Although they found that graphene makes very good chemical sensors, researchers at the University of Illinois at Urbana-Champaign have discovered an unexpected "twist"that the sensors are better when the graphene is "worse"more imperfections improved performance.
"This is quite the opposite of what you would want for transistors, for example," explained Eric Pop, an assistant professor of electrical and computer engineering and a member of the interdisciplinary research team. "Finding that the less perfect they were, the better they worked, was counter intuitive at first."
The research group, which includes researchers from both chemical engineering and electrical engineering, and from a startup company, Dioxide Materials, reported their results in the November 23, 2011 issue of Advanced Materials.
"The objective of this work was to understand what limits the sensitivity of simple, two-terminal graphene chemiresistors, and to study this in the context of inexpensive devices easily manufactured by chemical vapor deposition (CVD)," stated lead authors Amin Salehi-Khojin and David Estrada.
The researchers found that the response of graphene chemiresistors depends on the types and geometry of their defects.
"Nearly-pristine graphene chemiresistors are less sensitive to analyte molecules because adsorbates bind to point defects, which have low resistance pathways around them," noted Salehi-Khojin, a research scientist at Dioxide Materials and post-doctoral research associate in the Department of Chemical and Biomolecular Engineering (ChemE) at Illinois. "As a result, adsorption at point defects only has a small effect on the overall resistance of the device. On the other hand, micrometer-sized line defects or continuous lines of point defects are different because no easy conduction paths exist around such defects, so the resistance change after adsorption is significant."
"This can lead to better and chea
|Contact: Eric Pop|
University of Illinois College of Engineering