Author
Wei Lu
Other affiliations: Huaqiao University, Lawrence Berkeley National Laboratory
Bio: Wei Lu is an academic researcher from Rice University. The author has contributed to research in topics: Graphene nanoribbons & Graphene. The author has an hindex of 26, co-authored 44 publications receiving 10783 citations. Previous affiliations of Wei Lu include Huaqiao University & Lawrence Berkeley National Laboratory.
Papers
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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: It is demonstrated that unzipping multiwalled carbon nanotubes into graphene nanoribbons can enable their utilization as high-performance additives for mechanical properties enhancement in composites that rival the properties of singlewalledcarbon nanotube composites yet at an order of magnitude lower cost.
Abstract: It is well established that pristine multiwalled carbon nanotubes offer poor structural reinforcement in epoxy-based composites. There are several reasons for this which include reduced interfacial contact area since the outermost nanotube shields the internal tubes from the matrix, poor wetting and interfacial adhesion with the heavily cross-linked epoxy chains, and intertube slip within the concentric nanotube cylinders leading to a sword-in-sheath type failure. Here we demonstrate that unzipping such multiwalled carbon nanotubes into graphene nanoribbons results in a significant improvement in load transfer effectiveness. For example, at ∼0.3% weight fraction of nanofillers, the Young’s modulus of the epoxy composite with graphene nanoribbons shows ∼30% increase compared to its multiwalled carbon nanotube counterpart. Similarly the ultimate tensile strength for graphene nanoribbons at ∼0.3% weight fraction showed ∼22% improvement compared to multiwalled carbon nanotubes at the same weight fraction of n...
274 citations
TL;DR: It is demonstrated that graphene nanoribbons free of oxidized surfaces can be prepared in large batches and 100% yield by splitting multiwalled carbon nanotubes (MWCNTs) with potassium vapor, comparable to that of graphene derived from mechanically exfoliated graphite.
Abstract: Here we demonstrate that graphene nanoribbons (GNRs) free of oxidized surfaces can be prepared in large batches and 100% yield by splitting multiwalled carbon nanotubes (MWCNTs) with potassium vapor. If desired, exfoliation is attainable in a subsequent step using chlorosulfonic acid. The low-defect density of these GNRs is indicated by their electrical conductivity, comparable to that of graphene derived from mechanically exfoliated graphite. The possible origins of directionally selective splitting of MWCNTs have been explored using computer modeling, and plausible explanations for the unique role of potassium were found.
230 citations
TL;DR: The metal-graphene-CNT structure is used to directly fabricate field-emitter devices and double-layer capacitors, and can stimulate the development of several energy-efficient technologies.
Abstract: Graphene was grown directly on porous nickel films, followed by the growth of controlled lengths of vertical carbon nanotube (CNT) forests that seamlessly emanate from the graphene surface. The metal–graphene–CNT structure is used to directly fabricate field-emitter devices and double-layer capacitors. The three-dimensional nanostructured hybrid materials, with better interfacial contacts and volume utilization, can stimulate the development of several energy-efficient technologies.
210 citations
TL;DR: In this paper, a facile process to decorate graphene sheets with well-dispersed Pd nanoparticles was reported, and a Pd/TEG composite was prepared and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer−Emmett−Teller (BET) surface area analysis.
Abstract: As a two-dimensional carbon nanomaterial, graphene has a high surface area and good chemical stability; therefore, its potential applicability in composite materials and as a catalyst support is high. Here, we report a facile process to decorate graphene sheets with well-dispersed Pd nanoparticles. By the in situ formation and adhesion of Pd nanoparticles to the thermally exfoliated graphene (TEG) sheets suspended in a solvent, a Pd/TEG composite was prepared and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer−Emmett−Teller (BET) surface area analysis. The migration and aggregation of Pd nanoparticles on the graphene sheets was directly observed by scanning transmission electron microscopy. As the composite was heated to 700 °C, there was little movement of the Pd nanoparticles; on heating to 800 °C, well below the melting temperature, the Pd nanoparticles began to migrate, coalesce, and agglomerate to form larger particles. The aggregation behavior was fu...
189 citations
Cited by
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TL;DR: Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,† Vimlesh Chandra, Namdong Kim, K. Kim,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim.
Abstract: 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
3,460 citations
TL;DR: A survey of the literature on polymer nanocomposites with graphene-based fillers including recent work using graphite nanoplatelet fillers is presented in this article, along with methods for dispersing these materials in various polymer matrices.
2,782 citations
University of Cambridge1, Istituto Italiano di Tecnologia2, Lancaster University3, University of Manchester4, Catalan Institution for Research and Advanced Studies5, Technical University of Denmark6, Nokia7, Queen Mary University of London8, University of Trento9, fondazione bruno kessler10, Technische Universität München11, Polytechnic University of Milan12, Centre national de la recherche scientifique13, University of Trieste14, University of Ioannina15, University of Geneva16, Trinity College, Dublin17, Texas Instruments18, University of Paris19, Spanish National Research Council20, Leiden University21, Delft University of Technology22, University of Patras23, École Normale Supérieure24, Radboud University Nijmegen25, Nest Labs26, Airbus UK27, Seoul National University28, Yonsei University29, University of Oxford30, Chalmers University of Technology31, University of Groningen32, STMicroelectronics33, Chemnitz University of Technology34, Max Planck Society35, Aalto University36
TL;DR: An overview of the key aspects of graphene and related materials, ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries are provided.
Abstract: We present the science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems, targeting an evolution in technology, that might lead to impacts and benefits reaching into most areas of society. This roadmap was developed within the framework of the European Graphene Flagship and outlines the main targets and research areas as best understood at the start of this ambitious project. We provide an overview of the key aspects of graphene and related materials (GRMs), ranging from fundamental research challenges to a variety of applications in a large number of sectors, highlighting the steps necessary to take GRMs from a state of raw potential to a point where they might revolutionize multiple industries. We also define an extensive list of acronyms in an effort to standardize the nomenclature in this emerging field.
2,560 citations
TL;DR: In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-Capacitance have been explored and show not only enhanced capacitance, but as well good cyclability.
Abstract: Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.
2,497 citations
TL;DR: The synthesis, characterization, properties, and applications of graphene-based materials are discussed and 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.
Abstract: 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.
2,246 citations