Potassium Ion‐selective Electrode with a Sensitive Ion‐to‐Electron Transducer Composed of Porous Laser‐induced Graphene and MoS2 Fabricated by One‐step Direct Laser Writing

Abstract

AbstractIn this study, an ion‐selective electrode with a sensitive ion‐to‐electron transducer composed of porous laser‐induced graphene (LIG) and MoS2 (LIG‐MoS2/ISE) was fabricated to measure the potassium ion concentration in a greenhouse nutrient solution for soilless culture. Additionally, a more effective and low‐cost method was proposed for the large‐batch production and manufacture of potassium ion‐selective electrodes (K+‐ISEs) using the direct laser writing technique, which differs considerably from existing methods. Moreover, the sensing mechanism of the proposed LIG‐MoS2/ISE for potassium ion detection was investigated. The morphology and physical properties of the LIG‐MoS2/SC‐K+‐ISEs were studied by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and energy‐dispersive spectroscopy. Potentiometric measurements, chronopotentiometry, potentiometric water layer tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to evaluate the analytical performance of the newly developed K+‐ISEs. A Nernstian slope of 30.1 mV/decade for the activity of potassium ions in a concentration range from 10−7 to 10−2 M was determined. The EIS and chronopotentiometry results revealed that the LIG‐MoS2/SC‐K+‐ISE had a larger resistance and double‐layer capacitance than the LIG/SC‐K+‐ISE. The ion‐selective membrane (ISM) and solid‐contact layer did not have any water film between them, according to the potentiometric water layer test. The results proved that the LIG‐MoS2 nanocomposite could possibly be used as a sensitive ion‐to‐electron transducer to fabricate K+‐ISEs. The K+‐ISE fabrication method using the direct laser writing technique had a higher efficiency, enabling its broad application prospects in agriculture.