Electrochemical Impedance Spectroscopy (EIS) of modified electrodes: bare GCE, GCE/Lac-Nafion, and GCE/Lac-PdBC-Nafion in 0.1 M KCl containing 5 mM Fe(CN)63−/4−. Frequency range: 0.01 Hz–100,000 Hz. Amplitude: 5 mV (A); Cyclic voltammograms of: (a) bare GCE; (b) GCE/Lac-Nafion; and (c) GCE/Lac-PdBC-Nafion in pH 7.0 PBS containing 100 µM dopamine at 100 mV·s−1 (B);Cyclic voltammograms of GCE/Lac-PdBC-Nafion in pH 7.0 PBS containing 100 µM dopamine at scan rates of 100, 150, 200, 250, 300, and 350 mV·s−1 (a–f), respectively (C); Plots of the corresponding anodic and cathodic peak currents vs. scan rate (D).