Abstract
Using square wave voltammetry, we show an increase in the electrochemical detection of trinitrotoluene (TNT) with a working electrode constructed from plasma modified graphene on a SiC surface vs. unmodified graphene. The graphene surface was chemically modified using electron beam generated plasmas produced in oxygen or nitrogen containing backgrounds to introduce oxygen or nitrogen moieties. The use of this chemical modification route enabled enhancement of the electrochemical signal for TNT, with the oxygen treatment showing a more pronounced detection than the nitrogen treatment. For graphene modified with oxygen, the electrochemical response to TNT can be fit to a two-site Langmuir isotherm suggesting different sites on the graphene surface with different affinities for TNT. We estimate a limit of detection for TNT equal to 20 ppb based on the analytical standard S/N ratio of 3. In addition, this approach to sensor fabrication is inherently a high-throughput, high-volume process amenable to industrial applications. High quality epitaxial graphene is easily grown over large area SiC substrates, while plasma processing is a rapid approach to large area substrate processing. This combination facilitates low cost, mass production of sensors.
Highlights
Being all surface, graphene is an excellent material to sense adsorbates as these can alter the charge carrier concentration, leading to measurable changes in conductivity
We show that plasma modified [32] epitaxial graphene [33] shows improved electrochemical detection of TNT (LOD ≈ 20 ppb) without the need for an accumulation step [29], or preconcentration step that utilizes large volume samples to provide sufficient analyte mass for obtaining a detectable signal [34], or an amplification step in which the TNT signal is enhanced using an electrochemical technique termed redox cycling [35], all to improve the electrochemical response
The C 1s peaks for untreated EG is composed of three components centered at about 283.6 eV, 284.5 eV and 285.3 eV which correspond to the silicon carbide substrate (Si–C), the epitaxial graphene film (C–C), and the interfacial layer between the SiC and epitaxial graphene, respectively [6]
Summary
Graphene is an excellent material to sense adsorbates as these can alter the charge carrier concentration, leading to measurable changes in conductivity. Using the epitaxial graphene approach, sensitive molecular sensors for many different analytes, i.e., adsorbates, have been successfully demonstrated by others [3,4,5]. This natural sensitivity to a range of analytes is a disadvantage and sensors should be designed to minimize or discriminate against the effects associated with non-target constituents in the operating ambient conditions [6,7]. It was implied that reaction sites can be controllably formed on epitaxial graphene as it was demonstrated that plasma-based, oxygen functionalization of epitaxial
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call