Optimized detection of calcium ion in serum using constant potential coulometry with metastable liquid-liquid contact doping enhanced PEDOT: PSS ink.

Highly stable calcium ion selective electrodes (Ca-ISEs) were developed by drop-casting a layer of poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) as an ion-to-electron transfer layer onto Au electrode. The conductive PEDOT: PSS ink was prepared using a metastable liquid-liquid contact (MLLC) doping method, which induced phase separation, removed excess PSS, and significantly enhanced charge transfer kinetics and conductivity. The resulting Ca-ISEs exhibited excellent electrochemical performance.