Effects of solvents on thermoelectric performance of PANi/PEDOT/PSS composite films

Organic thermoelectric materials based on conducting polymers, especially for polyaniline (PANi) and poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), have attracted great concern due to their tunable electron transport properties by controlling doping level. Here, the solvent effects of deionized H₂O and NH₃·H₂O were investigated on the electrical conductivity and Seebeck coefficient of PANi/PEDOT/PSS composite films. The introduction of PEDOT/PSS can not only effectively improve the quality of pure PANi film, but also enhance the electrical conductivity of PANi film. The different volumes of deionized H₂O as dilution have a great influence on the electrical conductivity of PANi/PEDOT/PSS composite thin film with a maximum electrical conductivity value of 63.5 S cm^?1, which is much higher than pure PANi and pristine PEDOT/PSS. The introduction of NH₃·H₂O shows a positive effect on Seebeck coefficient with a large decline on electrical conductivity of PANi/PEDOT/PSS. The Raman spectroscopy, scanning electron microscopy (SEM), and UV-vis spectroscopy were used to obtain the morphology and structure information of PANi/PEDOT/PSS.     

Development of nanostructured polyaniline–titanium dioxide gas sensors for ammonia recognition

The performance at room temperature of nanostructured polyaniline (PANi)–titanium dioxide (TiO₂) ammonia gas sensors was investigated. The PANi–TiO₂ thin-film sensors were fabricated with a spin-coating method on glass substrates. PANi–TiO₂ (0–50%) sensor films were characterized for their structural, morphological, optical, and various gas-sensing properties. The structural analysis showed the formation of nanocrystalline TiO₂, whereas PANi exhibited an amorphous nature. Morphological analysis of the PANi–TiO₂ nanocomposites film revealed a uniform distribution of TiO₂ nanoparticles in the PANi matrix. The absorption peaks in the Fourier transform infrared spectra and ultraviolet–visible spectra of the PANi–TiO₂ composite film were found to shift to higher wave numbers compared to those observed in pure PANi. The observed shifts were attributed to the interaction between the TiO₂ particles and the PANi molecular chains. The gas-sensing properties showed that the sensors exhibited selectivity to ammonia (NH₃) at room temperature. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrochemical preparation of electrically conducting polyurethane/polyaniline composite

Composite films from polyaniline (PANi) and polyurethane (PU), with flexibility and mechanical strength similar to pure PU and conductivity close to pure PANi, have been obtained by electropolymerizing amiline on a PU/Pt electrode in water/acetonitrile/ethylen glycol electrolyte solution. In the composite films, PANi is dispersed, in the form of particulate, inside and on the inner surface of the PU substrates. It is found that the electropolymerization reaction of aniline proceeds much faster in basic solution and composite film as prepared shows higher conductivity than that in acidic solution. PANi in PU/PANi composite film is protonic-acid-doped and is conducting even in case it is electropolymerized in a basic electrolyte solution.     

Microstructural and Optoelectronic Studies on Polyaniline: TiO2 Nanocomposites

Thin films of polyaniline (PANi) and PANi: titanium oxide (TiO₂) composites have been synthesized by sol–gel spin coating technique. The TiO₂ powder of particle size 50–60 nm was synthesized by the sol–gel technique and the polyaniline was synthesized by the chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and the four-probe method. The results were compared with corresponding data on pure polyaniline films. The intensity of diffraction peaks for PANi:TiO₂ composites is lower than that for TiO₂. The characteristic FTIR peaks of pure PANi are observed to shift to a higher wavenumber in PANi:TiO₂ composite, which is attributed to the interaction of TiO₂ particles with PANi molecular chains. The resistivity measurement shows that the molecular chain constitution of polyaniline is the most important carrier in the polyaniline: nano-TiO₂ composite.     

Synthesis,Characterization, and Reactivity of trans-Ru(X)(Cl)(nbd)(dppb) (X = H,Cl; nbd = 2,5-norbornadiene; dppb = 1,4-bis(diphenylphosphino)butane), Including the X-ray Crystal Structure of the Dichloride

The ruthenium (II) diene complexes [Ru(X)(Cl)(nbd)(dppb)] (X = Cl, H; nbd = 2,5-norbornadiene; dppb = PPh₂(CH₂)₄PPh₂) have been prepared and characterized spectroscopically. The X-ray crystal structure of RuCl₂(nbd)(dppb) (crystal data at 22°C: space group P1, a = 10.896 (1) Å, b = 15.168(2) Å, c = 10.829 (1) Å, α = 103.02(1)°, β = 107.08(1)°, γ = 81.65(1)°, Z = 2, R = 0.054 for 6420 reflections) shows an octahedral geometry at Ru, with the chloro ligands slightly distorted from a trans configuration (Cl)(1)-Ru-C1(2) = 168.4°); the unit cell contains two molecules of the complex and one molecule of benzene. Reaction of this complex with H₂, in presence of Proton Sponge (PS, 1,8-bis(dimethylamino)naphthalene) as base, is complicated by initial dissociation of nbd, and [Ru₂Cl₅(dppb)₂]⁻-PSH⁺ is the major product. A minor product, the hydrido(diene) complex trans-RuCl(nbd)(dppb) 5 , characterized spectroscopically, is more effectively synthesized from (a) trans-Ru(H)Cl(nbd)(PPh₃)₂, 1 , and dppb, or (b) reaction of RuCl₂(dppb)-(PPh₃) with H₂ in presence of nbd and PS. Complex 5 is unreactive toward H₂ or CO while 1 has been shown previously to give η²-H₂ and norbornenoyl derivatives, respectively; the differences in reactivity are discussed.     

Synthesis and Characterization of Polyaniline:TiO2 Nanocomposites

Thin films of polyaniline (PANi) and PANi:titanium oxide (TiO₂) composites have been synthesized by sol—gel spin coating technique. The TiO₂ powder of particle size 50–60 nm was synthesized by sol–gel technique and the polyaniline was synthesized by chemical oxidative polymerization of aniline. The composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) Fourier transform infrared (FTIR) and UV-vis spectroscopy, and the results were compared with polyaniline films. The intensity of the diffraction peaks for PANi:TiO₂ composites is lower than that for TiO₂. The characteristic FTIR peaks of PANi were found to shift to a higher wave number in the PANi:TiO₂ composite. These observed effects have been attributed to the interaction of TiO₂ particles with PANi molecular chains. The room temperature resistivity of polyaniline:nano-TiO₂ composite is 3.43 × 10³ Ω cm and the resistivity of pure nano-TiO₂ particles is 1.60 × 10⁶ Ω cm.     

Langmuir and Langmuir-Blodgett (LB) films of poly[(2-methoxy,5-n-octadecyl)-p-phenylenevinylene] (OC1OC18-PPV)

A PPV derivative, poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene) (OC₁OC₁₈-PPV), has been synthesized via the Gilch route and used to fabricate Langmuir and Langmuir-Blodgett (LB) films. True monomolecular films were formed at the air/water interface, which were successfully transferred onto different types of substrate. Using UV-visible absorption, FTIR, fluorescence and Raman scattering spectroscopies we observed that the polymer molecules were randomly distributed in the LB film, with no detectable anisotropy. This is in contrast to the anisotropic LB films of a previously reported PPV derivative, poly(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene (OC₁OC₆-PPV), which is surprising because the longer chain of OC₁OC₁₈-PPV investigated here was expected to lead to more ordered films. As a consequence of the lack of order, LB films of OC₁OC₁₈-PPV exhibit lower photoconductivity and require higher operating voltage in a polymer light-emitting diode (PLED) in comparison with LB films of OC₁OC₆-PPV. This result confirms the importance of molecular organization in the LB film to obtain efficient PLEDs.     

Reactivity of mononuclear dithiolato palladium and platinum metalloligands towards the formation of homo- and heterobimetallic complexes

The reactivity of mononuclear platinum and palladium dithiolato species as building blocks for homo- and heterobimetallic complexes is described. The heterobimetallic cationic complex [(PPh₃)₂Pt(μ-S(CH₂)₂S)Pd(dppb)](BF₄)₂ was obtained by reaction of [Pt(S(CH₂)₂S)(PPh₃)₂] with [PdCl₂(Ph₂P(CH₂)₄PPh₂)] in presence of AgBF₄.     

Electrochemical properties of carbon nanotubes-hydrogenase conjugates Langmuir-Blodgett films

We report the preparation of Langmuir-Blodgett (LB) films composed of oxidized carbon nanotubes (CNTs) and hydrogenase (H₂ase) conjugates and their electrochemical properties. Both single-walled (SWNTs) and multi-walled CNTs (MWNTs) were used to form mixed monolayers with H₂ase on the Tris-HCl subphase surfaces. By using the LB method, the CNTs-H₂ase monolayers were transferred onto CaF₂ and indium tin oxide (ITO) electrode surfaces. The LB film modified electrodes showed a couple of waves centered at around −500 mV (versus Ag/AgCl), which corresponding to the redox reaction of [4Fe-4S]^2+/1+ clusters in the H₂ase. The current intensity was enhanced after co-assembly with CNTs. Because of the different diameters of CNTs, this current intensity was proportional to the scan rate (υ) for the electrodes modified with the LB films of pure H₂ase and SWNTs-H₂ase, but to the root of scan rate (υ^1/2) for those modified with the MWNTs-H₂ase LB film. The products of diffusion coefficient and concentration (D^1/2C) increased in the order of pure H₂ase, SWNTs-H₂ase, and MWNTs-H₂ase LB films.     

Polymer/Trimer/Metal Complex Mixtures as Precursors of Gold Nanoparticles: Tuning the Morphology in the Solid-State

The pyrolysis of several physical mixtures of AuCl(PPh₃) with polymeric [NP(O₂C₁₂H₈)]_n or cyclic N₃P₃(O₂C₁₂H₈)₃ phosphazenes, formed as solid powders or films with different molar ratios, have been studied under air and at 800 °C. The characterization of the products has shown that the particle size and morphology are strongly dependent on the nature of the phosphazene, the phosphazene/AuCl(PPh₃) molar ratio and on the preparation methodology. Gold nanoparticles (NPs) with mean sizes as small as 3.5 nm were obtained from a [NP(O₂C₁₂H₈)]_n/AuCl(PPh₃) 1:1 film. The particle morphology was also strongly dependent on the experimentally conditions of the pyrolysis. Powdered materials exhibit a 3-D irregular morphology in the mixture [NP(O₂C₁₂H₈)]_n/AuCl(PPh₃) 3:1 film, and gold foams in the 1:1 ratio, both from the [NP(O₂C₁₂H₈)]_n/AuCl(PPh₃) as well as N₃P₃(O₂C₁₂H₈)₃/AuCl(PPh₃) mixtures. These results show for the first time the possibility of controlling morphology and size of gold particles obtained by solid-state reactions.     

Asymmetric transfer hydrogenation of ketones by N,N-containing quinazoline-based ruthenium(II) complexes

The novel set of quinazoline-based chiral ligands was synthesized starting from optically pure amino acids. Coordination with RuCl₂(PPh₃)dppb gave ruthenium(II) N-heterocyclic complexes 4b–d. The structure of complex 4b was fully illuminated by X-ray crystallography. The steric environment of these chiral ruthenium complexes 4b–d was evaluated in asymmetric transfer hydrogenation (ATH) of prochiral ketones in the presence of NaOⁱPr by using 2-propanol as the hydrogen source and solvent. The resultant catalytic system can achieve very good enantioselectivities (up to 91%) and high yields (up to 99%).     

Electrical behavior of cerium dioxide films exposed to different gases atmospheres

Here we present an easy-reproducible microwave-assisted hydrothermal route for preparing pure nanocrystalline CeO₂ films. The produced materials were characterized using a wide range of techniques (X-ray diffraction, field emission gun scanning electron microscopy, Raman spectroscopy) to understand the synthesis dependent changes in crystallographic structure, and crystallite size. Raman and X-ray diffraction techniques revealed that the films were free of secondary phases and that they crystallize in the cubic structure. The observed hydrodynamic particle size larger than the crystallite size confirms the aggregation phenomenon. Gas sensing measurements have been carried out to rationalize the type and number of surface adsorbed groups and overall nanostructure. Electrical conductance variations, owing to gases adsorption onto semiconductor oxide films surfaces, were observed in this work. Chemiresistive CeO₂ film properties depend on the intergranular barrier heights and width.     

Preparation and properties of conducting arachidic acid/polypyrrole composite langmuir–blodgett films

Electrically conducting arachidic acid/polypyrrole (PPy) composite films were prepared by exposing the arachidic acid LB films containing ferric chloride to pyrrole vapor. The optimum conditions to deposit matrix LB film were the subphase temperature of 23–25°C, pH of 6.0 and ferric chloride concentration of 5.0 × 10⁻⁵ M. The formation of PPy in the arachidic acid matrix LB films was confirmed by UV-visible spectra, FTIR spectra, and scanning electron micrographs. The average thickness of the composite LB films prepared at 0°C was 1525 Å. The composite films prepared at lower temperatures have more uniform surface and exhibit higher electrical conductivity than the films prepared at higher temperatures do. The in-plain conductivity and the transverse conductivity of the composite film were 10⁻³−10⁻² S/cm and 10⁻⁶S/cm, respectively, and, thus, the conductivity anisotropy was about 10³ © 1996 John Wiley & Sons, Inc.     

Electrochemical preparation and characterization of V2O5/polyaniline composite film cathodes for Li battery

Vanadium pentoxide/polyaniline (V₂O₅/PANi) composite films were prepared by a two-step electrochemical method and evaluated for their application in lithium batteries. As a first step the PANi film was potentiodynamically grown in an acid solution containing aniline monomer, and secondly vanadium oxide was oxidatively deposited on the polyaniline film in a temperature controlled VOSO₄ solution. The increased current efficiency obtained with the larger anodic current in the high temperature solutions results in high contents of V₂O₅ in the composites, even if the oxidative dissolution of PANi also occurs. The large value of the diffusion coefficient estimated from the cyclic voltammograms for the composite film provides evidence for the synergistic effect of the conducting polymer and the inorganic composite. The cell exhibited excellent cycle stability with a high charge storage capacity. The large increase in the specific capacity for the composite film prepared in this work demonstrates that the conducting polymer in the composite acts as a binding and conducting element by contributing its electroactivity. The V₂O₅/PANi composite film cathodes show a large specific capacity (ca. 270 mAh/g) and improved cyclability with an extremely small amount of capacity fading (ca. 3.4%) during repeated charge/discharge cycles.     

Structural,magnetic and electronic structure properties of pure and Ti doped Mg0.95Mn0.05Fe2O4 nanocrystalline thin films

Thin films of pure and Ti doped Mg_0.95Mn_0.05Fe₂O₄ deposited using pulsed laser deposition technique, have been characterized using X-ray diffraction, Raman spectroscopy, dc magnetization, atomic force microscopy, magnetic force microscopy and near edge X-ray absorption fine structure spectroscopy measurements. X-ray diffraction and Raman spectroscopy measurements indicate that both the films have single phase and the polycrystalline behavior with FCC structure. The grain size calculated using XRD data was 18 and 27 nm for pure and Ti doped films, respectively. Magnetic measurements reflect that pure film has superparamagnetic behavior while Ti doped film has soft ferrimagnetic behavior at room temperature. Atomic force microscopy measurements indicate that both the films are nanocrystalline in nature. Near edge X-ray absorption fine structure spectroscopy measurements clearly infer that Fe ions are in mixed valence state.     

Improved conductivity in tape casted Li-NASICON supported thick films: Effect of temperature treatments and lamination

In this work, the influence of different thermal sintering treatments on Li_1.3Al_0.3Ti_1.7(PO₄)₃ NASICON thick films has been investigated. The isostatic lamination step performed before the thermal sintering of thick films has demonstrated to improve film density and grain size, increasing "bulk" and grain boundary Li-conductivities. The confocal Raman spectroscopy characterization allowed the observation of the connectivity of the particles present in the ceramic samples and so a deeper understanding of ionic conductivity. The dependence of total and "bulk" Li conductivity on the samples microstructure is discussed. The films sintered by slow heating sintering with a previous lamination step, displayed an overall Li- conductivity >10^?4 Ω^-1 cm^-1, that is superior to that reported in commercial OHARA Li- NASICON glass ceramics. The tape casting deposition method is scalable for preparation of large area thick supported electrolyte films with high conductivity for novel Li ion all solid state batteries (ASSB) architectures.     

Multilayer porous Pd-doped SnO2 thin film: Preparation and H2 sensing performance

Porous pure and Pd-doped SnO₂ films are prepared using sol-gel synthesis with polystyrene (PS) microspheres as the template. Different characterizations are performed to analyze the microstructure and morphology of the films. The sensing performance of the films at various temperatures and hydrogen concentrations is investigated. Results show that high concentration of PS template significantly influences the continuity of films and the H₂ sensing performance. The porous SnO₂ film with 0.1 wt% PS microspheres exhibits the best performance. At 225 °C, the response magnitude of the porous 1 mol% Pd-doped SnO₂ thin film to 1000 ppm H₂ is 93.18, which is approximately 10.58 times of the pure sample.     

Wetchemical surface modification of plasticized PVC. Characterization by FTIR-ATR and Raman microscopy

The chemical modification of plasticized PVC films with amino thiophenol in mixtures of DMF/H₂0 has been studied. The degree of modification and the distribution of modified groups within the films were determined using Raman spectroscopy and FTIR-ATR. The amounts of plasticizer (bis-2-ethylhexyl phtalate, DOP) bleached out during the reaction and the amount of dimethylformamide (DMF) penetrated into the film were analysed in control reactions without the reactant using ¹H NMR spectroscopy and Raman spectroscopy.Reaction kinetics and surface selectivity of the modification reaction were compared with the corresponding reactions of PVC films without plasticizer.     

Corrosion inhibition of stainless steel by polyaniline,poly(2-chloroaniline), and poly(aniline-co-2-chloroaniline) in HCl

Polyaniline (PANi), poly(2-chloroaniline) (PClANi), and poly(aniline-co-2-chloroaniline) (co-PClANi) films were synthesized by electrochemical deposition on 304-stainless steel (SS) from an acetonitrile solution. The structural properties of these polymer films were characterized by spectroscopic (FTIR and UV–vis) and electrochemical (cyclic voltammetry) methods. Open circuit potential–time (E_ocp–time) curves, potentiodynamic polarization, and electrochemical impedance (EIS) measurements showed that these films have significant protective performance against corrosion of SS in 0.5 M HCl solution. It was found that co-PClANi film has acted as a passivator as well as barrier for cathodic reduction reaction in a similar manner as PANi film. However, PClANi film has behaved only as barrier for corrosion protection of SS in 0.5 M HCl.     

Preparation, Characterization, and Photoelectric Properties of Langmuir–Blodgett Films of Some Europium-Substituted Polyoxometalates and 2-Aminofluorene with Tunable Emission Color

A new series of organic/inorganic composite Langmuir–Blodgett (LB) films consisting of 2-aminofluorene (Fl–NH₂) as the π-conjugated organic molecule, an europium-substituted polyoxometalate (POM, POM = Na₉EuW₁₀O₃₆, K₁₃[Eu(SiW₁₁O₃₉)₂] and K₅[Eu(SiW₁₁O₃₉)(H₂O)₂], which are denoted by EuW₁₀, EuW₂₂ and EuW₁₁, respectively) as the inorganic component, were prepared. Structural and photophysical characterization of these LB films were achieved by π–A isotherms, UV–Vis absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and surface photovoltage spectroscopy. Our experimental results indicate that stable Langmuir and LB films are formed in pure water and POM sub-phases. Luminescence spectra of the prepared hybrid LB films show that tunable emission color can be obtained due to the dual-emissive nature of the mixed Fl–NH₂/POM blends. These 2-aminofluorene-based LB films displayed interesting electrical conductivity behavior. Among them, Fl–NH₂/EuW₁₁ 3-layer films showed a good electrical response with the a tunneling current up to ± 100 nA when the voltage was monitored at ?0.8 to 1.5 V. These LB composites show good photovoltage responses and a photovoltage of 2.7 μV can be obtained for the Fl–NH₂/EuW₂₂ system when it is excited by light.