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#Mix of graphene nanoribbons, polymer has potential for cars, soda, beera discovery at Rice university aims to make vehicles that run on compressed natural gas more practical.

By adding modified single-atom-thick graphene nanoribbons (GNRS) to thermoplastic polyurethane (TPU) the Rice lab made it 1000 times harder for gas molecules to escape Tour said.

The researchers acknowledged that a solid two-dimensional sheet of graphene might be the perfect barrier to gas

but the production of graphene in such bulk quantities is not yet practical Tour said. But graphene nanoribbons are already there.

Tour's breakthrough unzipping technique for turning multiwalled carbon nanotubes into GNRS first revealed in Nature in 2009 has been licensed for industrial production.

But the overlapping 200-to 300-nanometer-wide ribbons dispersed so well that they were nearly as effective as large-sheet graphene in containing gas molecules.

The GNRS'geometry makes them far better than graphene sheets for processing into composites Tour said.

The Air force Research Laboratory through the University Technology Corp. the Office of Naval Research MURI graphene program and the Air force Office of Scientific research MURI program supported the research.

and to analyze their characteristics The hope is that MDS could be joined with graphene which has no band gap

Last year Lou and Ajayan revealed their success at making intricate patterns of intertwining graphene and hbn among them the image of Rice's owl mascot.

The study of graphene prompted research into a lot of 2-D materials; molybdenum disulfide is just one of them.

Essentially we are trying to span the whole range of band gaps between graphene which is a semimetal and the boron nitride insulator.

MDS is distinct from graphene and hbn because it isn't exactly flat. Graphene and hbn are flat with arrays of hexagons formed by their constituent atoms.

But while MDS looks hexagonal when viewed from above it is actually a stack with a layer of molybdenum atoms between two layers of sulfur atoms.

We would like to stick graphene and MDS together (with hbn) into what would be a novel 2-D semiconductor component.

or graphene Najmaei said. We started learning that we could control that nucleation by adding artificial edges to the substrate

With ORNL's images in hand they were not only able to calculate the energies of a much more complex set of defects than are found in graphene

#Even with defects, graphene is strongest material in the worldin a new study published in Science Columbia Engineering researchers demonstrate that graphene

even if stitched together from many small crystalline grains is almost as strong as graphene in its perfect crystalline form.

Graphene consists of a single atomic layer of carbon arranged in a honeycomb lattice. Our first Science paper in 2008 studied the strength graphene can achieve

if it has no defects--its intrinsic strength says James Hone professor of mechanical engineering who led the study with Jeffrey Kysar professor of mechanical engineering.

But defect-free pristine graphene exists only in very small areas. Large-area sheets required for applications must contain many small grains connected at grain boundaries

This our second Science paper reports on the strength of large-area graphene films grown using chemical vapor deposition (CVD)

and we're excited to say that graphene is back and stronger than ever. The study verifies that commonly used methods for postprocessing CVD-grown graphene weaken grain boundaries resulting in the extremely low strength seen in previous studies.

The Columbia Engineering team developed a new process that prevents any damage of graphene during transfer.

We substituted a different etchant and were able to create test samples without harming the graphene notes the paper's lead author Gwan-Hyoung Lee a postdoctoral fellow in the Hone lab. Our findings clearly correct the mistaken consensus that grain boundaries of graphene

are weak. This is great news because graphene offers such a plethora of opportunities both for fundamental scientific research and industrial applications.

In its perfect crystalline form graphene (a one-atom-thick carbon layer) is the strongest material ever measured as the Columbia Engineering team reported in Science in 2008--so strong that as Hone observed it would take an elephant balanced on a pencil to break through a sheet

of graphene the thickness of Saran wrap. For the first study the team obtained small structurally perfect flakes of graphene by mechanical exfoliation or mechanical peeling from a crystal of graphite.

But exfoliation is a time-consuming process that will never be practical for any of the many potential applications of graphene that require industrial mass production.

Currently scientists can grow sheets of graphene as large as a television screen by using chemical vapor deposition (CVD) in

which single layers of graphene are grown on copper substrates in a high-temperature furnace. One of the first applications of graphene may be as a conducting layer in flexible displays.

But CVD graphene is stitched'together from many small crystalline grains--like a quilt--at grain boundaries that contain defects in the atomic structure Kysar explains.

These grain boundaries can severely limit the strength of large-area graphene if they break much more easily than the perfect crystal lattice

and so there has been intense interest in understanding how strong they can be. The Columbia Engineering team wanted to discover what was making CVD graphene so weak.

In studying the processing techniques used to create their samples for testing they found that the chemical most commonly used to remove the copper substrate also causes damage to the graphene severely degrading its strength.

Their experiments demonstrated that CVD graphene with large grains is exactly as strong as exfoliated graphene showing that its crystal lattice is just as perfect.

And more surprisingly their experiments also showed that CVD graphene with small grains even when tested right at a grain boundary is about 90%as strong as the ideal crystal This is an exciting result for the future of graphene

because it provides experimental evidence that the exceptional strength it possesses at the atomic scale can persist all the way up to samples inches

or more in size says Hone. This strength will be invaluable as scientists continue to develop new flexible electronics and ultrastrong composite materials.

Strong large-area graphene can be used for a wide variety of applications such as flexible electronics

and strengthening components--potentially a television screen that rolls up like a poster or ultrastrong composites that could replace carbon fiber.

Or the researchers speculate a science fiction idea of a space elevator that could connect an orbiting satellite to Earth by a long cord that might consist of sheets of CVD graphene

since graphene (and its cousin material carbon nanotubes) is the only material with the high strength-to-weight ratio required for this kind of hypothetical application.

The team is excited also about studying 2d materials like graphene. Very little is known about the effects of grain boundaries in 2d materials Kysar adds.

Our work shows that grain boundaries in 2d materials can be much more sensitive to processing than in 3d materials.

This is due to all the atoms in graphene being surface atoms so surface damage that would normally not degrade the strength of 3d materials can completely destroy the strength of 2d materials.

However with appropriate processing that avoids surface damage grain boundaries in 2d materials especially graphene can be nearly as strong as the perfect defect-free structure.

Graphene a single sheet of carbon atoms is the thinnest electrical conductor we know. With the addition of the monolayer molybdenum disulfide and other metal dichalcogenides we have all the building blocks for modern electronics that must be created in atomically thin form.

For example we can now imagine sandwiching two different monolayer transition metal dichalcogenides between layers of graphene to make solar cells that are only eight atoms thick--20 thousand times smaller than a human hair!

#New test reveals purity of graphene: Scientists use terahertz waves to spot contaminantsgraphene may be tough

Because it's so easy to accidently introduce impurities into graphene labs led by physicists Junichiro Kono of Rice

They expect the finding to be important to manufacturers considering the use of graphene in electronic devices.

It was made possible by the Rice-based Nanojapan program through which American undergraduates conduct summer research internships in Japanese labs. Even a single molecule of a foreign substance can contaminate graphene enough to affect its electrical and optical properties

The researchers used it as a substrate for graphene. Hitting the combined material with femtosecond pulses from a near-infrared laser prompted the indium phosphide to emit terahertz back through the graphene.

Imperfections as small as a stray oxygen molecule on the graphene were picked up by a spectrometer.

The change in the terahertz signal due to adsorption of molecules is said remarkable Kono. Not just the intensity but also the waveform of emitted terahertz radiation totally and dynamically changes in response to molecular adsorption and desorption.

The laser gradually removes oxygen molecules from the graphene changing its density and we can see that Kono said.

The experiment involved growing pristine graphene via chemical vapor deposition and transferring it to an indium phosphide substrate.

Laser pulses generated coherent bursts of terahertz radiation through a built-in surface electric field of the indium phosphide substrate that changed due to charge transfer between the graphene and the contaminating molecules.

For any future device designs using graphene we have to take into account the influence of the surroundings said Kono.

Graphene in a vacuum or sandwiched between noncontaminating layers would probably be stable but exposure to air would contaminate it he said.

The Rice and Osaka labs are continuing to collaborate on a project to measure the terahertz conductivity of graphene on various substrates he said.