All‐solid‐state Fluoride Ion‐selective Electrode using LaF3 Single Crystal with Poly(3,4‐ethylenedioxythiophene) as Solid Contact Layer

An all‐solid‐state fluoride ion‐selective electrode (ISE) was prepared using LaF3 single crystal with poly(3,4‐ethylenedioxythiophene (PEDOT) as the solid contact layer. In contrast to polymer‐based ISEs, crystalline membrane‐based ISEs have not been used for all‐solid‐state device, thereby prohibiting the integration of ISEs on a chip. The all‐solid‐state fluoride ISE developed in this study exhibited superior sensitivity (−56.0±0.9 mV/dec) and selectivity compared to those of conventional inner filling solution ISE. The effects of PEDOT as a solid contact layer were analyzed using chronopotentiometry and electrochemical impedance spectroscopy, which revealed that PEDOT promoted electrode stability. The all‐solid‐state device can miniaturize the fluoride ISE and facilitate environmental, industrial, agricultural, and physiological monitoring.