Soil Potassium Sensor Using a Valinomycin-Decorated Reduced Graphene Oxide (rGO-v)-Based Field-Effect Transistor for Precision Farming

A precise measurement of soil potassium (K) concentration is crucial for enhancing agricultural productivity and promoting sustainable land management. The efficiency of real-time soil quality monitoring is hampered by the time-consuming laboratory analysis that is commonly associated with conventional methods. The present research introduces an innovative approach utilizing a field-effect transistor (FET) structure coated with reduced graphene oxide-decorated valinomycin (rGO-v) for the detection of potassium ions in soil samples. The sensor exploits the distinctive electrical properties of reduced graphene oxide (rGO) and the specific affinity of valinomycin for potassium ions. To construct the device, we applied rGO-v onto an FET substrate. The conductance of the FET can be modified by the interaction between valinomycin and potassium ions, enabling the detection of potassium ions. Some of the advantages of this technology are its high sensitivity, fast response time, and potential for miniaturization. In addition, the device is tuned to demonstrate an enhanced sensitivity of 0.98 μA/(kg/ha) below the threshold voltage. The sensor exhibits a response time of 40 s and demonstrates exceptional stability in the face of unfavorable conditions, specifically humidity. Therefore, valinomycin-decorated reduced graphene oxide, when subjected to appropriate gate bias, demonstrates promising results as a versatile, cost-effective, and easy-to-use potassium ion sensor.