2.2.5. Electrochemical Impedance Measurements

Electrochemical impedance spectroscopy was conducted with an Autolab potentiostat (Model PGSTAT302N, Metrohm, Poland) coupled with an FRA2 module. A four-probe cell with two Ag/AgCl reference electrodes was employed for sensing and two platinum electrodes were used to carry the current for the measurements. The cell was presented in [37]. EIS data were registered in the frequency range of 0.1–100,000 Hz. A sinusoidal voltage excitation of 4 mV versus open circuit potential was applied. No direct current was used.

Analysis of the data obtained during EIS measurements was performed using NOVA software (v. 1.10) with the fitting model shown in Scheme 1. This electrical circuit was described previously for the lipid bilayer unmodified by channels formers or carriers [45]. The circuit consists of the solution resistance (*R*e) in series with a membrane resistance (*R*m) and a membrane capacitance (*C*m), which are in parallel and correspond with the electric and dielectric properties of the bilayer. The values of the *R*<sup>m</sup> and *C*<sup>m</sup> were normalized to the bilayer area. Each value represents the average of 6–10 independent measurements.

**Scheme 1.** The equivalent circuit model used to fit EIS data.
