Electropolymerization Of O-phenylenediamine Research Articles

Development and characterization of an electrochemical sensor for furosemide detection based on electropolymerized molecularly imprinted polymer

A novel electrochemical sensor based on a molecularly imprinted polymer, poly(o-phenylenediamine) (PoPD), has been developed for selective and sensitive detection of furosemide. The sensor was prepared by incorporating of furosemide as template molecules during the electropolymerization of o-phenylenediamine on a gold electrode. To develop the molecularly imprinted polymer (MIP), the template molecules were removed from the modified electrode's surface by washing it with 0.25molL−1 NaOH solution. The imprinted layer was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The sensor′s preparation conditions including furosemide concentration, the number of CV cycles in the electropolymerization process, extraction solution of the template from the imprinted film, the incubation time and the pH level were optimized. The incubation of the MIP-modified electrode, with respect to furosemide concentration, resulted in a suppression of the K4[Fe(CN)6] oxidation process. Under the optimal experimental conditions, the response of the imprinted sensor was linear in the range of 1.0×10−7–7.0×10−6molL−1 of furosemide. The detection limit was obtained as 7.0×10−8molL−1 for furosemide by using this sensor. The sensor was successfully used to determine the furosemide amount in the tablet and in human urine samples with satisfactory results.

Molecularly imprinted polymer-based sensors for atrazine detection by electropolymerization of o-phenylenediamine

A sensitive and selective atrazine (ATZ) electrochemical sensor was developed based on a molecularly imprinted polymer (MIP).

A gold nanoparticle functionalized multiwalled carbon nanotube–poly(o-phenylenediamine) composite film for glucose biosensing applications

A new biosensor based on immobilization of glucose oxidase on a multiwalled carbon nanotube–gold nanoparticle coated glassy carbon electrode (GCE) was fabricated for the electrochemical determination of glucose. First, a carboxylated multiwalled carbon nanotube (cMWCNT) was functionalized with 4-aminothiophenol (ATP) by a coupling agent, N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, and then gold nanoparticles (AuNPs) were covalently linked to the ATP–cMWCNT via the formation of a covalent Au–S bond. Finally, glucose oxidase was immobilized simultaneously by the electropolymerization of o-phenylenediamine on the AuNP–ATP–cMWCNT coated GCE. The biosensor showed a linear range from 0.05 mM to 8.85 mM with a sensitivity of 27.93 μA mM−1 cm−2 and a detection limit of 0.015 mM for the detection of glucose. The biosensor was successfully applied to estimate the glucose concentration in human blood serum samples. Furthermore, the AuNP–ATP–cMWCNT was investigated for the non-enzymatic detection of hydrogen peroxide by using voltammetric and amperometric techniques, indicating a linear relationship in the range of 5 × 10−3 to 13.10 mM.

A β2-agonist sensor based on a molecularly imprinted poly-o-phenylenediamine film on a columnar-structured platinum electrode

A novel strategy for preparing highly sensitive molecularly imprinted sensors based on the electro-polymerization of o-phenylenediamine (o-PD) on a columnar-structured platinum (CSPt) electrode was proposed for β2-agonist determination. The CSPt electrode was used as a working electrode to increase the specific surface area and to extend the linear range. The sensor surface morphology was characterized by scanning electron microscopy. The preparation process of the sensor was characterized by an electrochemical quartz crystal microbalance. The electrochemical performance of the sensor was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. Additionally, sodium dodecyl sulfonate, which was used in the electro-polymerization reaction of o-PD, prevented the hydrolysis degradation of poly-o-phenylenediamine (PoPD) and enhanced the stability of the PoPD film in the anionic micellar media. The recognition and determination of the sensor were carried out by measuring the changes of the amperometric response of [Fe(CN)6]3−/4−. The proposed sensor was successfully applied to detect β2-agonists in real human serum samples.

An electrochemical sensor for dopamine based on poly(o-phenylenediamine) functionalized with electrochemically reduced graphene oxide

The electropolymerization of o-phenylenediamine was performed on an electrochemically reduced graphene oxide (E-RGO)/glass carbon electrode (GCE) (E-RGO/GCE). It was found that this novel poly(o-phenylenediamine) (PoPD)/E-RGO (PoPD/E-RGO) hybrid composite showed good electrocatalytic activity toward dopamine (DA) and good specificity for the detection of DA without interference from ascorbic acid (AA) or uric acid (UA). Differential pulse voltammetry was used for the electrochemical DA detection. The response peak current for the electrochemical sensor was linear over the ranges of 10 to 400 μM (r = 0.996) and 400 μM to 800 μM (r = 0.997). The detection limit was estimated to be 7.5 μM. The electrochemical sensor also exhibited good stability. In addition, the electrochemical sensor was successfully applied to the detection of DA in human urine samples using the standard adding method with satisfactory results.

Fabrication of Minimally-Invasive Patch Type Glucose Sensors

A fine tube type glucose sensor, which has a sensing region at the inside wall of fine tube tip, was prepared and applied for minimally invasive glucose monitoring. The enzyme glucose oxidase was immobilized on the platinum surface located in the tube by the combination of electrodeposition and electropolymerization of o-phenylenediamine. Amperometric responses of the prepared electrodes to glucose were measured at a potential of 0.60 V (vs Ag/AgCl). The tube type electrode showed good response with good linear relationship up to the glucose concentration of 22.4 mM, which was actually higher than general sensor without outer film for permeability restriction. This may be due to it unique sensor structure.

Highly selective and stable microdisc biosensors for l-glutamate monitoring

Glutamate mediates most of the excitatory synaptic transmission in the brain, and its abnormal regulation is considered a key factor underlying the appearance and progression of many neurodegenerative and psychiatric diseases. In this work, a microdisc-based amperometric biosensor for glutamate detection with highly enhanced selectivity and good stability is proposed. The biosensor utilizes the enzyme glutamate oxidase which was dip-coated onto 125μm diameter platinum discs. To improve selectivity, phosphatidylethanolamine was pre-coated prior to enzyme deposition, and electropolymerization of o-phenylenediamine was performed to entrap the enzyme within a polymer matrix. A variety of coating configurations were tested in order to optimize biosensor performance. For stability measurements, biosensors were biased continuously and calibration curves calculated each day for a period of 5–6 days. The optimized biosensors exhibited very high sensitivity (71±1mAM−1cm−2), low detection limit of ∼2.5μM glutamate, selectivity (over 87% against ascorbic acid), very good temporal stability during continuous use, and a response time of <5s. These biosensors are therefore good candidates for further development as devices for continuous monitoring during traumatic brain injury or neurosurgery.

Electrochemical and Mass Change Study of the Growth of Poly-(o-Phenylenediamine) Films on Au Substrates

The electropolymerization of o-Phenylenediamine (oPDA), both in the absence and presence of Fe3+ in solution, was investigated in detail using cyclic voltammetry concurrently with the quartz crystal microbalance (QCMB) technique. It is shown that a set of redox peaks (A1/C1), seen between 0.05 and 0.4 V is characteristic of the phenazine-like PoPDA polymer, produced by the irreversible radical oxidation of the oPDA monomer at a Au surface and forming an oPDA radical cation that initiates the polymerization step at >0.8 V vs. RHE. The QCMB results showed that ca. 20% of the oxidized product deposits on the Au surface as a redox-active polymer film, with charge compensation by H+ injection/expulsion along with some inhalation/exhalation of water. The presence of Fe3+ in solution during electropolymerization led to very similar electrochemistry, with ca. 50% of the oxidized product forming the redox-active polymer film. The PoPDA films are very smooth and uniform, while films formed in the presence of Fe3+ are coated with Fe-containing nodules ca. 0.8 μm in diameter, which hinder the further growth of the PoPDA film.

The electrochemical synthesis of poly(o-phenylenediamine) on stainless steel and its corrosion protection ability in 3.5 % NaCl solution

In this study, electrochemical synthesis of poly(o-phenylenediamine) (PoPDA) on 316L stainless steel and its corrosion inhibition effect were studied. Electropolymerization of o-phenylenediamine (oPDA) was carried out by a potentiodynamic method using 0.5 M H2SO4 solution containing 0.05 M oPDA monomer. The corrosion protection ability of the PoPDA in 3.5 % NaCl was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, and change of open circuit potential with immersion time (EOCP − t). The results showed that PoPDA acted as a protective layer on stainless steel against corrosion in 3.5 % NaCl solution.

Electrochemical Sensors for L-Tryptophan Based on Molecularly Imprinted Polymers

A novel sensing element for direct detection of L-Tryptophan (L-Trp) in human serum was proposed by combination of electrochemical transduction and molecular imprinting technique. The sensing element was prepared by electropolymerization of o-phenylenediamine (o-PD) on the gold electrode in the presence of template L-Trp. The electrochemical property of the sensor was characterized by differential pulse voltammetry (DPV). The linear response range of the sensor for L-Trp concentration was 1×10-8 mol/L~21×10-8 mol/L with a detection limit of 0.3×10-8 mol/L. The results show that this approach has the potential to generate a universal inexpensive assay methodology of high sensitivity, specificity and simplicity to detect L-Trp.

Electrochemical sensor of 4-aminobutyric acid based on molecularly imprinted electropolymer

A simple and effective procedure based on a molecularly imprinted polymer (MIP) was developed for preparing a selective 4-aminobutyric acid (4-ABA) sensor. The sensitive layer was prepared by electropolymerization of o-phenylenediamine (o-PD) on a gold electrode in the presence of 4-ABA, which acts as a template. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) measurements were used to monitor the process of electropolymerization. The molecularly imprinted sensor was tested by CV as well as DPV to verify the changes of redox currents of hexacyanoferrate. The concentration of 4-ABA in the range of 0.2–20.0 μmol L−1 can be determined with a detection limit of 0.08 μmol L−1 (defined as S/N = 3) under the optimum conditions. The MIP sensor shows high selectivity, sensitivity and reproducibility. The results from sample analysis indicate that the MIP-4-ABA sensor can be used for quantitative analysis.

One-dimensional composites based on single walled carbon nanotubes and poly(o-phenylenediamine)

The direct mixing of aqueous ferric chloride and o-phenylenediamine (OPD) solution at room temperature in the absence and presence of carbon nanotubes (CNTs) has been used to prepare poly(o-phenylenediamine) (POPD) micro-fibers and composites of the type CNTs/POPD having nanotubes incorporated in polymer fiber mass. Using surface enhanced infrared absorption (SEIRA) spectroscopy significant modifications in the low frequency range of the polymer spectrum are revealed when Au is used as metallic support. Similar variations are reported for the POPD samples prepared by the electropolymerization of OPD onto rough Au electrode. A covalent functionalization of CNTs with POPD and a doping process of POPD with radical anions of CNTs is proved by surface enhanced resonant Raman scattering and SEIRA spectroscopy. The X-ray diffraction (XRD) studies indicate a high crystallinity both for POPD and CNTs/POPD composites prepared by chemical or electrochemical methods.

Electrocatalytic oxidation of methanol on carbon ceramic electrode modified by platinum nanoparticles incorporated in poly (o-phenylenediamine) film

Carbon ceramic electrode, a new electrode substrate, was prepared by sol–gel procedure and used for the electropolymerization of o-phenylenediamine and incorporation of platinum nanoparticles into the resulting poly(o-phenylenediamine) (PoPD) film. The modified electrode was used for electrooxidation of methanol in 0.3 M H2SO4 as supporting electrolyte. The presence of PoPD film increased considerably the efficiency of deposited Pt nanoparticles toward the electrocatalytic oxidation of methanol. The effective parameters on the electrooxidation of methanol, i.e., amounts of polymer and Pt catalyst, medium temperature, working potential limit in anodic direction, and potential scan rate, were investigated, and the results were discussed.

Ultrathin, Protective Coatings of Poly(o-phenylenediamine) as Electrochemical Proton Gates: Making Mesoporous MnO2 Nanoarchitectures Stable in Acid Electrolytes

We have created hybrid organic−inorganic nanoarchitectures by electrodepositing ultrathin (<10-nm-thick) polymer coatings onto nanostructured MnO2 birnessite-type electrodes with surface areas in excess of 200 m2 g-1. By choosing a self-limited growth process, based on the electropolymerization of o-phenylenediamine, the resulting polymer conformally coats the oxide nanoscale network without disrupting the continuous mesoporosity of the initial MnO2 nanoarchitecture. These polymer coatings serve as pinhole-free physical barriers to external, acidic electrolyte, specifically, H2O and hydrated protons, and protect the underlying MnO2 nanoarchitecture from dissolution. The underlying metal oxide remains electrochemically addressable via an electrochemical proton-gating mechanism in which charge-compensating unsolvated protons are transported through the polymer coating. The 3D-templated electrochemical fabrication of polymer at an electrified metal oxide nanoarchitecture provides a new model for the developm...

Characterization of soluble oligomers produced by electrochemical oxidation of o-phenylenediamine by electrospray ionization sequential mass spectrometry.

Soluble species generated during the electropolymerization of o-phenylenediamine (o-PD) on platinum electrodes in aqueous buffers at different pH values were investigated by electrospray ionization ion trap sequential mass spectrometry (ESI-ITMS(n)). The main protonated molecules (MH(+)) detected in the full scan ESI-MS spectra of the electrolytic solutions were isolated in the ion trap and sequentially fragmented (MS(n), with n up to 5) to obtain fragmentation patterns. The latter led to hypotheses as to the molecular structures of the soluble products of o-PD electropolymerization; it appeared that all of them are actually oligomeric species in different oxidation states. In particular, o-PD dimers, trimers and tetramers could be identified and three common structural features were found, namely: the presence of phenazine, 1,4-benzoquinonediimine, and secondary amine (acting as bridges between benzene rings) units. These findings are in agreement with those already reported for the surface structure of the polymeric films formed on the platinum electrodes during o-PD polymerization, thus suggesting that a close relationship exists between the soluble oligomers and the polymer itself.

Capacitive detection of glucose using molecularly imprinted polymers

A novel glucose biosensor based on capacitive detection has been developed using molecularly imprinted polymers. The sensitive layer was prepared by electropolymerization of o-phenylenediamine on a gold electrode in the presence of the template (glucose). Cyclic voltammetry and capacitive measurements monitored the process of electropolymerization. Surface uncovered areas were plugged with 1-dodecanethiol to make the layer dense, and the insulating properties of the layer were studied in the presence of redox couples. The template molecules and the nonbound thiol were removed from the modified electrode surface by washing with distilled water. A capacitance decrease could be obtained after injection of glucose. The electrode constructed similarly but with ascorbic acid or fructose only showed a small response compared with glucose. The stability and reproducibility of the biosensor were also investigated.

Electrochemical Deposition of Poly(o-phenylenediamine) Films on Type 304 Stainless Steel

Adherent electroactive films of poly(o-phenylenediamine) (PPD) were obtained by electropolymerization of o-phenylenediamine (o-PD) on 304 stainless steel under potentiostatic conditions. The in situ Fourier transform infrared reflectance spectroscopy study suggests a phenazine ring ladder-structure polymer. Open circuit potential and potentiodynamic studies of PPD-coated steel electrodes, in chloride aqueous solution show a positive shift of the corrosion potential. © 2001 The Electrochemical Society. All rights reserved.

Electrochemical assembly of nano-organized poly- o-phenylenediamine films

Potential-dependent surface-enhanced Raman scattering spectra reveal that the orientation of o-phenylenediamine (OPD) molecules adsorbed on a Au electrode depends on the electrode potential and electropolymerization of OPD can be carried out at +0.3 V. The electrochemical-assembly technique was successfully applied to the fabrication of a nano-structured o-phenylenediamine oligomer (POPD) film on a bare Au substrate and on a p-aminothiophenol (PATP) self-assembled Au substrate in phosphate buffer solution (pH=7.0). Electrochemistry and scanning tunneling microscopy measurements indicate that a POPD/Au(111) surface displays a nano-scale dot array structure. At the same time, a POPD/PATP/Au(111) surface shows a nano-scale line array structure.

Studies of the formation and redox transformation of poly( o-phenylenediamine) films using a quartz crystal microbalance

The electropolymerization of o-phenylenediamine on gold and the redox behaviour of poly( o-phenylenediamine) films were studied in acid media using the electrochemical quartz crystal microbalance technique. It was established that the film formation is not an autocatalytic process and takes place mainly during the negative-going potential scan. The results indicate that the films are swollen by solvent molecules and ions in both reduced and oxidized states, and the extent of swelling increases with film thickness. At least two electron transfer steps should be considered in the redox mechanism. In the first oxidation step anion insertion and/or proton expulsion occur, while in the second oxidation step anions and/or protons are expelled. The magnitude of the mass changes accompanying the redox transformations depends on the pH of the bulk solution, which indicates that protonation—deprotonation processes play an important role in the overall mechanism. Dimerization of sites of different oxidation states may also occur. A counter-flux of water molecules can be assumed during the second oxidation step, i.e. the fully oxidized films are more hydrated.

The performance of sintered TiO 2-x electrodes and the electrochemical polymerization of O-phenylene diamine at surface imperfections

TiO 2-x electrodes were fabricated under atmospheric conditions using the ceramic method at 1400°C. Photoelectrochemical and capacitance measurements permitted verification of the relation of the performance of such electrodes to the presence of surface imperfections. The electropolymerization of o-phenylene diamine ( OPD ) on TiO 2-x ceramic electrodes in the dark was investigated and compared with the electropolymerization of OPD on smooth platinum electrodes. The results indicate that polymerization occurs only on the surface imperfections of the TiO 2-x semiconductor and effectively blocks the electrode surface and prevents electron exchange with the solution. The photoelectrical response of electrodes subjected to this treatment shows the decrease of the dark current intensity in the potential region of oxygen adsorption in comparison with untreated electrodes. The flat band potential determined from Mott-Schottky plots did not correlate well with the potential for the onset of anodic photocurrent and photopotential. Evidence for the electrochemical incorporation of hydrogen in the oxide and oxide surface reduction are discussed.