Making graphene visible

Controlled growth of high-quality graphene is still the bottleneck of practical applications. The widely used chemical vapour deposition process generally suffers from an uncontrollable carbon precipitation effect that leads to inhomogeneous growth and strong correlation to the growth conditions. Here we report the rational design of a binary metal alloy that effectively suppresses the carbon precipitation process and activates a self-limited growth mechanism for homogeneous monolayer graphene. As demonstrated by an ni-mo alloy, the designed binary alloy contains an active catalyst component for carbon source decomposition and graphene growth and a black hole counterpart for trapping the dissolved carbons and forming stable metal carbides. This type of process engineering has been used to grow strictly singlelayer graphene with 100% surface coverage and excellent tolerance to variations in growth conditions. With simplicity, scalability and a very large growth window, the presented approach may facilitate graphene research and industrial applications.

show abstract

“…S1). The graphene film can be clearly visualized due to its light interference 23 . An optical microscope image (Fig.…”

Section: Resultsmentioning

confidence: 99%

Rational design of a binary metal alloy for chemical vapour deposition growth of uniform single-layer graphene

et al. 2011

View full text Add to dashboard Cite

show abstract

“…1B) by mechanical exfoliation from graphite on SiO 2 13 . Monolayer graphene is identified by its particular optical contrast 14 in the optical microscope and by Raman measurements (Fig. 1C).…”

Section: -3 -mentioning

confidence: 99%

DNA Translocation through Graphene Nanopores

Schneider¹,

Kowalczyk²,

Calado³

et al. 2010

Nano Lett.

940

930

View full text Add to dashboard Cite

In the past few years, nanopores have emerged as a new powerful tool to interrogate single molecules. They have been successfully used to rapidly characterize biopolymers like DNA 3,4 , RNA 5 , as well as DNA-ligand complexes 6 and local protein structures along DNA 7 at the single-molecule level. A key driving force for nanopore research in the past decade has been the prospect of DNA sequencing. However, a major roadblock for achieving high-resolution DNA sequencing with pores is the finite length of the channel constituting the pore (Fig. 1A). In a long nanopore, the current blockade resulting from DNA translocation is due to a large number of bases (for typical devices ~10-100 bases) present in the pore. Here, we demonstrate that this limitation can be overcome by realizing an ultimately thin nanopore in a graphene monolayer. We obtain single-layer graphene (Fig. 1B) by mechanical exfoliation from graphite on SiO 2 13 . Monolayer graphene is identified by its particular optical contrast 14 in the optical microscope and by Raman measurements (Fig. 1C). At ~ 1590 cm -1 , we measure the socalled G resonance peak and at ~2690 cm -1 the 2D resonance peak. In the case of multilayer graphene, the 2D resonance peak splits off in multiple peaks in contrast to monolayer graphene which has a very sharp single resonance peak. In this way, we are well able to distinguish single-layer graphene from multilayer graphene 15 .Next we select a monolayer of graphene and transfer it onto a SiN support membrane with a 5 micron sized hole 16 by use of our recently developed 'wedging transfer' technique 17 . This transfer procedure is straightforward: flakes can be overlaid to support membranes in less than an hour. Briefly, a hydrophobic polymer is spun onto a hydrophilic substrate (here plasma-oxidized SiO 2 ) with graphene flakes, and wedged off the substrate by sliding it at an angle in water. Graphene flakes are peeled off the SiO 2 along with the -4 -polymer. The polymer is then floating on the water surface, located near a target SiN substrate, the water level is lowered, and the flakes are positioned onto the SiN membrane with micrometer lateral precision. In the final step the polymer is dissolved.We then drill a nanopore into the graphene monolayer using the highly focused electron beam of a transmission electron microscope (TEM). The acceleration voltage is 300 kV, well above the 80-140 kV knock-out voltage for carbon atoms in graphene 18 (see Methods).Drilling the holes by TEM is a robust well-reproducible procedure (we drilled 31 holes with diameters ranging from 2 to 40 nm, in monolayer as well as in multilayer graphene; some examples of pores are shown in Fig. 2). Because of the high acceleration voltage of the electron beam, drilling could potentially induce damage to the graphene around the pore. However, electron beam diffraction measurements across the hole ( Fig. 2B and C) confirm the crystallinity of the monolayer surrounding the hole, as evidenced by the well-defined hexagonal diffraction patterns (Fig. 2C).Su...

show abstract

“…Figure 3 illustrates the morphological changes in GO during the reduction, and Figure 4 provides an indirect representation of the varying GO sizes and hydrophilicity changes. Fewer layered graphene sheets in the GO solution were optically identified because of a rather weak contrast with the surroundings [39]. However, multilayered sheets with some crumples/ripples were occasionally found.…”

Section: Graphene Oxide and Reductantsmentioning

confidence: 99%

Graphene oxide adsorption enhanced by in situ reduction with sodium hydrosulfite to remove acridine orange from aqueous solution

Sun

Fugetsu

2012

Journal of Hazardous Materials

206

107

View full text Add to dashboard Cite

Graphene oxide (GO) is a highly effective adsorbent, and its absorbing capability is further enhanced through its in situ reduction with sodium hydrosulfite as the reductant. Acridine orange is the selected target to eliminate with GO as the adsorbent.Under identical conditions, GO without the in situ reduction showed a maximum adsorption capacity of 1.4 g g -1 , and GO with the in situ reduction provided a maximum adsorption capacity of 3.3 g g -1 . Sodium hydrosulfite converts carbonyl groups on GO into hydroxyl groups, which function as the key sites for the adsorption enhancement.

show abstract

Making graphene visible

Cited by 1,835 publications

References 11 publications

Rational design of a binary metal alloy for chemical vapour deposition growth of uniform single-layer graphene

Rational design of a binary metal alloy for chemical vapour deposition growth of uniform single-layer graphene

DNA Translocation through Graphene Nanopores

Graphene oxide adsorption enhanced by in situ reduction with sodium hydrosulfite to remove acridine orange from aqueous solution

Contact Info

Product

Resources

About