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This paper reviews the development of all-solid-state ion-selective electrodes (ASSISEs) for agricultural crop detection. Both nutrient ions and heavy metal ions inside and outside the plant have a significant influence on crop growth. This review begins with the detection principle of ASSISEs. The second section introduces the key characteristics of ASSISE and demonstrates its feasibility in crop detection based on previous research. The third section considers the development of ASSISEs in the detection of corps internally and externally (e.g., crop nutrition, heavy metal pollution, soil salinization, N enrichment, and sensor miniaturization, etc.) and discusses the interference of the test environment. The suggestions and conclusions discussed in this paper may provide the foundation for additional research into ion detection for crops. [ABSTRACT FROM AUTHOR]

Abstract: Negatively charged multi-walled carbon nanotubes (MWCNTs) were used as dopants in the electrochemical synthesis of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). The resulting electroactive film, PEDOT(CNT), was used as ion-to-electron transducer (solid contact) in potassium ion-selective electrodes (K+-ISEs) based on plasticized PVC membrane containing valinomycin as neutral ionophore. Potentiometric measurements were carried out to study the analytical performance of solid-contact K+-ISEs, the influence of dissolved O2 and CO2 on the potential of the electrodes, and the formation of the interfacial aqueous film. The prepared electrodes were also characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry. The experimental results showed that PEDOT(CNT) has the capability to function as solid contact in fabrication of K+-ISEs. These electrodes, based on PEDOT(CNT) as ion-to-electron transducer, showed high sensitivity and selectivity to K+ ion which can be related to the plasticized PVC-based ion-selective membrane containing valinomycin. The stability of the electrode potential, however, was found to depend on the conducting substrate used for deposition of the PEDOT(CNT) film. Results from the CV and EIS revealed that the PEDOT(CNT) contact exhibits high redox capacitance that is favorable for a solid contact. [Copyright &y& Elsevier]

Nanostructured materials have attracted considerable interest over the last few decades to enhance sensing capabilities thanks to their unique properties and large surface area. In particular, noble metal nanostructures offer several advantages including high stability, non-toxicity and excellent electrochemical behaviour. However, in recent years the great expansion of point-of-care (POC) and wearable systems and the attempt to perform measurements in tiny spaces have also risen the need of increasing sensors miniaturization. Fast constant potential electrodeposition techniques have been proven to be an efficient way to obtain conformal platinum and gold nanostructured layers on macro-electrodes. However, this technique is not effective on micro-electrodes. In this paper, we investigate an alternative one-step deposition technique of platinum nanoflowers on micro-electrodes by linear sweep voltammetry (LSV). The effective deposition of platinum nanoflowers with similar properties to the ones deposited on macro-electrodes is confirmed by morphological analysis and by the similar roughness factor (~200) and capacitance (~18 μ F/mm 2 ). The electrochemical behaviour of the nanostructured layer is then tested in an solid-contact (SC) L i + -selective micro-electrode and compared to the case of macro-electrodes. The sensor offers Nernstian calibration with same response time (~15 s) and a one-order of magnitude smaller limit of detection (LOD) ( 2.6 × 10 − 6 ) with respect to the macro-ion-selective sensors (ISE). Finally, sensor reversibility and stability in both wet and dry conditions is proven. [ABSTRACT FROM AUTHOR]