A novel inorganic redox buffer of r-GO/Ag@AgCl/TMMCl utilized as an effective ion-to-electron transducer for a solid contact calcium ion-selective electrode

The Ag@AgCl/1-tetradecyl-3-methylimidazolium chloride (TMMCl) reported as an inorganic redox buffer for solid contact ion-selective electrodes (SC-ISEs) suffers from minimized specific area for an aggregation of Ag nanoparticles and decreased electron transfer for a presence of AgCl coating. Herein, a novel optimized inorganic redox buffer of r-GO/Ag@AgCl/TMMCl with improved capacitance and electron transfer behaving well as an effective ion-to-electron transducer for a SC-Ca2+-ISE has been highlighted. With reduced graphene oxide (r-GO) introduced as a substrate, the produced Ag nanoparticles as well as the subsequently synthesized core-shell Ag@AgCl nanomaterials display high dispersity with diameters decreased to 10–40 nm. Cyclic voltammetry with better redox reversibility and higher areas for the r-GO/Ag@AgCl/TMMCl verifies its improved redox capacitance and acceleration in electron transfer. Taking advantage of the r-GO/Ag@AgCl/TMMCl, the fabricated SC-Ca2+-ISE exhibits a near Nernst slope about 28.5 mV/dacade between potentials to Ca2+ concentrations ranging from 10−6 to 10−3M. Additionally, a diminished Rbc and Rct as well as an increased capacitance are also exemplified by the EIS and chronopotentiometric techniques, which would ensure a fast and stable potentiometric response. Moreover, the fabricated SC-Ca2+-ISE displays a good selectivity and water layer resistance. Thanks to the increased redox capacitance of the r-GO/Ag@AgCl/TMMCl, the fabricated SC-Ca2+-ISE demonstrates stable potentiometric response and good E0 reproducibility.