Graphene-based transistor promises 1ppb gas sensing

December 05, 2016 // By Julien Happich
Researchers from Fujitsu Laboratories Ltd. have developed a new type of gas sensor based on graphene, which they claim has a sensitivity to NO2 an order of magnitude greater than conventional resistivity-based graphene sensors and commercially available electrochemical sensors.

The novel gas sensor uses a sheet of graphene as its sensing site, which replaces the gate part of a conventional silicon transistor. When a gas molecule adheres to the graphene, the graphene's work function changes, altering the switching characteristics of the silicon transistor and enabling the gas to be detected. When the gas molecule separates from the graphene, the graphene returns to its original state.

The sensor was reported to be able to detect concentrations lower than tens of parts per billion (ppb) of nitrogen dioxide (NO 2) and ammonia (NH 3); with nitrogen dioxide in particular, sensitivity has improved more than tenfold, to less than 1 ppb.

A scanning electron microscope image
of the graphene-based gas sensing transistor.

This sensor's detection area is only a few hundred micrometers wide, but could be made even smaller, according to Fujitsu Laboratories. The sensor returns to its original state through heating.

In future research, the researchers aims to detect gases other than nitrogen dioxide and ammonia by combining graphene with other molecules.

Fujitsu Laboratories expect this technology to enable real-time measurements of air quality, which previously may have taken tens of hours depending upon the gas being measured. It will also simplify the detection of gas components in breath as a health indicator.

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