The use of graphene oxide as a fixed charge carrier in ion-selective electrodes

• Ion-selective membranes containing graphene oxide (GO) were prepared and studied.
• An inverse dependence between GO concentration and bulk resistance was observed.
• Potentiometric calibrations showed that the membranes were permselective to cations.
• Proof-of-principle membrane pH sensors were evaluated using ETH-1907 and GO.

Here we present for the first time the use of graphene oxide nanoparticles as fixed-charge carriers for the development of membrane-based cation selective ion-selective electrodes (ISEs). The GO nanoparticles are dispersed into tetrahydrofuran, and thus easily incorporated into the ISE membrane. The effect of GO concentration on bulk membrane resistance (Rb) is measured using electrochemical impedance spectroscopy, and a significant decrease in Rb is observed with increasing [GO]. The permselectivity of these membranes was investigated using conventional potentiometry, and the results suggest that GO is able to decrease membrane resistance through electrostatic interactions between the negatively charged particles and the positively charged cations. The use of these nanostructures in the pH-sensitive ISE based on ETH-1907 ionophore paves the way to a new method of constructing potentiometric sensors. ISEs with increased lifetimes and stabile potentials could be developed based on these materials, allowing ionophore and charge carrier to be combined in a way that promotes miniaturization of ISEs with more optimal analytical characteristics.