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.

Graphene oxide, a two-dimensional aromatic scaffold decorated by oxygen-containing functional groups, possesses rich chemical properties and may present a green alternative to precious metal catalysts. Graphene oxide-based carbocatalysis has recently been demonstrated for aerobic oxidative reactions. However, its widespread application is hindered by the need for high catalyst loadings. Here we report a simple chemical treatment that can create and enlarge the defects in graphene oxide and impart on it enhanced catalytic activities for the oxidative coupling of amines to imines (up to 98% yield at 5 wt% catalyst loading, under solvent-free, open-air conditions). This study examines the origin of the enhanced catalytic activity, which can be linked to the synergistic effect of carboxylic acid groups and unpaired electrons at the edge defects. The discovery of a simple chemical processing step to synthesize highly active graphene oxide allows the premise of industrial-scale carbocatalysis to be explored.

The separation of chemical vapor deposited (CVD) graphene from the metallic catalyst it is grown on, followed by a subsequent transfer to a dielectric substrate, is currently the adopted method for device fabrication. Most transfer techniques use a chemical etching method to dissolve the metal catalysts, thus imposing high material cost in large-scale fabrication. Here, we demonstrate a highly efficient, nondestructive electrochemical route for the delamination of CVD graphene film from metal surfaces. The electrochemically delaminated graphene films are continuous over 95% of the surface and exhibit increasingly better electronic quality after several growth cycles on the reused copper catalyst, due to the suppression of quasi-periodical nanoripples induced by copper step edges. The electrochemical delamination process affords the advantages of high efficiency, low-cost recyclability, and minimal use of etching chemicals.

We demonstrate injection, transport and detection of spins in spin valve arrays patterned in both copper based chemical vapor deposition (Cu-CVD) synthesized wafer scale single layer (SLG) and bilayer graphene (BLG). We observe spin relaxation times comparable to those reported for exfoliated graphene samples demonstrating that CVD specific structural differences such as nanoripples and grain boundaries do not limit spin transport in the present samples. Our observations make Cu-CVD graphene a promising material of choice for large scale spintronic applications. KEYWORDS Spin transport, Hanle precession, graphene, CVD growth, rippleHigh charge mobility, (1) small spin-orbit coupling, (2) negligible hyperfine interaction, (3) the electric field effect (4) and last but not least the ability to sustain large current densities (5) make graphene an exceptional material for spintronic applications. The demonstration of micrometer long spin relaxation length in exfoliated SLG and BLG even at room temperature (RT) (6)-(12) and spin relaxation times in the order of nanoseconds (11)-(12) may pave the way to realize several of the recently proposed spin based device concepts. (13)- (15) However, for realistic device applications it remains to be seen, if such impressive spin transport properties can also be achieved in wafer scale CVD graphene. Equally important, spin transport studies based on micromechanically exfoliated graphene sheets are often too slow for the quick exploration of the basic spin properties of graphene and for testing potential device architectures. The recent progress in the Cu-based CVD growth of graphene has a strong impact on charge based graphene device applications. (16) However, CVD graphene has a large number of structural differences when compared to exfoliated graphene such as grain boundaries, (17) defects like pentagons, heptagons, octagons, vacancies, 1D line charges (18) and in the case of bilayer graphene possibly interlayer stacking faults. (19)-(20) In addition, the current growth and transfer process introduces residual catalysts, wrinkles, quasi-periodic nanoripple arrays and new classes of organic residues. (19) Despite all of these defects, charge mobilities in CVD graphene field effect transistors (FETs) have been comparable to what has been reported for most exfoliated graphene FETs on Si/SiO 2 substrates. (21) 3 Whether this synthesis route will also play an important role for spin transport studies and large scale spin-based device applications depends on how the same defects affect the spin relaxation times.In this Letter, we demonstrate spin transport in Cu-CVD grown SLG and BLG transferred onto conventional Si/SiO 2 substrates and discuss the role of nano-ripples, a ubiquitous surface structure of Cu-CVD graphene (19) . The growth and transfer of large-scale Cu-CVD graphene are the same as in Ref.(17). By controlling the post-growth annealing time of CVD graphene, we can obtain films with SLG coverage up to 95% or additional BLG coverage up to 40%. The latter...