Overoxidized Polypyrrole Film Research Articles

Electrochemical preparation of cobalt hexacyanoferrate nanoparticles under the synergic action of EDTA and overoxidized polypyrrole film

The cobalt hexacyanoferrate nanocrystals (Nano-CoHCF) with uniform shape and size were electrochemical deposited on the electrode surface modified with the overoxidized polypyrrole (OPyox) film in the presence of ethylene diamine tetraacetic acid (EDTA). The conceivable effect of EDTA and OPyox film was studied using SEM and electrochemical techniques. The experiment results showed that the nucleation and deposition rate of CoHCF on the electrode surface were controlled by the synergic action of EDTA and OPyox film, which resulted in the formation of uniform Nano-CoHCF. Moreover, some electrodeposition conditions for Nano-CoHCF film had been optimized such as pH, concentration of EDTA, as well as deposition cycles. The resulting modified electrode exhibited excellent catalytic activity and improved stability for the oxidation of hydrazine. Hydrodynamic amperometry was applied for the determination of hydrazine with a linear range of 2.0×10−7 to 1.1×10−5molL−1 and 1.1×10−5 to 4.1×10−4molL−1 with the maximum sensitivity of 2719.5μAmM−1cm−2.

Nanostructured conducting molecularly imprinted polymer for selective uptake/release of naproxen by the electrochemically controlled sorbent

A conducting molecularly imprinted polymer (CMIP) film, based on polypyrrole, was electrosynthesized for selective uptake/release and determination of naproxen. The film was prepared by incorporation of a template anion (naproxen) during the electropolymerization of pyrrole into a platinum electrode using the cyclic voltammetry method. Overoxidized polypyrrole films with cavities complementary to the template were used as a potential-induced selective recognition element in the solid-phase sorbent. Various important fabricating factors, which control the performance of the CMIP film, were investigated using fluorescence spectroscopy. The measured fluorescence intensities of released solutions were related to the concentrations of naproxen taken up into the films. Several key parameters such as applied potential and time for uptake and release were varied to achieve the optimal sorption procedure. The film template with naproxen exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5×10−8 to 3×10−7molml−1 and 7×10−6 to 8×10−4molml−1, and the limit of detection was 1×10−8molml−1. The CMIP films, as the electrochemically controlled solid-phase sorbent, were applied for the selective cleanup and quantification of trace amounts of naproxen from physiological samples. Scanning electron microscopy confirmed the nanostructure morphology of the films.

Voltammetric Determination of Folic Acid with a Overoxidized Polypyrrole Film Modified Sol-Gel Carbon Ceramic Electrode

The electrochemical behavior of folic acid (FA)was studied at an overoxidized polypyrrole modified carbon ceramic electrode using cyclic voltammetry. The numerous factors affecting the oxidation peak currents of folic acid on the response of the electrode were optimized to maximize sensitivity. The modified electrode presented a linear response range for FA concentration from 7 to 55 µM, 0.1 to 25 µM, and from 0.49 to 7.8 µM with detection limits of 1.8 × 10−6, 3.1 × 10−8, and 2.7 × 10−7 for cyclic voltammetry, differential pulse voltammetry, and amperometric techniques, respectively. The results showed that the OPPy-modified electrode has very high catalytic ability for electrooxidation of FA. The modified electrode exhibited excellent sensitivity and stability. The application of the modified electrode was demonstrated for determination of folic acid in biological and other real samples.

Permeable porous 1–3 nm thick overoxidized polypyrrole films on nanostructured carbon fiber microdisk electrodes

Ionically conducting 1–3 nm thick porous films of overoxidized polypyrrole (OPPY) were electrodeposited on nanostructured 7 μm diameter carbon fiber microdisk electrodes. The microdisk electrodes were fabricated from two types of polyacrylonitrile (PAN) carbon fibers, PAN T650 and PAN HCB. The electrodes were nanostructured by electrochemical etching of the microdisk electrode surface. Ultrathin porous polypyrrole (PPY) films were electrodeposited by the electropolymerization of pyrrole (PY) to PPY by a short (10 ms) single potential pulse. During the electropolymerization, the polymer “precipitated” on the nanostructured surface producing ultrathin porous film. OPPY films were fabricated by constant potential overoxidation of PPY. In steady-state voltammetry of ferricyanide, the nanostructured electrodes behave as a random array of microscopic nodules and pores. At potential scan rates of 0.050 V s −1 diffusion fields at the 300–600 nm nodules on the 7 μm diameter microdisk electrode overlap. The surface area of the electroactive nanofeatures decreases after deposition of insulating OPPY. Kinetics of ferricyanide at bare and OPPY-coated nanostructured electrodes reflect the electrode surface area, as predicted by the model for charge transfer at a partially blocked surface. A model reflecting the 58–94% coverage of the nanostructured electrodes by OPPY was developed to address the high permeability of the porous OPPY-coated microdisk electrodes.

Simultaneous Determination of Ascorbic Acid and Uric Acid in Blood Serum Using an Overoxidized Polypyrrole Film Modified Glassy Carbon Electrode

The present study reports the simultaneous determination of ascorbic acid (AA) and uric acid (UA) at pH = 7.0 using an overoxidized polypyrrole (OPPy) modified glassy carbon electrode (GCE). The bare GCE does not separate the voltammetric signals of AA and UA, whereas OPPy-modified GCE not only can completely separate the overlapped oxidation peaks of AA and UA but also dramatically enhances their oxidation currents compared with the bare GCE. Factors influencing determination including pH and scan rate were optimized. A linear response was observed in the concentration range from 7.7 × 10−7 to 2.1 × 10−5 M and 3.8 × 10−5 to 1.1 × 10−3 M with a correlation coefficient of 0.998 and 0.999 for UA and AA, respectively. The detection limit calculated was 7.2 × 10−7 for UA and 1.6 × 10−5 M for AA. The relative standard deviations (R.S.D.) for the oxidation of 7.5 × 10−4 M AA and 5.0 × 10−5 M UA are 3.5% and 1.1%, respectively. The application of the modified electrode was demonstrated by measuring the concentration of UA and AA in human blood serum.

Characterization of a very thin overoxidized polypyrrole membrane: application to H2O2 determination

AbstractIn the design of amperometric biosensor based on the electrochemical detection of enzymatically generated H2O2, an inert membrane is often present on the electrode in order to separate it from the solution to prevent interferences. The inert membrane could be an overoxidized polypyrrole film. Generally, the overoxidized polypyrrole films are obtained in two steps, the first one being the electrosynthesis of the polypyrrole film and the second one its overoxidation in an indifferent electrolyte. In this article, a new electrochemical one‐step process allowing the formation of a very thin overoxidized polypyrrole film is used. This film is characterized by SEM, XPS and cyclic voltammetry in the presence of monoelectronic reversible redox couples. Actually, the film is an electrical insulating compact layer about 10‐nm thick and pin hole free. This overoxidized polypyrrole membrane was tested on one hand for the rejection of anions and large molecules such as Fe(CN)63/4− and Ru(NH3)62/3+, respectively, and on the other hand, for the determination of hydrogen peroxide. The results show a very good efficiency of the membrane for the rejection of the redox species tested. Finally, it is shown that the membrane/Pt electrode allows quantitative electrooxidation of H2O2. Indeed, using this electrode, under potentiostatic condition, a linear response of the anodic current in function of the H2O2 electrolyte concentration was found. Copyright © 2010 John Wiley & Sons, Ltd.

Molecularly imprinted polypyrrole prepared by electrodeposition for the selective recognition of tryptophan enantiomers

AbstractHerein we report the electrosynthesis of polypyrrole with L‐tryptophan (L‐Trp) as a template to prepare molecularly imprinted polymers (MIPs). Overoxidized polypyrrole films with cavities complementary to the template were used for the enantioselective detection of L‐Trp and D‐tryptophan (D‐Trp). Important parameters, such as the electropolymerization potential, overoxidization potential and time, thickness of the polypyrrole films, and scanning rate of the stripping voltammetric experiments, were varied to achieve an optimum sensor response. We found that L‐Trp was inserted about 2 times higher into the imprinted polymer film than D‐Trp. Also, in this study, an electrochemical quartz crystal microbalance technique was used to investigate the performance of overoxidized polypyrrole films. The enantioselectivity of the MIPs was attributed to the cavities in the imprinted films, which were complementary to the target molecules, both in shape and in positioning of the functional groups. The results also suggest the feasibility of preparing MIPs by electropolymerization for the enantioselective recognition of other amino acid enantiomers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Electrosynthesized molecularly imprinted polypyrrole films for enantioselective recognition of l-aspartic acid

The electrosynthesis, overoxidation and characterization of l-aspartic acid ( l-Asp) imprinted polypyrrole (PPy) films have been performed by using electrochemical quartz crystal microbalance (EQCM). Following the determination of the optimal electrosynthesis parameters for the formation of a smooth and uniform PPy/ l-Asp films, the overoxidized polypyrrole (oPPy) matrix templated with either l- or d-aspartic acid ( l-, d-Asp) was evaluated as a potential enantioselective recognition element. Under potentiodynamic conditions and in strongly acidic media a significantly higher sensitivity of the l-Asp acid imprinted overoxidized polypyrrole film (oPPy/ l-Asp) for l-Asp than d-Asp was observed. The results suggest the feasibility of preparing molecularly imprinted films by electropolymerization for the enantioselective recognition of amino acids and the suitability of EQCM for both monitoring the selective recognition as well as to electrochemically modulate the binding process.

Glucose Biosensor Based on Immobilization of Glucose Oxidase in Electrochemically Polymerized Polytyramine Film and Overoxidised Polypyrrole Film on Platinized Carbon Paste Electrode

An amperometric glucose biosensor has been developed based on immobilization of glucose oxidase (GOD) in electrochemically polymerized polytyramine (PTY) and overoxidised polypyrrole (OPPY) on platinized carbon paste electrode (PCPE). By providing a large apparent surface area with the micropores of the electrodeposited platinum particles on the PCPE, GOD was added, and the sensor was more sensitive. Owing to the polymerized polytyramine film and overoxidised polypyrrole film on the PCPE, the sensor was more anti-interferential and more stable. The sensor responds to β-D-glucose linearly over a concentration range of 1 × 10 −5–1.8 × 10 −2 M, and the detection limit is 5 × 10 −6 M. The response time of the sensor is less than 10 s, and the life time is over 2 months. Due to the permselective characteristics of PTY film and OPPY film, the effects of electroactive interferents, such as ascorbic acid, uric acid, and fructose, can be significantly reduced.

Electrodeposition of gold nanoclusters on overoxidized polypyrrole film modified glassy carbon electrode and its application for the simultaneous determination of epinephrine and uric acid under coexistence of ascorbic acid

A novel biosensor was fabricated by electrochemical deposition of gold nanoclusters on ultrathin overoxidized polypyrrole (PPyox) film, formed a nano-Au/PPyox composite on glassy carbon electrode (nano-Au/PPyox/GCE). The properties of the nanocomposite have been characterized by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and electrochemical investigations. The nano-Au/PPyox/GCE had strongly catalytic activity toward the oxidation of epinephrine (EP), uric acid (UA) and ascorbic acid (AA), and resolved the overlapping voltammetric response of EP, UA and AA into three well-defined peaks with a large anodic peak difference. The catalytic peak currents obtained from differential pulse voltammetry increased linearly with increasing EP and UA concentrations in the range of 3.0 × 10 −7 to 2.1 × 10 −5 M and 5.0 × 10 −8 to 2.8 × 10 −5 M with a detection limit of 3.0 × 10 −8 and 1.2 × 10 −8 M ( s/n = 3), respectively. The results showed that the modified electrode can selectively determine EP and UA in the coexistence of a large amount of AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The nano-Au/PPyox/GCE has been applied to determination of EP in epinephrine hydrochloride injection and UA in urine samples with satisfactory results.

Flow injection determination of choline in milk hydrolysates by an immobilized enzyme reactor coupled to a selective hydrogen peroxide amperometric sensor

A choline oxidase (ChO) immobilized enzyme reactor (IMER) prepared by glutaraldehyde coupling of the enzyme on aminopropyl modified controlled pore glass beads is described. The ChO–IMER was coupled, in a flow injection configuration system, to an interference free hydrogen peroxide amperometric sensor based on a Pt surface modified by an overoxidized polypyrrole film. The resulting analytical device responds selectively to choline and displays a sensitivity of 46.9 ± 0.2 μC mM −1 and a limit of detection, calculated at a signal-to-noise ratio equal to 3, of 7 μM. Sensitivity remains constant for about 20 days and then starts to slowly deteriorate and after 2 months a 70% of the initial sensitivity was still retained. The application to choline determination in milk hydrolysates is demonstrated. Short- and long-term drift observed in the analytical response can be corrected by a bracketing technique.

Electrocatalytic oxidation of hydrazine at overoxidized polypyrrole film modified glassy carbon electrode

Electrocatalytic oxidation of hydrazine (HZ) was studied on an overoxidized polypyrrole (OPPy) modified glassy carbon electrode using cyclic voltammetry and chronoamperometry techniques. The OPPy-modified glassy carbon electrode has very high catalytic ability for electrooxidation of HZ, which appeared as a reduced overpotential in a wide operational pH range of 5–10. The overall numbers of electrons involved in the catalytic oxidation of HZ, the number of electrons involved in the rate-determining and diffusion coefficient of HZ were estimated using cyclic voltammetry and chronoamperometry. It has been shown that using the OPPy-modified electrode, HZ can be determined by cyclic voltammetry and amperometry with limit of detection 36 and 3.7 μM, respectively. The results of the analysis suggest that the proposed method promises accurate results and could be employed for the routine determination of HZ.

Overoxidized polypyrrole film directed single-walled carbon nanotubes immobilization on glassy carbon electrode and its sensing applications

In this paper, the films of overoxidized polypyrrole (PPyox) directed single-walled carbon nanotubes (SWNTs) have been electrochemically coated onto glassy carbon electrode (GCE). Electroactive monomer pyrrole was added into the solution containing sodium dodecyl sulfate (SDS) and SWNTs. Then, electropolymerization was proceeded at the surface of GCE, and a novel kind of conducting polymer/carbon nanotubes (CNTs) composite film with the orientation of CNTs were obtained correspondingly. Finally, this obtained polypyrrole (PPy)/SWNTs film modified GCE was oxidized at a potential of +1.8V. It can be found that this proposed PPyox/SWNTs composite film modified GCE exhibited excellent electrocatalytic properties for some species such as nitrite, ascorbic acid (AA), dopamine (DA) and uric acid (UA), and could be used as a new sensor for practical applications. Compared with previous CNTs modified electrodes, SWNTs were oriented towards the outside of modified layer by PPyox and SDS, which made the film easily conductive. Moreover, this proposed film modified electrode was more stable, selective and applicable.

One-Step Electrochemical Synthesis of a Very Thin Overoxidized Polypyrrole Film

Generally, the electrochemical oxidation of pyrrole results in polypyrrole film in its doped conducting form. In this paper, it is shown that, in the presence of weak-acidic anions, pyrrole electro-oxidation leads to the formation of a very thin nonconducting overoxidized polypyrrole film. This phenomenon is due to the release of protons at the electrode/electrolyte interface during pyrrole oxidation. XPS analyses confirm (i) the film does not contain doping anions and (ii) the presence of carbonyl bonds; both features are characteristic of overoxidized polypyrrole. © 2007 The Electrochemical Society.

An electroenzymatic l-glutamate microbiosensor selective against dopamine

In designing an amperometric l-glutamate biosensor based on the electrochemical detection of enzymatically generated H2O2, the key challenges are selectivity against electrooxidizable interferents, micromolar detection limit, and response time of seconds or less. With these issues in mind, a glutamate microbiosensor consisting of Pt black (PtBlk) electrodeposited on a 125-μm-dia. Pt wire with a permselective film of electropolymerized, overoxidized polypyrrole (OPP) and a top layer of l-glutamate oxidase (l-GluOx) crosslinked with glutaraldehyde was constructed. The OPP film permits passage of H2O2 to the electrode surface while rejecting the common interferents of brain extracellular fluid, ascorbate (AA) and dopamine (DA). The PtBlk treatment of Pt electrodes was adopted since the microscale roughness of PtBlk increases the effective surface area of the electrode and promotes electrochemical H2O2 oxidation at lower potential. This microbiosensor was highly sensitive (80 ± 10 nA μM−1 cm−2) to l-glutamate at 450 mV versus Ag/AgCl, a significantly lower potential than the ∼700 mV used with most similar l-glutamate sensors prepared on polished Pt electrodes. Notably, microbiosensor response to both AA and DA was undetectable at concentrations exceeding physiological extracellular concentrations of these compounds. The described l-glutamate biosensor also showed excellent response time (∼1–2 s) and temporal stability (∼3 week half-life). In addition, this microbiosensor was robust enough for insertion into live brain tissue where it responded rapidly to l-glutamate, but was insensitive to dopamine.

Molecular Recognition for Bile Acids Using a Molecularly Imprinted Overoxidized Polypyrrole Film

An electrochemical technique for preparation of a molecularly imprinted overoxidized polypyrrole (oPPy) film and its recognition property for bile acids are investigated, aiming for application to a bile acid sensor and clarification of the principle of the recognition mechanism with the quartz crystal microbalance. The molecularly imprinted oPPy has been prepared through a potentiodynamical overoxidation process in an alkaline solution from a taurocholate (TC) doped polypyrrole (PPy) film grown on an Au electrode. The molecularly imprinted film exhibited a high selectivity and sensitivity toward bile acids. Cholate, chenodeoxycholate, deoxycholate, TC, and artificially synthesized dehydrocholate showed a linear relationship between the resonance frequency and their logarithmic concentrations in a range from with detection limits for trace concentrations . The sensitivity of an oPPy film imprinted with TC increased in the sequence of TC , and was found to depend on the molecular volume of bile acids (increasing in the sequence ).

Polymer films as permselective coatings for H 2O 2-sensing electrodes

The performance of amperometric biosensors based on oxidation of the H 2O 2 generated by an oxidase suffers frequently from interference due to electrooxidizable species in a sample. For example, an effective biosensor of this type for the neurotransmitter, glutamate, in brain extracellular fluid (ECF) should show little or no amperometric response to readily oxidizable dopamine (DA) and ascorbate (AA), which are common constituents of ECF. In this work, platinum electrodes treated with four different polymeric, permselective films are compared quantitatively in terms of sensitivity to H 2O 2, DA and AA; and selectivity for H 2O 2 relative to either interferent. Here, the selectivity is defined as the ratio of the H 2O 2 sensitivity to the interferent sensitivity. Platinum electrodes coated with electrodeposited, overoxidized polypyrrole (OPP) and polyphenylenediamine films display H 2O 2 selectivities relative to AA of ⩾130 and ⩾240, respectively, and relative to DA of ⩾100 and 80, respectively. The impressive rejection of DA by OPP films observed in this study contrasts with published results showing enhanced DA permeability of polypyrrole electrode coatings. Nafion- and polyaniline-coated electrodes give inferior selectivity performance. The OPP-treated electrodes are judged superior overall given the best combination of H 2O 2 sensitivity (390 nA μM −1 cm −2), detection limit (0.5 μM), response time (∼5 s), and stability (>2 weeks), in addition to high H 2O 2 selectivities.

Overoxidized polypyrrole film directed DNA immobilization for construction of electrochemical micro-biosensors and simultaneous determination of serotonin and dopamine

A promising electrochemical microsensor was fabricated by electrochemical immobilization of calf-thymus DNA on a carbon fiber electrode (CFE) through an overoxidized polypyrrole (PPyox) template for simultaneous determination of serotonin (5-HT) and dopamine (DA). Such a DNA–PPyox biocomposite modification layer of nano-thickness exhibited superior selectivity and sensitivity towards these neuronal amines comparing with a simple PPyox or DNA coating. This microsensor gave three separated differential pulse voltammetric (DPV) peaks at 0.38, 0.20 and −0.02 V for 5-HT, DA and 25,000-fold excess of ascorbic acid (AA). The linear response was obtained in the range of 1.0 × 10 −8 to 1.0 × 10 −6 M with a detection limit of 7.0 × 10 −9 M for 5-HT, and in the range of 3.0 × 10 −7 to 1.0 × 10 −5 M with a detection limit ( s/ n = 3.0) of 5.0 × 10 −8 M for DA. A stronger interaction of 5-HT with the modification layer was observed, which led to a higher detection sensitivity for 5-HT than for DA. The utility of this modified electrode was demonstrated by the determination of 5-HT and DA in human blood serum.

Preparation of sulfonated overoxidized polypyrrole film applicable as an SPME tool for cationic analytes

The use of a solid-phase microextraction (SPME) method with a new design of functionalized stable overoxidized sulfonated polypyrrole (OSPPy) film electrode to extract metal ions (Ni(II) and Cd(II)) without derivatization from water of high saline content is described. Different cation uptake behavior is obtained for OSPPy and overoxidized polypyrrole. The cation uptake and release properties of the OSPPy film electrode were examined under both open circuit and controlled potential conditions for prospective applications in electrochemically controlled solid-phase microextraction (EC-SPME). The cation uptake is enhanced if a positive potential is applied to the electrode. Accumulated cations are released rapidly from the film if the applied potential is switched to a negative value. The cation uptake and release mechanism is affected both by the cation exchange at the negative sulfonate and carboxylate groups on the film and by the altered solution pH occurring at the counter electrode caused by the applied potential. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) measurements on the two films have confirmed the presence of a sulfur content in the films and shown that covalently bound sulfonate preferentially dopes the polymer even in the presence of a large excess of BF 4 − anions. Our preliminary fundamental results show that this new polymer offers a wide potential range for electroanalytical exploration from selective electrodes to separation and/or preconcentration sampling devices.

Fabrication Process and Characterization of a Novel Structural Isomer Sensor

The preparation process of a molecularly imprinted overoxidized-polypyrrole film has been studied with the quartz crystal microbalance. The film has been derived from 1-naphthalenesulfonate (1-NS)-doped polypyrrole through overoxidation. The extraction of I-NS (dedoping) has created a shape-complementary cavity at the surface. The resulting overoxidized-polypyrrole film imprinted with 1-NS exhibited an excellent selectivity to the structural isomer, 1-NS. Aqueous 0.010 M 1-NS showed a frequency decrease of 110 Hz, while 2-NS shows only a negligible change. Thus, the shape-complementary cavity can recognize the difference in the spatial configuration of the SO - 3 substituent between the 1 and 2 positions.