Two-faced edge makes nanotubes obey

Rice theorists find mechanism behind nearly pure nanotubes from the unusual catalyst

Growing a batch of carbon nanotubes that are all the same may not be as simple as researchers had hoped, according to Rice University scientists.

Rice materials theorist Boris Yakobson and his team bucked a theory that when growing nanotubes in a furnace, a catalyst with a specific atomic arrangement and symmetry would reliably make carbon nanotubes of like chirality, the angle of its carbon-atom lattice.

Instead, they found the catalyst in question starts nanotubes with a variety of chiral angles but redirects almost all of them toward a fast-growing variant known as (12,6). The cause appears to be a Janus-like interface that is composed of armchair and zigzag segments – and ultimately changes how nanotubes grow.

The Rice theoretical study detailed in the American Chemical Society journal Nano Letters could be a step toward catalysts that produce homogeneous batches of nanotubes, Yakobson said.

– See more at Rice News

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