Intercalation compounds of trimethylphosphate in graphitic oxide

The intercalation compounds of trimethylphosphate (TMP) in graphite oxide (GO) have been synthezized. Two compounds have been characterized, corresponding to intercalation of one or two molecules of TMP, and have been characterized by gravimetric adsorption, X-ray diffraction and infrared spectroscopy. Bonding between TMP and graphitic oxide takes place through hydrogen bonding with OH groups of the layered material.     

Facile synthesis of gold nanoparticles with narrow size distribution by using AuCl or AuBr as the precursor

Gold(I) halides, including AuCl and AuBr, were employed for the first time as precursors in the synthesis of Au nanoparticles. The synthesis was accomplished by dissolving Au(I) halides in chloroform in the presence of alkylamines, followed by decomposition at 60 degrees C. The relative low stability of the Au(I) halides and there derivatives eliminated the need for a reducing agent, which is usually required for Au(III)-based precursors to generate Au nanoparticles. Controlled growth of Au nanoparticles with a narrow size distribution was achieved when AuCl and oleylamine were used for the synthesis. FTIR and mass spectra revealed that a complex, [AuCl(oleylamine)], was formed through coordination between oleylamine and AuCl. Thermolysis of the complex in chloroform led to the formation of dioleylamine and Au nanoparticles. When oleylamine was replaced with octadecylamine, much larger nanoparticles were obtained due to the lower stability of [AuCl(octadecylamine)] complex relative to [AuCl(oleylamine)]. Au nanoparticles can also be prepared from AuBr through thermolysis of the [AuBr(oleylamine)] complex. Due to the oxidative etching effect caused by Br(-), the nanoparticles obtained from AuBr exhibited an aspect ratio of 1.28, in contrast to 1.0 for the particles made from AuCl. Compared to the existing methods for preparing Au nanoparticles through the reduction of Au(III) compounds, this new approach based on Au(I) halides offers great flexibility in terms of size control.     

Reactions of water, dihydrogen, dinitrogen, dinitrogen oxide, methane over illuminated ultraclean graphite

Some photocatalytic reactions of different gases on ultraclean graphite have been studied by means of quadrupole mass spectrometry. With water vapor, dihydrogen, dinitrogen and dinitrogen oxide, the UV-illuminated graphite acts as a reducing agent. TPD measurements indicate that photocatalytic processes are strongly affected by adsorption-desorption equilibria.     

SYNTHESIS OF POLY(VINYL ACETATE)-INTERCALATED GRAPHITE OXIDE BY AN IN SITU INTERCALATIVE POLYMERIZATION*

Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder byoxidization with KMnO_4 in concentrated H_2SO_4. The poly(vinyl acetate)-intercalated graphite oxide nano-composite wasprepared by an in situ intercalative polymerization reaction, in which n-octanol-graphite oxide intercalation compounds werefirst obtained, vinyl acetate monomer was then dispersed into the interlayer of modified graphite oxide, followed by thermalpolymerization of the monomer. It was experimentally shown that the c-axis space of poly(vinyl acetate)-intercalated graphiteoxide was increased to 0.115 nm, which suggested there existed a monolayer of poly(vinyl acetate) chain between the layersof graphite oxide. The nanocomposite was also characterized with thermal analysis and FT-IR spectrometry.     

Large-scale synthesis of uniform silver orthophosphate colloidal nanocrystals exhibiting high visible light photocatalytic activity

Silver orthophosphate nanocrystals with controlled particle size have been synthesized using a simple, reproducible and easily scaled up route based on the reaction between silver ions, oleylamine and phosphoric acid. The obtained nanocrystals are highly uniform in size and exhibit high visible light activity for the photodecomposition of organic compounds.     

Micromechanical properties of intercalated compounds of graphite oxide with dodecahydro-<Emphasis Type="Italic">closо</Emphasis>-dodecaboric acid

The micromechanical properties (Young’s modulus, deformation, and adhesion) of the intercalated compound of graphite oxide with dodecahydro-closo-dodecaboric acid were studied by atomic force microscopy, transmission electron microscopy, and Raman spectroscopy and compared with the same characteristics of the starting graphite oxide. The significant difference in the micromechanical properties of the materials under study is dictated by differences in the topography and properties of their film surface, which, in turn, can be determined by their chemical composition. The introduction of dodecahydro-closo-dodecaboric acid in the interplanar space of graphite oxide affects the structuring of the latter. A considerable increase in the adhesion of the intercalated compound relative to that of oxide graphite is explained by high adhesive properties of the introduced acid, the Young’s modulus of graphite oxide being higher than that of the intercalated compound. This was attributed to the high hydrophilicity of dodecahydro-closo-dodecaboric acid and the difficulty of water removal from the interplanar space; water plasticizes the material, which becomes softer than graphite oxide. The difference in the structure of the coating of the intercalated compounds and the starting graphite oxide was found to be also reflected by their Raman spectra, namely, by the increased intensity of the D line with the preserved position of the G line, which points to the impurity nature of the intercalate and the unchanged hexagonal lattice of graphite.     

Effect of the perfluoroalkyl groups on the preparation of carbon-based transparent and conductive thin films from silylated graphite oxides

Carbon-based transparent thin films were prepared from the pyrolysis of silylated graphite oxide containing perfluoroalkyl groups. The saturated amount of n-hexadecylamine molecules which accommodated between the layers of silylated graphite oxide containing larger pefluoroalkyl groups was smaller than that observed for silylated graphite oxide without perfluoroalkyl groups. The resulting intercalation compounds were dispersed in a chloroform/cyclohexane solution and precursor thin films were obtained by a cast method. The sheet resistance of the obtained carbon-based films was about 5 times smaller than that of the films prepared from silylated graphite oxide prepared with the analogous hydrocarbon substituents. The spectroscopic measurements indicated that the number of defects within the carbon layers was larger, however, that of carbon atoms participating π-conjugating system was larger. This probably ascribed to the active fluorine species formed as the result of thermal decomposition of perfluoroalkyl groups. The latter was responsible for the lower sheet resistance of carbon-based thin films.     

Polymérization anionique de l'isoprène par les insertions ternaires graphite–métal alcalin–solvant

The examination by HR–NMR of the microstructure of polyisoprenes synthesized in the presence of alkali metal–graphite compounds reveals that the polymerization has an anionic character. The microstructure of the polymers depends on the nature of the active centers, which depends on the solvent used in the preparation of the graphite compounds or as polymerization medium. With powdered alkali metal–graphite compounds, the propagation does not differ from the anionic one occurring in a homogeneous medium. Except for K–graphite, an enhancement of the 1–4 addition mode is observed if grains of Li or Na–graphite are used in mass polymerization. This change in the microstructure could be explained by the competition between the rate of propagation and the rate of diffusion of the growing chains from the grains to the homogeneous phase of the polymerization medium.     

Preparing graphene oxide–copper composite material from spent lithium ion batteries and catalytic performance analysis

The wide use of lithium ion batteries (LIBs) has created much waste, which has become a global issue. It is vital to recycle waste LIBs considering their environmental risks and resource characteristics. Anode graphite from spent LIBs still possess a complete layer structure and contain some oxygen-containing groups between layers, which can be reused to prepare high value-added products. Given the intrinsic defect structure of anode graphite, copper foils in LIB anode electrodes, and excellent properties of graphene, graphene oxide–copper composite material was prepared in this work. Anode graphite was firstly purified to remove organic impurities by calcination and remove lithium. Purified graphite was used to prepare graphene oxide–copper composite material after oxidation to graphite oxide, ultrasonic exfoliation to graphene oxide (GO), and Cu²⁺ adsorption. Compared with natural graphite, preparing graphite oxide using anode graphite consumed 40% less concentrated H₂SO₄ and 28.6% less KMnO₄. Cu²⁺ was well adsorbed by 1.0 mg L^?1 stable GO suspension at pH 5.3 for 120 min. Graphene oxide–copper composite material could be successfully obtained after 6 h absorption, 3 h bonding between GO and Cu²⁺ with 3/100 of GO/CuSO₄ mass ratio. Compared to CuO, graphene oxide–copper composite material had better catalytic photodegradation performance on methylene blue, and the electric field further improved the photodegradation efficiency of the composite material.     

Tailoring CuO nanostructures for enhanced photocatalytic property

Composites of cobalt (hydr)oxide and graphite oxide (GO) were obtained and evaluated as adsorbents of hydrogen sulfide at ambient conditions. The surface properties of the initial and exhausted samples were studied by FTIR, TEM, SEM/EDX, XRD, adsorption of nitrogen, potentiometric titration, and thermal analysis. The results obtained show a significant improvement in their adsorption capacities compared to parent compounds. The importance of the OH groups of cobalt (hydr)oxide/GO composites and new interface chemistry for the adsorption of hydrogen sulfide on these materials is revealed. The oxygen activation by the carbonaceous component resulted in formation of sulfites. Water enhanced the removal process. This is the result of the basic environment promoting dissociation of H(2)S and acid-base reactions. Finally, the differences in the performance of the materials with different mass ratios of GO were linked to the availability of active sites on the surface of the adsorbents, dispersion of these sites, their chemical heterogeneity, and location in the pore system.     

Monodisperse superparamagnetic nanoparticles by thermolysis of Fe(III) oleate and mandelate complexes

Monodisperse superparamagnetic iron oxide nanoparticles of controlled size were synthesized by thermal decomposition of organic iron compounds in different high-boiling solvents in the presence of oleic acid and/or oleylamine. The compounds included Fe(III) oleate and mandelate, formed from FeCl₃ and the respective acids. The size of the nanoparticles was easily tuned to 8–27 nm by varying the experimental conditions. The nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetization measurements. The hydrophobic coating of the particles was analyzed by thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). To make the particles biocompatible and water dispersible, nontoxic hydrophilic poly(ethylene glycol) derivatives were synthesized and used for phase transfer of hydrophobic particles into water using a ligand-exchange procedure.     

Carcinogenic Organic Residual Compounds Readsorbed on Thermally Reduced Graphene Materials are Released at Low Temperature

The preliminary oxidation of graphite to graphite oxide followed by a thermal exfoliation is one of the methods most frequently employed in the preparation of graphene. Such thermally reduced graphene can be widely used for several applications that range from coatings to sensing device fabrication. It is therefore important to investigate in detail the fabrication procedure, the structural features of the resulting graphene, and its potential toxicological effects. Low‐molecular‐weight and carcinogenic compounds are known to be generated during the thermal reduction/exfoliation of graphite oxide. Such compounds are readsorbed onto the reduced material during the cooling process. We investigate here the composition of the organic compounds that are adsorbed onto the graphene material and show that they can be easily released during the following processing steps even at temperatures as low as 50 °C. Some of the released organic compounds are classified as highly carcinogenic. The results shown here are important not only from a chemical point of view to better understand the composition and properties of the graphene material produced, but also to bring attention to the potential toxicological effects that the synthesis itself or the post‐production processes can cause.     

Mass transfer kinetics of graphene oxide prepared by chemical oxidation intercalationg assisted ultrasonic field

The key step of the control reaction for the preparation of graphene oxide (GO) by chemical oxidation of KMnO₄/ concentrated H₂SO₄ oxidation system is the intercalation mass transfer process of oxidizer in graphite. Ultrasonic field can promote the intercalation mass transfer process, but the mass transfer kinetics remains unclear. In this paper, the kinetic model of mass transfer coefficient of graphene oxide sheet intercalated by Mn₂O₇ oxidizer in ultrasonic field was established. The Mn₂O₇ intercalation process after the intervention of the ultrasonic was simulated by COMSOL Multiphysics 5.5 simulation software. The results show that the ultrasonic field makes the Mn₂O₇ solution inside and outside the graphite layer turbulent, and the ultrasonic intervening time has little influence on the concentration distribution and diffusion rate of the solution outside the graphite layer, while it has great influence on the concentration distribution and little influence on the diffusion rate change inside the graphite layer. These results contribute to the improvement of the mass transfer theory for the preparation of GO by ultrasonic assisted chemical oxidation.     

Properties of polyamide 6 and thermoplastic polyurethane blends containing modified montmorillonites

In this paper are reported some experimental data related to the influence of preparation regimes and characteristics of exfoliated graphite based sorbents produced by thermal expansion of H₂SO₄-graphite intercalation compounds (H₂SO₄-GICs) on their sorption properties. Investigations involving X-ray diffraction analyses, surface area, bulk density and oil sorption capacity measurements, have been performed. Sorption capacity was discussed as a function of bulk density, total pore volume and surface area. Some empirical correlation between studied characteristics of exfoliated graphite have been found. The differences among the obtained samples, as a consequence of synthesis conditions, were also put in evidence by thermal analysis (TG, DTG and DTA) performed after their exposure to oil sorption.It was found that thermal analysis method could provide information about the exfoliated graphite pore system related to the sorbed oil oxidation rate. The capacity for oil uptake was also discussed in the case of graphite oxide soot.     

Nanostructures in Physical Materials Chemistry: An Exploratory Laboratory

The blend of nanotechnology and material science is often beyond the scope of undergraduate laboratories. Through undergraduate research, graphite-intercalated compounds have been incorporated in the production of carbon-based nanostructures. Based on this work a series of exploratory exercises were designed for the undergraduate physical chemistry laboratory emphasizing nanostructure material science. This rapidly expanding area of science and technology can be introduced at an undergraduate level using a high temperature oven to produce nanostructure samples that are analyzed by Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy at research university laboratories, infrared spectroscopy, and a bomb calorimeter. In these experiments we use samples of pure graphite, fluorinated graphite, and lanthanum oxide to induce the formation of nanostructures. An overview of fullerenes, nanotubes, boron nitride and Si nanostructures, other carbon forms, graphite-intercalated compounds, and the storage of hydrogen in nanotubes are provided in an appendix. Several extensions of the laboratory are proposed.     

Simulation and synthesis of graphene oxide from expanded graphite

Russian Journal of General Chemistry - Expanded graphite oxide and multilayered graphene oxide have been synthesized. The processes of thermal expansion of intercalated graphite and oxidation of...     

Initiating electropolymerization on graphene sheets in graphite oxide structure

Because of its special chemical composition, graphite oxide has peculiar influences on electrochemical processes. The existence of various functional groups significantly affects electropolymerization processes and the formation of conductive polymers. Electrochemical synthesis of polyaniline (as a prototype of conductive polymers) on a paste‐based substrate of graphite oxide was investigated. In this case, the electropolymerization is significantly different from conventional cases, and the polymer is generated just during the first potential cycle. This can be attributed to the fact that graphite oxide can assist the monomer oxidation. Alternatively, electropolymerization was successfully performed inside the graphite oxide layers via electrochemical treatment of aniline‐intercalated graphite oxide in the supporting electrolyte. Although these phenomena are related to the chemical composition of graphite oxide, the graphite prepared by the reduction of graphite oxide also displayed some advantages for the electropolymerization (over natural graphite). There is an emphasis on the morphological investigations throughout this study, because novel morphologies were observed in the system under investigation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2204–2213, 2010     

Polymerization of ethylene oxide with potassium-graphite inclusion compounds

The polymerization of ethylene oxide (EO) in tetrahydrofuran (THF) initiated by inclusion compounds of potassium in graphite (C₂₄K) at 50°C was studied. During the initial slow stage of the polymerization the catalyst efficiency increases, while during the second rapid stage the reaction proceeds at a constant concentration of the active centers. The influence of the catalyst and monomer concentrations on the concentration of the active centers and on the catalyst efficiency was studied. The existence of the slow stage is explained by diffusion of ethylene oxide between the graphite planes, where both initiation and initial chain growth take place. The diffusion of the growing chains from the catalyst into the solution brings about the formation of a necessary concentration of active centers in the solution, which ensures the rapid growth of the polymer chains under homogeneous conditions. An x-ray study of the catalyst after polymerization shows a strongly disturbed crystal structure of the graphite. Poly-(ethylene oxide) obtained at a higher degree of conversion, does not contain low molecular weight fractions.     

Synthesis and optical properties of colloidal tungsten oxide nanorods

Thermal decomposition of W(CO)6 in oleylamine in the presence of mild oxidant Me3NO.2H2O produces tungsten oxide nanorods with diameters ranging from 3 to 6 nm. The size of nanorods can be easily varied by the employed surfactant ratio or reaction temperature. The prepared tungsten oxide nanorods exhibit strong photoluminescence (PL) peaks in 300-500 nm, which show a weak size dependency.