An ecodesigned reagent-free paper-based electrochemical sensor modified with carbon black for the detection of essential oils

In the era of sustainability, the use of natural compounds as antimicrobial compounds is the rational selection to avoid the release of pollutants into the environment. Among natural compounds, essential oils are characterized by reliable antimicrobial activity and their use is estimated to grow in the future, thus their detection is an asked point. Herein, we report an electrochemical reagent-free paper-based device for the detection of essential oils, namely thymol, eugenol, and carvacrol by adding 5 µL of solution onto the electrode. We functionalized the working electrode with carbon black by drop casting, demonstrating for the first time the improved sensitivity in essential oil detection using this affordable nanomaterial. To deliver a reagent-free device, the paper-based electrode was loaded with the working buffer for asking the end-user only the addition of the sample. This sensor detected the selected essential oils in a dynamic linear range of up to 16 ppm, with a detection limit equal to 0.1, 0.1, and 0.2 ppm for thymol, eugenol, and carvacrol, respectively. Moreover, the sensor's sustainability was evaluated using the RGBfast method, highlighting its whiteness compared to conventional chromatographic techniques. The reliable results obtained using the paper-based electrochemical sensor demonstrated the versatility, eco-friendliness, and practicality of this sensing tool, enlarging its use in essential oil detection.