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 (NaSUP+/SUP and KSUP+/SUP 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. NaSUP+/SUP and KSUP+/SUP 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 (10SUP-5/SUP M to 10SUP-1/SUP M), and excellent selectivity of NaSUP+/SUP and KSUP+/SUP against NH₄SUP+/SUP, MgSUP2+/SUP and CaSUP2+/SUP. 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.