Scientists stabilize atomic thin boron for therapeutic use

Researchers at Northwestern University have, for the first time, created borophane – a thin atomic boron that is stable at normal temperature and air pressure.

Researchers have long been fascinated by the promise of borophene – a single-atom-thick boron leaf – because of its strength, flexibility and electronic properties. Stronger, lighter and more flexible than graphene, borophene could recharge batteries, electronics, sensors, photovoltaics and quantum computing.

Unfortunately, borophene only exists inside an ultrahigh vacuum chamber, limiting practical use outside of the laboratory. By combining borophene with atomic hydrogen, the Northwestern team created borophane, which has the same interesting properties as borophene and is stable externally.

“The problem is, if you take borophene out of the ultrahigh desert and into the air, it oxidizes instantly,” said Mark C. Hersam, who led the research. “As soon as it oxidizes, it is no longer borophene and no longer behaves. The field will be restricted in the study of its use in the real world if borophene cannot be given stable side outside an ultrahigh empty room. “

The research will be published March 12 in the journal Science and appears on the cover. The study marks the first time scientists have reported on borophane synthesis.

Hersam is Professor Walter P. Murphy in Materials Science and Engineering at the McCormick School of Engineering at Northwestern and director of the Center for Materials Research Science and Engineering.

Although borophene is often compared to its predecessor graphene precursor, it is much more difficult to form borophene. Graphene is a thin layer of graphite, a material covered with stacks of two-dimensional sheets. To remove a double-sided coating from graphite, scientists simply cut it off.

Boron, on the other hand, is not put in big shape. Five years ago, Hersam and colleagues created borophene for the first time by growing it directly on a substrate. The resulting material, however, was highly reactive, making it vulnerable to oxidation.

“The boron atoms in borophene are highly susceptible to further chemical reactions,” Hersam said. “We’ve found that once the boron atoms are bound to hydrogen, they no longer react with oxygen when they’re out.”

Now that borophane can be exported to the real world, Hersam said researchers will be able to more quickly investigate the properties of borophane and its potential applications.

“Material synthesis is a bit like baking,” Hersam said. “Once you know the recipe, it’s not difficult to reproduce. However, if you only have a little bit of the recipe, the end result can flop terribly. By sharing the best recipe for borophane with the world, we expect its practice to rapidly multiply. “

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The study, “Synthesis of borophane polymorphs by hydrogenation of borophene,” was supported by the Office of Naval Research (award number ONR N00014-17-1-2993), the National Science Foundation (award number DMR-1720139) and the U.S. Department of Office of Energy Science (award number DE-AC02-06CH11357).