A Hybrid Electronic Nose and Tongue for the Detection of Ketones: Improved Sensor Orthogonality Using Graphene Oxide-Based Detectors

In this contribution, the selectivity toward a diabetes biomarker was demonstrated by a non-specific impedance-metric chemical sensor array from blends of graphene oxide (GO)-based materials as a multivariate system for simultaneous aqueous and gaseous analyte investigation. The electrical impedance of bare graphene either oxidized or after reduction (RGO) displayed high specificity toward ammonia. The sensitivity of GO thin-film capacitance was 10.4 %/ppm of ammonia dissolved in ultrapure water, whereas RGO resistance featured 1.8 %/ppm to gaseous ammonia. However, composites with metal oxides, despite even providing a superior sensitivity to ammonia, completely alter the sign of sensor response to enable distinction of alcohols. Ceria and cyclodextrin allowed GO to operate in air at room temperature with improved stability and a faster response of approximately 60 s. These materials made for an increase in sensitivity to acetone of 11 and 3.2 times, respectively, compared to RGO. Therefore, GO-based composites, as well as the junction of electronic nose and tongue arrays were fundamental to enable the separation of acetone from alcohols and ammonia after principal component analysis.