fig1

Figure 1. Structure characterizations of Fe₃O₄@RF and Fe₃O₄@C microspheres. (A) SEM image of Fe₃O₄@RF; the inset shows their optical photograph; (B) SEM image of Fe₃O₄@C; (C) TEM image of Fe₃O₄@RF; (D) TEM image of Fe₃O₄@C. RF: Resorcinol-formaldehyde; SEM: scanning electron microscopy; TEM: transmission electron microscopy.