Researchers Find Boron Buckyball

Brown University researchers have found Boron buckyballs, which are made of a cluster of 40 boron atoms.

Carbon buckyballs, called so because they resemble a hollow soccer ball, were discovered in 1985. The finding revolutionized nanotechnology. Other scientists soon found carbon nanotubes and even one-atom thick graphene.

Researchers at the Brown University, along with their colleagues at Shanxi University and Tsinghua University in China, have for the first time, demonstrated that a cluster of 40 boron atoms form a hollow molecular cage. The structure, researchers say, is the evidence that boron buckyballs exist and that they are stable.

"This is the first time that a boron cage has been observed experimentally," said Lai-Sheng Wang, a professor of chemistry at Brown who led the team that made the discovery, according to a news release. "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."

According to the researchers, the new borospherene molecule isn't as spherical as carbon buckyballs.

Borospherene has 48 triangles, four seven-sided rings and two six-membered rings. Some atoms stick out from the structure, giving it an uneven look.

Researchers aren't sure about the possible applications for the borospherene, but say that the structures could be used to store Hydrogen.

The study is published in the journal Nature Chemistry.

Carbon buckyballs are made of 60 carbon atoms that are arranged in pentagons and hexagons to form a sphere. The shape of the buckyball resembles that of a soccer-ball. Boron, carbon's neighbour, was considered to be capable of forming hollow, spherical structures. However, Boron has one less electron than carbon and so can't form the 60-atom structure.

Wang and colleagues have been studying boron chemistry for years. They had earlier found that 36 boron atoms could make one-atom-thick disks, which resembled graphene. These structures were called borophene. During their research, the team found that clusters of 40 boron atoms were surprisingly more stable than the 36-atom structures.

Researchers used a combination of experimental work and high-powered supercomputers to see how the 40 atom clusters were arranged. The supercomputer even estimated the electron binding energy for each structure. The spectrum of binding energies is used as fingerprint for each structure.

First, researchers sifted through over 10,000 possible structures that the 40 atoms could make. Then, researchers used a technique called photoelectron spectroscopy to see if they could experimentally verify the existence of boron structures predicted by the supercomputer.

The team exposed boron to lasers to create a vapour of boron atoms. A jet of helium was then used to freeze clusters of the atoms. The team then isolated the 40-atom cluster of boron and zapped it again with a laser. The second laser released an electron from the cluster, which then moves along a long tube. The team studied the structural fingerprint of the cluster using the speed at which the knocked-out electron moved down the tube.

Laboratory work showed that 40-atom-clusters can exist in two structures with distinct binding spectra. Researchers found that the boron structures obtained via experiments resembled the structures predicted by the computer models.

One of the structures was a hollow, rough sphere, while the other was semi-flat.

U.S. National Science Foundation (CHE-1263745) and the National Natural Science Foundation of China funded the research.