Annotation of the results obtained in 2020
1) We studied the interaction of Fe (III) and Gd (III) with model small-molecule and polymer ligands in an attempt to mimic the structure of graphene oxide. None of the model ligands (even polyacrylic acid consisting solely of carboxyl groups) is capable of imitating graphene oxide in binding metal cations. Based on the obtained data, we conclude that there are no preexisting functional groups fragments in GO capable of binding the metal ions. Instead, these groups are generated by graphene oxide when interacting with metals. The research results are published in the Journal of Molecular Liquids: https://www.sciencedirect.com/science/article/pii/S0167732220349606 2) For the first time we revealed unique details of the mechanism of formation of graphene oxide when produced by the Hammers method. It is shown that the species, attacking carbon atoms in graphite is not an oxo-derivative of manganese, as it was commonly believed, but water molecules. It is shown that the as-formed C-O bonds can freely migrate along the graphene plane, creating the illusion of the process reversibility of the oxidation. The proposed reaction mechanism explains the well-known but yet poorly understood phenomena in graphene chemistry, in particular, the existence of so-called graphene and oxidized domains in graphene oxide. The results of research have been published in the journal Carbon: https://www.sciencedirect.com/science/article/pii/S0008622320304462. This research was acknowledged in several press releases: https://www.thegraphenecouncil.org/blogpost/1501180/352351/Mysterious-mechanism-of-graphene-oxide-formation-explained?hhSearchTerms=%22dimiev%22&terms= https://eurekalert.org/pub_releases/2020-07/kfu-mmo071720.php https://phys.org/wire-news/356433801/mysterious-mechanism-of-graphene-oxide-formation-explained.html 3) We have developed a preparation method for, and have fabricated new nanocomposite catalysts, based on palladium and nickel on a reduced graphene oxide substrate. The prepared catalysts were tested on Suzuki cross-coupling and nitrophenol reduction reactions. For the cross-coupling reaction, when using mixed Pd-Ni catalysts, replacing half of palladium with nickel only slightly reduces the conversion of the reagent at the same selectivity of the process. Thus, a significant reduction in the price / quality ratio is achieved compared to the use of pure palladium. A new catalyst based on nickel and graphene oxide (rGO/Ni) has been developed and successfully tested to catalyze the reduction of para-nitrophenol. A low-cost nickel-based catalyst has been shown to successfully catalyze the reaction previously catalyzed by precious metals such as silver, platinum and gold. The rGO/Ni sample exhibited an activity factor 4 times higher than the other Ni-based catalyst described in literature. Importantly, in our rGO/Ni material, nickel is present in the form of individual atoms or clusters of few atoms, which are not detected by HRTEM. Thus, this reaction can be considered as an example of single-atom catalysis. 4) We have developed the fabrication method, and have prepared samples of polymer composites based on epoxy resins and reduced graphene oxide. It has been found that the in-situ chemical reduction of GO in resin leads to a higher conductivity of the RGO filler in comparison with the so-called "thermal reduction" that was used earlier. Such a reduction yields higher viscosities of liquid formulations, and higher permittivity of cured composites. An explanation is proposed for the unusual dielectric properties of the obtained composites. In particular, the mechanism of polarization is proposed, and the factors influencing the dielectric properties of polymer composites are described. Long polarization times and relatively high values of the real part of permittivuty are explained by the charge transfer between individual rGO sheets in their clusters. The research results are published in the Journal of Physical Chemistry: https://pubs.acs.org/doi/10.1021/acs.jpcc.0c02208 5) A method has been developed for the manufacture of anisotropic polymer composites based on UV curable resins and epoxy resins as a polymer matrix, and a graphene oxide / magentite nanocomposite as a filler. Materials have been manufactured that have a pronounced anisotropy of both dielectric and optical properties. 6) Pristine graphite oxide (PGO), formed by the oxidation of graphite by the modified Hummers’ method, when still in synthetic mixture, can be re-intercalated by methanol, while keeping its c-axis registry. The as-formed structure contains two molecular layers of methanol, sandwiched between the neighboring graphene oxide (GO) sheets. The typical water-washed and dried GO intercalates only by one molecular layer of methanol. This finding suggests the route for preparing alcohol-intercalated GO straight from PGO, while bypassing water-purification, drying, and intercalating steps. The findings are published in Carbon: https://www.sciencedirect.com/science/article/pii/S0008622320310733

 

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Annotation of the results obtained in 2019
We have synthesized the graphene oxide (GO) / nickel (Ni) composites in a wide range of the nickel content. It was established that under the synthetic conditions nickel does not form pronounced nanocrystals, but is uniformly distributed over the GO substrate at the atomic level, or in the form of very small clusters that cannot be resolved by electron microscopy. The resulting composites catalyze the p-nitrophenol reduction reaction, which does not proceed in the absence of a catalyst. Catalytic activity is manifested even when the nickel content is <0.5%, and is expectedly increased with the nickel content. It was found that the alloyed nanocrystals of iron and nickel (Fe-Ni) are formed on the GO substrate by self-assembly, similar in composition to the well-known alloy Invar. Thus, it has been shown that Invar can be formed not only in bulk at temperatures above the melting points of individual metals, as it is manufactured in industry, but also at the nanoscale level. With the correct ratio of iron and nickel, nanocrystals of Fe-Ni alloy are formed; the formation of nanoparticles of individual metals (as might be expected) is not observed. It is noteworthy that mixed crystals are formed at the temperatures well below the melting points of the individual metals in their bulk forms. The polymer composites based on the epoxy resin matrix with the multifunctional anisotropy have been fabricated. The anisotropy is achieved by introducing into the matrix two-dimensional nanostructured particles of the GO/magnetite filler, and by their subsequent orientation by applying an external magnetic field before and during the curing of the epoxy resin. In the as-manufactured samples, the two-dimensional filler sheets are oriented parallel to each other in the entire volume of macroscopic samples made. The prepared samples possess pronounced anisotropy of dielectric and optical properties. Based on our findings, we published four papers in the journals, belonging to the first quartile (Q1).

 

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