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The behavior of novel electroactive material based on reduced graphene oxide (RGO), poly-o-phenylenediamine (PPD), and silicotungstic acid (SiW) is studied using the methods of cyclic voltammetry (CVA) and electrochemical impedance. It is found that graphene oxide (GO) has a catalytic effect on the electrochemical codeposition of PPD and SiW onto the GO film during fabricating the RGO–PPD–SiW composite. It is shown that the composite has at least six redox transitions depending on the chosen range of cycling potentials. It is found that, at the potentials of 200 and 500 mV (Ag/AgCl), the conductivity of the composite is by 4 orders of magnitude higher than that of PPD. By the example of quinone-hydroquinone and ferro-ferricyanide redox reactions, it is shown that, in this potential range, the composite exhibits electrocatalytic properties, though neither PPD nor SiW individually exhibit pronounced redox transitions in this potential range.

The methods of silicotungstic acid (SiW) immobilization on conducting substrates were studied. For SiW immobilization by codeposition, poly-o-phenylenediamine (PPD) redox polymer was used. The most effective codeposition of SiW and PPD was demonstrated on a graphene oxide (GO) film. Meanwhile, GO is reduced to form RGO-PPD-SiW electroactive composite. The structure of the novel material was evidenced by cyclic voltammetry and IR and Raman spectra. PPD-SiW and RGO-PPD-SiW composites were studied by impedance spectroscopy, where an equivalent circuit was proposed. Film resistance Rf was shown to decrease in the series of PPD → RGO-PPD → RGO-PPD-SiW. Further, RGO-PPD-SiW has better transfer properties (bulk film diffusion rate). This enabled suggesting that the composite has better electrocatalytic properties than PPD and RGO-PPD as was evidenced for example of [Fe(CN)6]4−/3− redox transfer on the electrode coated with the novel material.

The possibility of using a reduced form of graphene oxide (RGO) and unreduced form of graphene oxide (GO) as a potential basis to be used for “designing” supramolecular structures was illustrated by the example of three different types of particles. As it can form bonds of various nature, GO may be also used (being in the reduced form) as an electrically conducting component of a composite and (remaining in the non-conducting oxidized form) as an accumulator of any particles. The electrochemical behavior of the obtained composites was studied.

The formation of a nanocomposite coating based on reduced graphene oxide (RGO) and poly(o-phenylenediamine) (PPD) in the chemical reaction of graphene oxide (GO) and o-phenylenediamine (OPD) has been studied by cyclic voltammetry (CVA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It has been shown that the action of cyclic polarization provides a more uniform structure of the nanocomposite films (decrease in the corrugation effect). In addition, it has been found that the polarization of GO films containing the OPD monomer distributed inside to the PPD synthesis potentials leads to the formation of uniformly distributed globular structures, which most probably correspond to a polymer electrochemically synthesized in the space between the GO nanosheets.

The formation of the composite of reduced graphene oxide (RGO) with poly-o-phenylenediamine (PPD) on the surface of SnO2-coated conducting glasses (CG) is studied by the methods of voltammetry, atomic force microscopy (AFM), electron microscopy (SEM) with energy-dispersive X-ray spectroscopic (EDXS) microanalysis, and electron spectroscopy, When a CG with deposited graphene oxide is placed into aqueous solution of o-phenylenediamine (OPD), the monomer is strongly fixed in the GO matrix, as confirmed by EDXS data. The further redox interaction in the two-phase system GO–OPD initiates polymerization of OPD in the GO film. When anodic polarization in switched on, the oxidation and the further polymerization of OPD go on, while GO is reduced to RGO as a result of mediated reaction to yield the RGO–PPD composite even in the absence of cathodic polarization. The electron spectra of composites reveal the presence of an absorption band close to absorption of individual PPD. According to AFM and SEM data, OPD incorporated into the composite structure keeps RGO from being folded in acidic media. As the time of impregnation increases, the degree of reduction of GO to RGO changes, which is reflected in the surface morphology and the amount of monomer in the composite (RGO–PPD)-1. The coating becomes black, which is typical of RGO, and its conductivity increases by 4–5 orders of magnitude.

Formation of an electroactive composite based on graphene oxide and poly-o-phenylenediamine (PPD) was studied. Electron absorption spectra were used to confirm formation of a strong chemical bond at a prolonged contact of unreduced graphene oxide on a conducting support (glassy carbon, SnO2) and o-phenylenediamine monomer solution. Here, graphene oxide is partially reduced and oxidation and partial polymerization of o-phenylenediamine starts. It is shown that electrochemical oxidation of the obtained composite under the conditions of cyclic voltammetry results in the further polymerization of o-phenylenediamine bound to graphene oxide; here, reduction of graphene oxide continues, and at much lower cathodic potentials than in the absence of o-phenylenediamine. Morphology of the obtained composite was studied using the AFM technique. PPD embedded into the composite structure does not allow nanosheets of reduced graphene oxide (RGO) to corrugate and imparts the morphology of the composite the shape of globules with a clearly pronounced structure. As a result, the RGO–PPD composite was obtained that demonstrated pronounced electroactivity in a wider range of potentials than in the case of nonmodified PPD.

A novel electroactive composite based on silicotungstic acid (SiW), poly-о-phenylenediamine (PPD) and reduced form of graphene oxide (RGO) was prepared by electrochemical synthesis on a planar screen printed carbon electrode (SPCE) coated with graphene oxide (GO). The new material was shown to have expressed electrocatalytic activity for the example of electrochemical behavior of the p-benzoquinone/hydroquinone redox couple on the RGO-PPD-SiW-modified electrode. Unlike most composites containing heteropolyacid anions, RGO-PPD-SiW demonstrates its properties not only in an acid but also in a neutral saline solution. The potential cycling in a saline solution retains some cyclic voltammogram (CVA) peaks observed in 1 М H2SO4 environment. An addition of a local anesthetic of amide series (lidocaine, naropin, or chirocaine) to a saline solution was shown to change the CVA shape immediately. This example demonstrates that the novel composite may be further used in creating a sensor of planar design.

This work studies various methods of electrode surface modification by graphene oxide. A technique of application of reduced graphene oxide (RGO) onto the electrode in a thin-layer cell is developed. Preparation of RGO composite with the redox polymer, poly-o-phenylenediamine (PPD) is studied. Conducting RGO and RGO–PPD coatings with a developed surface are obtained; the RGO–PPD composite is an electroactive material.

This study concerns a simple method for modifying graphene oxide (GO) and its poly-o-phenylene diamine composite with palladium microparticles. When the films of graphene oxide (GO) or composite thereof with poly-o-phenylenediamine (RGO-PPD) are immersed into a solution containing palladium ions, the latter were shown to fix within the films and can be further reduced to the metal state. The changes following penetration of Pd2+ into GO and RGO-PPD films were recorded by means of cyclic voltammetry, Raman spectroscopy, and XPS. UV spectra evidenced the loss of palladium ions in the solution after immersion of GO films therein. GO appeared a good basis for creating composites with pre-selected particles that can be further used for preparing materials with target properties.

Carbonized cloth (CC) of various types was modified with silicododecamolybdic acid (SiMo), poly-o-phenylenediamine (PPD) and stratified composite thereof. As a full-value carbon material with highly developed surface, carbonized cloth with specific surface area about 15 m2/g shows good adsorption of SiMo from a solution as well as a serves a good electrode material for PPD electrosynthesis. If modified with SiMo/o-phenylenediamine (OPD) composite, CC with specific surface area about 1500 m2/g accumulates palladium ions from a solution.

Carbonized tissue (CT) was used for the first time to prepare developed surface coated with electroactive polymer. A stable monolayer of electroactive heteropolyacid was found to result from CT impregnation with silicododecamolybendic acid (SiMo) solution. Successful electrochemical oxidation of o-phenylenediamine (OPD) was first demonstrated both on pure carbonized tissue and on the tissue coated with SiMo monolayer, while the oxidation potential on both pure and impregnated CT is shifted by 0.6 V more cathode from the OPD oxidation potential on “smooth” electrodes. OPD oxidation was found to yield primarily water-soluble oligomers on pure CT and solid PPD layer on SiMo-modified tissue.

This study compares chemical and electrochemical methods of o-phenylenediamine oxidation into oligomers and their further polymerization into poly-o-phenylenediamine (PPD). Iron tetrasulfophthalocyanine oxygen complex was first demonstrated to catalyze effectively OPD oxidation with air oxygen. If catalyzed with iron tetrasulfophthalocyanine, chemical oxidation of OPD into oligomers accelerates electropolymerization.

Accumulation of palladium ions in poly-o-phenylenediamine (PPD) redox polymeric matrix was studied by means of cyclic voltammetry (CVA), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and spectroelectrochemistry. CVA and XPS studies demonstrated nitrogen atoms binding palladium cations upon impregnation of PPD film with palladium chloride solution. Higher residual reduced or partially reduced PPD form of cathodic polymer doping was shown to increase the number of palladium cations in the polymeric matrix. AFM recorded a significant effect produced to the film surface structure by intercalation of both palladium cations and metal formed by reduction of cations.

A new method is developed to prepare alladium dispersed in a polymeric matrix. Exposure of poly-o-phenylenediamine films in PdCl2 solution showed palladium cations strongly linked by the polymeric matrix to enable reduction of the metal accumulated in the polymer bulk. Optical absorption spectra were studied for poly-ophenylenediamine saturated with palladium ions and poly-o-phenylenediamine with palladium electroreduced upon impregnation. Method of X-ray photoelectron spectroscopy confirmed the presence of palladium cations in unreduced poly-o-phenylenediamine film and palladium metal upon reduction in polymeric matrix.

Various methods for modification of poly-o-phenylenediamine (PPD) redox polymer with polyaniline (PANI) electron-conducting polymer, ReO 4 − and [SiMo12O40]4− anions, and palladium clusters are compared. Participation of anions is proven in the processes of PPD synthesis and redox transformations. Formation mechanisms and properties of composites consisting of a redox polymer and electron-conducting polymer and those of two different electron-conducting polymers are compared for example of PPD-PANI and ethylene-dioxythiophene-polybithiophene. A comparison of these systems shows the main change in the potential drop to take place at the metal/polymer interface for a redox polymer and at the polymer/solution interface, for an electron-conducting polymer.

A new method for chemical production of composites based on poly-o-phenylidenediamine (PPD) by oxidizing o-phenylidenediamine (OPD) with silicomolybdic acid (SiMo) in neutral and acidic media is developed. Electrochemical and spectroelectrochemical studies reveal the presence of small deviations in the properties of composites synthesized. Cyclic voltammetry studies show that the composites are active and exhibit sufficiently high electrochemical stability. The presence of SiMo anions in the PPD matrix is confirmed by electrochemical and spectral studies in combination with x-ray microanalysis of composites. The ratio between the number of phenylazine polymeric links and heteropolyanions is found.

Poly-o-phenylenediamine films applied to ITO are modified by rhenium oxides using cyclic voltammetry in an ammonium perrhenate sulfate solution. Electrochemical and spectroelectrochemical properties of the composite thus obtained are studied. It is shown that all its components undergo reversible redox conversion.

Spectroelectrochemical properties of poly-o-phenylenediamine (PPD) and the synthesized composite of PPD and polyaniline—two chemically related polymers containing an amino-substituted benzene ring but having different conduction nature—are studied. The polyaniline synthesis on PPD-modified electrodes involves stages of the reaction initiation, the copolymer formation, and the formation of a polyaniline layer at the copolymer/solution interface.

For different samples of poly(anyline) (PAni) and poly(paraphenylene) (PPP) impregnated with electrolyte solutions the real (swelled) structure was measured. The swelled (PAni) and PPP films and powders show an appreciable internal porosity (some tens %) and a high internal surface (250–600 m2/g). The main range of pore radii is between 1 and 102–103 nm. The mean radius of single nonporous fibrils is 2–7 nm for PAni and 4–19 nm for PPP. The doping degree, the nature of the counterions and the method of preparation (chemical or electrochemical) have a considerable influence upon the porous structure. On the base of these data a model for the behaviour of electrodes from conducting polymers was established. An investigation of the kinetic behaviour of such electrodes gives the possibility to assess the intrinsic values of some important parameters: diffusion coefficients of counterions in the solid polymer phase, exchange current density of the doping-undoping reactions and the specific capacity of the polymer/electrolyte interface.

A striking difference between the kinetics of hydroquinone/p-benzoquinone redox-couple reaction on polyaniline and poly-o-phenylenediamine coated electrodes has been observed and explained in terms of the difference in equilibrium potential distribution across the polymer/solution interfaces.

Poly( p -phenylene) (PPP) films deposited from benzene in concentrated H 2 SO 4 emulsion reveal a highly crystalline structure under TEM, SEM and XDA in contrast to nearly completely amorphous films deposited from C 6 H 5 NO 2 medium. Possible effects of solvent and electrolyte specificity on the morphology and mechanical properties of PPP films are discussed in view of these results.

Redox-charging rate was shown to be reduced as a consequence of regular highly crystalline structure of electrochemically synthesized poly(p-phenylene) films.

Application of both cyclic voltammetry and rotating disc electrode technique to the study of the mechanism and kinetics of dissolved redox-species reactions (such as Fe 2+/3+ , Fe(CN) 4−/3− 6 and ce 3+/4+ ) at a Au electrode coated with poly- o -phenylenediamine (PPD) are discussed. The results show that the half-wave potential values for the reduction of these species at polymer modified electrode are distributed near the standard (formal) potential of PPD. In this case the reactions occur at the polymer/solution interface. One extra wave is observed for negatively charged redox-species due to occurrence of the reaction at the metal/polymer interface under semi-infinite diffusion conditions. The difference between the mechanism of electrochemical reactions at electrodes coated with electronically conducting and conventional redox-polymer films is connected with the difference of the equilibrium potential distribution in these two systems.

A phenomenological model for reactions of solute redox couples at electrodes covered with conducting polymer films has been proposed. The mechanism and kinetics of these reactions are strongly dependent on the difference in value of standard potentials of solute redox couple and polymer film under investigation. Experimental investigations of the voltammetric behaviour of various redox couples at polythiophene-, poly- p -phenylene- and poly- o -phenylenediamine-modified electrodes are in qualitative agreement with this model.

Both the internal and external porous structure of poly( p -phenylene) films, synthesized electrochemically via oxidation of benzene in concentrated H 2 SO 4 , was shown to be highly regular, possessing two characteristic ranges of pore radii, up to 2.5 and 80–200 nm.

The anodic synthesis of a poly-o-phenylenediamine film at gold, platinum, and ITO electrodes and peculiarities of its doping–undoping are studied by cyclic voltammetry. Absorption spectrum of undoped films is obtained in visible and near-IR light.