An improved method for the preparation of graphene oxide (GO) is described. Currently, Hummers’ method (KMnO4, NaNO3, H2SO4) is the most common method used for preparing graphene oxide. We have found that excluding the NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9:1 mixture of H2SO4/H3PO4 improves the efficiency of the oxidation process. This improved method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers’ method or Hummers’ method with additional KMnO4. Moreover, even though the GO produced by our method is more oxidized than that prepared by Hummers’ method, when both are reduced in the same chamber with hydrazine, chemically converted graphene (CCG) produced from this new method is equivalent in its electrical conductivity. In contrast to Hummers’ method, the new method does not generate toxic gas and the temperature is easily controlled. This improved synthesis of GO may be important for large-scale production of GO as well as the ...

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Improved Synthesis of Graphene Oxide

Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

Functionalization of Graphene: Covalent and Non-Covalent Approaches, Derivatives and Applications

Isolated graphene, a nanometer-thick two-dimensional analog of fullerenes and carbon nanotubes, has recently sparked great excitement in the scientific community given its excellent mechanical and electronic properties. Particularly attractive is the availability of bulk quantities of graphene as both colloidal dispersions and powders, which enables the facile fabrication of many carbon-based materials. The fact that such large amounts of graphene are most easily produced via the reduction of graphene oxide--oxygenated graphene sheets covered with epoxy, hydroxyl, and carboxyl groups--offers tremendous opportunities for access to functionalized graphene-based materials. Both graphene oxide and graphene can be processed into a wide variety of novel materials with distinctly different morphological features, where the carbonaceous nanosheets can serve as either the sole component, as in papers and thin films, or as fillers in polymer and/or inorganic nanocomposites. This Review summarizes techniques for preparing such advanced materials via stable graphene oxide, highly reduced graphene oxide, and graphene dispersions in aqueous and organic media. The excellent mechanical and electronic properties of the resulting materials are highlighted with a forward outlook on their applications.

Graphene oxide, highly reduced graphene oxide, and graphene: versatile building blocks for carbon-based materials.

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.

Graphene-Based Materials: Synthesis, Characterization, Properties, and Applications

Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review

In this study, we report an inexpensive, massively scalable, fast, and facile method for preparation of graphene oxide and reduced graphene oxide nanoplatelets. The basic strategy involved the preparation of graphite oxide (GO) from graphite through reaction with benzoyl peroxide (BPO), complete exfoliation of GO into graphene oxide sheets, followed by their in situ reduction to reduced graphene oxide nanoplatelets. The mechanism of graphene oxide producing is mainly the generation of oxygen-containing groups on graphene sheets. In addition, inserted BPO and expansion of CO2 evolved during reaction will expand the distance between graphite layers, which are also main factors for exfoliation. Thermogravimetric analysis, Raman spectroscopy, and Fourier transform infrared spectroscopy indicated the successful preparation of GO. X-ray diffraction proved the mechanism of intercalation and exfoliation of graphite. Transmission electron microscopy and atomic force microscopy were used to demonstrate the structur...

Fast and Facile Preparation of Graphene Oxide and Reduced Graphene Oxide Nanoplatelets

Graphene, a flat monolayer of carbon atoms tightly packed into a two-dimensional honeycomb lattice, has attracted a great deal of attention in recent years for potential applications in many technological fields, such as nanoelectronics, nanocomposites, and hydrogen supercapacitors. One possible route to harnessing these properties would be to incorporate graphene sheets into composite materials. The manufacturing of such composites requires not only that the graphene sheets are produced on a sufficient scale, but also that they are incorporated, and homogeneously distributed, into various matrices. Graphite, which consists of a stack of flat graphene sheets, is available in large quantities from natural sources. It is likely the most readily available and least expensive source for the production of bulk graphene sheets. Graphite oxide (GO) is a layered material produced by the oxidation of graphite. In contrast to pristine graphite, the graphene-derived sheets in GO are heavily oxygenated and bear hydroxyl and epoxide functional groups on their basal planes, in addition to carbonyl and carboxyl groups located at the sheet edges. Unfortunately, owing to their hydrophilic nature, graphene oxide sheets can only be dispersed in aqueous media that are incompatible with most organic solvents and polymers. In addition, GO is electrically insulating, which limits its usefulness for the synthesis of composites. However, it has been demonstrated that the electrical conductivity of GO can be significantly increased and very thin graphene-like sheets can be obtained through the chemical reduction of exfoliated GO. Just like carbon nanotubes, a key challenge in the synthesis and processing of bulk-quantity graphene sheets is aggregation. Graphene sheets, due to their high specific surface area, tend to form irreversible agglomerates or even restack to form graphite through van der Waals interactions. As with carbon nanotubes, full utilization of graphene sheets in polymer nanocomposite applications will inevitably depend on their ability to achieve complete dispersion in the polymer matrix of choice.

Synthesis of amphiphilic graphene nanoplatelets.

In this report, graphene nanoplatelets were self-assembled through the layer-by-layer (LBL) method The graphene surface was modified with poly(acrylic acid) and poly(acryl amide) by covalent bonding, which introduced negative and positive charge on the surface of graphene, respectively Through electrostatic interaction, the positively and negatively charged graphene nanoplatelets assembled together to form a multilayer structure Thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy were used to demonstrate the modification of graphene nanoplatelets Fourier transform infrared spectroscopy and SEM proved this method is feasible for preparing graphene-containing films Ultraviolet−visible spectroscopy confirmed that the adsorption technique resulted in uniform film growth

Layer-by-Layer Self-Assembly of Graphene Nanoplatelets

Pt-Co supported on single-walled carbon nanotubes as an anode catalyst for direct methanol fuel cells

The grafting of polystyrene-polyacrylamide (PS–PAM) block copolymer to single-walled carbon nanotubes (SWNTs) was achieved by in situ living free radical polymerization. The resulting dispersions were stable and had homogeneous dark ink-like appearance, consisting mainly of long isolated nanotubes and thin bundles, which were confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–vis spectrometry. Long-term stabilization was achieved by covalently bonding of copolymer. This method is beneficial because the amphiphilic property of the block copolymer can help to stabilize SWNTs in both polar and non-polar solvents at the same time.

Dispersion behavior of single-walled carbon nanotubes by grafting of amphiphilic block copolymer

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