Cyclic voltammograms in PBS buffer recorded at carbon fiber electrodes (A–C) and PPF electrodes (D–I). Carbon fiber microelectrodes were cycled at 60 Hz to the potential limits shown for 30 min prior to the recording of these voltammograms. Background currents for PPF electrodes are shown prior to cycling (D–F) and at the end (30 min) (G–I) of cycling. The anodic potential limits are 1.0 V for A, D and G (300 V/s), 1.3 V for B, E and H (400 V/s), and 1.4 V for C, F and I (400 V/s).