2.1. Apparatus

Voltammetric experiments were undertaken using a µAutolab analyzer (Eco Chemie, Utrecht, The Netherlands) controlled by GPES 4.9 software. The measurements were performed in a classic electrochemical cell with a commercially available screen-printed sensor (Metrohm-DropSens, Oviedo, Spain). The same analyzer controlled by FRA 4.9 software was also used to record Nyquist plots in the electrochemical impedance spectroscopy (EIS) method. The three-electrode sensor consisted of a boron-doped diamond (BDD) working electrode, a carbon auxiliary electrode, and a silver pseudo-reference electrode. In order to characterize the aSPBDDE, the optical profiles and the microscopic images of the sensors were recorded using a Contour GT-K1 optical profilometer (Veeco, New York, NY, USA) and a high-resolution scanning electron microscope Quanta 3D FEG (FEI, Hillsboro, OR, USA). The optical profiles were obtained using vertical scanning interferometry (VSI) mode with magnification of 40×. The SEM experiments were carried out under conditions (acceleration voltage of 5.0 kV, horizontal field width of 5.97 µm, working distance of 9.8 mm, magnification of 25,000×). Chromatographic measurements were performed on a VWR Hitachi Elite LaChrom HPLC system equipped with a spectrophotometric detector (PDA), an XB-C18 reversed phase core-shell column (Kinetex, Phenomenex, Aschaffenburg, Germany) (25 cm × 4.6 mm i.d., 5 μm), and EZChrom Elite software (version 3.2 SP2, Merck, Germany).