Fig. 3

TEM images of (a) Fe₃O₄, (b) Fe₃O₄@SiO₂ and (c) Fe₃O₄@SiO₂/Schiff-base/Zn (II); SEM images of (d) Fe₃O₄, (e) Fe₃O₄@SiO₂ and (f) Fe₃O₄@SiO₂/Schiff-base/Zn (II); particle size distributions of (g) Fe₃O₄, (h) Fe₃O₄@SiO₂, and (i) Fe₃O₄@SiO₂/Schiff-base/Zn (II).