fig2

Figure 2. TEM images of Fe₃O₄@RF with RF shell thickness obtained at different reaction concentrations of resorcinol. (A) 7 nm (in 1 mg/mL); (B) 15 nm (in 2 mg/mL); (C) 75 nm (in 3 mg/mL); (D) 150 nm (in 5 mg/mL). TEM: Transmission electron microscopy; RF: resorcinol-formaldehyde.