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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.