Graphene-reinforced aluminum composites combine high strength with attractive electrical performance for advanced structural and functional uses. In this work, AA 1020 aluminum (hereafter abbreviated as AA 1020 Al) sheets were processed by hot accumulative roll bonding (ARB) at 380 degrees C with 50% thickness reduction per pass, while a graphene oxide (GO) emulsion was interlayer sprayed prior to rolling to fabricate GO/Al laminates. After four passes, the composite achieved 37.1% higher tensile strength than the unprocessed sheet and 6.0% higher strength than preheated ARB AA 1020 without GO at the same pass, together with improved elongation and strain energy density. Optical microscopy, combined with image-based gray-scale intensity analysis, showed that increasing the number of passes promoted a more uniform through-thickness GO distribution; 15 GO-rich planes were detected after four passes, consistent with ARB interface multiplication. Electrical resistance measurements indicate that hot ARB increased the resistance of unreinforced AA 1020 Al sheets, primarily because process-induced defects (dislocations, grain boundaries) and interfacial oxide layers increase electron scattering and contact resistance. Incorporation of GO lowered measured resistance relative to unreinforced hot-ARB sheets across passes (largest drop at Pass 1), consistent with improved interlayer connectivity and the formation of conductive pathways. These results demonstrate that hot ARB provides a scalable route to graphene oxide-reinforced AA 1020 Al with a favorable balance of strength, ductility, and electrical performance.

The efficiency of platinum-based catalysts used in low-temperature fuel cells strongly depends on the properties of the carbon support. In this work, we develop a three-component hybrid support composed of thermally reduced graphene oxide (trGO), carbon black (CB), and multi-walled carbon nanotubes (MWCNT), prepared via a specifically designed protocol to achieve uniform blending of the components. Eight hybrid supports with varying trGO/CB/MWCNT ratios were synthesized, all exhibiting surface areas and pore volumes significantly higher than those of the individual components. Platinum catalysts supported on these hybrids were evaluated for the oxygen reduction reaction and compared with a commercial CB-based catalyst. All hybrid-supported catalysts showed higher electrochemical surface area (ECSA), attributed to the formation of additional voids between carbon components that improve accessibility of catalytic sites. Seven of the eight catalysts also demonstrated superior stability, with the best composition exhibiting only a 4% loss in ECSA after 1000 cycles, compared to a 30% loss for the commercial catalyst. This enhanced durability is attributed to strong interactions between Pt nanoparticles and binding sites on trGO and modified MWCNT, which suppress nanoparticle agglomeration. Furthermore, six of the eight compositions outperformed the commercial catalyst in mass activity, with the best sample achieving a current density of 453 mA mg-1(Pt) versus 148 mA mg-1(Pt) for the commercial sample. The optimal pre-annealing support compositions were GO/CB/MWCNT ratios of 2.5/4.0/3.5 and 2.5/3.5/4.0. These results demonstrate that the synergistic combination of trGO, CB, and MWCNT enables simultaneous enhancement of activity and durability in Pt-based ORR electrocatalysts.

Strong interest in graphene oxide (GO) over the past decades has resulted in significant advances toward numerous applications and progress in understanding its chemistry. A rather broad community of scientists is involved in GO research including specialists in chemistry, physics, life, and materials sciences. While this diversity is a strength, common characterization techniques, such as Raman spectroscopy, FTIR, XPS, and XRD are often misused and inconsistently interpreted. Errors in data processing and analysis often invalidate key conclusions made in research papers. In many cases, experimental data provided in different studies are difficult to compare due to the lack of standardized ways of interpretations. The purpose of this review is to clarify common misunderstandings and errors in GO characterization by the four above-mentioned methods and to provide useful recommendations for best practices in data acquisition, processing, and interpretation. It also aims to offer guidance for new researchers entering the field of GO. The review is based on the authors' extensive experience in the field. By promoting standardized approaches, this review seeks to improve data comparability, enhance reliability in GO research, and establish a solid foundation for analyzing the structure and reactivity of GO-based materials.

Graphene oxide (GO), while being intensively studied in application related research, still has open questions concerning its structure and chemistry. In particular, its interaction with salts of transition metals is difficult to envision in the frames of the commonly accepted Lerf-Klinowski structural model. In this work, for the first time, we investigated interaction between Brodie GO (BGO) and Gd3+ ions in aqueous dispersions by the NMR Relaxation method, and compared it to that for Hummers GO (HGO). Unlike HGO, the measurements with BGO are possible only starting from pH > 7.5, when it forms stable dispersions. The spin-spin (r1) and spin-lattice (r2) relaxivities of the BGO/Gd3+ dispersions have maximum values at pH similar to 9.5, and gradually decrease from pH 9.5 through pH 12 due to the partial hydrolysis of Gd3+ ions in basic solutions. However, even at pH 12, BGO efficiently screens Gd3+ ions from full hydrolysis. The r1 and r2 values increase with the GO/Gd3+ ratio. Saturation of Gd3+ by BGO is registered at the ratio 100 g BGO to 1 mmol Gd3+. Despite the negligible content of the carboxyl groups in the BGO structure, its binding capacity toward Gd3+ ions is only 2.5 time lower than that of HGO. The binding mechanism is discussed in the frames of the Dynamic Structural Model of GO, suggesting transformations of the GO structure at reaction conditions.

Despite recent progress, the chemistry behind the sorption of transition metal ions by graphene oxide (GO) remains largely elusive. The literature data on the sorption capacity varies broadly, and is difficult to reconcile in the frames of the popular GO structural model. In this work, for the first time, we used Cu2+ ions as the Nuclear Magnetic Resonance (NMR) Relaxation and Electron Paramagnetic Resonance (EPR) active probes to investigate the nature of the GO-Cu2+ bonding and the structure of resulted composites. The two methods, combined with high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM), evidence that copper exists on GO surface in the form of individual Cu2+ ions, bound to GO functional groups via coordinate-covalent bonding. Namely, the NMR relaxation measurements in aqueous GO/Cu2+ dispersions show that GO's functional groups replace certain number of water molecules in the first coordination sphere of Cu2+ ions. The EPR spectra of solid GO/Cu products, acquired at 80 K, consist of two components: component-1, originating from individual isolated Cu2+ ions, and component-2, originating from the Cu2+ ions located in close proximity to each other, and thus prone to exchange interactions. The high-resolution HAADF STEM imaging supports EPR data, clearly showing two different types of atomic arrangements of individual Cu2+ ions on GO surface, contributing to the two components of the EPR spectra. Magnetic measurements additionally support the EPR based data. Based on the experimental findings, for the first time, we introduce and define the term "binding capacity" of GO with respect to metal ions as opposed to commonly used "sorption capacity". Unlike the latter, the former includes only ions, strongly bound to GO by coordinate-covalent bonding. The registered values binding capacity can be interpreted within the framework of the Dynamic Structural Model of GO.

Graphene oxide (GO) has been successfully used as a filler to modify various properties of polymers and fiber-reinforced composites. The resulting properties depend on the filler content and on the distribution of GO in the polymer matrix. In this work, for the first time, we introduced GO into the highly viscous DEN-438 epoxy novolac resin and investigated rheological properties of the resulting compositions. In particular, we studied the functions of complex viscosity, storage and loss moduli, and mechanical loss tangent on temperature and GO content. The unusual behavior of the newly prepared formulations compared to typical GO/epoxy mixtures was discovered. At low GO content, introduction of GO led not to an increase, but to a decrease in the resin viscosity, with the minimum registered at 0.29 wt.% GO. After this threshold value, viscosity increased with GO content, which we explained by formation of the liquid crystalline structure. At higher GO concentrations, the formulations changed their state from solid-like at rest to liquid-like under load, with the properties being highly desired for film binders. The discovered properties of the GO/novolac epoxy resin formulations suggest their potential use as the new generation of film binders for Resin Film Infusion technology.

In this work, hybrid membranes from reduced graphene oxide/graphene oxide (rGO/GO) have been prepared. The membrane material was characterized by thermal gravimetry analysis (TGA), X-Ray diffractometry (XRD) and scanning electron microscopy (SEM) analysis. The effect of the membrane thickness on their flux for organic substances has been analyzed. The increased selectivity of the rGO/GO membrane to 2-propanol–1-butanol pair was found that exceeds the known literature data on GO-based membranes, which opens up the possibility to isolate 1-butanol from the isopropanol–butanol–ethanol (IBE) fermentation broth. It is found that hybrid rGO/GO membranes retain methylene blue and separate a mixture of methylene blue–methyl orange more efficiently than pure GO membranes. The hybrid rGO/GO membrane rejects 85.6

Nowadays, platinum based electro-catalysts are made mostly from hexachloroplatinic acid and its salts. The possibility of using other platinum sources such as platinum(iv) nitrate has been largely overlooked. In this study, we employed this precursor and prepared platinum based catalysts on an annealed graphene oxide support using two different synthetic protocols. The structure and morphology of the obtained composites have then been investigated using a set of advanced instrumental methods, which, in particular, allowed us to visualize individual Pt atoms. The use of platinum(iv) nitrate and the synthesis in non-aqueous medium lead to a size of platinum species, not attainable via alternative methods/precursors. In the material prepared at 25 degrees C in isopropanol, platinum is present in the form of nanoparticles with an average size of 1.4 nm, as well as in the form of single atoms. In the material synthesized at 180 degrees C in ethylene glycol, platinum exists in the form of nanoparticles with an average size of 2.8 nm. Both materials exhibit excellent catalytic activities towards the oxygen reduction reaction. The catalyst with smaller platinum species demonstrates higher efficiency and promotes the 4e- mechanism by reducing oxygen to water.

Porous metallic substrate for metal-supported solid oxide fuel cells was developed utilizing stainless-steel powder and triethanolamine as a new binder. Starch was added as an additional agent to increase porosity and gas permeability of the samples. The structure and functional properties of the obtained substrates as the function of the additives content and the processing conditions were investigated. The optimal parameters have been determined. When the combined percentage of the binder and pore-former was raised up to 5 ∼ 14× 10^-6 has been obtained. The results demonstrate how the preparation process affects all of the major parameters, including porosity, permeability, hardness and roughness. Both the content of additives and processing conditions may vary in relatively broad range to attain particular required properties of the substrates. Better to similar properties compared to literature data have been obtained.

In this work, we synthesized two hybrid copper-platinum composites and two mono-metallic control samples on the carbon black (CB) support with the use of the polyol-formaldehyde method. The bi-metallic composites were prepared by the two different experimental protocols: consecutive deposition of the two metals CB/CuPt-1 and co-deposition of CB/CuPt-2. With both methods, the use of copper facilitates deposition of platinum, leading to a higher platinum content in the products, compared to the mono-metallic CB/Pt control sample. SEM and HRTEM images show that, in monometallic CB/Cu, copper does not form any nanoparticles, being atomically dispersed on the CB surface. The other three samples have uniformly dispersed nanoparticles with a size of 2-4 nm, densely covering the CB support. XRD and XPS data suggest that copper facilitates more efficient reduction of platinum, and is incorporated into the nanoparticles. Next, all the synthesized composites were tested for the hydrogen evolution reaction (HER). The two bi-metallic composites outperform not only the mono-metallic CB/Pt sample, but also the commercial catalyst with a similar or an even higher platinum content. Interestingly, the catalytic efficiency is not directly related to the platinum content in the tested materials. As a result, CB/CuPt-2, which has a lower Pt content, demonstrates greater efficiency in certain parameters compared to CB/PtCu-1, which contains a higher Pt content. This observation suggests that incorporation of copper into the structure of the composite materials leads to synergistic effects. Our results show the role of copper in the efficiency of the platinum catalysts for the HER and open routes for increasing the efficiency of the hydrogen generation reaction on an industrial scale.

Despite potential attractiveness of the electrochemical reduction of graphene oxide (GO), the existent approaches suffer inevitable drawbacks making them not applicable for large scale processing. In this work, for the first time, we report the mediator assisted electrochemical reduction of GO by using methyl viologen. Unlike the previously reported methods, this process occurs in the entire volume of the electrolyte solution, rather than being confined to the electrode surface. This let one to avoid the diffusion related constraints, making the reaction extremely efficient. The amount of electricity, needed for full reduction is somehow lower than that theoretically anticipated based on the GO stoichiometry; this suggests that additional non-electrochemical deoxygenation processes take place in parallel with the main reaction. The reduction reaction is in part reversible: the reduced GO can be re-oxidized both electrochemically and in open air. The reduced product has a high degree of reduction with C/O ratio similar to 49/1, but it remains highly exfoliated while in the form of an alcohol-wet powder, affording formation of relatively stable dispersions in water and alcohols. The developed method combines advantages of both chemical and electrochemical reduction, and simultaneously lacks their drawbacks. In addition to be very interesting from the fundamental science perspectives, the method opens the rotes toward industrial scale production of a new product with advantageous properties.

In this work, membranes based on graphene oxide, modified with oleylamine, have been prepared by a simple wet chemistry protocol without the use of complex equipment, elevated temperature, and additional reagents. The membrane material was characterized by a set of physicochemical methods: thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy. The prepared membranes are stable in both aqueous and organic media. The membranes have a high flux for organic substances and do not permeate water at room temperature and atmospheric pressure. The selectivity of the membranes toward organic substances increases with their thickness. The highest flux among the tested organic liquids is registered for methanol. The membranes have high selectivity toward ethanol/1-butanol and acetone/1-butanol pairs, which opens up the possibility of separating actual industrial mixtures. The membrane retains 90% of methylene blue from the alcohol solution. Our work expands the possibilities of using modified GO-based membranes in purification and filtration technologies.

Potential genotoxicity and carcinogenicity of carbon nanotubes (CNT), as well as the underlying mechanisms, remains a pressing topic. The study aimed to evaluate and compare the genotoxic effect and mechanisms of DNA damage under exposure to different types of CNT.Immortalized human cell lines of respiratory origin BEAS-2B, A549, MRC5-SV40 were exposed to three types of CNT: MWCNT Taunit-M, pristine and purified SWCNT TUBALLTM at concentrations in the range of 0.0006-200 mu g/ml. Data on the CNT content in the workplace air were used to calculate the lower concentration limit. The genotoxic potential of CNTs was investigated at non-cytotoxic concentrations using a DNA comet assay. We explored reactive oxygen species (ROS) formation, direct genetic material damage, and expression of a profibrotic factor TGFB1 as mechanisms related to genotoxicity upon CNT exposure.An increase in the number of unstable DNA regions was observed at a subtoxic concentration of CNT (20 mu g/ ml), with no genotoxic effects at concentrations corresponding to industrial exposures being found. While the three test articles of CNTs exhibited comparable genotoxic potential, their mechanisms appeared to differ. MWCNTs were found to penetrate the nucleus of respiratory cells, potentially interacting directly with genetic material, as well as to enhance ROS production and TGFB1 gene expression. For A549 and MRC5-SV40, genotoxicity depended mainly on MWCNT concentration, while for BEAS-2B - on ROS production. Mechanisms of SWCNT genotoxicity were not so obvious. Oxidative stress and increased expression of profibrotic factors could not fully explain DNA damage under SWCNT exposure, and other mechanisms might be involved.

For the first time, the mechanism of metal aluminum dissolution in NaF-ScF3 eutectic melts and the chemical interaction between the constituents of this mixture have been thoroughly studied by a combination of differential thermal analysis (DTA), high temperature and solid-state nuclear magnetic resonance (NMR), and X-ray diffraction (XRD) coupled with the molecular dynamic simulations. The formation of an insoluble Al3Sc alloy in molten (NaF-ScF3)(eut) system was proven, and the chemical mechanism of this aluminothermic Al3Sc alloy production was elucidated. Corresponding ex situ examinations bring to light the formation of NaScF4 and solid solution of Na-3(Al,Sc)F-6 in cooled bath. The molecular dynamics calculations of the bath allow us to construct the structural model and to predict viscosity, density and electrical conductivity of the reagent melt to help to optimize the conditions of the alloy synthesis.

Despite enormous popularity of graphene oxide (GO) several open questions remain regarding the structure and properties of this material. One of those questions is the role of a graphite precursor on the properties of GO product. In this study, we investigate the oxidation process and the structure of GO products, made from the four different graphite precursors: synthetic graphite, two natural flaky graphites, and expanded graphite. The highest rate of the oxidation reaction was registered for the small particle size synthetic graphite. Thermal expansion of natural flaky graphite did not significantly affect the rate of the reaction. The nature of the graphite precursor does not notably affect the chemical composition of the synthesized GO products. However, it affects stability of respective aqueous dispersions. The solutions of the three GO samples, prepared from the natural graphite sources demonstrate excellent stability due to complete exfoliation of GO to single-atomic-layer sheets. GO from synthetic graphite forms unstable dispersions due to the presence of numerous multi-layered particles. This, in turn, is explained by the presence of not fully graphitized, amorphous inclusions in synthetic graphite. Our observations suggest that synthetic graphite should not be used as GO precursor when the ability to completely exfoliate and the stability of dispersions are critical for intended applications.

The applicability of infrared spectroscopy toward graphene oxide (GO) and its derivatives is currently very limited, because the exact location of absorbance bands, originated by the main functional groups of GO, in the spectrum is still under debate. This obstacle leads to widespread misinterpretation of FTIR spectra in literature, and to invalid conclusions on attaining target functionalization reactions. In this work, by involving GO in four types of reactions, for the first time, we identify absorbance bands, originated by the main functional groups of GO: epoxides and tertiary alcohols. Also, we identify the bands, associated with carboxyl and carboxylate groups. In addition, we reconfirm the band assignment for absorbed water molecules (1619 cm-1 ) and covalent sulfates (1221 cm-- 1 and 1410 cm- 1 ). Finally, we show conditions for appearance, and the exact position of the band of the C=C bond stretch. All together we accurately assign eight previously unidentified or incorrectly assigned absorbance bands in the fingerprint region of the spectrum, plus three bands which appear in the spectra of specific forms of GO. The assignment of the bands is independently confirmed by the 13 C SSNMR spectroscopy. Summing up the newly assigned and the re-confirmed bands, for the first time, we report a complete library of the main absorbance bands in the FTIR spectrum of GO and GO derivatives.

Graphene oxide (GO) is of great interest due to its unique structure and properties and potential applications, including water purification. In this work, we report the synthesis of GO samples with different oxidation degree from two different sources of graphite using Hummers method. Natural flake graphite with a high degree of crystallinity, and synthetic fine powder graphite were used. All produced materials were characterized by CHNS analysis, X-Ray Diffractive analysis (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It was shown that the oxidation process for natural and synthetic graphite sources proceeds in different ways. The factors, affecting for the structure and properties of GO are the degree of crystallinity and the lateral size of the graphite flakes. The sorption activity of underoxidized, normally oxidized and overoxidized GO was compared toward the methylene blue (MB) dye in aqueous solution. The most efficient sorption was registered for GO produced from synthetic graphite with the use of 2.0 and 4.5 wt. eq. KMnO4. The sorbents removed 94 % and 100 % of MB from the solution, respectively, in approximately 10 min. Our results reveal that the structure and sorption properties of GO can be tuned by varying the oxidation degree as well as the graphite source, which may open the way to new developments in the GO-based materials applications.

Chelating by graphene oxide (GO) results in dramatic shortening of the proton relaxation times of Gd3+ aqueous solutions. However, the factors, leading to the increase of relaxivity values, and the mechanisms behind the observed phenomena remain elusive. In this work, we investigated how the relaxation times of the GO/Gd3+ solutions depend on the oxidation level and the flake size of GO. The values of spin-lattice (r1) and spin-spin (r2) relaxivities increase with the oxidation degree of the used GO samples. The relaxivity also increases with decreasing the particle size of GO flakes by sonication. The observed phenomena are explained by the increase in the number of the edge functional groups, generated under the influence of both parameters. The content of these groups, their formation, and chelation of Gd3+ ions is discussed in the manuscript. Viscosity of solutions does not directly affect the relaxation times. With the use of high oxidation level and small particle size GO samples we have registered the record high relaxivity values: r2 = 114.7 mM-1 s-1, and r1 = 97.0 mM-1 s-1. This opens straight routes for developing the GO/Gd3+ based MRI contrast agents.

The search for new biodegradable fertilizers to increase the productivity of agricultural plants is an urgent task. In this study, a complex microfertilizer was developed based on a chelating agent—glutamic-N,N-diacetic acid (GLDA). The evaluation encompassed assessments of biodegradability and effectiveness in fostering lettuce plant growth in hydroponic and conventional soil settings. The impact on endospheric bacteria, a sensitive indicator, was also examined. Results indicated a 59.8% degradation rate of the GLDA complex on the 28th day. The most notable positive effects were observed in above-ground plant biomass, with a 4.6-fold increase for hydroponics and 1.5 to 1.8-fold increases for root and foliar treatments in soil. In hydroponics, GLDA-treated plants showed 24 and 45 operational taxonomic units (OTUs) for leaves and 272 and 258 for roots (GLDA-treated and control plants). In soil, the OTU counts were 270 and 101, 221 and 111, and 198 and 116 in the leaves and roots of GLDA-treated and control plants (under root and foliar treatments), respectively. Non-metric multidimensional scaling (NMDS) and Indicator Species Analysis (ISA) demonstrated significant distinctions in endospheric communities between substrates (hydroponics and soil) in the presence of GLDA. Importantly, GLDA use simplified the composition of endospheric bacterial communities.

In this work, we prepare a material termed oxidatively modified carbon (OMC), which significantly outperforms commercial activated carbon products available on the gold mining market. The intriguingly high sorption efficiency of OMC is explained by the graphene oxide (GO) like fine chemical structure of the particles' surface. At the same time, OMC can be easily prepared from readily available carbon sources by wet chemistry protocols with the cost of production ~10 lower than that for GO. The particulate structure of OMC allows simple separation from the used-up solutions. Addition of ammonia to the gold-cyanide solution, additionally boosts sorption capacity of OMC. The developed material can be used in gold mining industry as a sorbent, which can potentially increase the efficiency of the gold extraction process.