Real-time, high-resolution, simultaneous measurement of multiple ionic species is challenging. This paper presents wafer-scale graphene transistor technology for creating ion-sensitive field-effect transistors (ISFETs) arrays to overcome limitations in resolution and selectivity of existing potentiometric ion sensors. Nikolskii-Eisenman analysis is applied to account for cross-sensitivity, achieving high selectivity and enabling real-time, simultaneous concentration measurement of K+, Na+, NH4+, NO3-, SO42-, HPO42-, and Cl- with high resolution and accuracy. The array's capabilities are demonstrated by monitoring ion uptake by duckweed in an aquarium over three weeks.

Ibrahim Fakih, Oliver Durnan, Farzaneh Mahvash, Ilargi Napal, Alba Centeno, Amaia Zurutuza, Viviane Yargeau, Thomas Szkopek