An international team of researchers from six countries have designed a highly sensitive gas sensor made from boron-doped graphene, 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. These sensors can be used for 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 lead to improved lithium-ion batteries and field-effect transistors. 

The sensor reaches a 27 times greater sensitivity to nitrogen oxides and 10,000 times greater sensitivity to ammonia compared to pristine graphene. The researchers believe these results will open a path to high-performance sensors that can detect trace amounts of many other molecules.

Since boron compounds are extremely air sensitive and decompose rapidly when exposed to the atmosphere, designing the boron-doped graphene proved difficult and demanded global collaboration. One-centimeter-square sheets were synthesized at Penn State in a one-of-a-kind bubbler-assisted CVD system and experts around the world confirmed the research and tested the properties of the material. The result was large-area, high-quality boron-doped graphene sheets.

Once fabricated, the researchers sent boron graphene samples to researchers at the Honda Research Institute USA Inc., 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. Theory collaborators in the U.S. and Belgium matched the scanning tunneling microscopy images to experimental images, confirmed 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.

The scientists state that this approach combines novel nanomaterials with continuous ultraviolet light radiation in the sensor design that have been developed in the last five years. They 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. 



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