Polypyrrole Matrix Research Articles

One-stage periodical anodic-cathodic double pulse deposition of nanocomposite materials. Application to Prussian Blue/polypyrrole film coated electrodes

Novel electrochemical method of one-stage deposition of composite films on electrode surface has been proposed. The procedure includes a periodical series of potentiostatic or galvanostatic pulses of alternative polarity imposed at electrode in contact with a mixture of two solute precursors, one of which is able to generate a solid phase under its electrooxidation while another one is transformed into another solid phase under its electroreduction. Parameters of anodic and cathodic pulses (potential or current, pulse duration) may be chosen independently from one another, their relation allows one to vary the relative contents of components in the deposited composite. Thickness of the composite film may be regulated by the number of pulses. For illustration this method has been applied for growing films where particles of Prussian Blue are distributed inside polypyrrole matrix. Such modified electrode demonstrates a high catalytic activity and a good stability in the reaction of hydrogen peroxide electroreduction.

Dependence of the carrier mobility and trapped charge limited conduction on silver nanoparticles embedment in doped polypyrrole nanostructures

The present article demonstrates an intensive study upon the temperature dependent current density (J)-voltage (V) characteristics of moderately doped polypyrrole nanostructure and its silver nanoparticles incorporated nanocomposites. Analysis of the measured J–V characteristics of different synthesized nano-structured samples within a wide temperature range revealed that the electrical conduction behavior followed a trapped charge-limited conduction and a transition of charge transport mechanism from deep exponential trap limited conduction to shallow traps limited conduction had been occurred due to the incorporation of silver nanoparticles within the polypyrrole matrix. A direct evaluation of carrier mobility as a function of electric field and temperature from the measured J–V characteristics illustrates that the incorporation of silver nanoparticles within the polypyrrole matrix enhances the carrier mobility at a large extent by reducing the concentration of traps within the polypyrrole matrix. The calculated mobility is consistent with the Poole-Frenkel form for the electrical field up to a certain temperature range. The nonlinear low temperature dependency of mobility of all the nanostructured samples was explained by Mott variable range hopping conduction mechanisms. Quantitative information regarding the charge transport parameters obtained from the above study would help to extend optimization strategies for the fabrication of new organic semiconducting nano-structured devices.

Fixation of laccase enzyme into polypyrrole, assisted by chemical interaction with modified magnetite nanoparticles: A facile route to synthesize stable electroactive bionanocomposite catalysts

Effective bio-electrocatalysts require stable immobilization of sufficient amounts of the bioactive component. In this study, a novel and efficient method for specific binding of laccase enzyme onto magnetite nanoparticles (NPs) is presented. The interaction between the chemically modified magnetite NPs and the enzyme was evidenced by both infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Subsequently, the enzyme-coated magnetite NPs were successfully incorporated into polypyrrole (PPy) matrix during galvanostatic electropolymerization. The encapsulation of laccase covered NPs was proved by EQCN, TEM, and FT-IR spectroscopy; whereas the electrochemical behaviour of the formed bionanocomposite was characterized by cyclic voltammetry. In oxygen saturated solution a cathodic charge surplus was observed, related to the electrochemical reduction of oxygen. This surplus was two times higher in the case of the laccase containing layer compared to its only magnetite containing counterpart. Kinetic aspects of the oxygen reduction reaction (ORR) on the laccase containing films were investigated by hydrodynamic voltammetry, and the four-electron route was found to be exclusive, which is promising from the fuel cell perspective. Such synergistic combination of inorganic NPs and enzymes may open new avenues in the application of these bio-nanocomposite materials.

Elaboration of ammonia gas sensors based on electrodeposited polypyrrole—Cobalt phthalocyanine hybrid films

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix.

Amperometric biosensing of organophosphate and organocarbamate pesticides utilizing polypyrrole entrapped acetylcholinesterase electrode

The work presented here describes a novel, easy and low-cost method of fabrication of a highly sensitive acetylcholinesterase biosensor and its application to detect organophosphate and organocarbamate pesticides. Acetylcholinesterase was electro-immobilized into a thick conducting layer of polypyrrole. Porcine skin gelatin and gluteraldehyde mixture was used for stabilizing the system. Acetylthiocholine chloride was used as the substrate. Polypyrrole catalyzed the electrochemical oxidation of thiocholine and promoted the electron transfer, thus lowering the oxidation potential and increasing the detection sensitivity. Electro oxidation of thiocholine in polypyrrole matrix occurred at 0.1V under low potential scan rate. The thiocholine sensitivity of the electrode was found to be 143mA/M. The sensor was applied to detect the sample organophosphate pesticide ethylparaoxon and organocarbamate pesticide carbofuran. The detection limit for paraoxon was found to be 1.1ppb and that for carbofuran is 0.12ppb. The sensor showed good intra and inter state precision with relative standard deviation (RSD) 0.742% and 6.56% respectively. Both dry and wet storage stability were studied. The sensor stored at 0°C in dry condition had a good storage stability retaining 70% of its original activity for 4 months. During wet storage, the activity decrease followed the same trend, however, the operational stability at the end of the storage period was found to be less compared to the dry storage case. The developed biosensor is as a promising new tool for analysis of cholinesterase inhibitors.

Removal of Cd (II) by using polypyrrole and its nanocomposites

Polypyrrole was successfully synthesized by using ferric chloride as an oxidant in the presence of sodium dodecylhydrogensulfonate, poly(vinyl pyrrolidone) and poly(vinyl alcohol) as surfactants in aqueous media. The effect of polypyrrole and its nanocomposites for the removal of Cd (II) was investigated. The products were characterized in terms of, morphology and chemical structure. The FTIR spectra show that the intensity of peaks was related to the type of surfactant. The crystalline nature of nanocomposites was determined from XRD analysis. The extra peaks in the XRD pattern of nanocomposites indicate the presence of Al2O3 nanoparticles in the polypyrrole matrix. The aim of this research was to investigate the sorption characteristic of polypyrrole nanocomposites for the removal of Cd (II) from aqueous solution. The removal percentage of Cd (II) was carried out by using batch method. The optimum conditions of sorption were found to be: contact time of 45min and pH 5. The Langmuir and Freundlich model are subjected to sorption data to estimate the sorption capacity and intensity. The data was better fitted by using Langmuir model.

Supercapacitors from Free-Standing Polypyrrole/Graphene Nanocomposites

Interfacial/in situ oxidative polymerization of polypyrrole in the presence of functionalized graphene sheets produces high-quality composites for supercapacitors, as analyzed by electrochemical impedance spectroscopy and cyclic voltammetry analysis. The synergistic interaction induced by the growth of p-type polypyrrole on the surface of negatively charged carboxylate functionalized graphene sheets results in higher storage capacity than graphene-only or polymer-only films. The high conductivity of p-doped polypyrrole and high surface area of graphene promote high charge accumulation in capacitors. We report the optimization of the relative concentrations of carboxylate functionalized graphene in the polypyrrole matrix to maximize the composition’s capacitance to 277.8 F/g.

Electrically conductive and hydrophobic cotton fabrics by polypyrrole-oleic acid coating

Hydrophobic polypyrrole-coated fabrics with improved electrical conductivity were produced embedding oleic acid as counter-ion. Hydrophobisation of polypyrrole was carried out by means of an ion exchange process after deposition of polypyrrole on cotton fabrics. The fabrics coated with oleic acid-doped polypyrrole showed contact angle of 111°, drop absorption time of 7 minutes and high water repellence, while electrical conductivity increased of ∼2 times and heat generation improved, too. Moreover, oleic acid demonstrated a great stability as counter-ion in polypyrrole matrix being present also after washing.

Superoxide Anion Radical Sensor Using GC Electrode Modified with Heparin/PEDOT and Polymerized Iron Porphyrin

Blood coagulation on the electrode surface is a serious problem for a superoxide anion radical (O2−∙) sensor because it causes deterioration of the current signal especially in vivo. In order to solve this problem, we have developed iron porphyrin-based O2−∙ sensors immobilizing heparin, which is an anti-thrombotic compound, on the surface. In the present study, we immobilized heparin with a polyethylenedioxythiophene (PEDOT) matrix on poly[iron tetrakis(3-thienyl)porphyrin]-modified glassy carbon (GC) electrode, and the stability of the modified sensor to blood coagulation was investigated. The PEDOT matrix was found to be more effective for stable electrochemical detection of O2−∙ after immersion in a fibrinogen/thrombin solution for two weeks, while serious electrode fouling due to blood clot formation was occurred at a sensor using a polypyrrole matrix after immersion in the solution for one week.

Polypyrrole/lanthanum strontium manganite oxide nanocomposites: Elaboration and characterization

The synthesis of organic–inorganic hybrid polypyrrole (PPy)–lanthanum strontium manganite oxide La0.8Sr0.2MnO3 (LSMO) nanocomposites via chemical oxidative polymerization of pyrrole in presence of LSMO nanoparticles using ferric chloride as oxidant and sodium p-toluene sulfonate as efficient dopant is investigated. The morphology of polypyrrole and its nanocomposites was examined by scanning electron microscopy which have shown that the presence of LSMO nanoparticles strongly affects the particle size of the nanocomposites. The specific interactions between the conducting polymer and the inorganic nanoparticles is highlighted by FTIR characterizations. Transmission electron microscopy and X-ray diffraction measurements of the nanocomposites confirm a core–shell structure with LSMO coated by polypyrrole macromolecular chains. Electrochemical properties of nanocomposites were investigated by cyclic voltammetry measurements in 2M KOH. In such a media, polypyrrole nanocomposite electrode with 30wt% LSMO nanoparticles has shown specific capacitance of 530Fg−1 which is significantly higher than pristine polypyrrole i.e., 246Fg−1. These charge storage differences between the pristine polypyrrole and polypyrrole/LSMO nanocomposite has been attributed to the morphology of the nanocomposite in which the particle sizes, the specific surface area, and pore size distribution have been modified with the incorporation of nanoparticles in the polypyrrole matrix.

Gold Nanoparticles with Self-Assembled Cysteine Monolayer Coupled to Nitrate Reductase in Polypyrrole Matrix Enhanced Nitrate Biosensor

Gold Nanoparticles with Self-Assembled Cysteine Monolayer Coupled to Nitrate Reductase in Polypyrrole Matrix Enhanced Nitrate Biosensor

Electrorheological and magnetorheological response of polypyrrole/magnetite nanocomposite particles

Magnetic nanoparticles of magnetite (Fe3O4) were synthesized within a conducting polypyrrole (PPY) matrix using a facile method, and employed as both electrorheological (ER) and magnetorheological (MR) materials to provide a well dispersed suspension of either ER or MR fluids. The PPY to Fe3O4 weight ratio was adjusted to 5 % to avoid possible deterioration of the magnetic properties of the Fe3O4 particles. Transmission electron microscopy and X-ray diffraction provided information on the structure and particle size of the PPY/Fe3O4. Both ER and MR performance of pure Fe3O4 and PPY/Fe3O4 nanocomposites were examined through rotational and oscillatory tests using a rotational rheometer under an applied electric and magnetic field, respectively, demonstrating typical ER and MR characteristics.

Electrochemical aspects and in vitro biocompatibility of polypyrrole/TiO2 ceramic nanocomposite coatings on 316L SS for orthopedic implants

With a view to developing a smart coating combining both biocompatibility and corrosion resistance over bioimplants, polypyrrole/TiO2 nanocomposite coatings were electrochemically synthesized by cyclic voltammetric technique on 316L stainless steel (SS) in an aqueous solution of oxalic acid. The presence of TiO2 nanoparticles in polypyrrole (PPy) matrix was confirmed using FT-IR spectroscopy and XRD analysis. The surface morphology of coated 316L SS substrates was observed by the Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Microhardness of coated 316L SS was examined by the Vickers hardness method. The electrochemical studies were carried out using Cyclic Polarization and Electrochemical Impedance Spectroscopy (EIS) measurements. In order to describe the biocompatibility, contact angle measurements and in vitro characterization were carried out in Simulated Body Fluid (SBF) solution. The results showed that the nanocomposite coatings exhibit superior biocompatibility and enhanced corrosion protection performance over 316L SS than that of pure polypyrrole coatings.

Photo-induced synthesis of polypyrrole-silver nanocomposite films on N-(3-trimethoxysilylpropyl)pyrrole-modified biaxially oriented polyethylene terephthalate flexible substrates

Polypyrrole-silver (PPy–Ag) nanocomposite films were prepared on a N-(3-trimethoxysilylpropyl)pyrrole modified biaxially oriented polyethylene terephthalate (BOPET) substrate by photopolymerisation of pyrrole using AgNO3 as a photo-initiator. The films were prepared for a fixed molar concentration of pyrrole (0.5 M), varying molar concentrations of AgNO3 (0.05–0.7 M) and different UV exposure times (15 min–180 min). With increasing AgNO3 concentration or with increasing polymerisation time, the film morphology shows a transition from two dimensional lamellar to granular structures. The films are adherent, flexible and exhibit a maximum room temperature electrical conductivity of ∼15 S cm−1 (for AgNO3 ∼ 0.5 M, 120 min of UV exposure). However, the films directly prepared on pristine BOPET show granular morphology and their conductivity value is ∼0.5 S cm−1. The high conductivity of PPy–Ag films is attributed to the high conjugation length, the incorporation of Ag nano-particles between the polypyrrole chains and the ordered structure due to the templating effect of the silanised pyrrole layer, as confirmed by GIXRD, FTIR, Raman and temperature dependent conductivity measurements. The metallic state of the embedded Ag nano-particles in the polypyrrole matrix is confirmed by XRD and XPS. The films with the least amount of Ag (AgNO3 ∼ 0.1 M) only show a reversible conductivity change in the opposite manner on exposure to ppm levels of H2S and NH3 gases. The mechanism has been proposed to explain these antagonistic responses for reducing gases.

Enhanced charge transportation in a polypyrrole counter electrode via incorporation of reduced graphene oxide sheets for dye-sensitized solar cells

In this work, reduced graphene oxide (RGO) sheets are successfully introduced into the conductive polypyrrole (PPy) matrix as conductive channels and co-catalyst, through simple incorporation of graphene oxide (GO) into PPy and subsequent in situ reduction from GO/PPy to RGO/PPy composite film. The RGO/PPy film is fabricated as a counter electrode for dye-sensitized solar cells, and it exhibits excellent catalytic performance for reduction of triiodide. For this reason, the incorporated RGO sheets significantly improve short-circuit photocurrent density from 14.27 to 15.81 mA cm(-2) and power conversion efficiency from 7.11% to 8.14%, which is comparable with that for the cell based on a Pt cathode.

STRUCTURAL AND OPTICAL PROPERTIES OF SINGLE CRYSTALLINE BISMUTH NANOPARTICLES IN POLYMER

We report here the structural and optical properties of Bi nanoparticles in polymer (polypyrrole) matrix. The nanoparticles are synthesized following a wet chemical route. The X-ray diffraction data clearly shows the growth of single crystalline Bi nanoparticles within the host polymer. The microstructure of the Bi nanoparticles obtained by transmission electron microscopy (TEM) reveals clearly the formation of spherical shaped nanoparticles of average size∼27 nm with a narrow size distribution. The optical absorption spectrum exhibits a distinct peak at 278 nm which is attributed to the surface plasmon band of Bi nanoparticles. The absorption spectrum is found to be described well following Mie theory.

Facile synthesis of SnO2-polypyrrole hybrid nanowires by cathodic electrodeposition and their application to Li-ion battery anodes

SnO2-polypyrrole hybrid nanowires are synthesized in a one-step process by a simple electrochemical method from an aqueous solution at room temperature. This novel and facile technique involves the rapid electropolymerization of pyrrole and the relatively slow chemical deposition of SnO2, which leads to the incorporation of uniformly dispersed SnO2 nanoparticles inside polypyrrole nanowires. Notably, the synthesized nanowires are directly deposited as a thin film on the substrate in a three-dimensional porous and interconnected network structure composed of numerous fine nanowires. This open architecture is highly desirable in energy storage devices because of its excellent mass transfer and high specific surface area, and therefore, the SnO2-polypyrrole hybrid nanowires are evaluated for their use as high-performance anode materials in Li-ion batteries. Over 200 cycles, the hybrid nanowires show superior cyclic performance and a charge capacity higher than 0.307 mA h cm−2, most likely because the polypyrrole matrix effectively prevents the agglomeration of the SnO2 nanoparticles and elastically buffers the volumetric change in the nanoparticles that occurs during cycling.

Nanomaterial-based electrochemical biosensors for cytochrome c using cytochrome c reductase

Emerging evidences have pointed out that the release of cytochrome c (cyt c) from mitochondria into cytosol is a critical step in the activation of apoptosis. This article presents a novel approach for the detection of mitochondrial cyt c release for the first time using cytochrome c reductase (CcR) immobilized on nanoparticles decorated electrodes. Two kinds of nanomaterial-based biosensor platforms were used: (a) carbon nanotubes (CNT) incorporated polypyrrole (PPy) matrix on Pt electrode and (b) self-assembled monolayer (SAM) functionalized gold nanoparticles (GNP) in PPy-Pt. Scanning electron microscope was used to characterize the surface morphologies of the nanomaterial modified electrodes. Cyclic voltammograms of both the biosensors showed reversible redox peaks at −0.45 and −0.34V vs Ag/AgCl, characteristic of CcR. In comparison, the CcR-CNT biosensor gave a detection limit of 0.5±0.03μM cyt c, which was 4-fold better than the CcR-GNP biosensor (2±0.03μM). Moreover, the CcR-CNT biosensor achieved a much larger linear range (1–1000μM) over the CcR-GNP biosensor (5–600μM) with 2-fold better sensitivity. The CcR-CNT-PPy-Pt biosensor was further applied to quantify the mitochondrial cyt c released in cytosol of A549 cells upon induction of apoptosis with doxorubicin, the results agreed well with standard western blot analysis.

Influence of zirconia nanoparticles on the surface and electrochemical behaviour of polypyrrole nanocomposite coated 316L SS in simulated body fluid

Current efforts of recent implant technology have been aimed principally at the improvement of corrosion resistance and biocompatibility. The present study demonstrates that the electro polymerisation of pyrrole and incorporation of zirconia (ZrO2) nanoparticles can be successfully combined to produce bioactive polypyrrole nanocomposite coatings for orthopaedic implants. Polypyrrole/ZrO2 nanocomposite coatings were electrochemically synthesised by cyclic votametric technique on 316L stainless steel (SS) in aqueous solution of oxalic acid. The existence of ZrO2 nanoparticles in polypyrrole (PPy) matrix was confirmed by Fourier Transform Infrared (FT-IR) spectroscopy and X ray diffraction (XRD) analysis. The surface morphology of coated 316L SS substrates was observed using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Micro hardness of coated 316L SS was examined using Vickers hardness method. The electrochemical studies were carried out using cyclic polarisation and electrochemical impedance spectroscopy (EIS) measurements. In order to describe the biocompatibility, contact angle measurements and in vitro characterisation were carried out in simulated body fluid (SBF) solution. The results showed that the nanocomposite coatings exhibit superior biocompatibility and enhanced corrosion protection performance over 316L SS due to their hydrophilic, smooth, compact and less porous surface morphology than that of pure polypyrrole coatings.

Preparation and electrochemical application of a new biosensor based on plant tissue/polypyrrole for determination of acetaminophen

Banana tissue containing polyphenol oxidase was incorporated into polypyrrole matrix to make a biosensor for the analysis of acetaminophen (ACT). The electrocatalytic behaviour of oxidized acetaminophen was studied at the surface of the biosensor, using various electrochemical methods. The advantages of this biosensor for the determination of acetaminophen are excellent catalytic activity, good detection limit and high exchange current density. The electrochemical and structural properties of the electrode were assessed using cyclic voltammetry, differential voltammetry, chronoamperometric techniques. The analytical properties (sensitivity, I p ) of this biosensor increased with plant tissue loading. Also this new biosensor was successfully applied for determination of acetaminophen in biologic samples.