A boron buckyball has been discovered by researchers from Brown University.
Buckyballs, named after pioneering architect Buckminster Fuller, are usually composed of carbon. Shaped much like a soccer ball, they were first seen 30 years ago, and led to a new generation of research into nanotechnology.
Boron takes the place of carbon in this new buckyball, which is composed of 40 atoms of the element. Brown researchers, working with colleagues in China, named the new substance borospherene.
Chemists had theorized it may be possible to develop a hollow cage from boron atoms, but this is the first time it has been observed.
"This is the first time that a boron cage has been observed experimentally. As a chemist, finding new molecules and structures is always exciting. The fact that boron has the capacity to form this kind of structure is very interesting," Lai-Sheng Wang, chemistry professor at Brown University, said.
Soon after the discovery of buckyballs in 1985, researchers discovered other shapes that could be created with carbon, including nanotubes, and sheet-like graphene. Each of these forms is just one atom thick. Wang published a paper earlier this year after he found boron can form into disks, composed of 36 atoms. These could, theoretically, be pieced together into larger sheets, creating a material much like graphene.
The most stable form of carbon has six protons and an equal number of electrons. Boron has only has five of each particle. With a different number of electrons, the lighter element cannot form into the same 60-atom structure produced by carbon. Before the discovery of borospherene, theoretical chemists knew production of such a substance would require a different number of atoms.
Wang knew from his earlier research that his disc-shaped borophene was stable with 36 atoms in the molecular structure. Mathematical models showed 40 atoms would also produce a stable arrangement. His team went to work, trying to understand how 40 boron atoms could join together.
They used supercomputers to model 10,000 possible combinations. These simulations examined both the shape of the structure, and the electron binding energy - how tightly the molecule holds on to the negatively-charged particles. This acts as a 'fingerprint' for each type of structure. Boron atoms were then zapped with a laser, and the resulting vapor was sized by mass. They were then impacted by a second laser, releasing an electron, which races down a track. The speed at which they do measures the binding energy, in a process called photoelectron spectroscopy.
The discovery of borospherene was detailed in the journal Nature Chemistry.