Development of A Laser Induced Graphene-based Sensor for Onsite Measurement of Soil Nitrogen.

Laser-induced graphene (LIG) sensors are becoming popular in various agricultural applications due to their ease of fabrication and superior characteristics. These LIG sensors can be used for real-time nutrient monitoring. By using a one-step laser engraving process, it is possible to create flexible graphene electronics on polyimide substrates. A CO2 laser was used for engraving purpose as it changes sp3-hybridized carbon which is present in substrates like polyimide into sp2-hybridized carbon. Selective patterns of polyimide film (Kapton tape) can be converted into sp2-hybridized carbon using laser beam. A 30W CO2 laser was used to engrave the LIG sensor on polyamide sheet with optimized settings i.e. 11% power and 1.2 % speed. Distinct ionophores specific to NH4+ (nonactin) or NO3− (tridodecylmethylammonium nitrate) were functionalized within poly (vinyl chloride)-based membranes to create distinct solid contact ion-selective electrodes (SC-ISEs) for NH4 + and NO3− ion sensing cocktails by drop casting on working electrode, respectively. An Ag/AgCl electrode printed with Ag/AgCl ink operated as the reference electrode, while the LIG electrode worked as the working and counter electrode. The electrochemical ion-selective detection of plant accessible nitrogen (i.e., including ammonium and nitrate ions: NH4 + and NO3-) in soil samples was conducted using these LIG sensors. Using a three-electrode setup, Cyclic Voltammetry (CV) scans were performed to determine the various concentrations of ammonium and nitrate in soil samples.