Ultrasensitive gas detection by boron-doped graphene. Image: Terrones, Penn State.
Ultrasensitive gas detection by boron-doped graphene. Image: Terrones, Penn State.

Ultrasensitive gas sensors based on the infusion of boron atoms into graphene – a single-atom-thick layer of carbon – may soon be possible, according to an international team of researchers from six countries.

Graphene is known for its remarkable strength and ability to transport electrons at high speed, but this latest research shows that it can also make a highly sensitive gas sensor. Adding boron atoms to graphene produces boron graphene sensors able to detect noxious gas molecules at extremely low concentrations, parts per billion in the case of nitrogen oxides and parts per million for ammonia, the two gases tested to date. Compared to pristine graphene, this translates into a 27 times greater sensitivity to nitrogen oxides and 10,000 times greater sensitivity to ammonia. The researchers believe these results, reported in the Proceedings of the National Academy of Sciences, will open a path to high-performance sensors that can detect trace amounts of many other molecules.

"This is a project that we have been pursuing for the past four years," said Mauricio Terrones, professor of physics, chemistry and materials science at Penn State. "We were previously able to dope graphene with atoms of nitrogen, but boron proved to be much more difficult. Once we were able to synthesize what we believed to be boron graphene, we collaborated with experts in the United States and around the world to confirm our research and test the properties of our material."

Both boron and nitrogen lie next to carbon on the periodic table, making their substitution feasible, but boron compounds are very air sensitive, decomposing rapidly when exposed to the atmosphere. Using a one-of-a-kind bubbler-assisted chemical vapor deposition system at Penn State, however, the researchers were able to fabricate 1cm2 boron-doped graphene sheets.

Once fabricated, the researchers sent the boron graphene samples to researchers at the Honda Research Institute USA Inc in Columbus, Ohio, who tested the samples against their own highly sensitive gas sensors. Konstantin Novoselov's lab at the University of Manchester, UK, studied the transport mechanism of the sensors; Novoselov was one of the recipients of the 2010 Nobel prize in physics for the discovery of graphene. Theory collaborators in the US and Belgium matched scanning tunneling microscopy images to experimental images, confirming the presence of the boron atoms in the graphene lattice and their effect when interacting with ammonia or nitrogen oxide molecules. Collaborators in Japan and China also contributed to the research.

"This multidisciplinary research paves a new avenue for further exploration of ultrasensitive gas sensors," said Avetik Harutyunyan, chief scientist and project leader at Honda Research Institute USA Inc. "Our approach combines novel nanomaterials with continuous ultraviolet light radiation in the sensor design that have been developed in our laboratory by lead researcher Dr Gugang Chen in the last five years. We believe that further development of this technology may break the parts per quadrillion level of detection limit, which is up to six orders of magnitude better sensitivity than current state-of-the-art sensors."

These sensors can be used by labs and industries that use ammonia, a highly corrosive health hazard, or to detect nitrogen oxides, a dangerous atmospheric pollutant emitted from automobile tailpipes. In addition to detecting toxic or flammable gases, theoretical work indicates that boron-doped graphene could also lead to improved lithium-ion batteries and field-effect transistors, the researchers report.

This story is adapted from material from Penn State, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.