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Graphene Films (graphene + film)
Selected AbstractsA Controllable Self-Assembly Method for Large-Scale Synthesis of Graphene Sponges and Free-Standing Graphene FilmsADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Fei Liu Abstract A simple method to prepare large-scale graphene sponges and free-standing graphene films using a speed vacuum concentrator is presented. During the centrifugal evaporation process, the graphene oxide (GO) sheets in the aqueous suspension are assembled to generate network-linked GO sponges or a series of multilayer GO films, depending on the temperature of a centrifugal vacuum chamber. While sponge-like bulk GO materials (GO sponges) are produced at 40,°C, uniform free-standing GO films of size up to 9,cm2 are generated at 80,°C. The thickness of GO films can be controlled from 200,nm to 1,µm based on the concentration of the GO colloidal suspension and evaporation temperature. The synthesized GO films exhibit excellent transparency, typical fluorescent emission signal, and high flexibility with a smooth surface and condensed density. Reduced GO sponges and films with less than 5,wt% oxygen are produced through a thermal annealing process at 800,°C with H2/Ar flow. The structural flexibility of the reduced GO sponges, which have a highly porous, interconnected, 3D network, as well as excellent electrochemical properties of the reduced GO film with respect to electrode kinetics for the [Fe(CN)6]3,/4, redox system, are demonstrated. [source] Superhydrophobic to Superhydrophilic Wetting Control in Graphene FilmsADVANCED MATERIALS, Issue 19 2010Javad Rafiee The wetting of graphene films from superhydrophobic (contact angle of ,160°) to superhydrophilic (,0°) is controlled using surface chemistry/roughness effects. Graphene sheets dispersed in water/acetone solvents are deposited on various substrates, where the contact angle of the graphene films could be tuned from superhydrophobic to superhydrophilic by simply controlling the relative proportion of acetone and water in the solvent. [source] Field Emission of Single-Layer Graphene Films Prepared by Electrophoretic DepositionADVANCED MATERIALS, Issue 17 2009Zhong-Shuai Wu Homogeneous single-layer graphene films are fabricated using an electrophoretic deposition technique, and their field-emission properties are investigated. The graphene films show high density, uniform thickness, numerous edges normal to the film surface, and good interface contact and adhesion with the substrate, and consequently show excellent field-emission properties. [source] A Controllable Self-Assembly Method for Large-Scale Synthesis of Graphene Sponges and Free-Standing Graphene FilmsADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Fei Liu Abstract A simple method to prepare large-scale graphene sponges and free-standing graphene films using a speed vacuum concentrator is presented. During the centrifugal evaporation process, the graphene oxide (GO) sheets in the aqueous suspension are assembled to generate network-linked GO sponges or a series of multilayer GO films, depending on the temperature of a centrifugal vacuum chamber. While sponge-like bulk GO materials (GO sponges) are produced at 40,°C, uniform free-standing GO films of size up to 9,cm2 are generated at 80,°C. The thickness of GO films can be controlled from 200,nm to 1,µm based on the concentration of the GO colloidal suspension and evaporation temperature. The synthesized GO films exhibit excellent transparency, typical fluorescent emission signal, and high flexibility with a smooth surface and condensed density. Reduced GO sponges and films with less than 5,wt% oxygen are produced through a thermal annealing process at 800,°C with H2/Ar flow. The structural flexibility of the reduced GO sponges, which have a highly porous, interconnected, 3D network, as well as excellent electrochemical properties of the reduced GO film with respect to electrode kinetics for the [Fe(CN)6]3,/4, redox system, are demonstrated. [source] Atomic-Layer Graphene as a Saturable Absorber for Ultrafast Pulsed LasersADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Qiaoliang Bao Abstract The optical conductance of monolayer graphene is defined solely by the fine structure constant, ,,=, (where e is the electron charge, is Dirac's constant and c is the speed of light). The absorbance has been predicted to be independent of frequency. In principle, the interband optical absorption in zero-gap graphene could be saturated readily under strong excitation due to Pauli blocking. Here, use of atomic layer graphene as saturable absorber in a mode-locked fiber laser for the generation of ultrashort soliton pulses (756 fs) at the telecommunication band is demonstrated. The modulation depth can be tuned in a wide range from 66.5% to 6.2% by varying the graphene thickness. These results suggest that ultrathin graphene films are potentially useful as optical elements in fiber lasers. Graphene as a laser mode locker can have many merits such as lower saturation intensity, ultrafast recovery time, tunable modulation depth, and wideband tunability. [source] Preparation, Structure, and Electrochemical Properties of Reduced Graphene Sheet FilmsADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Longhua Tang Abstract This paper describes the preparation, characterization, and electrochemical properties of reduced graphene sheet films (rGSFs), investigating especially their electrochemical behavior for several redox systems and electrocatalytic properties towards oxygen and some small molecules. The reduced graphene sheets (rGSs) are produced in high yield by a soft chemistry route involving graphite oxidation, ultrasonic exfoliation, and chemical reduction. Transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy clearly demonstrate that graphene was successfully synthesized and modified at the surface of a glassy carbon electrode. Several redox species, such as Ru(NH3)63+/2+, Fe(CN)63,/4,, Fe3+/2+ and dopamine, are used to probe the electrochemical properties of these graphene films by using the cyclic voltammetry method. The rGSFs demonstrate fast electron-transfer (ET) kinetics and possess excellent electrocatalytic activity toward oxygen reduction and certain biomolecules. In our opinion, this microstructural and electrochemical information can serve as an important benchmark for graphene-based electrode performances. [source] Superhydrophobic to Superhydrophilic Wetting Control in Graphene FilmsADVANCED MATERIALS, Issue 19 2010Javad Rafiee The wetting of graphene films from superhydrophobic (contact angle of ,160°) to superhydrophilic (,0°) is controlled using surface chemistry/roughness effects. Graphene sheets dispersed in water/acetone solvents are deposited on various substrates, where the contact angle of the graphene films could be tuned from superhydrophobic to superhydrophilic by simply controlling the relative proportion of acetone and water in the solvent. [source] Field Emission of Single-Layer Graphene Films Prepared by Electrophoretic DepositionADVANCED MATERIALS, Issue 17 2009Zhong-Shuai Wu Homogeneous single-layer graphene films are fabricated using an electrophoretic deposition technique, and their field-emission properties are investigated. The graphene films show high density, uniform thickness, numerous edges normal to the film surface, and good interface contact and adhesion with the substrate, and consequently show excellent field-emission properties. [source] Epitaxial graphene: a new materialPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2008Th. Seyller Abstract Graphene, a two-dimensional sheet of sp2 -bonded carbon arranged in a honeycomb lattice, is not only the building block of fullerenes, carbon nano tubes (CNTs) and graphite, it also has interesting properties, which have caused a flood of activities in the past few years. The possibility to grow graphitic films with thicknesses down to a single graphene layer epitaxially on SiC{0001} surfaces is promising for future applications. The two-dimensional nature of epitaxial graphene films make them ideal objects for surface science techniques such as photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy. The present article summarizes results from recent photoemission studies covering a variety of aspects such as the growth of epitaxial graphene and few layer graphene, the electronic and structural properties of the interface to the SiC substrate, and the electronic structure of the epitaxial graphene stacks. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||