In borophene, boundaries are no barrier

Rice, Northwestern researchers make and test atom-thick boron’s unique domainsA scanning electron microscope image (top) shows two periodic assemblies of borophene, a synthetic, two-dimensional array of boron atoms, that join at a line defect. Computational models in the middle and bottom images correspond to the regions, with 1-to-6 borophene in red and 1-to-5 in blue. Researchers at Rice and Northwestern universities determined that phases of borophene line up in such a way that the material's conductive, metallic nature is maintained. (Credit: Graphics by Luqing Wang/Rice University)

The research led by Rice materials theorist Boris Yakobson and Northwestern materials scientist Mark Hersam appears in Nature Materials.

Borophene differs from graphene and other 2D materials in an important way: It doesn’t appear in nature. When graphene was discovered, it was famously yanked from a piece of graphite with Scotch tape. But semiconducting bulk boron doesn’t have layers, so all borophene is synthetic. Also unlike graphene, in which atoms connect to form chicken wire-like hexagons, borophene forms as linked triangles. Periodically, atoms go missing from the grid and leave hexagonal vacancies. The labs investigated forms of borophene with “hollow hexagon” concentrations of one per every five triangles and one per every six in the lattice.

Yakobson and Hersam also co-authored a recent Nature Nanotechnology perspective about “the lightest 2D metal.”In that piece, the authors suggested borophene may be ideal for flexible and transparent electronic interconnects, electrodes and displays. It could also be suitable for superconducting quantum interference devices and, when stacked, for hydrogen storage and battery applications.

– See more at Rice News

Salt boosts creation of 2D materials

Rice scientists show how salt lowers reaction temperatures to make novel materials

A dash of salt can simplify the creation of two-dimensional materials, and thanks to Rice University scientists, the reason is becoming clear.

Boris Yakobson, a Rice professor of materials science and nanoengineering and of chemistry, was the go-to expert when a group of labs in Singapore, China, Japan and Taiwan used salt to make a “library” of 2D materials that combined transition metals and chalcogens. These compounds could lead to smaller and faster transistors, photovoltaics, sensors and catalysts, according to the researchers.

Through first-principles molecular dynamics simulations and accurate energy computations, Yakobson and his colleagues determined that salt reduces the temperature at which some elements interact in a chemical vapor deposition (CVD) furnace. That makes it easier to form atom-thick layers similar to graphene but with the potential to customize their chemical composition for specific layer-material and accordingly electrical, optical, catalytic and other useful properties.

The research team including Yakobson and Rice postdoctoral researcher Yu Xie and graduate student Jincheng Lei reported its results this week in Nature.

The clip shows a molecular dynamics simulation of a layer of salt and molybdenum oxide mixing together to form molybdenum oxychloride. The atoms are oxygen (red), sodium (yellow), chlorine (green), and molybdenum (purple).

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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.

New Wave of 2D Boron

Rice University researchers say 2-D boron may be best for flexible electronics

2d-b-waveThough they’re touted as ideal for electronics, two-dimensional materials like graphene may be too flat and hard to stretch to serve in flexible, wearable devices. “Wavy” borophene might be better, according to Rice University scientists.

The Rice lab of theoretical physicist Boris Yakobson and experimental collaborators observed examples of naturally undulating, metallic borophene, an atom-thick layer of boron, and suggested that transferring it onto an elastic surface would preserve the material’s stretchability along with its useful electronic properties.

Highly conductive graphene has promise for flexible electronics, Yakobson said, but it is too stiff for devices that also need to stretch, compress or even twist. But borophene deposited on a silver substrate develops nanoscale corrugations. Weakly bound to the silver, it could be moved to a flexible surface for use.

The research appears this month in the American Chemical Society journal Nano Letters.

In The News

Polyphony in B flat

At last, experiments offer two-dimensional boron… on a silver platterb_cards

In an extensive “News & Views” in Nature Chemistry, we provide a critical view of the latest breakthrough in materials flatland: the synthesis of two-dimensional boron. It also reflects on a decade-long effort in Yakobson’s group towards understanding and eventually predicting the structure of low-dimensional boron: from the B80 fullerene, to the polymorphism of 2D boron, to practical routes for its synthesis.

2D Boron among the Angew. Chem. covers

angew_chem_cover

Two-dimensional boron would take different forms, depending on the substrate used in chemical vapor deposition growth. Image by Zhuzha Zhang

Our most recent work on 2D boron will be featured on a cover of the upcoming issue of Angewandte Chemie International Edition. The study builds on two of our previous works on two-dimensional boron  and provides further clues as to how this elusive material can be synthesized and what the product may look like.

Calculation of the atom-by-atom energies involved in creating a sheet of boron revealed that the metal substrate – the surface upon which two-dimensional materials are grown in a chemical vapor deposition (CVD) furnace – would make all the difference.

The new calculations show it may be possible to guide the formation of 2D boron by tailoring boron-metal interactions.Theoretical physicist Boris Yakobson and his Rice colleagues discovered that copper, a common substrate in graphene growth, might be best to obtain flat boron, while other metals would guide the resulting material in their unique ways.

– See more at: Rice News