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 electrically conducting polyaniline (PANI) as the ion-to-electron transducer (solid-contact) in Ca2+-selective solid-contact electrodes (CaSCISEs). The drop cast transducer deposited from the graphene-PANI dispersion in N-methylpyrrolidone makes use of the synergistic effect of these two materials. It maintains the 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 compared to the neat PANI based electrodes and increases the hydrophobicity of the transducer (ca. 30 degrees higher water 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 the response 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 potential reproducibility of only +/- 4 mV (n=3) for the CaSCISEs having graphene-PANI as the solid-contact. The CaS-CISEs in this study had a detection limit of 5 x 10(-8) M Ca2+, which was obtained without any sophisticated pre-treatment protocols. (C) 2015 Elsevier B.V. All rights reserved.