Gate-Optimized rGO-Flake-Based Field-Effect Transistor for Selective Detection of Nitrogen in Soil for Precision Farming

The inadequate use of fertilizer leads to an imbalance of nitrogen in soil, which presents significant challenges to sustainable agriculture. To address this issue, a novel soil nitrogen sensor using reduced graphene oxide (rGO)-based field-effect transistor (FET) is proposed. In soil, nitrogen is present in the form of nitrate, nitrite, and ammonium ion, but as nitrite content is exceptionally low, detection of nitrite is not possible. Most of the research focus on nitrate detection, but simultaneous detection of nitrate and ammonium ions is highly significant and challenging. The proposed concept enables a single FET device to detect both ammonium and nitrate ions at different gate potentials. The sensor demonstrates a very high response of 1050 % for 3.5 ppm nitrate ion with the sensitivity of 0.9 μA/ppm and 860 % for 3.5 ppm ammonium ion with the sensitivity of 0.45 μA/ppm at an optimized Vgs of 3.9 V and 0.8 V, respectively. Moreover, the sensor exhibits promising attributes, including high selectivity and rapid response (35 seconds for NO3- ions and 41 seconds for NH4+ ions). This facilitates real-time monitoring of soil nitrogen levels for precision agriculture applications.