Odorant sensing with functionalized graphene field-effect transistors utilizing impedance spectroscopy

The label-free detection of odorant biomolecules on bases of electrochemical devices is the first step towards an artificial nose.
In this work the unique electrochemical properties of graphene are utilized to create a biosensing platform for the detection of odorants, using surface-immobilized odorant binding proteins.

Herein, the suitability of impedance spectroscopy applied to reduced graphene oxide based field-effect transistors for detection of biological binding events is demonstrated. The impedance Z as a function of the analyte bulk concentration in aqueous solution was measured. The immobilized odorant binding proteins influence the charge carriers in the channel of the graphene field-effect transistor (gFET) significantly, changing the impedance Z during the binding of specific analytes. Negative control measurements of the analyte without immobilized odorant binding proteins have been performed to validate the specificity of the biosensor. Furthermore, the dependencies to pH values and ionic concentrations of the aqueous solutions are shown. Different protective layers on the graphene surface were applied to reduce the unspecific responses. The Langmuir isotherm was used to determine the affinity of ligands to odorant binding proteins and the advantages of impedance spectroscopy measurements on the graphene field-effect transistor are discussed for further investigations.