Showing papers on "Graphene oxide paper published in 2013"
TL;DR: In this paper, a three-dimensional network of interconnected and ordered open cells, the open cells being defined by cell walls, the cell walls being formed of graphene sheets, partially reduced graphene oxide sheets, or a combination thereof.
Abstract: The present invention relates to graphene-based foam, the graphene-based foam having a structure defined by a three-dimensional network of interconnected and ordered open cells, the open cells being defined by cell walls, the cell walls (i) being formed of graphene sheets, partially reduced graphene oxide sheets, reduced graphene oxide sheets, or a combination thereof, and (ii) having a thickness defined by the thickness of a plurality of graphene sheets, partially reduced graphene oxide sheets, reduced graphene oxide sheets, or a combination thereof.
1,344 citations
TL;DR: Graphene CVD on various metal substrates with an emphasis on Ni and Cu is reviewed, showing how few-layer graphene grown on Ni can function as flexible transparent conductive electrodes for organic photovoltaic cells and in field effect transistors.
Abstract: Since its debut in 2004, graphene has attracted enormous interest because of its unique properties. Chemical vapor deposition (CVD) has emerged as an important method for the preparation and production of graphene for various applications since the method was first reported in 2008/2009. In this Account, we review graphene CVD on various metal substrates with an emphasis on Ni and Cu. In addition, we discuss important and representative applications of graphene formed by CVD, including as flexible transparent conductors for organic photovoltaic cells and in field effect transistors.Growth on polycrystalline Ni films leads to both monolayer and few-layer graphene with multiple layers because of the grain boundaries on Ni films. We can greatly increase the percentage of monolayer graphene by using single-crystalline Ni(111) substrates, which have smooth surface and no grain boundaries. Due to the extremely low solubility of carbon in Cu, Cu has emerged as an even better catalyst for the growth of monolayer ...
1,253 citations
TL;DR: It is demonstrated that few- and several-layered graphene and graphene oxide (GO) sheets can be engineered to exhibit the desired gas separation characteristics, and tunable gas transport behavior was strongly dependent on the degree of interlocking within the GO stacking structure.
Abstract: Graphene is a distinct two-dimensional material that offers a wide range of opportunities for membrane applications because of ultimate thinness, flexibility, chemical stability, and mechanical strength. We demonstrate that few- and several-layered graphene and graphene oxide (GO) sheets can be engineered to exhibit the desired gas separation characteristics. Selective gas diffusion can be achieved by controlling gas flow channels and pores via different stacking methods. For layered (3- to 10-nanometer) GO membranes, tunable gas transport behavior was strongly dependent on the degree of interlocking within the GO stacking structure. High carbon dioxide/nitrogen selectivity was achieved by well-interlocked GO membranes in high relative humidity, which is most suitable for postcombustion carbon dioxide capture processes, including a humidified feed stream.
1,252 citations
TL;DR: In this paper, the authors reported ultrathin graphene oxide (GO) membranes, with thickness approaching 1.8 nm, which showed mixture separation selectivities as high as 3400 and 900 for H2/CO2 and H2 /N2 mixtures, respectively, through selective structural defects on GO.
Abstract: Ultrathin, molecular-sieving membranes have great potential to realize high-flux, high-selectivity mixture separation at low energy cost. Current microporous membranes [pore size < 1 nanometer (nm)], however, are usually relatively thick. With the use of current membrane materials and techniques, it is difficult to prepare microporous membranes thinner than 20 nm without introducing extra defects. Here, we report ultrathin graphene oxide (GO) membranes, with thickness approaching 1.8 nm, prepared by a facile filtration process. These membranes showed mixture separation selectivities as high as 3400 and 900 for H2/CO2 and H2/N2 mixtures, respectively, through selective structural defects on GO.
1,152 citations
TL;DR: It was found that the presence of surface oxygen could limit the number of nucleation sites and allowed centimeter-scale domains to grow through a diffusion-limited mechanism, and the electrical conductivity of the graphene was comparable to that of exfoliated graphene.
Abstract: The growth of high-quality single crystals of graphene by chemical vapor deposition on copper (Cu) has not always achieved control over domain size and morphology, and the results vary from lab to lab under presumably similar growth conditions. We discovered that oxygen (O) on the Cu surface substantially decreased the graphene nucleation density by passivating Cu surface active sites. Control of surface O enabled repeatable growth of centimeter-scale single-crystal graphene domains. Oxygen also accelerated graphene domain growth and shifted the growth kinetics from edge-attachment–limited to diffusion-limited. Correspondingly, the compact graphene domain shapes became dendritic. The electrical quality of the graphene films was equivalent to that of mechanically exfoliated graphene, in spite of being grown in the presence of O.
1,006 citations
TL;DR: In this paper, a grey metallic luster has been fabricated for the first time, by a convenient one-step method on a large scale, where the assembly of graphene oxide dispersion into ordered paper occurs simultaneously with the chemical reduction of the oxide to graphene.
Abstract: Free-standing graphene paper with a grey metallic luster has been fabricated for the first time, by a convenient one-step method on a large scale. Herein, the assembly of graphene oxide dispersion into ordered paper occurs simultaneously with the chemical reduction of graphene oxide to graphene. The graphene paper presents the advantages of good flexibility, low weight (0.2 g cm−3) and high electrical conductivity (15 Ω sq−1). Moreover, the size and shape of the graphene paper are freely exchanged for those of the Teflon substrate used. The flexible graphene–PANI paper subsequently exhibits excellent supercapacitor performance with an enhanced specific capacitance (763 F g−1) and good cycling stability by electropolymerization of PANI nanorods on the above graphene paper. The method presented here shows great promise for the development of low-cost electrode materials in potential energy storage devices.
935 citations
TL;DR: This Account describes recent work to develop such a processing route inspired by previous theoretical and experimental studies on the solvent dispersion of carbon nanotubes, and extends this process to exfoliate other layered compounds such as BN and MoS(2).
Abstract: Due to its unprecedented physical properties, graphene has generated huge interest over the last 7 years. Graphene is generally fabricated in one of two ways: as very high quality sheets produced in limited quantities by micromechanical cleavage or vapor growth or as a rather defective, graphene-like material, graphene oxide, produced in large quantities. However, a growing number of applications would profit from the availability of a method to produce high-quality graphene in large quantities.This Account describes recent work to develop such a processing route inspired by previous theoretical and experimental studies on the solvent dispersion of carbon nanotubes. That work had shown that nanotubes could be effectively dispersed in solvents whose surface energy matched that of the nanotubes. We describe the application of the same approach to the exfoliation of graphite to give graphene in a range of solvents. When graphite powder is exposed to ultrasonication in the presence of a suitable solvent, the ...
879 citations
TL;DR: The epitaxial growth of single-domain graphene on h-BN by a plasma-assisted deposition method and the synthesis method is potentially applicable on other flat surfaces could open new ways of graphene band engineering through epitaxy on different substrates.
Abstract: The epitaxial growth of large-area single-domain graphene on hexagonal boron nitride by plasma-assisted deposition is now reported. New sets of Dirac points are produced as a result of a trigonal superlattice potential, while Dirac fermion physics near the original Dirac point remain unperturbed. This growth approach could enable band engineering in graphene through epitaxy on different substrates.
870 citations
TL;DR: Graphene films can be crumpled into tailored self-organized hierarchical structures that mimic superhydrophobic leaves by harnessing the mechanical instabilities of graphene adhered on a biaxially pre-stretched polymer substrate and by controlling the relaxation of the pre-strains in a particular order.
Abstract: It is shown that by controlling the relaxation of graphene adhered on a biaxially pre-stretched polymer substrate, graphene films can be reversibly crumpled and unfolded to form tailored hierarchical structures with tunable wettability and transmittance, and that the crumpled graphene–polymer laminates can be used as actuators.
714 citations
TL;DR: Nanostrand-channelled graphene oxide ultrafiltration membranes with a network of nanochannels with a narrow size distribution and superior separation performance are reported, which offers a 10-fold enhancement without sacrificing the rejection rate compared with that of graphene oxide membranes.
Abstract: Pressure-driven ultrafiltration membranes are important in separation applications. Advanced filtration membranes with high permeance and enhanced rejection must be developed to meet rising worldwide demand. Here we report nanostrand-channelled graphene oxide ultrafiltration membranes with a network of nanochannels with a narrow size distribution (3-5 nm) and superior separation performance. This permeance offers a 10-fold enhancement without sacrificing the rejection rate compared with that of graphene oxide membranes, and is more than 100 times higher than that of commercial ultrafiltration membranes with similar rejection. The flow enhancement is attributed to the porous structure and significantly reduced channel length. An abnormal pressure-dependent separation behaviour is also reported, where the elastic deformation of nanochannels offers tunable permeation and rejection. The water flow through these hydrophilic graphene oxide nanochannels is identified as viscous. This nanostrand-channelling approach is also extendable to other laminate membranes, providing potential for accelerating separation and water-purification processes.
684 citations
TL;DR: The giant size and regular alignment of graphene sheets render the fibers with high mechanical strength and good conductivity, which promise wide applications in functional textiles, flexible and wearable sensors, and supercapacitor devices.
Abstract: Continuous, ultrastrong graphene fibers are achieved by wet-spinning of giant graphene oxide liquid crystals, followed by wet-drawing and ion-cross-linking. The giant size and regular alignment of graphene sheets render the fibers with high mechanical strength and good conductivity. Such graphene fibers promise wide applications in functional textiles, flexible and wearable sensors, and supercapacitor devices.
TL;DR: In this article, a sugar-blowing approach based on a polymeric predecessor was used to synthesize a 3D graphene bubble network, which consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts.
Abstract: Three-dimensional graphene architectures in the macroworld can in principle maintain all the extraordinary nanoscale properties of individual graphene flakes. However, current 3D graphene products suffer from poor electrical conductivity, low surface area and insufficient mechanical strength/elasticity; the interconnected self-supported reproducible 3D graphenes remain unavailable. Here we report a sugar-blowing approach based on a polymeric predecessor to synthesize a 3D graphene bubble network. The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts. Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties. The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work.
TL;DR: In this article, the authors discuss the genesis of impermeability in graphene and its extraordinary applications in fluid-encasement for wet electron-microscopy, selective gas-permeation, nanopore-bio-diffusion, and barrier coating against rusting and environmental hazards.
TL;DR: The strengthening mechanism of the RGO is investigated by a double cantilever beam test using the graphene/Cu model structure and the yield strength of the 2.5 vol% RGO/Cu nanocomposite is 1.8 times higher than that of pure Cu.
Abstract: RGO flakes are homogeneously dispersed in a Cu matrix through a molecular-level mixing process. This novel fabrication process prevents the agglomeration of the RGO and enhances adhesion between the RGO and the Cu. The yield strength of the 2.5 vol% RGO/Cu nanocomposite is 1.8 times higher than that of pure Cu. The strengthening mechanism of the RGO is investigated by a double cantilever beam test using the graphene/Cu model structure.
TL;DR: The electrochemical performance of the bent asymmetric device with a total active mass of 15 mg remains similar to the one in the flat configuration, demonstrating good mechanical robustness of the device.
Abstract: Well-separated RGO sheets decorated with MnO2 nanoparticles facilitate easy access of the electrolyte ions to the high surface area of the paper electrode, enabling the fabrication of a thicker electrode with heavier areal mass and higher areal capacitance (up to 897 mF cm(-2) ). The electrochemical performance of the bent asymmetric device with a total active mass of 15 mg remains similar to the one in the flat configuration, demonstrating good mechanical robustness of the device.
TL;DR: A new pathway is reported to greatly reduce the graphene nucleation density from ~10(6) to 4 nuclei cm(-2), enabling the growth of giant single crystals of monolayer graphene with a lateral size up to 5 mm and Bernal-stacked bilayers graphene with the lateral sizes up to 300 μm, both the largest reported to date.
Abstract: The growth of large-domain single crystalline graphene with the controllable number of layers is of central importance for large-scale integration of graphene devices. Here we report a new pathway to greatly reduce the graphene nucleation density from ~10(6) to 4 nuclei cm(-2), enabling the growth of giant single crystals of monolayer graphene with a lateral size up to 5 mm and Bernal-stacked bilayer graphene with the lateral size up to 300 μm, both the largest reported to date. The formation of the giant graphene single crystals eliminates the grain boundary scattering to ensure excellent device-to-device uniformity and remarkable electronic properties with the expected quantum Hall effect and the highest carrier mobility up to 16,000 cm(2) V(-1) s(-1). The availability of the ultra large graphene single crystals can allow for high-yield fabrication of integrated graphene devices, paving a pathway to scalable electronic and photonic devices based on graphene materials.
TL;DR: In this article, a unique and convenient hydrothermal process for controlled synthesis and structural adjustment of the nitrogen-doped graphene hydrogel (GN-GH) was presented, which can be readily scaled-up for mass production of GN-GH by using organic amine and graphene oxide as precursors.
TL;DR: Two- and three-electrode cell measurements showed that energy storage in the B-rG-O supercapacitors was contributed by ion adsorption on the surface of the nanoplatelets in addition to electrochemical redox reactions.
Abstract: Chemically modified graphene (CMG) nanoplatelets have shown great promise in various applications due to their electrical properties and high surface area. Chemical doping is one of the most effective methods to tune the electronic properties of graphene materials. In this work, novel B-doped nanoplatelets (borane-reduced graphene oxide, B-rG-O) were produced on a large scale via the reduction of graphene oxide by a borane-tetrahydrofuran adduct under reflux, and their use for supercapacitor electrodes was studied. This is the first report on the production of B-doped graphene nanoplatelets from a solution process and on the use of B-doped graphene materials in supercapacitors. The B-rG-O had a high specific surface area of 466 m2/g and showed excellent supercapacitor performance including a high specific capacitance of 200 F/g in aqueous electrolyte as well as superior surface area-normalized capacitance to typical carbon-based supercapacitor materials and good stability after 4500 cycles. Two- and three...
TL;DR: This work has shown that the WS2 /rGO hybrid nanosheets show much better electrocatalytic activity for the hydrogen evolution reaction than WS2 nanOSheets alone.
Abstract: Composite materials: Tungsten disulfide and WS2 /reduced graphene oxide (WS2 /rGO) nanosheets were fabricated by hydrothermal synthesis using tungsten chloride, thioacetamide, and graphene oxide (GO) as starting materials. The WS2 nanosheets are efficiently templated on the rGO layer. The WS2 /rGO hybrid nanosheets show much better electrocatalytic activity for the hydrogen evolution reaction than WS2 nanosheets alone.
TL;DR: It is demonstrated that electrochemical exfoliation of graphite furnishes graphene sheets of high quality and that the patterned EG can serve as high-performance source/drain electrodes for organic field-effect transistors.
Abstract: Solution-processable thin layer graphene is an intriguing nanomaterial with tremendous potential for electronic applications. In this work, we demonstrate that electrochemical exfoliation of graphite furnishes graphene sheets of high quality. The electrochemically exfoliated graphene (EG) contains a high yield (>80%) of one- to three-layer graphene flakes with high C/O ratio of 12.3 and low sheet resistance (4.8 kΩ/□ for a single EG sheet). Due to the solution processability of EG, a vacuum filtration method in association with dry transfer is introduced to produce large-area and highly conductive graphene films on various substrates. Moreover, we demonstrate that the patterned EG can serve as high-performance source/drain electrodes for organic field-effect transistors.
TL;DR: This study reports a highly efficient one-pot reduction of graphene oxide using a sodium-ammonia solution as the reducing agent and demonstrates a new, low-temperature solution processing approach to high-quality graphene materials with lowest sheet resistance and highest carrier mobility.
Abstract: Chemical reduction of graphene oxide can be used to produce large quantities of reduced graphene oxide for potential application in electronics, optoelectronics, composite materials and energy-storage devices. Here we report a highly efficient one-pot reduction of graphene oxide using a sodium-ammonia solution as the reducing agent. The solvated electrons in sodium-ammonia solution can effectively facilitate the de-oxygenation of graphene oxide and the restoration of π-conjugation to produce reduced graphene oxide samples with an oxygen content of 5.6 wt%. Electrical characterization of single reduced graphene oxide flakes demonstrates a high hole mobility of 123 cm2 Vs−1. In addition, we show that the pre-formed graphene oxide thin film can be directly reduced to form reduced graphene oxide film with a combined low sheet resistance (~350 Ω per square with ~80% transmittance). Our study demonstrates a new, low-temperature solution processing approach to high-quality graphene materials with lowest sheet resistance and highest carrier mobility. The chemical reduction of graphene oxide can provide large quantities of reduced graphene oxide for potential application in electronics and composite materials. Feng et al. report a highly efficient low-temperature one-pot reduction of graphene oxide that uses sodium-ammonia solution as the reducing agent.
TL;DR: This finding indicates the possibility of GO-based perfect two-dimensional proton-conductive materials for applications in fuel cells, sensors, and so on.
Abstract: We measured the proton conductivity of bulk graphite oxide (GO'), a graphene oxide/proton hybrid (GO-H), and a graphene oxide (GO) nanosheet for the first time. GO is a well-known electronic insulator, but for proton conduction we observed the reverse trend, as it exhibited superionic conductivity. The hydrophilic sites present in GO as -O-, -OH, and -COOH functional groups attract the protons, which propagate through hydrogen-bonding networks along the adsorbed water film. The proton conductivities of GO' and GO-H at 100% humidity were ∼10(-4) and ∼10(-5) S cm(-1), respectively, whereas that for GO was amazingly high, nearly 10(-2) S cm(-1). This finding indicates the possibility of GO-based perfect two-dimensional proton-conductive materials for applications in fuel cells, sensors, and so on.
TL;DR: In this paper, a high-quality graphene transparent conductive film was fabricated by roll-to-roll chemical vapor deposition (CVD) synthesis on a suspended copper foil and subsequent transfer.
Abstract: A high-quality graphene transparent conductive film was fabricated by roll-to-roll chemical vapor deposition (CVD) synthesis on a suspended copper foil and subsequent transfer. While the high temperature required for the CVD synthesis of high-quality graphene has prevented efficient roll-to-roll production thus far, we used selective Joule heating of the copper foil to achieve this. Low pressure thermal CVD synthesis and a direct roll-to-roll transfer process using photocurable epoxy resin allowed us to fabricate a 100-m-long graphene transparent conductive film with a sheet resistance as low as 150 Ω/sq, which is comparable to that of state-of-the-art CVD-grown graphene films.
TL;DR: The graphene edge showed 4 orders of magnitude higher specific capacitance, much faster electron transfer rate and stronger electrocatalytic activity than those of graphene basal plane, making it an ideal electrode for electrocatalysis and for the storage of capacitive charges.
Abstract: Graphene has a unique atom-thick two-dimensional structure and excellent properties, making it attractive for a variety of electrochemical applications, including electrosynthesis, electrochemical sensors or electrocatalysis, and energy conversion and storage. However, the electrochemistry of single-layer graphene has not yet been well understood, possibly due to the technical difficulties in handling individual graphene sheet. Here, we report the electrochemical behavior at single-layer graphene-based electrodes, comparing the basal plane of graphene to its edge. The graphene edge showed 4 orders of magnitude higher specific capacitance, much faster electron transfer rate and stronger electrocatalytic activity than those of graphene basal plane. A convergent diffusion effect was observed at the sub-nanometer thick graphene edge-electrode to accelerate the electrochemical reactions. Coupling with the high conductivity of a high-quality graphene basal plane, graphene edge is an ideal electrode for electrocatalysis and for the storage of capacitive charges.
TL;DR: The protocol allows the wet chemical synthesis of graphene from a new form of graphene oxide that consists of an intact hexagonal σ-framework of C-atoms that can be easily reduced to graphene that is no longer dominated by defects.
Abstract: A suitable technology for the preparation of graphene based on versatile wet chemistry is presented for the first time. The protocol allows the wet chemical synthesis of graphene from a new form of graphene oxide that consists of an intact hexagonal σ-framework of C-atoms. Thus, it can be easily reduced to graphene that is no longer dominated by defects.
TL;DR: Super gas barrier thin films, fabricated with layer-by-layer assembly of polyethylenimine and graphene oxide, exhibit significantly reduced oxygen and carbon dioxide transmission rates and provide high gas selectivity for hydrogen.
Abstract: Super gas barrier thin films, fabricated with layer-by-layer assembly of polyethylenimine and graphene oxide, exhibit significantly reduced oxygen and carbon dioxide transmission rates. This thin film's nanobrick wall structure also provides high gas selectivity for hydrogen.
TL;DR: Covalently grafting reduced graphene oxide (rGO) sheets with sulfophenyl or ethylenediamine groups can produce chemically modified graphene (CMG) for fabricating high-performance gas sensors that exhibit sensitivities 4 to 16 times higher than that of a sensor based on rGO.
Abstract: Covalently grafting reduced graphene oxide (rGO) sheets with sulfophenyl or ethylenediamine groups can produce chemically modified graphene (CMG) for fabricating high-performance gas sensors. The NO(2) sensors based on these CMGs exhibit sensitivities 4 to 16 times higher than that of a sensor based on rGO. They also show excellent selectivity and repeatability without the aid of UV-light or thermal treatment.
TL;DR: Structural properties, syntheses, chemistry, stabilities, and electronic properties of fluorographene and other partially fluorinated, chlorinated, and brominated graphenes are discussed and patterned halogenation is presented as an interesting approach for generating materials with applications in the field of graphene-based electronic devices.
Abstract: Graphene derivatives containing covalently bound halogens (graphene halides) represent promising two-dimensional systems having interesting physical and chemical properties. The attachment of halogen atoms to sp2 carbons changes the hybridization state to sp3, which has a principal impact on electronic properties and local structure of the material. The fully fluorinated graphene derivative, fluorographene (graphene fluoride, C1F1), is the thinnest insulator and the only stable stoichiometric graphene halide (C1X1). In this review, we discuss structural properties, syntheses, chemistry, stabilities, and electronic properties of fluorographene and other partially fluorinated, chlorinated, and brominated graphenes. Remarkable optical, mechanical, vibrational, thermodynamic, and conductivity properties of graphene halides are also explored as well as the properties of rare structures including multilayered fluorinated graphenes, iodine-doped graphene, and mixed graphene halides. Finally, patterned halogenati...
TL;DR: Highly blue-luminescent nitrogen-doped graphene quantum dots are obtained by hydrothermal treatment of graphene oxide in the presence of ammonia and showed bright luminescence and excellent biocompatibility.
Abstract: Highly blue-luminescent nitrogen-doped graphene quantum dots (N-GQDs) are obtained by hydrothermal treatment of graphene oxide in the presence of ammonia. The yield of N-GQDs is about 8.7% in weight. A high quantum yield of maximum 24.6% at an excitation wavelength of 340 nm is achieved. They are applied for bioimaging of HeLa cells, and showed bright luminescence and excellent biocompatibility.
TL;DR: The current study delivers a message that various condensation reactions engaging GO sheets can be a general synthetic approach for restacking-inhibited graphene in scalable solution processes.
Abstract: Graphene has received considerable attention in both scientific and technological areas due to its extraordinary material properties originating from the atomically single- or small number-layered structure. Nevertheless, in most scalable solution-based syntheses, graphene suffers from severe restacking between individual sheets and thus loses its material identity and advantages. In the present study, we have noticed the intercalated water molecules in the dried graphene oxide (GO) as a critical mediator to such restacking and thus eliminated the hydrogen bonding involving the intercalated water by treating GO with melamine resin (MR) monomers. Upon addition of MR monomers, porous restacking-inhibited GO sheets precipitated, leading to the carbonaceous composite with an exceptionally large surface area of 1040 m2/g after a thermal treatment. Utilizing such high surface area, the final graphene composite exhibited excellent electrochemical performance as a supercapacitor electrode material: specific capac...