Further studies on the role of redox-active monolayer as intermediate phase of solid-state sensors

The aim of this work was to further study the impact of polyacrylate membrane and the self assembled monolayer (SAM) on the elimination of CO2 interferences in solid-state ion-selective sensors with gold internal electrode. For this purpose permeability to CO2 of polyacrylate-based membranes has been examined. Application of differential system consisting of two H+-selective electrodes differing in the composition of internal electrolyte (with and without pH-buffer system) allowed to find that CO2 is able to permeate hexanediol diacrylate (HDDA)/isodecyl acrylate (IDA)/acrylonitrile (ACN) membrane. The second goal of this work was to confirm that hydrophobic properties of applied SAMs based on ferrocene-terminated thiols mixed with n-hexanethiol is mainly responsible for the prevention of aqueous layer formation between the ion-selective membrane and the surface of inner electrode. For this purpose two types of “aqueous layer” tests, based on transmembrane ion fluxes as well as CO2 diffusion, were carried out.