Showing papers on "Graphene oxide paper published in 2010"
TL;DR: An improved method for the preparation of graphene oxide (GO) is described, finding that excluding the NaNO(3), increasing the amount of KMnO(4), and performing the reaction in a 9:1 mixture of H(2)SO(4)/H(3)PO(4) improves the efficiency of the oxidation process.
Abstract: 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 ...
9,812 citations
TL;DR: The roll-to-roll production and wet-chemical doping of predominantly monolayer 30-inch graphene films grown by chemical vapour deposition onto flexible copper substrates are reported, showing high quality and sheet resistances superior to commercial transparent electrodes such as indium tin oxides.
Abstract: The outstanding electrical, mechanical and chemical properties of graphene make it attractive for applications in flexible electronics. However, efforts to make transparent conducting films from graphene have been hampered by the lack of efficient methods for the synthesis, transfer and doping of graphene at the scale and quality required for applications. Here, we report the roll-to-roll production and wet-chemical doping of predominantly monolayer 30-inch graphene films grown by chemical vapour deposition onto flexible copper substrates. The films have sheet resistances as low as approximately 125 ohms square(-1) with 97.4% optical transmittance, and exhibit the half-integer quantum Hall effect, indicating their high quality. We further use layer-by-layer stacking to fabricate a doped four-layer film and measure its sheet resistance at values as low as approximately 30 ohms square(-1) at approximately 90% transparency, which is superior to commercial transparent electrodes such as indium tin oxides. Graphene electrodes were incorporated into a fully functional touch-screen panel device capable of withstanding high strain.
7,709 citations
TL;DR: Graphene has emerged as a subject of enormous scientific interest due to its exceptional electron transport, mechanical properties, and high surface area, and when incorporated appropriately, these atomically thin carbon sheets can significantly improve physical properties of host polymers at extremely small loading.
Abstract: Graphene has emerged as a subject of enormous scientific interest due to its exceptional electron transport, mechanical properties, and high surface area. When incorporated appropriately, these atomically thin carbon sheets can significantly improve physical properties of host polymers at extremely small loading. We first review production routes to exfoliated graphite with an emphasis on top-down strategies starting from graphite oxide, including advantages and disadvantages of each method. Then solvent- and melt-based strategies to disperse chemically or thermally reduced graphene oxide in polymers are discussed. Analytical techniques for characterizing particle dimensions, surface characteristics, and dispersion in matrix polymers are also introduced. We summarize electrical, thermal, mechanical, and gas barrier properties of the graphene/polymer nanocomposites. We conclude this review listing current challenges associated with processing and scalability of graphene composites and future perspectives f...
2,979 citations
TL;DR: This paper prepares a self-assembled graphene hydrogel (SGH) via a convenient one-step hydrothermal method and shows that the high-performance SGH with inherent biocompatibility of carbon materials is attractive in the fields of biotechnology and electrochemistry.
Abstract: Self-assembly of two-dimensional graphene sheets is an important strategy for producing macroscopic graphene architectures for practical applications, such as thin films and layered paperlike materials. However, construction of graphene self-assembled macrostructures with three-dimensional networks has never been realized. In this paper, we prepared a self-assembled graphene hydrogel (SGH) via a convenient one-step hydrothermal method. The SGH is electrically conductive, mechanically strong, and thermally stable and exhibits a high specific capacitance. The high-performance SGH with inherent biocompatibility of carbon materials is attractive in the fields of biotechnology and electrochemistry, such as drug-delivery, tissue scaffolds, bionic nanocomposites, and supercapacitors.
2,931 citations
TL;DR: Techniques for preparing such advanced materials via stable graphene oxide, highly reduced grapheneoxide, and graphene dispersions in aqueous and organic media are summarized with a forward outlook on their applications.
Abstract: 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.
2,397 citations
TL;DR: In this paper, chemically modified graphene and polyaniline (PANI) nanofiber composites were prepared by in situ polymerization of aniline monomer in the presence of graphene oxide under acid conditions.
Abstract: Chemically modified graphene and polyaniline (PANI) nanofiber composites were prepared by in situ polymerization of aniline monomer in the presence of graphene oxide under acid conditions. The obtained graphene oxide/PANI composites with different mass ratios were reduced to graphene using hydrazine followed by reoxidation and reprotonation of the reduced PANI to give the graphene/PANI nanocomposites. The morphology, composition, and electronic structure of the composites together with pure polyaniline fibers (PANI-F), graphene oxide (GO), and graphene (GR) were characterized using X-ray diffraction (XRD), solid-state 13C NMR, FT-IR, scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). It was found that the chemically modified graphene and the PANI nanofibers formed a uniform nanocomposite with the PANI fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structur...
2,025 citations
TL;DR: The fundamental structure and properties of GO-based thin films are discussed in relation to their potential applications in electronics and optoelectronics.
Abstract: Chemically derived graphene oxide (GO) possesses a unique set of properties arising from oxygen functional groups that are introduced during chemical exfoliation of graphite. Large-area thin-film deposition of GO, enabled by its solubility in a variety of solvents, offers a route towards GO-based thin-film electronics and optoelectronics. The electrical and optical properties of GO are strongly dependent on its chemical and atomic structure and are tunable over a wide range via chemical engineering. In this Review, the fundamental structure and properties of GO-based thin films are discussed in relation to their potential applications in electronics and optoelectronics.
2,020 citations
TL;DR: This method provides a facile and straightforward approach to deposit MnO(2) nanoparticles onto the graphene oxide sheets (single layer of graphite oxide) and may be readily extended to the preparation of other classes of hybrids based on GO sheets for technological applications.
Abstract: A composite of graphene oxide supported by needle-like MnO2 nanocrystals (GO−MnO2 nanocomposites) has been fabricated through a simple soft chemical route in a water−isopropyl alcohol system. The formation mechanism of these intriguing nanocomposites investigated by transmission electron microscopy and Raman and ultraviolet−visible absorption spectroscopy is proposed as intercalation and adsorption of manganese ions onto the GO sheets, followed by the nucleation and growth of the crystal species in a double solvent system via dissolution−crystallization and oriented attachment mechanisms, which in turn results in the exfoliation of GO sheets. Interestingly, it was found that the electrochemical performance of as-prepared nanocomposites could be enhanced by the chemical interaction between GO and MnO2. This method provides a facile and straightforward approach to deposit MnO2 nanoparticles onto the graphene oxide sheets (single layer of graphite oxide) and may be readily extended to the preparation of othe...
1,953 citations
TL;DR: A novel reducing agent system (hydriodic acid with acetic acid (HI-AcOH) that allows for an efficient, one-pot reduction of a solution-phased RG-O powder and vapour-phasingRG-O (VRG-O) paper and thin film is reported.
Abstract: Reduced graphene oxides (RG-Os) have attracted considerable interest, given their potential applications in electronic and optoelectronic devices and circuits. However, very little is known regarding the chemically induced reduction method of graphene oxide (G-O) in both solution and gas phases, with the exception of the hydrazine-reducing agent, even though it is essential to use the vapour phase for the patterning of hydrophilic G-Os on prepatterned substrates and in situ reduction to hydrophobic RG-Os. In this paper, we report a novel reducing agent system (hydriodic acid with acetic acid (HI-AcOH)) that allows for an efficient, one-pot reduction of a solution-phased RG-O powder and vapour-phased RG-O (VRG-O) paper and thin film. The reducing agent system provided highly qualified RG-Os by mass production, resulting in highly conducting RG-O(HI-AcOH). Moreover, VRG-O(HI-AcOH) paper and thin films were prepared at low temperatures (40 °C) and were found to be applicable to flexible devices. This one-pot method is expected to advance research on highly conducting graphene platelets.
1,923 citations
TL;DR: Graphene-based nanomaterials can effectively inhibit the growth of E. coli bacteria while showing minimal cytotoxicity and it is demonstrated that macroscopic freestanding GO and rGO paper can be conveniently fabricated from their suspension via simple vacuum filtration.
Abstract: Graphene is a monolayer of tightly packed carbon atoms that possesses many interesting properties and has numerous exciting applications. In this work, we report the antibacterial activity of two water-dispersible graphene derivatives, graphene oxide (GO) and reduced graphene oxide (rGO) nanosheets. Such graphene-based nanomaterials can effectively inhibit the growth of E. coli bacteria while showing minimal cytotoxicity. We have also demonstrated that macroscopic freestanding GO and rGO paper can be conveniently fabricated from their suspension via simple vacuum filtration. Given the superior antibacterial effect of GO and the fact that GO can be mass-produced and easily processed to make freestanding and flexible paper with low cost, we expect this new carbon nanomaterial may find important environmental and clinical applications.
1,741 citations
TL;DR: The chemical changes of oxygen-containing functional groups on the annealing of graphene oxide are elucidated and the simulations reveal the formation of highly stable carbonyl and ether groups that hinder its complete reduction to graphene.
Abstract: The excellent electrical, optical and mechanical properties of graphene have driven the search to find methods for its large-scale production, but established procedures (such as mechanical exfoliation or chemical vapour deposition) are not ideal for the manufacture of processable graphene sheets. An alternative method is the reduction of graphene oxide, a material that shares the same atomically thin structural framework as graphene, but bears oxygen-containing functional groups. Here we use molecular dynamics simulations to study the atomistic structure of progressively reduced graphene oxide. The chemical changes of oxygen-containing functional groups on the annealing of graphene oxide are elucidated and the simulations reveal the formation of highly stable carbonyl and ether groups that hinder its complete reduction to graphene. The calculations are supported by infrared and X-ray photoelectron spectroscopy measurements. Finally, more effective reduction treatments to improve the reduction of graphene oxide are proposed.
TL;DR: A controlled growth of nitrogen-doped graphene layers by liquid precursor based chemical vapor deposition (CVD) technique is demonstrated, making this a feasible and efficient process for integration into current battery manufacture technology.
Abstract: We demonstrate a controlled growth of nitrogen-doped graphene layers by liquid precursor based chemical vapor deposition (CVD) technique. Nitrogen-doped graphene was grown directly on Cu current collectors and studied for its reversible Li-ion intercalation properties. Reversible discharge capacity of N-doped graphene is almost double compared to pristine graphene due to the large number of surface defects induced due to N-doping. All the graphene films were characterized by Raman spectroscopy, transmission electron microscopy, and X-ray photoemission spectroscopy. Direct growth of active electrode material on current collector substrates makes this a feasible and efficient process for integration into current battery manufacture technology.
TL;DR: Graphene is an emerging carbon material that may soon find practical applications as discussed by the authors, and it is a potential electrode material for electrochemical energy storage, with desirable properties to meet the specific requirements for the design and configuration of advanced supercapacitor devices.
Abstract: Graphene is an emerging carbon material that may soon find practical applications. With its unusual properties, graphene is a potential electrode material for electrochemical energy storage. This article highlights recent research progress in graphene-based materials as supercapacitor electrodes. With a brief description of the working principle of supercapacitors, research progress towards the synthesis and modification of graphene-based materials, including graphene oxide, fullerenes, and carbon nanotubes, is presented. Applications of such materials with desirable properties to meet the specific requirements for the design and configuration of advanced supercapacitor devices are summarized and discussed. Future research trends towards new approaches to the design and synthesis of graphene-based nanostructures and architectures for electrochemical energy storage are proposed.
TL;DR: It is shown that when immersed in an ionic solution, a layer of graphene becomes a new electrochemical structure that is called a trans-electrode, which is an ideal substrate for very high resolution, high throughput nanopore-based single-molecule detectors.
Abstract: Isolated, atomically thin conducting membranes of graphite, called graphene, have recently been the subject of intense research with the hope that practical applications in fields ranging from electronics to energy science will emerge. The atomic thinness, stability and electrical sensitivity of graphene motivated us to investigate the potential use of graphene membranes and graphene nanopores to characterize single molecules of DNA in ionic solution. Here we show that when immersed in an ionic solution, a layer of graphene becomes a new electrochemical structure that we call a trans-electrode. The trans-electrode's unique properties are the consequence of the atomic-scale proximity of its two opposing liquid-solid interfaces together with graphene's well known in-plane conductivity. We show that several trans-electrode properties are revealed by ionic conductance measurements on a graphene membrane that separates two aqueous ionic solutions. Although our membranes are only one to two atomic layers thick, we find they are remarkable ionic insulators with a very small stable conductance that depends on the ion species in solution. Electrical measurements on graphene membranes in which a single nanopore has been drilled show that the membrane's effective insulating thickness is less than one nanometre. This small effective thickness makes graphene an ideal substrate for very high resolution, high throughput nanopore-based single-molecule detectors. The sensitivity of graphene's in-plane electronic conductivity to its immediate surface environment and trans-membrane solution potentials will offer new insights into atomic surface processes and sensor development opportunities.
TL;DR: It is demonstrated that large area, high-quality graphene with controllable thickness can be grown from different solid carbon sources—such as polymer films or small molecules—deposited on a metal catalyst substrate at temperatures as low as 800 °C.
Abstract: The past few years have seen spectacular growth of interest in graphene, the carbon monolayer with novel electronic properties. Efforts to produce large sheets of monolayer (or few-layer) graphene could receive a welcome boost from a simple new procedure. Just by baking various solid carbon sources deposited on a metal catalyst substrate at a relatively modest 800 °C, it is possible to produce either pristine graphene or doped graphene in a single step. Suitable starting materials include polymer films and various small molecules. The past few years have seen a spectacular growth of interest in graphene. Efforts to produce large sheets of monolayer (or few-layer) graphene could receive a welcome boost from the simple procedure reported by these authors. They show how baking various solid carbon sources (for example polymer films) deposited on a metal catalyst substrate can produce either pristine graphene or doped graphene in a single step. Monolayer graphene was first obtained1 as a transferable material in 2004 and has stimulated intense activity among physicists, chemists and material scientists1,2,3,4. Much research has been focused on developing routes for obtaining large sheets of monolayer or bilayer graphene. This has been recently achieved by chemical vapour deposition (CVD) of CH4 or C2H2 gases on copper or nickel substrates5,6,7. But CVD is limited to the use of gaseous raw materials, making it difficult to apply the technology to a wider variety of potential feedstocks. Here we demonstrate that large area, high-quality graphene with controllable thickness can be grown from different solid carbon sources—such as polymer films or small molecules—deposited on a metal catalyst substrate at temperatures as low as 800 °C. Both pristine graphene and doped graphene were grown with this one-step process using the same experimental set-up.
TL;DR: F fluorographene is a high-quality insulator that inherits the mechanical strength of graphene, exhibiting a Young's modulus of 100 N m(-1) and sustaining strains of 15%.
Abstract: A stoichiometric derivative of graphene with a fluorine atom attached to each carbon is reported Raman, optical, structural, micromechanical, and transport studies show that the material is qualitatively different from the known graphene-based nonstoichiometric derivatives Fluorographene is a high-quality insulator (resistivity >10(12) Omega) with an optical gap of 3 eV It inherits the mechanical strength of graphene, exhibiting a Young's modulus of 100 N m(-1) and sustaining strains of 15% Fluorographene is inert and stable up to 400 degrees C even in air, similar to Teflon
TL;DR: The synthesis of ultra-low-density three-dimensional macroassemblies of graphene sheets that exhibit high electrical conductivities and large internal surface areas are reported, making these materials viable candidates for use in energy storage, catalysis, and sensing applications.
Abstract: We report the synthesis of ultra-low-density three-dimensional macroassemblies of graphene sheets that exhibit high electrical conductivities and large internal surface areas. These materials are prepared as monolithic solids from suspensions of single-layer graphene oxide in which organic sol−gel chemistry is used to cross-link the individual sheets. The resulting gels are supercritically dried and then thermally reduced to yield graphene aerogels with densities approaching 10 mg/cm3. In contrast to methods that utilize physical cross-links between GO, this approach provides covalent carbon bonding between the graphene sheets. These graphene aerogels exhibit an improvement in bulk electrical conductivity of more than 2 orders of magnitude (∼1 × 102 S/m) compared to graphene assemblies with physical cross-links alone (∼5 × 10−1 S/m). The graphene aerogels also possess large surface areas (584 m2/g) and pore volumes (2.96 cm3/g), making these materials viable candidates for use in energy storage, catalysis...
TL;DR: This study presents one particular synthetic method for GO and raGO, and reveals that the raGO material under study is greatly structurally dissimilar to graphene, being unstable under signifi cant electron beam.
Abstract: www.MaterialsViews.com C O M M Determination of the Local Chemical Structure of Graphene Oxide and Reduced Graphene Oxide U N IC A By Kris Erickson , Rolf Erni , Zonghoon Lee , Nasim Alem , Will Gannett , and Alex Zettl * IO N Although the unique electronic and mechanical properties of graphene suggest numerous intriguing applications, the requisite large-scale direct synthesis and solution-based handling have proven diffi cult. [ 1 , 2 ] It has been suggested that a functionalized form of graphene, graphene oxide (GO), could provide a solution-friendly route to facile, high-throughput graphene manipulation. [ 2 ] For such a route to be viable, however, GO must be convertible back to graphene, ostensibly via chemical reduction and thermal annealing. Unfortunately, transport measurements indicate that the reconstituted material, reduced and annealed graphene oxide (raGO), has electrical conductivity orders of magnitude lower than that of graphene. [ 2 , 3 ] This raises the question: can oxidized graphene be effectively converted back to graphene, and if not, what can it be converted to? Central to this question are the detailed atomic structures of GO and raGO, which, despite their importance, remain largely unknown. [ 4 ] We present here ultra-high-resolution transmission electron microscopy (TEM) images and dynamics studies of suspended sheets of graphene, GO, and raGO, obtained using aberration-corrected instrumentation. It should be noted that both the label GO and raGO (also referred to as “chemically converted graphene”) [ 5 ] refer to a wide variety of materials with the properties of each material being largely dependent upon the particular synthetic route employed. This study presents one particular synthetic method for GO and raGO. Among the various methods possible for synthesizing GO and raGO, we followed methods which have yielded the highest reported fi nal conductivities, as this material would be most suitable as a potential graphene alternative. [ 2 , 6–11 ] The local and global structure and stability of GO and raGO are revealed. We fi nd that the raGO material under study is greatly structurally dissimilar to graphene, being unstable under signifi cant electron beam
TL;DR: The effect of growth parameters such as temperature, and methane flow rate and partial pressure on the growth rate, domain size, and surface coverage of graphene as determined by Raman spectroscopy, and transmission and scanning electron microscopy is reported.
Abstract: The fundamental properties of graphene are making it an attractive material for a wide variety of applications. Various techniques have been developed to produce graphene and recently we discovered the synthesis of large area graphene by chemical vapor deposition (CVD) of methane on Cu foils. We also showed that graphene growth on Cu is a surface-mediated process and the films were polycrystalline with domains having an area of tens of square micrometers. In this paper, we report on the effect of growth parameters such as temperature, and methane flow rate and partial pressure on the growth rate, domain size, and surface coverage of graphene as determined by Raman spectroscopy, and transmission and scanning electron microscopy. On the basis of the results, we developed a two-step CVD process to synthesize graphene films with domains having an area of hundreds of square micrometers. Scanning electron microscopy and Raman spectroscopy clearly show an increase in domain size by changing the growth parameters...
TL;DR: The novel AFM imaging and FEM-based mapping methods presented here are of general utility for obtaining the elastic modulus and prestress of thin membranes.
Abstract: Mechanical properties of ultrathin membranes consisting of one layer, two overlapped layers, and three overlapped layers of graphene oxide platelets were investigated by atomic force microscopy (AFM) imaging in contact mode. In order to evaluate both the elastic modulus and prestress of thin membranes, the AFM measurement was combined with the finite element method (FEM) in a new approach for evaluating the mechanics of ultrathin membranes. Monolayer graphene oxide was found to have a lower effective Young’s modulus (207.6 ± 23.4 GPa when a thickness of 0.7 nm is used) as compared to the value reported for “pristine” graphene. The prestress (39.7−76.8 MPa) of the graphene oxide membranes obtained by solution-based deposition was found to be 1 order of magnitude lower than that obtained by others for mechanically cleaved graphene. The novel AFM imaging and FEM-based mapping methods presented here are of general utility for obtaining the elastic modulus and prestress of thin membranes.
TL;DR: In this article, reduced graphene oxide is used as a support to anchor semiconductor and metal nanoparticles and discussed potential applications in catalysis, light energy conversion, and fuel cells.
Abstract: Graphene based two-dimensional carbon nanostructures serve as a support to disperse catalyst nanoparticles. Reduced graphene oxide is used as a support to anchor semiconductor and metal nanoparticles. Such a design strategy would enable the development of a multifunctional catalyst mat. This Perspective focuses on the interaction between graphene oxide−semiconductor (TiO2, ZnO) and graphene oxide−metal (Au, Pt) nanoparticles and discusses potential applications in catalysis, light energy conversion, and fuel cells.
TL;DR: In this article, a mild thermal reduction of graphene oxide (GO) to graphene was achieved with the assistance of microwaves in a mixed solution of N,N-dimethylacetamide and water (DMAc/H2O).
TL;DR: Organic light-emitting diodes with solution-processed graphene thin film transparent conductive anodes are demonstrated, resulting in devices with a performance comparable to control devices on indium-tin-oxide transparent anodes.
Abstract: Theoretical estimates indicate that graphene thin films can be used as transparent electrodes for thin-film devices such as solar cells and organic light-emitting diodes, with an unmatched combination of sheet resistance and transparency. We demonstrate organic light-emitting diodes with solution-processed graphene thin film transparent conductive anodes. The graphene electrodes were deposited on quartz substrates by spin-coating of an aqueous dispersion of functionalized graphene, followed by a vacuum anneal step to reduce the sheet resistance. Small molecular weight organic materials and a metal cathode were directly deposited on the graphene anodes, resulting in devices with a performance comparable to control devices on indium−tin-oxide transparent anodes. The outcoupling efficiency of devices on graphene and indium−tin-oxide is nearly identical, in agreement with model predictions.
TL;DR: Flexible and lightweight chemiresistormade of a thin film composed of overlapped and reduced graphene oxide platelets (RGO film) that can reversibly and selectively detect chemicallyaggressive vapors such asNO.
Abstract: Described herein is a flexible and lightweight chemiresistormade of a thin film composed of overlapped and reducedgraphene oxide platelets (RGO film), which were printedonto flexible plastic surfaces by using inkjet techniques. TheRGO films can reversibly and selectively detect chemicallyaggressivevapors suchasNO
TL;DR: Composites of Si nanoparticles highly dispersed between graphene sheets, and supported by a 3-D network of graphite formed by reconstituting regions of graphene stacks exhibit high Li ion storage capacities and cycling stability.
TL;DR: A possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide is shown.
Abstract: Graphene oxide/TiO2 composites were prepared by using TiCl3 and graphene oxide as reactants. The concentration of graphene oxide in starting solution played an important role in photoelectronic and photocatalytic performance of graphene oxide/TiO2 composites. Either a p-type or n-type semiconductor was formed by graphene oxide in graphene oxide/TiO2 composites. These semiconductors could be excited by visible light with wavelengths longer than 510 nm and acted as sensitizer in graphene oxide/TiO2 composites. Visible-light driven photocatalytic performance of graphene oxide/TiO2 composites in degradation of methyl orange was also studied. Crystalline quality and chemical states of carbon elements from graphene oxide in graphene oxide/TiO2 composites depended on the concentration of graphene oxide in the starting solution. This study shows a possible way to fabricate graphene oxide/semiconductor composites with different properties by using a tunable semiconductor conductivity type of graphene oxide.
TL;DR: The electrochemically reduced graphene oxide (ER-G) has shown promising features for applications in energy storage, biosensors, and electrocatalysis as discussed by the authors, which can be used for energy storage.
Abstract: Graphene oxide is electrochemically reduced which is called electrochemically reduced graphene oxide (ER-G). ER-G is characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The oxygen content is significantly decreased and the sp2 carbon is restored after electrochemical reduction. ER-G exhibits much higher electrochemical capacitance and cycling durability than carbon nanotubes (CNTs) and chemically reduced graphene; the specific capacitance measured with cyclic voltammetry (20 mV s−1) is ∼165, ∼86, and ∼100 F g−1 for ER-G, CNTs, and chemically reduced graphene, respectively. The electrochemical reduction of oxygen and hydrogen peroxide are greatly enhanced on ER-G electrodes as compared with CNTs. ER-G has shown promising features for applications in energy storage, biosensors, and electrocatalysis.
TL;DR: In this paper, a simple yet versatile method to simultaneously achieve the exfoliation and reduction of graphite oxide was proposed, which was shown to achieve specific capacitance values as high as 191 F/g with KOH electrolyte.
TL;DR: The approach, which provides a physical mechanism for the introduction of defect and subsequent hetero dopant atoms into the graphene material in a controllable fashion, will be promising for producing graphene-based devices for multiple applications.
Abstract: Opening and tuning an energy gap in graphene are central to many electronic applications of graphene. Here we report N-doped graphene obtained by NH3 annealing after N+-ion irradiation of graphene samples. First, the evolution of the graphene microstructure was investigated following N+-ion irradiation at different fluences using Raman spectroscopy, showing that defects were introduced in plane after irradiation and then restored after annealing in N2 or in NH3. Auger electron spectroscopy (AES) of the graphene annealed in NH3 after irradiation showed N signal, however, no N signal was observed after annealing in N2. Last, the field-effect transistor (FET) was fabricated using N-doped graphene and monitored by the source−drain conductance and back-gate voltage (Gsd−Vg) curves in the measurement. The transport property changed compared to that of the FET made by intrinsic graphene, that is, the Dirac point position moved from positive Vg to negative Vg, indicating the transition of graphene from p-type to ...
TL;DR: Graphene nanosheets were prepared by complete oxidation of pristine graphite followed by thermal exfoliation and reduction in this paper, and the incorporation of graphene greatly improved the electrical conductivity of PET, resulting in a sharp transition from electrical insulator to semiconductor with a low percolation threshold of 0.47 vol.%.