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The electroactive composites based on reduced graphene oxide (RGO), poly‐o‐phenylenediamine (PPD) and heteropolyacids – H4SiW12O40nH2O (SiW) and H3[PW12O40] ⋅ nH2O (PW) was applied to a screen‐printed carbon electrode (SPCE) as a planar three‐electrode cell as the first step to creating various devices, in particular, sensors and catalysts. We studied potential use of the modified and unmodified SPCE planar electrode in determining the concentration of antitubercular antibiotic isoniazid (isonicotinic acid hydrazide C6H7N3O or INH). The best result was observed for SPCE+RGO‐PPD‐SiW. CV of normal saline with various concentrations of C6H7N3O demonstrated linear dependence of the relevant anodic peak current either in the bulk solution upon immersion of the modified electrode or in a droplet on the electrode surface. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

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 H 2 SO 4 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. ga1 • SiW immobilization upon co-precipitation with the redox active polymer involving graphene oxide as catalyst. • RGO-PPD-SiW composite exhibits the redox activity both in acid and neutral media. • RGO-PPD-SiW electroactive composite is usable in the mediator catalysis. [ABSTRACT FROM AUTHOR]

• A simple preparation of electroactive conducting material containing Pd particles by immersion of GO and RGO-PPD films in a PdCl 2 solution. • Being distributed in GO and RGO-PPD films, particles containing Pd2+ can be electrochemically reduced to Pd0 particles. • GO is reduced to RGO along with formation of palladium metal. • Due to adsorption properties, GO can be used as a basis to prepare novel electroactive composites. • Such composites are promising as electrocatalysts, sensors, and energy saving and converting devices. 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. [ABSTRACT FROM AUTHOR]