Findings on Graphene Surface Defects Pave Way to Develop Better and Low-Cost Gas Sensors

A research study conducted at the University of Illinois at Urbana-Champaign has revealed that sensors made of less-perfect graphene deliver enhanced sensitivity.

The team discovered that the sensitivity of graphene chemiresistors vary with the geometry and types of their imperfections.

The research team comprising electrical and chemical engineers and Dioxide Materials, a startup company, has reported its findings in the Advanced Materials journal. David Estrada and Amin Salehi-Khojin, lead authors of the report, stated that the research study’s aim is to find the reasons that restrict the sensitivity of two-terminal, simple graphene chemiresistors in order to facilitate the development of low-cost devices using chemical vapor deposition (CVD).

Due to its two-dimensional nature, the characteristics of chemiresistors made of CVD-grown defective graphene are different from that of chemiresistors made of carbon nanotubes, according to the authors. In order to improve this sensitivity, the research team created ribbons having a width equivalent to the size of line defects or micrometers from the nanomaterial.

Dioxide Materials’ Research Scientist, Salehi-Khojin, who is also a post-doctoral research associate of the Department of Chemical and Biomolecular Engineering (ChemE) at Illinois, stated that chemiresistors made of almost-pristine graphene have less sensitivity to analyte molecules due to the bonding of adsorbates to point defects surrounded by low resistance pathways. Hence adsorption at point imperfections has only minimal impact on the device’s overall resistance, he said. However, continuous lines of point imperfections or micrometer-sized line imperfections are not surrounded by easy conduction paths, causing significant change in resistance after adsorption, he added.

Eric Pop, one of the members of the research team, commented that sensitivity is higher in the line-like surface imperfections of graphene ribbons when compared to its wrinkle-like or point-like defects. Estrada, who is a Department of Electrical and Computer Engineering’s doctoral candidate, commented that these findings pave the way to develop low-cost and high-sensitivity gas sensors for numerous applications, including medical diagnostics, homeland security and energy.