The latest fashion: Graphene edges can be tailor-made

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Rice University theory shows it should be possible to tune material’s properties

Graphene nanoribbons can be enticed to form favorable "reconstructed" edges by pulling them apart with the right force and at the right temperature, according to researchers at Rice University. The illustration shows the crack at the edge that begins the formation of five- and seven-atom pair under the right conditions. Illustration by ZiAng Zhang

Theoretical physicists at Rice University are living on the edge as they study the astounding properties of graphene. In a new study, they figure out how researchers can fracture graphene nanoribbons to get the edges they need for applications.

New research by Rice physicist Boris Yakobson and his colleagues shows it should be possible to control the edge properties of graphene nanoribbons by controlling the conditions under which the nanoribbons are pulled apart.

In the work, which appeared this month in the Royal Society of Chemistry journal Nanoscale, the Rice team used sophisticated computer modeling to show it’s possible to rip nanoribbons and get graphene with either pristine zigzag edges or what are called reconstructed zigzags.

– See more at: Rice News

Sinuous grain boundaries in graphene demystified

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The January 21 issue of Adv. Funct. Mater. features on its back cover work on graphene grain boundaries

The image shows a simulated grain boundary stitching two graphene domains tilted at a 28° angle exhibits a well-defined sinuous shape, which is revealed to be energetically preferred. Such sinuous grain boundary, appeared to be a curved river on land, are highlighted by B. I. Yakobson and co-workers on page 367 as a new channel to explore novel electronic behavior in graphene and to reach the as yet unexplored flatlands of two-dimensional materials.

Sparking Industrial Breakthroughs

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2015 CASC Brochure features work from the group

Images illustrating two works from the group are featured in the 2015 Brochure published by the Coalition for Academic Scientific Computation – an alliance of 79 of America’s most forward thinking research universities, national labs and computing centers, including Rice’s Ken Kennedy Institute for Information Technology.  On page 2, the  highlight box “Something new under the sun” shows a collage based on a recent Nanoscale paper, and our extensive sampling of the CNT end-caps energy landscape, published in ACS Nano, is featured in the top box on page 3.


Study of Li nucleation on graphene earns “Best Poster” Nomination

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Mingjie Liu, a graduate student in Yakobson’s Group, has been named as a “Best Poster” nominee at the 2014 MRS Fall Meeting. 

The poster presents a recent work on the Li clustering process on graphene, reporting the geometries, nucleation barriers and electronic structure of the clusters using first principles calculations. The concentration-dependent nucleation barrier for Li on graphene was estimated as well. While the nucleation occurs more readily with increasing Li concentration, potentially leading to the dendrite formation and failure of the Li-ion battery, the existence of the barrier delays nucleation and may allow Li storage on graphene. The electronic structure and charge transfer analyses reveal how the fully-ionized Li adatoms transform to metallic Li during the cluster growth on graphene.

As a reward, nominees are offered the opportunity to record a short talk about their posters which will then be posted to MRS OnDemand®.

2D Phosphorus on the cover of Nano Letters

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Nano Letters features our work on the cover of its December 2014 issue

In a recent Nano Lett. article, we demonstrate that a 2D mono-elemental semiconductor is a promising candidate. This is exemplified by first-principles study of 2D phosphorus (P), a recently fabricated high-mobility semiconductor. Most of the defects, including intrinsic point defects and grain boundaries, are electronically inactive, thanks to the homoelemental bonding, which is not preferred in heteroelemental system such as MX2. Unlike MX2, the edges of which create deep gap states and cannot be eliminated by passivation, the edge states of 2D P can be removed from the band gap by hydrogen termination. We further find that both the type and the concentration of charge carriers in 2D P can be tuned by doping with foreign atoms.

The cover image represents a “phosphorescent” rendering of some structural and electronic signatures of 2D phosphorus arranged in a collage inspired by the digital rain from “The Matrix” movie.

See more at: Rice News: Phosphorus ‘rain’

Why do nanotubes grow chiral?

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Rice University theorists determine factors that give tubes their chiral angles

Many a great idea springs from talks over a cup of coffee. But it’s rare and wonderful when a revelation comes from the cup itself.

Rice University theoretical physicist Boris Yakobson, acting upon sudden inspiration at a meeting last year in Arlington, Va., obtained a couple of spare coffee cups from a server and a pair of scissors and proceeded to lay out – science fair-style – an idea that could have far-reaching implications for the nanotechnology industry.

As reflected in a new paper in Nature Communications, Yakobson and his Rice colleagues, postdoctoral researcher Vasilii Artyukhov and research scientist Evgeni Penev, had come up with the seed (or perhaps, bean) of a simple formula that describes why nanotubes have chirality. Chirality is the property that describes the angle of the carbon atom hexagons that make up a nanotube’s walls.

– See more at: Rice News

Phosphorus a promising semiconductor

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Rice University physicists find 2-D form pays no heed to defects

Defects damage the ideal properties of many two-dimensional materials, like carbon-based graphene. Phosphorus just shrugs.

That makes it a promising candidate for nano-electronic applications that require stable properties, according to new research by Rice University theoretical physicist Boris Yakobson and his colleagues.

In a paper in the American Chemical Society journal Nano Letters, the Rice team analyzed the properties of elemental bonds between semiconducting phosphorus atoms in 2-D sheets. Two-dimensional phosphorus is not theoretical; it was recently created through exfoliation from black phosphorus.

– See more at: Rice News

Carbyne morphs when stretched

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Rice University calculations show carbon-atom chain would go metal to semiconductor

Applying just the right amount of tension to a chain of carbon atoms can turn it from a metallic conductor to an insulator, according to Rice University scientists.

Stretching the material known as carbyne — a hard-to-make, one-dimensional chain of carbon atoms — by just 3 percent can begin to change its properties in ways that engineers might find useful for mechanically activated nanoscale electronics and optics.

The finding by Rice theoretical physicist Boris Yakobson and his colleagues appears in the American Chemical Society journal Nano Letters.

– See more at: Rice News

Caps not the culprit in nanotube chirality

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Rice study narrows the possibilities for gaining control of nanotube type

A single-walled carbon nanotube grows from the round cap down, so it’s logical to think the cap’s formation determines what follows. But according to researchers at Rice University, that’s not entirely so.

Theoretical physicist Boris Yakobson and his Rice colleagues found through exhaustive analysis that those who wish to control the chirality of nanotubes – the characteristic that determines their electrical properties – would be wise to look at other aspects of their growth.

In the study by Yakobson, research scientist Evgeni Penev and postdoctoral researcher Vasilli Artyukhov that was published recently by the American Chemical Society journal ACS Nano, the Rice researchers found that the elastic energy landscapes involved in cap formation are not strong enough to dictate the nanotube’s chirality….more

Flat boron by the numbers

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Rice University researchers calculate what it would take to make new two-dimensional material

It would be a terrible thing if laboratories striving to grow graphene from carbon atoms kept winding up with big pesky diamonds.

“That would be trouble, cleaning out the diamonds so you could do some real work,” said Rice University theoretical physicist Boris Yakobson, chuckling at the absurd image.

Yet something like that keeps happening to experimentalists working to grow two-dimensional boron. Boron atoms have a strong preference to clump into three-dimensional shapes rather than assemble into pristine single-atom sheets, like carbon does when it becomes graphene. And boron clumps aren’t nearly as sparkly…more

Advanced Materials is Owl about Rice

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High-impact journal publishes centennial edition with broad overview of materials science at Rice

Materials scientists who received Volume 24, Issue 36 of the respected journal Advanced Materials recently may have noticed it contained Rice University research and nothing else.

That is no mistake. The journal published a special issue this fall focused on Rice, the home of a large number of materials researchers that has been recognized by a Times Higher Education survey as the best in the world.  more…

Flat boron may take many forms

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When is nothing really something? When it leads to a revelation about boron, an element with worlds of unexplored potential.

Theoretical physicist Boris Yakobson and his team at Rice University have taken an unusual approach to analyzing the possible configurations of two-dimensional sheets of boron, as reported this week in the American Chemical Society journal Nano Letters. more…

Rice professor’s nanotube theory confirmed

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Air Force Research Laboratory experiment shows chirality of tube controls speed of growth

The Air Force Research Laboratory in Dayton, Ohio, has experimentally confirmed a theory by Rice University Professor Boris Yakobson that foretold a pair of interesting properties about nanotube growth: That the chirality of a nanotube controls the speed of its growth, and that armchair nanotubes should grow the fastest. more…