Robust Potentiometric Microelectrodes for <i>In Situ</i> Sensing of Ion Fluxes with High Sensitivity

Simple, reproducible, and reliable preparation of robust potentiometric microelectrodes is both challenging and of great importance for noninvasive real-time ion sensing. Herein, we report a simple strategy for the large-scale synthesis of nickel cobalt sulfide (NiCo2S4) nanowire arrays grown on carbon fibers for potentiometric microelectrodes. The highly uniform NiCo2S4 nanowire array serving as a transduction layer can provide a high capillary pressure and viscous resistance for loading the ion sensing membrane and exhibit a large redox capacitance for improving the stability. An all-solid-state lead-selective microelectrode, which presents a detection limit of 2.5 × 10–8 M in the simulated soil solution, was designed as a model for noninvasive, in situ, and real-time detection of ion fluxes near the rice root surface. Importantly, the microsensor enables sensitive detection of trace-level ion-fluxes. This work provides a simple yet general strategy for designing potentiometric microelectrodes