Graphene-based Solid-contact Ion Selective Electrodes

As a typical member of electrochemical sensors,solid-contact ion selective electrodes（SC-ISE）have been widely studied in environmental monitoring,food safety,and water analysis et al.Nowadays,research on ion-selective membrane is approaching maturity,and ion-electron transduction layer（solid contact layer,i.e.SC）has become the key to further improve the stability of SC-ISE’s potential.Graphene,being widely used solid in SC-ISEs,possesses many advantages such as facile synthesis,outstanding electrical conductivity,large capacitance,strong hydrophobicity and high specific surface area,et al.Among them,capacitance and hydrophobicity are main intrinsic properties of graphene affecting the performance of SC-ISE.Therefore,screening the graphene solid contact layer material with excellent performance is of great significance for the development and application of SC-ISE.Herein,we started out with process and crafts of electrode fabrication and sifted graphene with the best performance.Moreover,SC-ISE had been successfully applied for ion detection in mineral water and soil-soaked solution,which offers prerequisite for practical application of graphene-based SC-ISE.The detailed research is divided into the following three parts:（1）Proper pretreatment of the solid contact layer material,the appropriate dispersant solvent and binder for the material,advisable loading mass of solid contact material as well as suitable drying temperature and feasible drying approach were explored.（2）Difference of hydrophobicity between graphene was illuminated by performing physical characterizations including XRD,XPS,Raman spectrum and contact Angle test.In addition,electrochemical tests including cyclic voltammetry,charge-discharge tests were performed so as to insight the differentiate the capacitance of SC and SC-ISEs.Then water layer tests,long term stability tests and potentiometric time response were carried out to elucidate how capacitance and hydrophobicity determine the potential stability.（3）Based on the experiments above,K⁺,Na⁺and Ca²⁺SC-ISEs were prepared,and concentration of K⁺,Na⁺and Ca²⁺in mineral water and soil-soaked solution were precisely quantified to verify the eminent performance of graphene-based ion selective electrode in practical application.