Development of sodium and potassium ion-selective electrodes based on laser induced graphene

This paper describes the development of sodium and potassium ion-selective electrodes (Na⁺ and K⁺ ISEs) based on laser-induced graphene (LIG), which can selectively detect sodium and potassium ions in body fluids. LIG was formed on commercial polyimide film using a computer-controlled CO2 infrared laser and was characterized by FE-SEM and Raman spectroscopy. The results show that the LIG was composed of three-dimensional randomly stacked porous graphene layers. To minimize the potential drift of the ISEs, PEDOT:PSS was electrically polymerized on LIG working electrodes using potentiometry method and EIS spectrum confirmed that the LIG/PEDOT:PSS electrode has lower charge transfer resistance than pure LIG electrode. Na⁺ and K⁺ ISEs were made by drop casting the ion-selective membrane cocktail over the PEDOT:PSS layer. The fabricated Na⁺ and K⁺ ISEs show high sensitivity (63.08 mV/dec, 63.80 mV/dec), low detection limit (10^-5.0 M), wide linear range (10^-5 M to 10^-1 M), and excellent selectivity of Na⁺ and K⁺ against NH4⁺, Mg²⁺ and Ca²⁺. Combined with the advantages of a one-step processing of LIG, we expect this work to promote future applications in micro devices for commercial applications.