Ionic Liquid-gated Graphene FET Sensors for Detecting Nitrate Nitrogen (NO₃-N) in Agricultural Soil

We have developed and evaluated ionic liquidgated graphene field-effect transistor (FET) sensors as part of a precision farming for detecting nitrate nitrogen (NO3-N) concentrations in agricultural soil. We began by fabricating and testing of basic characteristics the ionic liquid-gated graphene FET sensors. Next, we examined transfer characteristic curves of the sensors in the presence of vapors of NO3-N standard solution 0.2-mL in 10-L chamber by setting up a soil simulated system. The drain-source current (Ids) at concentration of 100ppm and 1000ppm increased in both positive and negative directions from Dirac point. The Dirac point voltage shifted 0.1 V to the negative side as the NO3-N concentration increased from 100 ppm to 1000 ppm.