Fig. 3. Magnetite formation from a ferrihydrite precursor phase by ammonia diffusion. (a) Evolution of pH and total NH3 concentration over time during 2 vol% NH3 diffusion in 30 mL of 3 mM Fe solution. (b) Cryo-TEM image after 1 h reaction time that shows nanoparticulate ferrihydrite. (c) Low-dose SAED pattern of the precursor indexed to 2-line ferrihydrite. Inset: selected area. (d) TEM image of the resulting 17 ± 8 nm magnetite nanoparticles. (e) SAED pattern of the nanoparticles indexed to magnetite. Inset: selected area. Reproduced from ref. 83.
