Vanadium oxide-doped laser-induced graphene multi-parameter sensor to decouple soil nitrogen loss and temperature

Abstract Monitoring nitrogen utilization efficiency and soil temperature in agricultural systems for timely intervention is essential to monitor crop health, promote sustainable and precision agriculture, and reduce environmental pollution. Therefore, it is of vital significance to develop a multi-parameter sensor for effectively and accurately decoupled detection of nitrogen loss and soil temperature, which is yet to be reported. Herein, this work presents a high-performance multi-parameter sensor based on vanadium oxide (VOX)-doped laser-induced graphene (LIG) foam to completely decouple nitrogen oxides (NOX) and temperature. By exploiting the laser-assisted synthesis, the highly porous 3D VOX-doped LIG foam composite is readily obtained by laser scribing of vanadium sulfide (V5S8)-doped block copolymer and phenolic resin self-assembled films. Compared with the intrinsic LIG, the heterojunction formed at the LIG/VOX interface provides the sensor with a significantly enhanced response to NOX and an ultralow limit of detection (LOD) of 3 ppb at room temperature. Meanwhile, the sensor can accurately detect temperature over a wide linear range of 10–110℃ with a small detection limit of 0.2℃. The encapsulation of the sensor with a soft membrane further allows for temperature sensing without being affected by NOX, presenting an effective strategy to decouple nitrogen loss and soil temperature for accurate soil environmental monitoring. The sensor without encapsulation but operated at elevated temperature removes the influences of ambient relative humidity and temperature variations for accurate NOX measurements. The capability to simultaneously detect ultra-low NOX concentrations and small temperature changes paves the way for the development of future multimodal electronic devices with decoupled sensing mechanisms for health monitoring and precision agriculture.