(IMCS Second Place Best Paper Winner) Investigation of Room Temperature Ionic-Liquid (RTIL) Modified Electrode for Decoupling Soil Electrochemistry

Abstract

Room temperature ionic liquid (RTIL) is a unique zwitter-ionic compound, that possesses excellent physical and chemical properties, which enables electrochemical applications such as to be utilized as a transducer for probing a complex matrix such as soil. The wide electrochemical window and elevated double layer capacitance of RTIL helps to gauge soil parameters which is helpful to understand soil state. In this work we investigate the utility of RTIL modified electrodes as viable sensors for decoupling soil electrochemistry. Soil plays the key role in plant and crop production and is a vital parameter in the ecological structure of the planet and indispensable in the food ecosystem cycle. Soil health monitoring in the near past has been highly qualitative and speculative with more recent advancements still trying to fill the void of a holistic soil profile. In fields and crop-circles, testing methods to perform in-situ profiling however from one lab is likely to vary with another and hence results are not universally compatible. Additionally, these normalized techniques ideally involve empirical approaches, extensive sample preparation which adds on to a temporal factor along with equipment for extraction and subsequently-analysis. This therefore-stimulates the need for a testing methodology that is capable of rapid analysis in an in-situ environment that can be applicable universally.In this paper, we focus on: a rapid electrochemical point probing mechanism that acts as a soil state evaluation platform via a 3-electrode sensor modified by a widely characterized-RTIL [BMIM] [BF4] interfacial transducer medium. The proposed quantitative model –‘DENSE’ probes the soil diffuse double layer (DDL) dielectric to evaluate a thorough chemical profile of the soil matrix. The experimental design was implemented to capture the effect of electroactive species in the soil matrix altered by adding nutritional amendments. Non-faradaic probing was then performed in this design to gauge the inherent capacitive modulations of the soil system as a function its compositional changes. Therefore, by looking at the rate of electrochemical activity and inherent soil dielectric changes driven by an RTIL interfacial layer, it is possible to decouple information on nutrient availability in soils with potential for application towards temporal soil analysis.Figure: (A) Equivalent-circuit (DENSE) model of the soil-water matrix and a schematic representation of the model with respect to the electrode-electrolyte interface (B) Impedance nyquist plot and (C) Bode-phase to denote the pseudo-capacitive dominant nature of the soil matrix (1:1, 1:2) and the comparatively resistive behavior of the baseline and 2:1 mixture Figure 1