The integration of nanostructured materials into macroscopic devices that can translate phenomena at the nanoscale to the macroscopic level has proved key to paving the way to realizing applications of nanomaterials.[1] To date, although remarkable progress has been made in the self-assembly of building blocks such as nanocrystals, nanotubes, nanowires, and the newly discovered graphenes, [2][3][4][5][6][7][8][9][10] very little success has been achieved with three-dimensional (3D) macroscale assemblies. Herein we report the controlled assembly of single-layered graphene oxide (GO) into 3D macrostructures promoted by a noble-metal nanocrystal (Au, Ag, Pd, Ir, Rh, or Pt, etc.). Although the density of such macroassemblies is very low (ca. 0.03 g cm À3 ), they have shown excellent mechanical properties, and have been utilized as fixed-bed catalysts for a Heck reaction resulting in both 100 % selectivity and conversion. We expect our endeavor may further the research and practical applications of graphene-based materials.Graphene is a well-defined two-dimensional structure of carbon atoms. It has received a great deal of attention because of its unique electronic, thermal, and mechanical properties. [11][12][13] Micromechanical cleavage from highly ordered pyrolytic graphite (HOPG) and the reduction of exfoliated graphite oxide sheets (graphene oxide, GO) are commonly used to produce graphene; [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] the reduction of GO appears to be a viable approach to the large-scale production of graphene. GO is usually prepared by oxidation of graphite powder with strong oxidants such as a mixture of concentrated sulfuric acid and potassium permanganate. The abundant oxygen-containing groups on GO endow it with excellent aqueous dispersion and make it easy to modify. [16][17][18][19][20][21][22][23][24][25] Recently, efforts have focused on the fabrication of graphene films through the self-assembly of the well-dispersed GO or functionalized graphene sheets. [20][21][22][23] Herein, we demonstrate that the 3D assembly of GO into macroscopic porous structures has been achieved successfully with the assistance of noble-metal nanocrystals (Au, Ag, Pd, Ir, Rh, Pt, etc.). The macroscopic size of the obtained samples can be easily controlled by adjusting the volume of the vessel, and the microstructure (the number of the pores and the pore diameter) can be controlled by varying the effective concentration of GO. These results mean that the macroscopic and microscopic structure of the sample can be controlled in one step. It not only provides a simple way to fabricate porous structures from GO, but also shows that the GO can selfassemble into more complicated 3D structures. Furthermore, the combination of noble-metal nanocrystals and the GO single layers may result in some interesting properties. As an example, we show that the Pd-embedded assemblies exhibited excellent catalytic activity and selectivity for the Heck reaction; this indicates that the self-assembled 3D structure is...

The integration of nanostructured materials into macroscopic devices that can translate phenomena at the nanoscale to the macroscopic level has proved key to paving the way to realizing applications of nanomaterials. [1] To date, although remarkable progress has been made in the self-assembly of building blocks such as nanocrystals, nanotubes, nanowires, and the newly discovered graphenes, [2][3][4][5][6][7][8][9][10] very little success has been achieved with three-dimensional (3D) macroscale assemblies. Herein we report the controlled assembly of single-layered graphene oxide (GO) into 3D macrostructures promoted by a noble-metal nanocrystal (Au, Ag, Pd, Ir, Rh, or Pt, etc.). Although the density of such macroassemblies is very low (ca. 0.03 g cm À3 ), they have shown excellent mechanical properties, and have been utilized as fixed-bed catalysts for a Heck reaction resulting in both 100 % selectivity and conversion. We expect our endeavor may further the research and practical applications of graphene-based materials.Graphene is a well-defined two-dimensional structure of carbon atoms. It has received a great deal of attention because of its unique electronic, thermal, and mechanical properties. [11][12][13] Micromechanical cleavage from highly ordered pyrolytic graphite (HOPG) and the reduction of exfoliated graphite oxide sheets (graphene oxide, GO) are commonly used to produce graphene; [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] the reduction of GO appears to be a viable approach to the large-scale production of graphene. GO is usually prepared by oxidation of graphite powder with strong oxidants such as a mixture of concentrated sulfuric acid and potassium permanganate. The abundant oxygen-containing groups on GO endow it with excellent aqueous dispersion and make it easy to modify. [16][17][18][19][20][21][22][23][24][25] Recently, efforts have focused on the fabrication of graphene films through the self-assembly of the well-dispersed GO or functionalized graphene sheets. [20][21][22][23] Herein, we demonstrate that the 3D assembly of GO into macroscopic porous structures has been achieved successfully with the assistance of noble-metal nanocrystals (Au, Ag, Pd, Ir, Rh, Pt, etc.). The macroscopic size of the obtained samples can be easily controlled by adjusting the volume of the vessel, and the

The conductance mismatch problem limits the spin-injection efficiency significantly, and spin-injection into graphene has been usually requiring high-quality tunnel barriers to circumvent the conductance mismatch. We introduce a novel approach, which enables generation of a pure spin current into single-layer graphene (SLG) free from electrical conductance mismatch by using dynamical spin injection. Experimental demonstration of spin-pumping-induced spin current generation and spin transport in SLG at room temperature was successfully achieved and the spin coherence was estimated to be 1.36 µm by using a conventional theoretical model based on Landau-Lifshitz-Gilbert equation. The spin coherence is proportional to the quality of SLG, which indicates that spin relaxation in SLG is governed by the Elliot-Yafet mechanism as was reported.

High-quality graphene flakes have been exfoliated directly from graphite by solvothermal treatment. By introducing the oil/water interface, graphene can be easily and quickly separated from the graphene/NMP solution, which overcomes shortcomings of the time-consuming method of filtration. At the same time, the graphene film can be fabricated at the oil/water interface by controlling the volume of graphene/NMP solution. Furthermore, carbon nanotube/carbon nanospheres films can also be prepared successfully through the same separation method.

Abstract