Conducting Polymer Layer Research Articles

Fundamental characteristics of a MEMS‐diaphragm actuator using a thermal expansion drive composed of a conductive polymer

Performance of a MEMS actuator using a thermal expansion drive of a conductive polymer (CP) is investigated by applying electricity to it. The actuator consists of a thin polymer diaphragm (5 mm diameter) and a thin CP (ion‐doped polythiophene) layer coated on the diaphragm surface. Polyimide (10 μm thickness) and PET (110 μm thickness) sheets were chosen as the diaphragm materials. The diaphragm is deflected by the thermal expansion of the CP by applying electricity to it. Merits of using the CP instead of metal are realizing flexible actuators and the applicability to a low‐heat‐resistant material diaphragm. The relationship between thickness of the CP layer (10–50 μm thickness) and electrical resistance (30–600 Ω) and the relationship between the input voltage (1–8 V) and the generated diaphragm displacement (several tens of micrometers) were investigated experimentally. These relationships were compared with those in the case of using the thermal expansion of a vapor‐deposited aluminum layer (0.1 μm thickness). The results of the investigation indicate that the diaphragm based on CP can produce the required displacement. In the case the CP‐layer‐based thermal expansion, however, larger input voltage than in the case of the aluminum‐layer‐based thermal expansion is needed to obtain the same displacement amplitudes. Therefore, the main problem concerning use of the CP‐based diaphragm is considered to be enhancing the electrical conductance of the CP layer. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Anticorrosion efficiency of zinc-filled epoxy coatings containing conducting polymers and pigments

Abstract The dependence of the corrosion-inhibiting properties of zinc-filled organic coatings on the nature of the conducting polymers and conducting pigments added and on the pigment particles’ surface coating with conducting polymer layers were investigated. The following materials were selected to examine the corrosion-inhibiting properties of the conducting polymers: polyaniline phosphate (PANI), polypyrrole (PPy), natural graphite, and carbon nanotubes. Conducting pigment combinations for application in coating materials were formulated by applying pigment volume concentrations (PVC) of 0.3%, 0.5% and 1%, which were completed with Zn dust to obtain pigment volume concentrations/critical pigment volume concentrations (PVC/CPVC) = 0.64. Such conducting pigment/zinc dust combinations represented corrosion inhibitors to be used as ingredients in protective coatings. Solvent-based 2K epoxy resin based coating materials containing the corrosion inhibitors so formulated were prepared to examine their anticorrosion properties. The pigmented coatings were subjected to laboratory corrosion tests in simulated corrosion atmospheres and to standardized mechanical resistance tests. The protective coatings so obtained exhibited a higher efficiency than coating materials containing zinc dust alone. The coating material containing carbon nanotubes at PVC = 1% and the coating material containing graphite coated with polypyrrole (C/PPy) at PVC = 0.5% emerged as the best zinc-filled coating materials with respect to their corrosion-inhibiting efficiency. Treatment with the conducting polymers had a beneficial effect on the coating materials’ mechanical properties.

Conducting polyaniline-wrapped lithium vanadium phosphate nanocomposite as high-rate and cycling stability cathode for lithium-ion batteries

This work introduces a facile strategy to improve the high-rate capability and cycling stability for carbon-free Li3V2(PO4)3 by coating with conducting polymer polyaniline. Core-shell Li3V2(PO4)3/polyaniline nanocomposite with typical sizes of 200nm has been synthesized via a microwave heating assisted sol-gel method followed by a self-assembly process. The highly conductive and uniform polyaniline layer coated on the surface of Li3V2(PO4)3 nanoparticles significantly enhances the electrochemical performance of the electrode, which exhibits better rate capability and excellent cycling stability compared with the pristine Li3V2(PO4)3. The resultant nanocomposite exhibits a high initial discharge capacity of 130.7mAhg−1 at 0.1C within a voltage range of 3.0-4.3V. When cycled at a rate of 10C the capacity can reach up to 101.5mAhg−1, and the capacity retention is 87.3% after 500 cycles. The likely contributing factor to the excellent electrochemical performance of core-shell Li3V2(PO4)3/polyaniline could be related to the uniform conducting polymer layer, which can improve the electrical conductivity of Li3V2(PO4)3.

Microcantilever sensors coated with a sensitive polyaniline layer for detecting volatile organic compounds.

This paper describes a silicon cantilever sensor coated with a conducting polymer layer. The mechanical response (deflection) of the bimaterial (the coated microcantilever) was investigated under the influence of several volatile compounds-methanol, ethanol, acetone, propanol, dichloroethane, toluene and benzene. The variations in the deflection of the coated and uncoated microcantilevers when exposed to volatile organic compounds were evaluated, and the results indicated that the highest sensitivity was obtained with the coated microcantilever and methanol. The uncoated microcantilever was not sensitive to the volatile organic compounds. An increase in the concentration of the volatile organic compound resulted in higher deflections of the microcantilever sensor. The sensor responses were reversible, sensible, rapid and proportional to the volatile concentration.

Enhanced Properties of Sulfur-Infiltrated Carbon Sphere with Conductive Polymer Coating for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) battery is promising energy system with a high theoretical energy density (2500 Wh kg-1), which is ~7 times larger than those of the current LIBs (~387 Wh kg-1) utilizing the unparalleled theoretical capacity of sulfur (1675 mAh g-1). Sulfur as a cathode material also has other advantages such as non-toxicity, low cost, and abundance of raw materials.For all its virtues, several challenges such as an insulating nature of sulfur (conductivity ~10-30), a large volume expansion by up to 80 % upon full lithiation and a severe capacity fading during cycling still remained unsolved. Sulfur, unlike the insertion based electrode, suffers a serious of structural and morphological changes during cycling with the formation of high-order lithium polysulfides (Li2Sn, 2<n≤8) and low-order lithium polysulfides (Li2S2 and Li2S), which are insulators. Besides, the high-order lithium polysulfides are soluble in current liquid electrolyte at the early stage of discharging. The dissolution of high-order polysulfides results in the so-called shuttling effects.Those problems should be addressed for utilization of lithium-sulfur battery in consumer electronics.In this present investigation, we developed sulfur infiltrated hollow carbon sphere with conductive polymer layer. The numerous small pores in carbon sphere were formed by evaporation of inner materials without damages of outer carbon layer. The conductive polymer layer (PEDOT) coated on the surface of carbon sphere could improve in the trapping of polysulfides and play a role in buffer layers against the volume changes of sulfur. The electrode design could improve the electrical performance with resolving the aforementioned issues.

Honeycomb-structured porous poly(3,4-ethylenedioxythiophene) composite layers on a gold electrode

Three microstructured electrodes modified with poly(3,4-ethylenedioxythiophene) (PEDOT) were obtained. One electrode was modified with PEDOT doped with poly(4-lithium styrenesulfonic acid) (PSSLi), the second one with a PEDOT+polyacrylic acid composite doped with PSSLi, and the third one with a PEDOT+anthranilic acid composite doped with poly(4-styrenesulfonic acid). The three electrodes were prepared using templates of polystyrene latex spheres (PS). The templates were deposited on the electrode using our dip-coating-like technique that we developed by optimizing key parameters, such as PS and sodium dodecyl sulfate concentration, angle of inclination, and decantation rate. The structure of the templates was verified by optical microscopy. A conducting polymer layer was obtained by electropolymerization from appropriate monomer solutions. In the final stage, the template was dissolved in toluene and the morphology of the resulting honeycomb-structure was examined by atomic force microscopy and scanning electron microscopy methods. The electrochemical properties of the electrodes were tested by cyclic voltammetry and electrochemical impedance spectroscopy.

Effect of surface treatment of pigment particles with polypyrrole and polyaniline phosphate on their corrosion inhibiting properties in organic coatings

The effect of pigment particle surface treatment with conductive polymers on the corrosion inhibiting properties of organic paints was investigated. Mixed oxides possessing the spinel and perovskite structures were synthesised for the study. Natural graphite and pigments based on ferric oxide and silicate were studied. Coating materials based on a water-based epoxy resin were prepared for the investigation of the corrosion protection properties of the pigments, the surfaces of which had been provided with a conductive polymer layer. Laboratory corrosion tests were applied to the paint films. A commercial corrosion protection pigment, based on modified zinc phosphate, served as the corrosion protection efficiency standard. Polyaniline phosphate was found preferable to polypyrrole as the modifying agent of the pigment surface regarding the pigment's corrosion inhibiting efficiency. Surface treatment with the conductive polymers is also beneficial to the mechanical properties of the paint.

Plasticizer-free solid-contact pH-selective microelectrode for visualization of local corrosion

The pH-sensitive solid-contact microelectrode (SCME) was developed for micro-potentiometric measurements for corrosion applications. A needle-shaped metallic body of the microelectrode was insulated with the exception of the 5 micron long apex where a layer of conductive polymer, poly(3-octhylthiophene-2,5-diyl) and then a pH sensitive membrane was deposited. The pH-selective membrane was based on plasticizer-free poly(methylmetacrilate–decylmetacrilate). The pH sensitivity was imparted on the membrane by a pH ionophore 4-nonadecylpyridine. The developed microelectrode is more robust than traditionally used glass capillary microelectrodes as it does not include any liquid in its construction nor is it as fragile. Thus, the main disadvantages of glass capillary microelectrodes, most importantly fragility and leakage of the liquid membrane, were eliminated. The properties of the improved microelectrodes, important for corrosion applications, were characterized. These include the slope, long- and short-term stability and reproducibility of potential, detection limits, selectivity coefficients, response time and life-time of the microelectrodes. The developed microelectrodes showed stable potential and short response time assuring reliable results during scanning measurements. Corrosion of hot dip galvanized steel sample was monitored by measuring local pH and current density quasi-simultaneously. The designed SCME showed its efficiency for practical applications for localized, scanning measurements in the field of corrosion.

Conducting polymers - mechanisms of cationic sensitivity and the methods of inducing thereof

Different methods for inducing open-circuit cationic sensitivity of the conducting polymer (CP) films doped with Metal Complexing Ligands (MCL) are presented. Selected MCLs have the R-(MCG-H)p(SO3H)n, structure and contain bulky organic group (R), “n” sulphonate groups responsible for CP doping and “p” metal complexing groups (-MCG-H) responsible for formation of the complexes with a narrow group of cations. MCLs molecules introduced to CP layer as bulky doping anions are immobilized inside CP layer and preserve their chemical properties known from water chemistry. Similarly, as ionophores, they can form complexes inside CP membrane with selected cations only. It was shown that formation of the complex inside the polymer layer is necessary for inducing preferred open-circuit sensitivity of the CP membrane. Various, efficient methods of the CP-MCL film sensitization towards calcium, magnesium as well as copper, cadmium, lead or zinc cations are presented.

Fabrication and Characterization of Biofilm-Based Hybrid Matrices in Bioelectrocatalysis

We exploited unique properties of biofilms, i.e. polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces, and they are characterized by of extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Although aqueous suspensions of gold, silver and certain transition metal oxide (TiO2 and ZrO2) nanoparticles tended to inhibit formation of biofilms produced by Pseudomonas aeruginosa, Staphylococcus aureus and Yersinia enterocolitic bacteria, application of composite matrices of inorganic nanostructures within porous conducting polymer layers, e.g. of poly(3,4-ethylenodioxythiophene (PEDOT), facilitated growth of robust and mature bacterial biofilms on glassy carbon electrodes. Independent diagnostic electroanalytical experiments showed that biofilms grown by the following bacteria, P. aeruginosa ATCC 9027, Y. enterocolitica Ye9, Y. enterocolitica AR4, L. monocytogenes 10403S and L. monocytogenes 1115, on inert carbon substrates exhibited by themselves electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes were found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that had been modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with cytochrome enzymatic sites. Co-existence of the above components leads to synergistic effect that was evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. The film exhibited high activity towards reduction of hydrogen peroxide. Most likely, the reduction of oxygen was initiated at cobalt porphyrin redox centers, and the undesirable hydrogen peroxide intermediate was further at the biofilm's cytochrome sites. Comparative measurements were also performed using metal nanoparticles (e.g. Au-Pt), conventional enzymes (e.g. laccase), molecular systems (e.g. metalloporphyrins) in the presence and absence of selected bacterial biofilms.Development of the biofilm and enzyme based anodes was considered too. To facilitate electron transfers between the electrode surface and the redox protein centers, the concept of co-deposition of MCNTs within the bioelectrocatalytic film was also pursued here. First, MCNTs were modified with ultra-thin layers of tetrathiafulvalene (TTF) or poly(dimethyldiallylammonium chloride) (PDDA). The presence of TTF or PDDA was expected to mediate effectively flow of electrons from enzyme active sites through biofilm to the electrode surface. Combination of derivatized MWCNTs with biofilm matrtices and appropriate enzymes produced biocatalytic systems capable of effective oxidation of glucose or ethanol in neutral buffer solution.Technical help of W. Lotowska, E. Szaniawska, E. Seta, B. Kowalewska, M. Gierwatowska, I. A. Rutkowska and S. Zoladek (Faculty of Chemistry, University of Warsaw), as well as collaboration with K. Brzostek and A. Raczkowska (Faculty of Biology, University of Warsaw) is highly appreciated.

Role of Conducting Polymers on Potentiometric and Floating Gate Field Effect Transistor (FGFET) Array-Based Immunoassays

Semiconductor-based diagnostics have revolutionized genome sequencing since the application of ion-sensitive field effect systems for the monitoring of pH changes during the polymerization of DNA. Similar charge-dependent changes can be monitored during protein-protein binding as in antibody-antigen reaction-based immunoassays. Organic semiconductors have several beneficial effects with such CMOS FET arrays. First, the organic semiconducting layer makes the covalent conjugation of the biospecific ligands on the gate surface very convenient: We have successfully used both thiolation and glutaraldehyde linkage, especially with polyaniline layer on the floating gate. Interfacial electrochemical polymerization gives the important control of surface area with the nanofiber formation for improved sensitivity. Depending on the device architecture, the band-gap engineering for optimal Schottky barrier performance or the additional capacitive effects, both give amplified threshold voltage changes.We have designed and manufactured autonomic floating gate (FG) field-effect transistor (FET) arrays and used them for monitoring biological reactions The advantage of FGFET array is that with a floating gate, the threshold voltage doesn't need to be “scanned”, but only the shifts in the threshold can be monitored. We compared the FET array in both IS (with reference electrode) and FGFET architecture to follow pH changes and bindings of cationic and anionic polyelectrolytes, always with a conducting polymer layer coated on the floating gate. Further on, we followed the change in the threshold voltage during protein binding on the surface, and also the effect of enzymatic substrate reacting with the conjugated enzyme as in the traditional ELISA test.

A facile hydrothermal route to iron(III) oxide with conductive additives as composite anode for lithium ion batteries

We report a facile hydrothermal route for the synthesis of Fe2O3 nanoparticles and their composites with conductive additives, reduced graphite oxide (rGO) and conductive polymer PEDOT:PSS, as anode materials for lithium ion batteries (LIBs). The addition of conductive polymer layer on Fe2O3 nanoparticles may facilitate the electron transport but hinders the Li+ ion insertion at higher current density. On the other hand, Fe2O3@rGO prepared by growing Fe2O3 nanoparticles directly on rGO sheets shows the best electrochemical behavior due to a beneficial combination of the rGO nanosheets partially wrapped around Fe2O3 which facilitates both the electron transport and the Li+ ion insertion. The enhanced conductivity of the composites was proved. The high specific capacity and stable rate performance of Fe2O3@rGO composites encourages their further study to be potential candidate for the anode materials in LIBs. These results will be helpful in further elucidation of the role of conductive additives in improving the electrochemical performance of Fe2O3 based composite anodes and this simple synthetic strategy can be applied for the large scale production of metal oxides with conductive additives for LIBs.

PEDOT coated Li4Ti5O12 nanorods: Soft chemistry approach synthesis and their lithium storage properties

Spinel Li4Ti5O12 nanorods coated with poly (3,4-ethylenedioxythiophene) (PEDOT) layer as an anode material for lithium ions battery were synthesized by a facile soft chemistry approach. The highly conductive and uniform PEDOT layer coated on the surface of Li4Ti5O12 nanorods significantly improves the electrochemical performance of the composite, which exhibits higher reversible capacity and better rate capability compared with the pure Li4Ti5O12 and Li4Ti5O12/C composite. The reversible capacity of Li4Ti5O12/PEDOT nanorods can be up to 171.5mA h g−1 at the rate of 0.2C. And a capacity of 168.7mA h g−1 was retained with only 0.5% capacity loss after 100 charge-discharge cycles at the rate of 1C, which confirms the good cycling behavior of Li4Ti5O12/PEDOT nanorods. The superior electrochemical performance of the Li4Ti5O12/PEDOT nanorods could be attributed to the one-dimensional (1D) morphology and uniform conducting polymer layer, which shortens the lithium-ion diffusion path and improves the electrical conductivity of Li4Ti5O12.

Layer-by-Layer Assembled Oxidative Films as General Platform for Electrodeless Formation of Conducting Polymers

Fabrication of precisely tailored layers of conductive polymers in thin film assemblies is an attractive extension of the layer-by-layer technique. This approach provides tools for fabricating thin films with customized optical and electrical properties. In this paper, we study inorganic layer-by-layer assembled films prepared using polyphosphate and cerium(IV). It is shown that these multilayers can oxidize certain monomers from the adjacent aqueous solution to produce conducting polymer layers. We studied the thermodynamic factors that allow the aforementioned autopolymerization. A five bilayer polyphosphate/cerium(IV) film was shown to possess high oxidative power in acidic solutions. It was found that the polymerization of pyrrole, aniline and 3,4-ethylenedioxythiophene in contact with the redox active multilayer is thermodynamically favored. The rate of polymer formation and the thickness of the conducting film could be controlled by the concentration of the monomer in solution and the number of cerium/polyphosphate bilayers in the oxidative film. The oxidative polymerization of pyrrole was unambiguously recognized on UV-vis spectra with characteristic reduction and oxidation bands. The film formation was not restricted by charge diffusion and the reaction formally followed first-order kinetics. The results suggest that the reaction takes place effectively within the whole pre-existing polypyrrole film and it continues until all oxidant in the film was used. The spectral changes that are characteristic for conducting polypyrrole are shown on spectroelectrochemical analysis of the films indicating that cationic (polaron) and dicationic (bipolaron) species are involved in the redox processes of the film. The functional polymer films formed are found to be electroactive and conducting. Therefore, they fully resemble of conducting polymer films prepared using traditional electropolymerization.

Improvement of the Cycling Performance of LiNi0.6Co0.2Mn0.2O2 Cathode Active Materials by a Dual-Conductive Polymer Coating

LiNi0.6Co0.2Mn0.2O2 cathode materials were surface-modified by coating with a dual conductive poly(3,4-ethylenedioxythiophene)-co-poly(ethylene glycol) (PEDOT-co-PEG) copolymer, and their resulting electrochemical properties were investigated. The surface-modified LiNi0.6Co0.2Mn0.2O2 cathode material exhibited a high discharge capacity and good high rate performance due to enhanced transport of Li(+) ions as well as electrons. The presence of a protective conducting polymer layer formed on the cathode also suppressed the growth of a resistive layer and inhibited the dissolution of transition metals from the active cathode materials, which resulted in more stable cycling characteristics than the pristine LiNi0.6Co0.2Mn0.2O2 cathode material at 55 (o)C.

Atmospheric Plasma Surface Activation of Poly(Ethylene Terephthalate) Film for Roll-To-Roll Application of Transparent Conductive Coating

An effective surface activation is crucial for high-speed roll-to-roll coating of functional films for printed electronics applications. In this article, we report a study of surface treatment of three types of poly(ethylene terephthalate) (PET) films by an argon/oxygen atmospheric pressure plasma and an ambient air atmospheric pressure plasma to obtain the required wettability for subsequent slot die coating of transparent conductive polymer layer using a poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) ink. Prior to plasma treatment, the PET surfaces, which differ in manufacturing process of their preparation, were characterized by X-ray photoelectron spectroscopy. The surface changes after the plasma treatments were characterized by water contact angle measurement and atomic force microscopy. We found that the water contact angles of the three types of untreated PET surfaces were 80.9°, 75.9°, and 66.3°, respectively, and the water contact angles after argon/oxygen plasma treatment at treatment speed of 1 m · min−1 decreased to 36.2°, 31.9°, and 40.9°, respectively. These conditions were stable from 1 up to 4 days, which are longer than reported values of 15–60 min and sufficient for roll-to-roll coating processes.

Electrochemical Biosensor consisted of conducting polymer layer on gold nanodots patterned Indium Tin Oxide electrode for rapid and simultaneous determination of purine bases

The present work focused on the development of new simple method for fabrication of conducting poly(4–aminothiophenol) nanostructures layered on gold nanodots patterned indium tin oxide (ITO) electrode based on the self assembly of the monomer. This was followed by electrochemical polymerization of 4–aminothiophenol molecules. In addition, we studied the electrochemical catalytic activity of the modified electrode towards a mixture of two protein bases (Adenine and Guanine). The modified gold nanodots ITO electrode was fabricated based on thermal evaporation of pure gold metal onto ITO surface through polystyrene monolayer. Then, a monolayer of 4–aminothiophenol was self–assembly immobilized onto the gold nanodots array/ITO electrode. This was followed by electrochemical polymerization process based on cyclic voltammetry technique. The electrochemical behavior of the adenine and guanine mixture at the modified electrode was investigated based on differential pulse voltammetry technique. The results indicated that the polymer nanostructures modified gold nanodots/ITO electrode exhibited an excellent electrocatalytic activity towards the oxidation of adenine and guanine with a detection limit of 500 and 250nM, respectively. Moreover, our finding demonstrated a linear relation between the concentration of both adenine and guanine and their oxidation current peaks (R=0.9953 and 0.9935, respectively). Finally, the modified electrode was successfully used to detect adenine and guanine in human serum sample. Therefore, we proposed that this biosensor could have high sensitivity for simultaneous determination of adenine and guanine in the related physiology process.

Enhanced cycle performance of a Li–S battery based on a protected lithium anode

A conductive polymer layer is prepared on the surface of a lithium anode as the protective layer for a Li–S battery.

Polypyrrole Based Nano-Biosensor for Sensing Low Concentrations of Hydrogen Peroxide

Abstract This paper discuss about a novel technique of developing a nano-structured polypyrrole biosensor for measurement of very low concentrations of hydrogen peroxide in liquid media. The proposed fabrication method is very effective in growing a nano-structured conducting polymer layer on a planar conducting substrate. In addition enzyme loading was done under a high electric field of 1000V/m. The developed sensor provides a liner range of 0-200μM of hydrogen peroxide and a measurement sensitivity of 6.5Acm-2M-1.

Electromagnetic Wave Absorbing Composites with a Square Patterned Conducting Polymer Layer for Wideband Characteristics

The applications of electromagnetic- (EM-) wave-absorbers are being expanded for commercial and military purposes. For military applications in particular, EM-wave-absorbers (EMWAs) could minimize Radar Cross Section (RCS) of structures, which could reduce the possibility of detection by radar. In this study, EMWA composite structure containing a square periodic patterned layer is presented. It was found that control of the pattern geometry and surface resistance induced EMWA characteristics which can create multiresonance for wideband absorption in composite structures.