Sniffing single molecules with graphene

Electronic sensors can now sniff out single gas molecules by using graphene, according to a research team from the Japan Advanced Institute of Science & Technology (Sci. Adv. 2016, DOI: 10.1126/sciadv.1501518). Graphene has previously shown itself capable of single-molecule sensitivity, but this earlier feat required high magnetic fields. Now, researchers have observed single carbon dioxide molecules with a graphene-based sensor that operates at modest, readily supplied voltages. This work could lead to compact, highly sensitive devices for personal environmental monitoring, says team member Jian Sun. Sun and his colleagues developed their sensor using an unorthodox architecture. Usually, graphene in a sensor lies flat on a substrate, the team says. In this geometry, however, interactions between graphene and its support can mask interactions between graphene and gas molecules. So the researchers angled a two-atom-thick graphene ribbon between two electrodes at different heights to lift the ribbon away from its silicon dioxide substrate. When a voltage is applied between the electrodes, each adsorbed CO₂ molecule scatters electrons in the graphene, creating discrete but discernible changes in its resistance, the team reports.