TP units when its parent polythieno[3,4-b]pyrazine shows excellent narrow band-gap properties. Therefore, the relatively low band-gap and intense absorption in long wavelength of PDTTP make itself a promising candidate for near-infrared photo-detector. The hole mobility of the PDTTP measured from the bottom contact field effect transistor is around 1.40 × 10−3  cm2/V s with a on/off ratio of 2100. The photo-detector based on bulk hetero-junction PDTTP and (6,6)-phenyl-C61-butyric acid methyl ester blend (PCBM) has the incident photon-to-electron conversion efficiency 28.9% at 1000 nm (−5 V) and 6.2% at 1100 nm (−5 V). This photo-detector can be operated at a high-speed of 1 MHz. The experimental result suggests the potential applications of low band-gap conjugated polymers on near-infrared photo-detectors.
Keywords: Polymer; Photo-detector; Low band-gap; Near infrared;

Preparation of polyaniline/2-dimensional hexagonal mesoporous carbon composite for supercapacitor by Shuangli Zhou; Shanshan Mo; Wujun Zou; Fengping Jiang; Tianxiang Zhou; Dingsheng Yuan (1623-1628).
► Polyaniline is linked with the functional groups on the surface of 2-D hexagonal mesoporous carbon via the chemical bonds. ► Between mesoporous carbon and polyaniline have a strong synergetic effect, enhancing the stability of polyaniline and increasing the capacitance and the energy density of the composite materials. ► A wide potential window of 1.1 V and a high specific capacitance up to 470 F/g for the composite are obtained in aqueous electrolyte.2-D hexagonal mesoporous carbon is combined with polyaniline by a simple chemical oxidation polymerization. As-prepared samples are characterized via Fourier transform infrared spectrum, nitrogen sorption analysis and transmission electron microscopy. The experimental results demonstrate that polyaniline is linked with the functional groups on the surface of mesoporous carbon via the chemical bonds. The electrochemical tests reveal mesoporous carbon and polyaniline have a strong synergetic effect, which not only enhances the stability of polyaniline, but also increases the capacitance and energy density of the composite materials. A wide potential window of 1.1 V for the composite is obtained in aqueous electrolyte. The specific capacitance and specific energy density are as high as 470 F/g and 76.4 Wh/kg, respectively.
Keywords: Supercapacitors; 2-D hexagonal mesoporous carbon; Polyaniline; Specific capacitance; Specific energy;

► The MWCNT shape behavior was first suggested by 3-dimensional structure using static bending persistence length (l sp) and outer diameter (d) of the MWCNT. ► The electrical conductivity of polycarbonate/MWCNT nanocomposites strongly depend on the mesoscopic shape of MWCNT (l sp/d).In this study, polycarbonate (PC)/multi-walled carbon nanotube (MWCNT) nancomposites have been prepared by pretreating MWCNT solutions with ultrasonication. We demonstrate that the electrical conductivity and rheological properties of PC/MWCNT nanocomposites strongly depend on the mesoscopic shape factor (l sp/d), which is represented by the ratio between the static bending persistence length (l sp) and outer diameter (d) of the MWCNT. The electrical conductivity of PC/MWCNT nanocomposites increases linearly with increasing (l sp/d)2 and the percolation threshold of PC/MWCNT nanocomposites decreases linearly with increasing (l sp/d)2 of MWCNTs. The storage modulus of PC/MWCNT nanocomposites increases linearly with increasing (l sp/d)2 of MWCNTs at all frequency ranges.
Keywords: Carbon nanotubes; Polymer composites; Percolation threshold; Electrical conductivity; Rheology;

The ultraviolet-ozone effects on organic thin-film transistors with double polymeric dielectric layers by Changhe Liu; Qingping Zhu; Weipeng Jin; Wen Gu; Jun Wang (1635-1639).
Organic thin-film transistors (OTFTs) were fabricated based on the double polymeric insulators consisting of polyvinyl alcohol (PVA) and polystyrene (PS). By exposing the polymer insulating layer (PS) under ultraviolet (UV) light for different times (0, 5, 10 and 15 min), the surface properties of the PS film has been further optimized for the growth of pentacene. As a result, a field-effect mobility of 1.38 cm2  V−1  S−1 and an on/off current ratio of 104 had been obtained by UV treatment for 10 min. All results indicate the surface energy of dielectric layer is a crucial factor to influence the devices performance that can be well tuned by UV treatment.Display Omitted► Organic transistors based on the double insulators consisting of polyvinyl alcohol and polystyrene have been demonstrated. ► The ultraviolet light was used to treat the polymeric insulator for different times. ► A field-effect mobility of 1.38 cm2  V−1  S−1 and an on/off current ratio of 104 had been obtained from the devices with UV treatment for 10 min. ► The surface energy of insulator is a crucial factor for OTFT that can be modulated by UV light.Organic thin-film transistors (OTFTs) were fabricated based on the double polymeric insulators consisting of polyvinyl alcohol (PVA) and polystyrene (PS). The using of double dielectric layers exhibited an improved device performance comparing with the conventional devices with single dielectric layer. By exposing the polymer insulating layer (PS) under ultraviolet (UV) light for different times (0, 5, 10 and 15 min), the surface properties of the PS film has been further optimized for the growth of pentacene. The grain size and crystallization of pentacene film grown on PS are apparently improved as the increase of surface energy of PS. As a result, a field-effect mobility of 1.38 cm2  V−1  S−1 and an on/off current ratio of 104 had been obtained by UV treatment for 10 min. All results indicate the surface energy of dielectric layer is a crucial factor to influence the devices performance that can be well tuned by UV treatment. The polymeric materials pair consisting of PS and PVA is a promised candidate as the dielectric layers for high-performance OTFTs.
Keywords: Organic thin-film transistor (OTFT); Pentacene; Polymer dielectric; Surface energy; Mobility; On/off current ratios (I on/I off);

Photoelectrochemical cells based on LB films of fullerene–thiophene derived dyads by Kornelia Lewandowska; Waldemar Bednarski; Grzegorz Milczarek; Stefan Waplak; Andrzej Graja; Eun Young Park; Tae-Dong Kim; Kwang-Sup Lee (1640-1645).
Photoelectrochemical properties of fullerene with three oligothiophenes (1T-F, 2T-F, 3T-F), ethylenedioxythiophenyl (EDOT-F) and hexylthiophenyl (HXT-F) groups were investigated with the photocurrent and EPR measurements.Display Omitted► Fullerene-tiophene LB dyads’ layers as photoelectrochemical materials. ► Light switching of photovoltage and photocurrent generation examinations. ► EPR identification and activation energy determination of C60 + and C60 centres.Photoelectrochemical properties of fullerene with three oligothiophenes (1T-F, 2T-F, 3T-F), ethylenedioxythiophenyl (EDOT-F) and hexylthiophenyl (HXT-F) groups were investigated with the photocurrent measurements. Electron paramagnetic resonance (EPR) spectroscopy has been used for study the fullerene–thiophene derived systems in wide temperature range. For electrochemical examination of these systems Langmuir–Blodgett (LB) layers deposited on a gold substrate were prepared. The light-induced photocurrent study shows that the structure of the dyad has an influence on both photovoltage and photocurrent, although these two variables are not correlated with each other. The role of the structure of the dyads is also seen in electron paramagnetic resonance investigations. All these results supported by previous IR and UV–vis spectral studies suggest, that the photoinduced electron transfer from oligothiophenes or EDOT and HXT to C60 is a primary process of the photocurrent generation in the fullerene–thiophene-derived dyads.
Keywords: Fullerene; Thiophene derivatives; Donor–acceptor systems; Photocurrent; EPR;

Formation of Ag2S nanowires and Ag2S/CdS heterostructures via simple solvothermal route by Shancheng Yan; Kai Shen; Xin Xu; Yi Shi; Jiansheng Wu; Zhongdang Xiao (1646-1650).
Ag2S nanowires and Ag2S/CdS heterostructures have been successfully prepared in anhydrous ethanol through a simple solvothermal route. To our knowledge, there is no report of synthesis of silver sulfide nanowires in anhydrous ethanol solution using CdS nanowires as sacrificial templating until now. Furthermore, the novel Ag2S/CdS heterostructures have been successfully synthesized under suitable condition which is obviously different from previous reports. The selectivity for cation exchange reaction is the novel discovery, which starts preferentially at the ends of the CdS nanowires to form novel Ag2S/CdS binary heterostructures. This is the first report in the paper for our knowledge.Display Omitted► Ag2S nanowires have been successfully prepared in anhydrous ethanol through a sacrificial templating route. ► The novel Ag2S/CdS heterostructures have been successfully synthesized under the suitable reaction condition. ► The growth of Ag2S nanoparticles at the end of CdS nanowires is attributed to the partial of Ag+ preferential exchange by controlling the experimental conditions.In our present work, Ag2S nanowires and Ag2S/CdS heterostructures have been successfully prepared in anhydrous ethanol through a simple solvothermal route. From the transmission electron microscopy (TEM) analysis, it is found that the factors influenced the final product are the concentration of Ag+, reaction temperature, reaction time, and solvent. Ag2S nanowires are formed by complete Ag+ cation exchange. Because of the selectivity for partial cation exchange, the reaction starts preferentially at the ends of the CdS nanowires to produce novel Ag2S/CdS heterostructures. In addition, as the two end facets of wurtzite CdS nanowires are crystallographically nonequivalent, the produced Ag2S/CdS heterostructures are asymmetric.
Keywords: Nanostructures; Crystal growth; CdS nanowire; Ag2S;

Surface characterization of P3OT thin films by variable temperature scanning force microscopy by E. López-Elvira; B. García-Pérez; J. Colchero; E. Palacios-Lidón (1651-1659).
In this work variable temperature scanning force microscopy techniques have been used to study poly(3-octylthiophene) (P3OT) thin film samples. Topography images in combination with scanning force spectroscopy have been applied to characterize the morphology and mechanical properties of the P3OT surface. It has been found that at room temperature lamellar islands appears on top of the polymer surface, while at temperatures higher than 35–45 °C these lamellas disappear and the polymer surface becomes homogeneous. This process is reversible and the lamellar structures are recovered when the sample is cooled down. In parallel, local force spectroscopy performed at each temperature shows a marked variation of the mechanical properties at about 30–40 °C, both in the polymer surface as well as in the lamellar islands. This points towards a conformational change in the P3OT molecules which loose planarity disrupting the close packing of the molecules on the lamellas.
Keywords: Variable temperature scanning force microscopy; Conductive polymers; Poly(3-octylthiophene); Phase transition;

Characterization, liquid crystalline behavior, optical and electrochemical study of new aliphatic–aromatic polyimide with naphthalene and perylene subunits by Ewa Schab-Balcerzak; Agnieszka Iwan; Marzena Grucela-Zajac; Michal Krompiec; Marzena Podgorna; Marian Domanski; Mariola Siwy; Henryk Janeczek (1660-1670).
► We obtained new thermotropic diamine and a six-membered polyimide. ► We analyse mesomorphic behaviour in the level of structural changes. ► We examine new application of polyimide by exploiting their photoluminescence, and electrochemical experiments paving the way toward stable organic optoelectronic devices.A new aliphatic–aromatic diamine with naphthalene diimide (DA) moiety and a polyimide with naphthalene and perylene diimide subunits (PI) were synthesized and their thermotropic liquid crystalline behavior was examined by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Both compounds exhibited liquid crystalline properties. The temperatures of 5% weight loss (T 5%) of the diamine and polyimide range from 350 to 373 °C in nitrogen. The optical properties, that is, UV–vis absorption and photoluminescence (PL) of obtained monomer and polyimide were studied in solution and in solid state as a blend with inert poly(methyl methacrylate) (PMMA). Influence of solvent polarity, excitation wavelength and concentration on DA and PI emission was found. The investigated compounds emitted green light in chloroform solution. Relative PL intensity of the DA and PI was investigated in NMP in relation to rhodamine-B used as a standard. The electrochemical behavior of diamine and polyimide was studied (in solution) by differential pulse voltammetry (DPV). The HOMO and LUMO levels of these compounds were in the range of −5.44 to −6.03 eV and −3.81 eV, respectively. Energy gap (E g) values were calculated using cyclic voltammetry (CV) and UV–vis measurements. Introduction of a perylene moiety (PI) resulted in increase of E g (2.22 eV) compared to DA which exhibited a E g value of approximately 1.63 eV. The electrical properties of DA and PI were investigated by current–voltage (IV) measurements on ITO/compound/Al devices.
Keywords: Naphthalene diimides; Polyperyleneimides; Polynaphthalimides; Liquid crystals; Thermotropic compounds; Photoluminescence; Electrochemistry; Current–voltage characteristics;

Novel 1,3,4-oxadiazole derivatives as efficient sensitizers for dye-sensitized solar cells: A combined experimental and computational study by Kola Srinivas; G. Sivakumar; Ch. Ramesh Kumar; M. Ananth Reddy; K. Bhanuprakash; V. Jayathirtha Rao; Chih-Wei Chen; Ying-Chan Hsu; Jiann T. Lin (1671-1681).
► Here we report efficient synthesis and characterization of new series of Triarylamine linked 1,3,4-oxadiazoles derivatives as sensitizers in DSSCs. ► The dye-based devices exhibited good IPCEs, ranging from 60%to 70%. ► The device using M4 (3.21%) has the best efficiency which reached ∼50% of an N719-based DSSC (6.31%). ► The efficiencies are enhanced due to the non-aggregation of the bulky molecules on the TiO2 surface.We have synthesized and characterized donor–π–spacer–acceptor type molecules in which 1,3,4-oxadiazoles are π-spacers, triphenylamines are the donors and cyanoacetic acid are the acceptors for use as sensitizers in dye-sensitized solar cells (DSSCs). Detailed absorption, emission, electrochemical, photoelectrochemical and computational studies have been carried out on five novel derivatives. The dyes have an absorption range of 377–388 nm, and an emission in the range of 494–540 nm. There is a large charge transfer from the donor side to the acceptor side on excitation. The propeller shape of the triphenylamine and the bulky substituents on it help in reducing the dye-aggregation on TiO2 surface. The dyes exhibited good overall conversion efficiency (2.79–3.21%). Plane wave calculations indicate that the dye has a reasonably strong binding to the TiO2 surface and the generated DOS picture shows an overlap of the molecular orbitals of the dye and the TiO2 bands. We conclude that the dyes have a promising role as sensitizers in DSSC.
Keywords: DSSC; Donor–π–acceptor dyes; Oxadiazole; Charge transfer; TD-DFT; Periodic DFT;

Synthesis of polypyrrole–Nafion composite films by gas phase electroformation by Abdulazeez. T. Lawal; Gordon G. Wallace (1682-1685).
► Gas phase electrochemical polymerisation is used to produce a uniform, homogeneous and conductive thin film of composite polymer. ► The composites obtained were characterised by cyclic voltammetery (CV) and redox performance were investigated. The relationship of the anodic current of the composite with the various experimental parameters such as concentration of nafion, current density, polymerisation time and temperature were investigated. ► Vapour phase polymerisation technique is versatile and can be used to obtain a polymer coating on a conducting substrate to form a composite. ► The formation of composite increased as we polymerising time, current density and temperature. The polymer process was fast as polymers were formed with in the first minutes.Nafion was introduced into polypyrrole (PPy) matrix by gas phase electrochemical polymerisation. This produced a uniform, homogeneous and conductive thin film of composite polymer. The films (PPy/Nafion) also show surface features of highly ordered structural regularity. The composites obtained were characterised by cyclic voltammetry (CV) and redox performance were investigated. The relationship of the anodic current of the composite with the various experimental parameters such as concentration of Nafion, current density, polymerisation time and temperature were investigated. Anodic current increases with the Nafion concentration, polymerising time, temperature and current density.
Keywords: Composite; Polypyrrole; Gas phase; Nafion; Electroformation;

► Electropolymerization of thiophene-3-boronic acid film in ionic liquid. ► Preparation a H2O2 biosensor via glycosidic bond to immobilize glycoprotein. ► This H2O2 biosensor displayed fast response, high sensitivity and good stability.In the present work, we have developed a novel hydrogen peroxide (H2O2) biosensor based on electropolymerization of thiophene-3-boronic acid film (TBA) in ionic liquid via glucosidic bond with glycoprotein horseradish peroxidase (HRP). A thin film of poly (thiophene-3-boronic acid) (PTBA) has been synthesized by electropolymerization using room temperature ionic liquids (RTIL) as the growth medium and the supporting electrolyte. Horseradish peroxidase (HRP) in this study shows affinity interaction with the formed PTBA thin film. With the aid of hydroquinone (H2Q) mediator, the biosensor has a fast response of less than 7 s with linear range of 5.0 × 10−6 to 1.75 × 10−4  M and a detection limit of 0.5 μM. The developed biosensor exhibits fast response, a low detection limit, high stability and very good reproducibility.
Keywords: Poly (thiophene-3-boronic acid); Glycosylation; Horseradish peroxidase; Hydrogen peroxide; Biosensor;

X-shaped tetra-substituted pyrenes: Synthesis, photophysics, and electroluminescence by Zuo-Qin Liang; Zeng-Ze Chu; Jia-Xiang Yang; Chun-Xue Yuan; Xu-Tang Tao; De-Chun Zou (1691-1698).
► Two X-shaped compounds based on pyrene are designed, synthesized, and characterized. ► Balancing the relationship between fluorescent enhancement and charge carrier. ► The fluorescence of compound 9 can be reversibly converted from red to orange. ► The device based on compound 7 exhibits better EL performances.Two X-shaped compounds (7 and 9) based on pyrene have been synthesized and well characterized. These compounds exhibit good thermal stabilities and high fluorescence yields. In addition, an interesting phenomenon is discovered that the fluorescence of compound 9 can be reversibly converted from red to orange in the solid state. Organic light-emitting diodes have been fabricated using the X-shaped compounds as the host emitter with low turn-on voltage up to 2.35 V. The device based on compound 7 exhibits orange-red electroluminescence (CIE: 0.58, 0.42) with a maximum luminance of 4798.4 cd/m2, a maximum current efficiency 1.26 cd/A, and a power efficiency of 1.06 l m/W.
Keywords: X-shaped; Pyrene; Organic light-emitting diodes; Intermolecular interactions;

Design and synthesis of a new thiophene based donor–acceptor type conjugated polymer with large third order nonlinear optical activity by K.A. Vishnumurthy; A. Vasudeva Adhikari; M.S. Sunitha; K.A. Ann Mary; Reji Philip (1699-1706).
► Here we report the synthesis monomers and polymer via Wittig condensation method. ► They were characterized using FT-IR, 1H NMR, UV–vis spectral and GPC techniques. ► Band gap of the polymer was determined by optical and electrochemical studies. ► Third-order NLO property was measured by Z-scan and DFWM techniques. ► The studies revealed that the polymer can be a potent candidate in photonics.In this communication we describe the design and synthesis of a new conjugated polymer (P) carrying 3,4-dialkoxythiophene, 1,3,4-oxadiazole and thienylene-vinylene units, from its monomers using Wittig condensation method. The structure of newly synthesized polymer was confirmed by FT-IR, 1H NMR, UV–vis spectral, elemental analysis and gel permeation chromatographic techniques. The polymer exhibited good thermal stability with the onset decomposition temperature around 320 °C in nitrogen atmosphere. Further, its electrochemical, linear and nonlinear optical properties have been investigated. The optical and electrochemical band gap was found to be 2.21 eV. Its third-order nonlinear optical property was investigated by Z-scan and DFWM techniques, using a Q-switched, frequency doubled Nd:YAG laser producing 7 ns laser pulses at 532 nm. Z-scan results reveal that the polymer exhibits self-defocusing nonlinearity. The operating mechanism involves reverse saturable absorption. The polymer shows strong optical limiting behavior due to effective two-photon absorption (2PA). The value of 2PA coefficient was found to be 3.0 × 10−11  mW, which is comparable to that of good optical limiting materials. The fluorescence quantum yield of the polymer in solution was determined using quinine sulfate as standard and it was found to be 35%.
Keywords: Donor–acceptor polymer; 3,4-Dialkoxythiophene; Thienylene-vinylene; Oxadiazole; NLO properties; DFWM;

► The citric acid (CA) and quinine hydrochloride (QH) at PPY–PCNFe/Pt electrode in aqueous medium can be determined using cyclic voltammetry. ► The PPY-PCNFe/Pt electrode exhibits different response in different analyte solutions. ► The electroactivity of PPY-PCNFe film is due to the movements of ions and electrons into and out of the film. ► The detection limits were obtained as 1.17 × 10−4  M and 1.08 × 10−5  M for CA and QH, respectively.Cyclic voltammetry was used to investigate the electrochemical behavior of citric acid (CA) and quinine hydrochloride (QH) at a polypyrrole-pentacyanoferrate/Platinum (PPY–PCNFe/Pt) electrode in aqueous medium. The analytical plots obtained were found to be linear in the concentration range between 1.0 and 9.0 mM for both the analyte solutions. The detection limits (3δ) were found to be 1.17 × 10−4  M and 1.08 × 10−5  M for CA and QH analyte solutions, respectively. It was further observed that the diffusion of ionic species into and out of the polymeric film made the PPY–PCNFe/Pt electrode highly electroactive thereby enabling it to efficiently detect the analyte solutions having concentration as low as 1 mM.
Keywords: Cyclic voltammetry; Pentacyanonitrosylferrate; Polypyrrole; Citric acid; Quinine hydrochloride;

Electrochemical characterization of in situ polypyrrole coated graphene nanocomposites by Sumanta Sahoo; G. Karthikeyan; Ganesh Ch. Nayak; Chapal Kumar Das (1713-1719).
► In this study we have prepared the in situ graphene/polypyrrole nanocomposite with varying percentage of graphene. ► The morphological, electrochemical and thermal analyses of the different nanocomposites are carried out. ► The specific capacitance, energy density and power density of the nanocomposites are found to be increasing with the increase in graphene percentage up to certain extent and then decreases.Graphene/polypyrrole nanocomposites were prepared by in situ oxidative polymerization method by varying the weight percentage of graphene. FTIR study confirmed the formation of polypyrrole in presence of graphene. Field Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM) were used to characterize the morphology of the nanocomposites which showed a uniform coating of graphene with the polypyrrole. From the cyclic voltammetry (CV) measurement it was found that the capacitances of the nanocomposites were increased up to a certain percentage of graphene and after which it showed a downward trend. The maximum capacitance value and energy density, among the composites studied, were found to be 409 F/g and 227.2 Wh/Kg at 10 mV/s scan rate. However, maximum power density achieved was 4617 W/kg at a scan rate of 200 mV/s.
Keywords: Graphene; Polypyrrole; Cyclic voltammetry; Specific capacitance;

The use of novel photobleachable phthalocyanines to image DNA by Burcu Turanlı-Yıldız; Tuğba Sezgin; Z. Petek Çakar; Canan Uslan; B. Şebnem Sesalan; Ahmet Gül (1720-1724).
Display Omitted► In this study a new CoPc and its quaternized derivative (1) was synthesized. ► Binding of compound (1) and (2) to CT-DNA was proved by UV/vis spectra, Thermal denaturation profiles and gel electrophoresis. ► Water soluble nature of (1) and (2) makes these compounds beneficial and preferable agents to be used as novel dyes for biological studies with the less harmful property.The interaction of cationic photobleachable cobalt 1 and palladium 2 phthalocyanines (pcs) with calf thymus (CT) DNA was investigated by UV/vis spectrophotometric methods and gel electrophoresis. With the addition of pcs, the change in the thermal denaturation profile of DNA was observed. The results indicated that these molecules exhibit efficient DNA binding activity. The new cationic cobalt derivative 1 was characterized by elemental analysis, UV, IR and mass spectrophotometry.
Keywords: DNA; Phthalocyanine; Water soluble;

Synthesis and supercapacitive behavior of carbon aerogel microbeads encapsulated by in situ Co3O4 nanoparticle by Xingyan Wang; Xianyou Wang; Li Liu; Lanhua Yi; Chuanyue Hu; Xiaoyan Zhang; Wei Yi (1725-1730).
Display Omitted► Co3O4/CAMB composite materials for supercapacitor were prepared by in situ coating method. ► The optimum amount of Co3O4 in Co3O4/CAMB composite is 10 wt.%. ► Coating nano-sized Co3O4 on the CAMB could improve the supercapacitive behaviors of composites.Co3O4/carbon aerogel microbead (Co3O4/CAMB) composites are prepared by in situ coating method and their supercapacitive behaviors are investigated. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrum are used to characterize the structure and morphology of Co3O4/CAMB. The results show that nano-sized Co3O4 particles are homogenously encapsulated on the surface of CAMB. Electrochemical performances of the composite electrodes with different Co3O4 amount are studied by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. It is found that Co3O4/CAMB composites show better electrochemical performance than CAMB, and the optimum content of Co3O4 in Co3O4/CAMB composites is 10 wt.%. The specific capacitance of 10%–Co3O4/CAMB composite in 6 mol L−1 KOH electrolyte is about 350.18 F g−1 at a current density of 1 A g−1. Moreover, 10%–Co3O4/CAMB composite supercapacitor exhibits relatively good high-rate capability and excellent cycle life.
Keywords: Carbon aerogel microbeads; Tricobalt tetroxide; Composite; Supercapacitor;

Electro-conductive composite fibers by melt spinning of polypropylene/polyamide/carbon nanotubes by Saleh Hooshmand; Azadeh Soroudi; Mikael Skrifvars (1731-1737).
► Increase in crystallization temperature and thermal stability of the blends by adding 5% CNTs. ► Enhancement of conductivity and tensile strength of fibers by increasing the blending temperature as well as adding 1% compatibilizer. ► Decrease in conductivity and increase in mechanical properties of fibers by fiber drawing.In this study, the blends of polypropylene/polyamide with carbon nanotubes (CNTs) have been prepared and melt spun to as-spun and drawn fibers. Thermal analysis showed that increasing the polyamide content, decreased the degree of crystallinity in the blends. Characterization of fibers showed that both conductivity and tensile strength have been improved by increasing the amount of polyamide in the blends as well as the melt blending temperature; furthermore, the morphology, electrical and mechanical properties of the blends were significantly influenced by adding 1 phr compatibilizer to the blend. The comparison between as-spun fibers and drawn fibers proved that although mechanical properties were improved after drawing, the electrical conductivity was decreased from the order of E−02 to E−06 (S/cm), due to applied draw-ratio of three.
Keywords: Conductive fiber; Melt spinning; Polypropylene (PP); Polyamide (PA); Carbon nanotube;

Room-temperature spin valve effects in La0.67Sr0.33MnO3/Alq3/Co devices by S. Wang; Y.J. Shi; L. Lin; B.B. Chen; F.J. Yue; J. Du; H.F. Ding; F.M. Zhang; D. Wu (1738-1741).
• Room-temperature spin valve effects are demonstrated in La0.67Sr0.33MnO3/Alq3/Co. • Indirect deposition significantly suppresses penetration of Co atoms into Alq3. • Magnetic dead-layer is verified at Co/Alq3 interface by directly depositing Co. • A penetration length of 12.5 nm in direct deposition Co on Alq3 is estimated.We report room-temperature spin valve effects in Alq3-based vertical organic spin valve (OSV) devices with direct interfaces between Alq3 and the bottom and top ferromagnetic electrodes. In contrast to conventional OSVs, where the top electrode is directly deposited on top of organic layer, we use indirect deposition method. We find this method can significantly suppress the penetration of Co atoms into Alq3 layer during deposition process, which is commonly found in conventional OSVs. The improved Alq3/Co interface is further confirmed by comparing the magnetic moment of depositing Co onto Alq3 and Si substrates by indirect and direct deposition methods. A penetration length of 12.5 nm in direct deposition Co on top of Alq3 is estimated. And the demonstration of room-temperature spin valve effects indicates the improvement of spin injection efficiency at sharp Alq3/Co interface.
Keywords: Organic spintronics; Indirect deposition; Organic spin valve effect; FM/organic interface;

Novel metal-free and metallo (Co, Cu, Fe, Mn and Sn) phthalocyanines were synthesized by cyclotetramerization of 4-(2,3-dihydro-1H-inden-5-yloxy)phthalonitrile and characterized by elemental analyses, IR, UV–vis, 1H NMR and MALDI-TOF mass spectral data. The effect of metals on electrical and spectroscopic properties and aggregation behaviours of the novel Pcs were investigated in different concentration and solvents.Display Omitted• Synthesis and characterization of novel metal-free, Co(II), Cu(II), Fe(II), Mn(II) and Sn(II) phthalocyanines peripherally tetra-substituted with 2,3-dihydro-1H-inden-5-yloxy moiety. • Investigation of electrical and spectroscopic properties of the novel phthalocyanines. • Metal effect on the aggregation behaviours of novel phthalocyanines.Novel metal-free and metal (Co, Cu, Fe, Mn and Sn) phthalocyanines were synthesized by cyclotetramerization of 4-(2,3-dihydro-1H-inden-5-yloxy)phthalonitrile and characterized by elemental analyses, IR, UV–vis and MALDI-TOF mass spectral data. The effect of metals on spectroscopic properties and aggregation behaviours of the novel Pcs were investigated in different concentration and solvents. Their electrical transport and dielectric properties were also investigated. The ac conductivity showed strong dependence on both temperature and frequency. The temperature dependence of frequency exponent s suggested a dominant hopping conduction process. It was observed that tan  δ increases as the frequency increases and reaches a maximum and thereafter decreases. As the temperature increases the frequency at which tan  δ reaches a maximum shifted towards higher frequencies.
Keywords: Synthesis; Cyclotetramerization; Phthalocyanine; MALDI-TOF; Conductivity;

Poly(p-phenylene vinylene) mixed with stearic acid at the air–water interface to form nanostructured films.Display Omitted• Block-poly(p-phenylene vinylene) was mixed with fatty acids at the air–water interface forming hybrid Langmuir monolayers. • Films were transferred to solid supports by the Langmuir–Blodgett technique. • Polymer has luminescence properties controlled in the Langmuir–Blodgett film.Properties of hybrid films can be enhanced if their molecular architecture is controlled. In this paper, poly (p-phenylene vinylene) was mixed with stearic acid in order to form stable hybrid Langmuir monolayers. Surface properties of these films were investigated with measurements of surface pressure, and also with polarization modulation infrared reflection–absorption spectroscopy (PM-IRRAS). The films were transferred from the air–water interface to solid supports through the Langmuir–Blodgett technique, and the viability of the film as optical device was investigated with fluorescence spectroscopy. Comparing the fluorescent spectra for the polymer in solution, as a casting film, and as an LB film, the emission bands for LB films were narrower and appeared at lower wavelengths. The interactions between the film components and the design for the LB film may take advantage of the method to immobilize luminescent polymers in mixed ultrathin films adsorbed in solid matrices.
Keywords: Langmuir–Blodgett films; PPV; Conjugated polymer; Stearic acid;

• Composite of multi-walled carbon nanotubes (MWNTs) and poly ortho aminophenol (POAP) electrodes are prepared by the in situ electropolymerization. • Surfactant has played a key role for dispersing CNTs within conducting polymer films. • Supercapacitor device made by nanotube composite films exhibited very high specific capacitance.Composites of multi-walled carbon nanotubes (MWCNTs) and poly ortho aminophenol (POAP) with good uniformity for use as electrodes in electrochemical capacitors were prepared by electropolymerization by using the ionic surfactant as electrolyte, for dispersing CNTs within conducting polymer/carbon nanotube composite films. The capacitance properties were investigated with cyclic voltammetry (CV), discharge tests and ac impedance spectroscopy. The composite electrode shows much higher specific capacitance, better power characteristics and is more promising for application in the capacitor than a pure POAP electrode. The effect and role of MWCNT in the composite electrode are discussed in detail. In comparison with a Ni–POAP/glassy carbon (GC), a Ni–MWCNT–POAP/GC electrode shows a better catalytic performance for the electrocatalytic oxidation of methanol.
Keywords: POAP; Composite; CNTs; Impedance;

Polypyrrole colloidal nanospheres as an effective fluorescent sensing platform for DNA detection by Wenbo Lu; Yonglan Luo; Guohui Chang; Xiaoyun Qin; Fang Liao; Xuping Sun (1766-1770).
In the present study, we demonstrate the first use of polypyrrole colloidal nanospheres (PPyCNPs) as an effective sensing platform for fluorescence-enhanced DNA detection by the following two steps: (1) PPyCNP adsorbs and quenches a dye-labeled single-stranded DNA (ssDNA) probe; (2) The subsequent hybridization of the probe with its target produces a double-stranded DNA (dsDNA) which detaches from PPyCNP, leading to recovery of dye fluorescence. The present system shows a detection limit as low as 1 nM and has a high selectivity down to single-base mismatch.
Keywords: Polypyrrole colloidal nanosphere; Fluorescence; DNA detection;

Display Omitted► The obtained bipolar copolymers involve Alq3 moieties and NVK segments. ► The bipolar copolymers have improved hole-transporting ability. ► EL mechanism of the copolymers: charge trapping and Förster energy transfer. ► Effects of substituted group and Alq3s content on EL of the copolymers.A series of bipolar copolymers containing quinoline aluminum moieties and N-vinylcarbazole segments exhibited excellent photoluminescence performance and improved hole-transporting ability, were used as light-emitting materials to fabricate polymeric light-emitting devices (PLEDs). Six simple devices with structure of ITO/PEDOT (40 nm)/copolymer (80 nm)/CsF (1.5 nm)/Al (120 nm) were fabricated by solution spin-coating. These devices gave dominant yellow-green emission from quinoline aluminum with excellent stability. Together with electrochemical data, the electroluminescence (EL) mechanism of the devices was studied. Moreover, effects of substituted group and quinoline aluminum's content on the EL properties of the devices were investigated in detail. The results indicate that the device based on the copolymer (P2-1) with substituted group of carbazole and 2 mol% quinoline aluminum possess optimal EL properties with a maximum luminance of 487 cd/m2 and a peak current efficiency of 0.545 cd/A.
Keywords: Quinoline aluminum; Bipolar copolymer; Polymeric light-emitting devices; Electroluminescence;

Structural and magnetic properties of iron, cobalt and nickel nanoparticles by M. Alagiri; C. Muthamizhchelvan; S. Ponnusamy (1776-1780).
► Iron, cobalt and nickel nanoparticles were synthesized with agarose polysaccharide by sol–gel method and heat-treating technique. ► XRD studies showed that the prepared products were iron, cobalt and nickel with bcc, fcc and fcc structure, respectively. ► Compared with bulk products, the nanoproducts exhibit significant increase in magnetic anisotropy as a reflection of nanodimension.This study focuses on the synthesis and characterization of iron, cobalt and nickel nanoparticles through sol–gel method and heat-treating technique in argon atmosphere. The structure, morphology and magnetic properties of the as-synthesized products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and superconducting quantum interference device (SQUID) magnetometer. XRD studies indicated that the as-prepared products were iron, cobalt and nickel with well crystallized bcc, fcc and fcc structure, respectively. TEM observations showed that the as-synthesized products composed of spherical shape with size around 2, 2 and 2 nm for iron, cobalt and nickel, respectively. Magnetization results revealed that the as-obtained products showed superparamagnetic character at 300 K. The magnetic anisotropy of the products is much higher than that of bulk owing to the nanostructure.
Keywords: Sol–gel; Nanoparticle; Iron; Cobalt; Nickel; X-ray diffraction; Transmission electron microscopy; High resolution transmission electron microscopy;