Last year, Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering at the University of Illinois at Chicago, discovered that he could make highly sensitive chemical sensors from graphene. He also determined why they were so sensitive: Defects.
The research unveiled not only highly sensitive sensors capable of detecting a single molecule of a chemical, but also that the sensitivity, which was directly tied to defects around the edges of the graphene, would be lost if those defects were to be removed.
When Salehi-Khojin and his colleagues looked a little deeper into the need for defects to maintain sensitivity in graphene nanosensors, they found something remarkable: The graphene could be free from defects and still be a highly sensitive sensor as long as the substrate it was on was a little ragged around edges.
“This was a very surprising result,” Salehi-Khojin said in a press release. “[The results] will open up entirely new possibilities for modulation and control of the chemical sensitivity of these sensors, without compromising the intrinsic electrical and structural properties of graphene.”
The research, which was published in the ACS journal Nano Letters (“The Role of External Defects in Chemical Sensing of Graphene Field-Effect Transistors”), revealed that the poor sensitivity of pristine graphene in terms of electrical conductivity is not necessarily intrinsic to the material but instead can be affected and approved upon by the underlying substrate.
“We could now say that graphene itself is insensitive unless it has defects—internal defects on the graphene surface, or external defects on the substrate surface,” noted UIC graduate student Poya Yasaei in the press release.
Now that graphene-based field effect transistors (FET) have been with us for a couple of years, this latest research opens up the potential for graphene-based chemFET sensors to be engineered for a number of various applications.
Photo: Roberta Dupuis-Devlin
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.