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A graphene oxide film fabricated by removing water from a graphene oxide dispersion is a characteristic dielectric. The graphene oxide layers in such a film are interconnected through van der Waals interactions of oxygen-containing functionalities and cluster interlayer water. It has been shown that, after treatment of the film with supercritical fluids based on water and isopropyl alcohol, its robust structure is not destroyed, but the surface is "graphenized" and it acquires new properties. The resulting materials were studied by physicochemical methods of analysis (C, H, N analysis, XRD, IR and Raman spectroscopy). An electrophysical study of the film treated with supercritical isopropanol has demonstrated that the temperature dependence corresponds to a narrow-gap semiconductor, and the resistivity determined by the four-probe method at room temperature was ~3 Ω m/mm2. [ABSTRACT FROM AUTHOR]

A simple method for producing a film of graphene oxide is described. The polymer film obtained was studied by transmission electron microscopy, scanning electron microscopy, X-ray diffraction analysis, elemental analysis, IR spectroscopy, and Raman spectroscopy. The results show that graphene oxide flakes are macromolecules that contain hydrogen bonds and are connected by van der Waals interactions. Thus, graphene oxide can be considered as an analogue of water-soluble polymers and has the characteristic properties of a polymer (tensile strength 17–18 MPa, flexibility, redispersibility). [ABSTRACT FROM AUTHOR]

Two methods to synthesize Bi/Gr composites of Bi nanoparticles on graphene were developed: a three-step one (method I) and a two-step one (method II). By these methods, the composites are synthesized in supercritical isopropanol (SCI) through bismuth oxide on graphene oxide (GO): Bi2O3/GO. A distinguishing feature of this work is the fact that SCI is both a reducer, and a reaction medium, and it reduces both GO, and Bi2O3 nanoparticles. The obtained nanocomposites were studied by X-ray powder diffraction analysis, transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. Methods I and II produced Bi/Gr nanocomposites with average bismuth nanoparticle sizes of ∼4 and 40–80 nm, respectively. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) synthesized according to the modified Hummers method was reduced by supercritical isopropyl alcohol (SCI), supercritical acetone (SCA), and supercritical water (SCW). Methods free of toxic reducing agents were developed for the graphene production. The composition, morphology, and structure of synthesized graphene were determined using CHN analysis, XRD, Raman spectroscopy, and scanning electron microscopy. The best results were acquired in the case of GO reduction in SCA and SCI at high parameters. [ABSTRACT FROM AUTHOR]

This paper describes a sequential, two-step process for the synthesis of a composite based on graphene and CeO nanoparticles using supercritical fluid. The process includes the reduction of a prepre-pared graphene oxide/CeO nanocomposite with supercritical propanol-2. The nanocomposites thus obtained have been characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

A new method for obtaining platinum, palladium, and rhodium nanoparticles on graphene (G) flakes via the reduction of an intermediate nanocomposite on the surface of graphene oxide (GO) in supercritical 2-isopropanol is described. The thus-prepared nanocomposites based on graphene and graphene oxide were characterized using transmission electron microscopy (TEM), including high-resolution microscopy; X-ray powder diffraction; and X-ray photoelectron spectroscopy (XPS). [ABSTRACT FROM AUTHOR]

Interactions of graphene oxide with Ag, Cu, Fe, Fe, and Bi ions were studied. The minimum (threshold) ion concentrations required for the interaction with graphene oxide to occur were deter-mined in a series of experiments. A possible model of the interaction between the metal ions and the oxygen-containing groups of graphene oxide was proposed. [ABSTRACT FROM AUTHOR]

Interactions of ZnO nanoparticles with graphene oxide in isopropanol were studied; graphene oxide was shown to perform as an efficient substrate to immobilize zinc oxide nanoparticles on its surface. Interactions of nanocomposites consisting of graphene oxide-zinc oxide nanoparticles with supercritical isopropanol were studied. The conversion of graphene oxide into graphene does not appreciably changes the composition, morphology, or structure of ZnO nanoparticles. [ABSTRACT FROM AUTHOR]

The possibility of obtaining concerted mechanisms of chemical activation in supercritical fluids (SCFs) with the formation of a multicenter general transition state that includes a group of reagent atoms in which the subsequent breaking of chemical bonds and the formation of new chemical bonds start and proceed simultaneously is discussed. Two processes are considered that can occur only in SCF media: the reduction of anthracene in an isopropyl alcohol SCF and the impregnation of the photochromic compound spiroanthrooxazine (SAO) in a polycarbonate matrix in SC CO accompanied by an irreversible conformational rearrangement of the SAO structure. Concepts of the possible dependence of the concerted mechanism of the considered processes on the intertwining or entanglement of electron subsystems in forming multicenter transition states are developed. The decisive role of the electromagnetic component of a physical vacuum in obtaining a high degree of correlation in systems of entangled electrons is discussed. [ABSTRACT FROM AUTHOR]

This paper describes a novel approach to the preparation of reduced graphene oxide and its dispersions in organic solvents. Graphite oxide, graphene oxide, and reduced graphene oxide have been prepared and characterized by a variety of physicochemical techniques. [ABSTRACT FROM AUTHOR]

This review analyzes what the term graphene means today, and examines graphene preparation and identification methods and its chemical properties. The applications of this novel carbon nanomaterial are briefly discussed. [ABSTRACT FROM AUTHOR]

Three-dimensional opal-matrix nanocomposites containing various bismuth selenides and tellurides with a particle size from 25 to 150 nm have been produced by reducing oxygen-containing compounds with supercritical isopropanol. The bismuth: chalcogen ratio in the reduction products has been shown to correlate with that in the starting mixtures, indicating that targeted synthesis in opal pores can be used to controllably fabricate nanocomposites. [ABSTRACT FROM AUTHOR]

Bi, Te, and Bi2Te3 nanoparticles have been prepared by reducing bismuth salts, telluric acid, and their decomposition products with supercritical isopropanol in opal pores. [ABSTRACT FROM AUTHOR]

We have studied the reactions between supercritical isopropanol and salts of various elements (silver, copper, gold, zinc, iron, nickel, cobalt, manganese, europium, ruthenium, antimony, bismuth, and tellurium) infiltrated into opal photonic crystals. According to transmission electron microscopy data, the diameter of the SiO2 spheres in the opal crystals is 260 nm, and the nanoparticles of the metals and incomplete reduction products range in size from 2 to 80 nm, i.e., are no greater in size than the opal pores. [ABSTRACT FROM AUTHOR]

Bismuth nanoparticles have been produced in pores of opal matrices by reducing bismuth salts and oxide compounds with supercritical isopropanol. According to transmission electron microscopy data, the diameter of the SiO2 spheres in the opal matrices is about 260 nm, and that of the bismuth nanoparticles does not exceed 80 nm. [ABSTRACT FROM AUTHOR]

Methods were developed for manufacturing of isolated nanoparticles of lead(II) and mercury(II) oxides produced by the thermal decomposition of metal compounds in a solution-melt of low-density polyethylene (LDPE) in mineral oil. The PbO and HgO nanoparticles stabilized in the LDPE matrix were characterized using X-ray powder diffraction and transmission electron microscopy (TEM). The metal oxides in the polyethylene matrix were reacted with a supercritical fluid of isopropanol (SCF i-PrOH). The PbO in the nanoparticles was reduced to the metal as a result of the reaction with SCF i-PrOH. When SCF i-PrOH was reacted with the HgO nanoparticles stabilized in the LDPE matrix, the oxide was also reduced to the metal. TEM showed that the nanoparticles were conserved after their reaction with SCF i-PrOH. [ABSTRACT FROM AUTHOR]

Heterogeneous reactions between supercritical isopropanol and metal oxides were studied for the first time. The results demonstrate that Bi2O3 is reduced by isopropanol to metallic bismuth, while MnO2 and Mn2O3 are reduced to Mn3O4 (hausmannite). The possibility of oxygen extraction from nonstoichiometric oxides is demonstrated by the example of the reaction Bi12Ti1 – xMn5+ xO20 + δ → Bi12Ti1– xMn2+ xO20 – δ . [ABSTRACT FROM AUTHOR]