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

In 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.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

“…[319] The first to synthesizing such composite materials is the deposition of a metal precursor phase over the graphitizable substrate, using solution processing approaches. [170,[320][321][322][323][324] A second approach is the formulation of liquid composite precursors, that present both the organic, LIG precursor phase and the metal precursor simultaneously. [325][326][327] Using both strategies, LIG-based composites with metallic elements have been produced, using the thermal laser stimulus to simultaneously graphitize the carbon organic precursor and reduce or oxidize the metallic precursor.…”

“…Besides metal and metal oxide embedded phases for LIG-based composite synthesis, concurrent synthesis of other semiconductor materials has been explored, including chalcogenides such as hafnium diselenide [323] and molybdenum disulfide. [324] Based solely on carbonization mechanisms, the writing of LIG doped with several carbides has also been explored. Molybdenum carbide nanostructures embedded in conductive carbon have been reported using paper substrates [257,258] by soaking the cellulose matrix with molybdenum metal ions.…”

A Co3O4 Nanoparticle-Modified Screen-Printed Electrode Sensor for the Detection of Nitrate Ions in Aquaponic Systems

“…These results confirmed that the Co3O4 NPs were successfully used as a transducer material. EIS measurements were performed over frequencies ranging from 10 Hz to 10 6 Hz with an open-circuit voltage of 0.358 V and an excitation amplitude of 0.005 V. Figure 6b depicts the equivalent circuit used to fit the resulting Nyquist plots, in which R b , R ct , R s , C dl , CPE, and W represent the bulk membrane resistance together with the contact resistance between the underlying conductor and the ISM, the charge-transfer resistance, the solution resistance, the double-layer capacitance, the constant phase angle element, and the Warburg impedance, respectively [41]. The R ct values of the SPE (red points) were approximately 0.72 kΩ.…”