Few-layer graphene and polyaniline composite as ion-to-electron transducer in silicone rubber solid-contact ion-selective electrodes

We have used for the first time a composite consisting of few-layer exfoliated graphene and electri-cally conducting polyaniline (PANI) as the ion-to-electron transducer (solid-contact) in Ca²⁺-selectivesolid-contact electrodes (CaSCISEs). The drop cast transducer deposited from the graphene–PANI dis-persion in N-methylpyrrolidone makes use of the synergistic effect of these two materials. It maintainsthe ion-to-electron transduction which is characteristic for the electrically conducting polymers (ECP),but in addition, graphene improves the reproducibility of the standard potential of the SCISEs comparedto the neat PANI based electrodes and increases the hydrophobicity of the transducer (ca. 30^◦ higherwater contact angle) which counteracts the water layer formation. Our results reveal that the incorporation of few-layer graphene in the transducer layer improved also the initial potential stability and theresponse characteristics of the CaSCISEs due to the electrocatalytic effect of the graphene–ECP composite, which facilitates the electron transfer at the transducer/substrate interface. We obtained a potentialreproducibility of only ±4 mV (n = 3) for the CaSCISEs having graphene–PANI as the solid-contact. The CaSCISEs in this study had a detection limit of 5 × 10⁻⁸ M Ca²⁺, which was obtained without any sophisticated pre-treatment protocols.