Borophene shines alone as 2-D plasmonic material

Rice University scientists calculate flat boron capable of visible plasmon emissions

Illustration by Sharmila Shirodkar.

An atom-thick film of boron could be the first pure two-dimensional material able to emit visible and near-infrared light by activating its plasmons, according to Rice University scientists. That would make the material known as borophene a candidate for plasmonic and photonic devices like biomolecule sensors, waveguides, nanoscale light harvesters and nanoantennas. Plasmons are collective excitations of electrons that flow across the surface of metals when triggered by an input of energy, like laser light. Significantly, delivering light to a plasmonic material in one color (determined by the light’s frequency) can prompt the emission of light in another color.

Models by Rice theoretical physicist Boris Yakobson and his colleagues predict that borophene would be the first known 2-D material to do so naturally, without modification. The lab’s simulations are detailed in a paper by Yakobson with lead authors Yuefei Huang, a graduate student, and Sharmila Shirodkar, a postdoctoral researcher, in the Journal of the American Chemical Society.

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2D Boron on the Cover of Chem Soc Rev

Chemical Society Reviews features our review on two-dimensional boron on its front cover

In a recent article, we review the current theoretical and experimental progress in realizing boron atomic layers. Starting by describing a decade-long effort towards understanding the size-dependent structures of boron clusters, we present how theory plays a role in extrapolating boron clusters into 2D form, from a freestanding state to that on substrates, as well as in exploring practical routes for their synthesis that recently culminated in experimental realization. While 2D boron has been revealed to have unusual mechanical, electronic and chemical properties, materializing its potential in practical applications remains largely impeded by lack of routes towards transfer from substrates and controlled synthesis of quality samples.

The review is on the list of referee-recommended articles, HOT Chem Soc Rev articles for October, and is free to access until 13th December 2017.

The quaternary 2D alloys are on Advanced Materials cover

Rice scientists create flat composite with tunable optical bandgap

Rice University scientists have discovered a two-dimensional alloy with an optical bandgap that can be tuned by the temperature used to grow it.

The Rice lab of materials scientist Pulickel Ajayan grew the four-component alloy of transition metals molybdenum and tungsten with chalcogens sulfur and selenium in a chemical vapor deposition furnace. They found changes in temperature made subtle changes in the way atoms assembled and also altered the properties that determine how they absorb and emit light.

Their experiments were built upon work by the lab of Rice theoretical physicist Boris Yakobson, which created scores of models to predict how various combinations of the four elements should work.

The process should be of interest to engineers looking to make smaller, more-efficient devices. Because the bandgap falls in the optical range of the electromagnetic spectrum, the researchers said solar cells and light-emitting diodes might be the first beneficiaries.

The paper appears as a cover story in the current issue of Advanced Materials.

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Landscapes give latitude to 2-D material designers

Rice, Oak Ridge scientists show growing atom-thin sheets on cones allows control of defects

Hands of Henry” (Nitant Gupta, c. 2017; WS2 on conical canvas)

Rice University researchers have learned to manipulate two-dimensional materials to design in defects that enhance the materials’ properties.

The Rice lab of theoretical physicist Boris Yakobson and colleagues at Oak Ridge National Laboratory are combining theory and experimentation to prove it’s possible to give 2-D materials specific defects, especially atomic-scale seams called grain boundaries. These boundaries may be used to enhance the materials’ electronic, magnetic, mechanical, catalytic and optical properties.

The key is introducing curvature to the landscape that constrains the way defects propagate. The researchers call this “tilt grain boundary topology,” and they achieve it by growing their materials onto a topographically curved substrate — in this case, a cone. The angle of the cone dictates if, what kind and where the boundaries appear.

The research is the subject of a paper in the American Chemical Society journal ACS Nano.

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Self-optimizing catalysts for hydrogen evolution on the cover of Nature Energy

Rice, Lawrence Livermore scientists replace expensive platinum for efficient hydrogen production

Scientists at Rice University and the Lawrence Livermore National Laboratory have predicted and created new two-dimensional electrocatalysts to extract hydrogen from water with high performance and low cost.

In the process, they also created a simple model to screen materials for catalytic activity.

Several catalysts were modeled by Rice theoretical physicist Boris Yakobson and lead author Yuanyue Liu, a former graduate student in his lab, and made and tested by Rice materials scientists led by Pulickel Ajayan and Jun Lou. They found the new dichalcogenide catalysts matched the efficiency of platinum — the most common hydrogen evolution reaction (HER) catalyst in water-splitting cells — and can be made at a fraction of the cost.

The study is a cover story in the September issue of Nature Energy.

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Nothing Boring about the Thinnest Boron Ever

Department of Energy’s Office of Science (BES) highlights our work on 2D boron

… Can boron, which is adjacent to carbon on the Periodic Table, also form a 2-D material and, if so, what are its properties? Researchers at Rice University used theory and simulation techniques to identify possible 2-D boron structures. Their findings showed that, based upon the metal substrate used during the fabrication process, the structure of monolayer boron changed drastically. Using this information, researchers from Argonne National Laboratory, Northwestern University, and their collaborators from other institutions utilized the Department of Energy’s Center for Nanoscale Material, a user facility, to attempt the synthesis of borophene on a silver substrate.

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Boron atoms stretch out, gain new powers

Rice simulations demonstrate 1-D material’s stiffness, electrical versatility

Hold on, there, graphene. You might think you’re the most interesting new nanomaterial of the century, but boron might already have you beat, according to scientists at Rice University.

A Rice team that simulated one-dimensional forms of boron — both two-atom-wide ribbons and single-atom chains — found they possess unique properties. The new findings appear this week in the Journal of the American Chemical Society.

For example, if metallic ribbons of boron are stretched, they morph into antiferromagnetic semiconducting chains, and when released they fold back into ribbons.

In The News

Nano-chimneys can cool circuits

chim_v2Rice scientists calculate tweaks to graphene would form phonon-friendly cones

A few nanoscale adjustments may be all that is required to make graphene-nanotube junctions excel at transferring heat, according to Rice University scientists.

The Rice lab of theoretical physicist Boris Yakobson found that putting a cone-like “chimney” between the graphene and nanotube all but eliminates a barrier that blocks heat from escaping.

The research appears in the American Chemical Society’s Journal of Physical Chemistry C.

Heat is transferred through phonons, quasiparticle waves that also transmit sound. The Rice theory offers a strategy to channel damaging heat away from next-generation nano-electronics.

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