Fig. 4

A Nyquist diagrams of (a) ZnFe₂O₄/NPs/IL/CPE, (b) IL/CPE, (c) ZnFe₂O₄ /NPs /CPE and (d) CPE. Conditions: 500 µM RC in PBS (0.1 M) pH 6, over the frequency range of 0.1 to 100,000 Hz. B Corresponding equivalent circuits