Electrodeposition Of Polypyrrole Research Articles

Determination of ascorbic acid by polypyrrole potentiometric detector in ion chromatography

A potentiometric detector, based on electrodeposition of polypyrrole onto Pt electrode, was investigated in this study. The chromatographic performance of the PPy detector was investigated in ion chromatography. The resulting PPy detector exhibited good performance for AA determination with a wide linear range (1.0 × 10 −6 to 1.0 × 10 −2 M), a highly reproducible response (R.S.D. of 2.45%), without any interference and long-term stability. The calculated detection limit was 7.0 × 10 −5 mM at 3 σ. The calibration results showed good Nernstian behavior and also satisfactory low detection limit. In order to verify the reliability of the PPy detector, it was applied to the determination of AA in pharmaceutical samples. The results were satisfactory and agreed closely with the manufacturers’ stated contents. The PPy electrode can be used as an alternative novel potentiometric detector material for determination of AA in standards and pharmaceutical samples.

Phase boundaries in layer-by-layer electrodeposited polypyrrole resulted from 2D–3D growths of polymer sublayers

Potentiostatic deposition of polypyrrole on gold and polypyrrole surfaces has been analyzed using theoretical models of metal electrodeposition. The so-called induction period of electrodeposition was not excluded from the analysis. Such global analysis of chronoamperograms of potentiostatic polymerization was presented for the first time. It was done under a general assumption that two different nucleation and growth mechanisms can proceed in parallel. At +0.8 V vs. SSCE, the mixed 2DI–3DI growth mechanism of the polymer was found and characterized by rates increasing with the electrode potential. The 2D structure of the polymer predominates at the initial stage of electrodeposition. It was proved by SEM images of the polymer layers electrodeposited at conditions derived from the mathematical analysis. A contribution of the 2D structure in the deposited polymer depends on the chemical nature of the substrate surface and it increases with the potential. The formation of the 2D polymer phase at the onset of each electrodeposition introduces new local phase boundaries in the multilayer polypyrrole electrodes prepared via layer-by-layer electrodeposition of polypyrrole on polypyrrole from solution of the same composition. The relaxation time of the decaying double layer current was found to increase with time of deposition from a usual 10 −3 s range to a 10 0 s range, mainly due to an increase in the double layer capacitance. EQCM data support results of chronoamperometry on contribution of the double layer current to the initial current of potentiostatic deposition monitored on a time scale up to few seconds. The double layer process accompanying 2D–3D deposition of polypyrrole was shown to depend on the nature of the substrate electrode (gold, polypyrrole). EQCM results indicate substantial differences in compositional changes of the interphase regions between gold/aqueous and polypyrrole/aqueous systems. The Sauerbrey’s equation is shown valid only when the resonant frequency change due to a thin rigid polymer deposit exceeds that due to reconstructions of the double layer and the diffusion layer of the electrodes.

Comparison of the corrosion protection of mild steel by polypyrrole–phosphate and polypyrrole–tungstenate coatings

AbstractThe electrodeposition of polypyrrole–phosphate (PPy–P) and polypyrrole–tungstenate (PPy–W) on mild steel (MS) were achieved in an oxalic acid medium with cyclic voltammetry techniques. Adherent and homogeneous PPy–P and PPy–W films were obtained. The corrosion behavior of mild steel with phosphate (PPy–P) and tungstenate (PPy–W) composite coatings in 3.5% NaCl solutions were investigated through a potentiodynamic polarization technique, open‐circuit potential–time curves, and electrochemical impedance spectroscopy (EIS). On the basis of a physical model for corrosion of mild steel composites, Zview (II) software was applied to the EIS to estimate the parameters of the proposed equivalent circuit. It was found that the PPy–W coatings could provide much better protection than the PPy–P and polypyrrole coatings. The effects of the phosphate and tungstenate process parameters on the morphology and structure of the passive films were investigated by scanning electron microscopy and electron dispersion X‐ray analyses. The results reveal that the PPy–P and PPy–W coated electrodes offered a noticeable enhancement in protection against corrosion processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

In situ atomic force microscopy investigation of copper behaviour and polypyrrole deposition from salicylate medium

The morphological modifications accompanying the electrochemical behaviour of copper in aqueous salicylate solution, have been investigated by in situ atomic force microscopy (AFM), with the purpose of elucidating the role of salicylate ions during polypyrrole electrodeposition onto this oxidisable metal. The surface changes revealed by in situ AFM images, are in agreement with previous attributed electrochemical processes, namely the formation of a non-uniform passivating layer, which does not completely block the copper surface. The presence of such layer prevents a strong anodic copper dissolution without hinder the pyrrrole oxidation. Pyrrole electropolymerization process has been also followed in real-time by AFM, and occurs through the formation of a first polymer layer, which follows the initial copper surfaces irregularities and is characterized by polypyrrole round nodules of different sizes, whereas for thick polymer films the influence of substrate defects is not detected.

The electrodeposition of polypyrrole on Al alloy from room temperature ionic liquids

The direct electrodeposition of conjugated polymers onto active metals such as aluminum and its alloys is complicated by the concomitant oxidation of the metal that occurs at the positive potential required for polymer formation/deposition. We previously described an approach that uses electron transfer mediation to reduce the deposition potential of polypyrrole (PPy) on aluminum and aluminum alloy by nearly 500 mV, permitting film deposition from aqueous solution with nearly 100% current efficiency. In this report, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM+TFSI−) has been successfully employed both as the growth medium and the supporting electrolyte for directly depositing uniform and conductive PPy coatings onto Al alloy 2024-T3 surface via a potentiodynamic technique. The depositions of PPy were carried out under cyclic voltammetric conditions from 0.3 M pyrrole in ionic liquid solutions. Film morphology was characterized by atomic force microscopy, optical microscopy, and scanning electron microscopy (SEM). Energy dispersive X-ray analysis and X-ray photoelectron spectroscopy verified that the TFSI− anion was incorporated into the polymer as the dopant ion. Thickness of the film was measured by SEM and film conductivity was determined by both a four-point probe technique and by conducting atomic force microscopy. Electrochemical activity of the film was assessed by cyclic voltammetry. Results from these preliminary studies will be reported.

Encapsulation of quantum dots and carbon nanotubes with polypyrrole in a syringe needle for automated molecularly imprinted solid phase pre-concentration of ochratoxin A in red wine analysis

Nanometer-sized semiconductor quantum dots (QDs with CdSe core and ZnS shell) and carbon nanotubes (CNTs with multi-walls) were encapsulated inside a stainless steel syringe needle by electrodeposition of polypyrrole (PPy). By cross-linking the PPy with ethylene glycol dimethacrylate (EGDMA) in the presence of ochratoxin A (OTA) as a template, molecularly imprinted polypyrrole (MIPPy) was formed on the nano-hybrid structure at an increased specific surface area. The MIPPy/CNTs/QDs-modified needle was readily adapted in an autosampler for micro-solid phase preconcentration (μSPP) of OTA from a red wine sample. After pulsed elution (PE) with 2% triethylamine (TEA), the OTA was determined by high performance liquid chromatography (HPLC) with fluorescence detection (FD). In comparison with MIPPy/CNTs, this new nano-hybrid structure of MIPPy/CNTs/QDs significantly improved the % recovery of OTA. The method, MIPPy/CNTs/QDs-μSPP-HPLC-FD, demonstrated that the MIPPy was truly a molecularly imprinted polymer (MIP) with specific recognition for OTA. All red wine matrix components could be differentially washed out, prior to accurate determination of the strongly bound OTA.

Electrodeposition of polypyrrole films on aluminum from tartrate aqueous solution

The electrochemical synthesis of polypyrrole films on aluminum surfaces from aqueous solutions containing tartaric acid and pyrrole was performed using cyclic voltammetry and galvanostatic techniques. A mechanism that considers a porous aluminum oxide layer growing in parallel with the polymeric film explains the polypyrrole electrodeposition on aluminum surfaces. The more homogeneous the distribution of pores on the aluminum oxide layer, the smaller is the resistance offered to the polypyrrole film growth. Polypyrrole films deposited by cyclic voltammetry are much less uniform than those galvanostatically formed. Polymeric films galvanostatically deposited at higher current densities were more susceptible to overoxidation processes than those films formed at lower current densities, as demonstrated by FTIR analyses. Furthermore, films formed at low current density perform better on protecting aluminum surfaces against corrosion.

Electrodeposition of polypyrrole–multiwalled carbon nanotube–glucose oxidase nanobiocomposite film for the detection of glucose

A nanobiocomposite film consisted of polypyrrole (PPy), functionalized multiwalled carbon nanotubes (cMWNTs), and glucose oxidase (GOx) were electrochemically synthesized by electrooxidation of 0.1M pyrrole in aqueous solution containing appropriate amounts of cMWNTs and GOx. Potentiostatic growth profiles indicate that the anionic cMWNTs is incorporated within the growing PPy-cMWNTs nanocomposite for maintaining its electrical neutrality. The morphology of the PPy-cMWNTs nanocomposite was characterized by scanning electron microscopy (SEM). The PPy-cMWNTs nanocomposite was deposited homogeneously onto glassy carbon electrode. The amperometric responses vary proportionately to the concentration of hydrogen peroxide at the PPy-cMWNTs nanocomposite modified electrode at an operating potential of 0.7V versus Ag/AgCl (3M). The results indicate that the electroanalytical PPy-cMWNTs-GOx nanobiocomposite film was highly sensitive and suitable for glucose biosensor based on GOx function. The GOx concentration within the PPy-cMWNTs-GOx nanobiocomposite and the film thickness are crucial for the performance of the glucose biosensor. The amperometric responses of the optimized PPy-cMWNTs-GOx glucose biosensor (1.5 mgmL(-1) GOx, 141 mCcm(-2) total charge) displayed a sensitivity of 95 nAmM(-1), a linear range up to 4mM, and a response time of about 8s.

Deposition of Polypyrrole on Porous Aluminum Oxide

We report the successful attempt of electrodeposition of polypyrrole (PPy) on the electrochemically developed porous oxide surface of aluminium alloy. Corrosion protection properties were assessed by potentiodynamic measurements and electrochemical impedance spectroscopy. It is shown that PPy on porous oxide significantly increases the corrosion potential making the surface more noble.

A Comparative Study of Conductive Polypyrrole and Polyaniline Coatings on Electro-Active Papers

A comparative study is performed on the conductive polymer-coated electro-active paper (EAPap) actuators by aiming at improving the overall performance of the actuators. Conductive Polymer coated Electro-active Paper [CP-EAPap] actuators are constructed using electro-deposition of polypyrrole and polyaniline on to cellulose paper. The actuation behavior is tested at different actuation frequency and humidity conditions on bilayer and trilayer types of CP-EAPap actuators. The effect of thickness variation, dopant ions and humidity conditions are compared for both conductive polymer-coated actuators. The trilayer actuators are superior than the bilayer counterparts, and polyaniline coated actuators gives better performance than polypyrrole based ones in terms of bending displacement and ruggedness to humidity. The possible actuation principle is also addressed along with X-ray diffraction and scanning electron microscope results.

Conditions to prepare PPy/Al 2O 3/Al used as a solid-state capacitor from aqueous malic solutions

The electrosynthesis of polypyrrole (PPy) has been achieved on aluminium in aqueous medium of malic acid by means of cyclic voltammetry, potentiostatic and galvanostatic techniques. Scanning electron microscopy (SEM) and X-ray microanalysis by dispersion energy spectroscopy (EDS) applying on surfaces show that the PPy coating is developed from the metal surface through the cracks of the initial Al 2O 3 layer. Moreover, the results reveal that the homogeneity of the film achieved increases with the time of electropolymerization. A mechanism involving the participation of the supporting electrolyte and the pyrrole (Py) in distinct active sites was proposed based on the linear sweep voltammetry. It is observed for all the applied electrochemical techniques that the pyrrole concentration has to be higher than 0.1 M to allow the polypyrrole electrodeposition in acid medium. Scanning electron microscopy, secondary electrons (SE) and backscattering electrons (BE), shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. The corrosion results in 3% NaCl medium show that the PPy coating decreases the corrosion behaviour of the aluminium. The bilayer Al 2O 3/PPy shows a capacitor with future applications.

Electrodeposition of polypyrrole on aluminium in aqueous tartaric solution

The electrosynthesis of polypyrrole (PPy) has been achieved on aluminium in aqueous medium of tartaric acid by means of cyclic voltammetry, potentiostatic and galvanostatic techniques. Scanning electron microscopy (SEM) and X-ray microanalysis by energy spectroscopy dispersion (EDS) applying on surfaces show that the PPy coating is developed from the metal surface through the cracks of the initial Al 2O 3 layer. A mechanism involving the participation of the supporting electrolyte and the pyrrole (Py) in distinct active sites was proposed based on the linear sweep voltammetry. It is observed for all applied electrochemical techniques that the pyrrole concentration has to be higher than 0.1 M to allow the polypyrrole electrodeposition in acid medium. Scanning electron microscopy, secondary electrons (SE) and backscattering electrons (BE), shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. Moreover, EDS reveals a good homogeneity and compactness of the film achieved in galvanostatic method. The corrosion results in 3% NaCl medium show that the PPy coating decreases the corrosion behaviour of the aluminium. The bilayer Al 2O 3/PPy shows a capacitor with future applications.

Electrochemical synthesis of polypyrrole films on copper electrodes in acidic and neutral aqueous media

The use of appropriate electrolyte allows to deposit Polypyrrole (PPy) films on oxidizable metals such as copper by electrochemical oxidation of Pyrrole. In this work, oxalic acid, sodium oxalate, sodium/potassium tartrate and sodium salicylate are used as electrolytes and compared in terms of easiness for polypyrrole deposition, and film characteristics. Electrochemical measurements in presence of these electrolytes with and without pyrrole demonstrate that copper can be efficiently passivated before polypyrrole electrodeposition. Moreover, FT-IR experiments reveal the chemical constitution of the thin passivating layer formed prior to the pyrrole electropolymerization and preventing copper corrosion without inhibiting the polymer formation: in oxalic acid medium, the presence of Cu(I) oxalate is clearly evidenced as the only passivating agent, whereas the weak transmission intensities of the spectra obtained with samples polarized in oxalate and tartrate media suggest thin layers thus non-fully identified and the salicylate medium is the only one for which one can distinguish successively the formation of the thin layer constituted of copper (II) ions complexed by the salicylate anion and then, the formed polypyrrole.

Solvent-free electrodeposition of polypyrrole as a base for the preparation of carbonised platinum microelectrodes

The combination of electropolymerisation of suitable monomers and pyrolysis for the local modification of the surface of Pt microelectrodes with pyrolytic carbon films is presented. For use in biological systems, carbon-based electrodes have several advantages over their inert metal counterparts. However, carbon electrodes with dimensions in the sub-μm range lack the required mechanical stability for practical applications. Platinum is employed as a robust support for carbon films to yield carbonised Pt electrodes. Pyrrole, aniline and a polyacrylic resin were investigated for their suitability for forming uniform and stable pyrolytic carbon films on Pt support. Polypyrrole deposited from solvent-free pyrrole (pyrrole concentration higher than 14 M) was found to be most suitable for the formation of stable and crack-free carbon films on Pt electrodes. The carbonised Pt electrodes obtained were characterised electrochemically.

Micropatterning of fluoropolymers

Fluoropolymer (PTFE and FEP) substrates have been patterned through micro-contact printing of an aminosilane. The silane pattern was activated with a palladium catalyst that allowed the electroless deposition of copper which was used to form micropatterned copper electrodes. Conducting polymer micropatterns were then fabricated by electrodeposition of polypyrrole (PPy) onto the copper. The resulting patterns of 80 μm and 10 μm grids and 2 μm and 5 μm checkerboards were characterized using imaging XPS, TOF-SIMS, AFM and SEM. The size and resolution of the smallest copper patterns were limited by the copper grain size created during electroless deposition. The polypyrrole patterns were also limited by the roughness of the electrolytically deposited polymer film.

Electrochemical synthesis of polypyrrole on ferrous and non-ferrous metals from sweet aqueous electrolytic medium

The electrodeposition of polypyrrole (PPy) on oxidizable metals such as aluminum and iron has been achieved in aqueous medium of saccharin and pyrrole. Scanning electron microscopy and X-ray photoelectron spectroscopy analysis reveal a good homogeneity of the obtained PPy film. The electrochemical synthesis of PPy coating has been achieved successfully under potentiodynamic, galvanostatic and potentiostatic techniques. The corrosion experiments performed in HCl show that the PPy coating increases the corrosion potential and decreases the corrosion current density.

Guiding water into carbon nanopipes with the aid of bipolar electrochemistry

The targeted bipolar electrodeposition of polypyrrole was carried out onto the tips of hydrophilic carbon nanopipes. By aligning an external electric field relative to the nanopipes, the deposition of polypyrrole onto selected ends could be achieved without physically contacting the nanopipes. After deposition, carbon nanopipes with both partially open and fully blocked tips were found. Experiments conducted in an environmental scanning electron microscope showed that water enters the nanopipes through the tip with polypyrrole due to the higher hydrophilicity of the polymer compared to the tube walls. As a result, it was possible to guide the entry of water from a specific end of the tube and fill the tube from the selected side. Condensation experiments conducted on nanopipes with polypyrrole on both tips shows the difference in hydrophilicity of the nanopipes compared to the polypyrrole. The ability to selectively control the site of condensation and uptake of fluid by carbon nanotubes or nanopipes is very important for the development of nanotube-based nanofluidic devices.

The Mediated Electrodeposition of Polypyrrole on Aluminium Alloy

The direct electrodeposition of conjugated polymers onto active metals such as aluminium and its alloys is complicated by the concomitant oxidation of the metal that occurs at the positive potential required for polymer formation/deposition. We have developed an approach that uses electron transfer mediation to reduce the deposition potential of polypyrrole on aluminium and aluminium alloy by nearly 500 mV, permitting film deposition from aqueous solution with nearly 100% current efficiency. The mediator used in this initial work was 4,5-dihydroxy-1,3-benzenedisulfonate (DHBDS, disodium salt), which also served as the dopant or counter ion in the polymer. To better understand the mediation process, a series of substituted benzene compounds have been explored for their mediating properties. From these studies, we conclude that both the hydroxyl and the sulfonate functionalities of DHBDS appear to play a role in the mediated electrodeposition at aluminium alloy. New mediators for the electrodeposition of polypyrrole on Al alloy are suggested.

Implications of layer-by-layer electrodeposition of polypyrrole from a solution of the same composition for ion transport in the polymer electrode

Layer-by-layer electrodeposition of thin polypyrrole films and the charge and mass transport in the resulting multilayer polypyrrole electrodes were studied using electrochemical methods: chronoamperometry, cyclic voltammetry, quartz crystal microbalance, impedance spectroscopy. The polypyrrole/aqueous sodium hexafluoroaluminate and polypyrrole/aqueous sodium chloride systems were investigated. Polypyrrole electrodes of sub-μm total thickness were studied mostly. It was shown that the multilayer structure of the polypyrrole electrode results in a hindrance of charge and mass transport between the sublayers of polypyrrole prepared from a solution of the same composition. The resistance to ion transport across the polymer|polymer interface causes slower ion diffusion in the multilayer polypyrrole electrode as compared to the single-layer electrode. The redox capacitances of both structures are similar. Current traces of potentiostatic layer-by-layer deposition differ significantly for nucleation and growth of polypyrrole on polypyrrole as compared to polypyrrole on gold.

Microcontact printing of copper and polypyrrole on fluoropolymers

This paper describes the use of microcontact printing (μCP) to form micrometer-scale patterns of copper on poly(tetrafluoroethylene) (PTFE), and illustrates the use of these patterned surfaces as substrates for electrodeposition of polypyrrole (PPy) sensor structures. A patterned elastomeric stamp was used to deliver a nitrogen-containing silane coupling agent to the argon plasma-pretreated PTFE surface. The surface was subsequently activated by PdCl 2, allowing the selective activation via the formation of Pd–N complex. Patterning of copper structures with feature sizes of 50–200 μm was achieved by immersing the activated surface into an electroless copper plating bath. Surface chemistry was investigated after each surface modification and deposition step using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). This study demonstrates a soft lithography approach for the fabrication of patterned copper and PPy structures on flexible PTFE films, offering new opportunities for the creation of polymer-based electronic devices and sensor arrays.