Thermal decomposition of ferritin core

Ferritin is an iron storage protein found in living organisms. It is an antiferromagnetic nanoparticle system consisting of an inorganic core surrounded by a protein shell. Ferritin is characterized by X-ray diffractometer, transmission electron microscope, atomic absorption spectrometer and thermogravimetric analyzer. We find that the ferritin core is poorly crystalline, 8 nm in size and consists of 10 wt% iron. It is believed that cores of ferritin consist of single-phase inorganic mineral ferrihydrite. Recently, we have shown that ferrihydrite decomposes directly to α - Fe 2 O 3 on heating in air at 440 ∘ C. In the present work, we show that ferritin cores gradually decompose to a mixture of γ - Fe 2 O 3 and α - Fe 2 O 3 on heating in air. This mixture finally stabilizes to α - Fe 2 O 3 on further heating. The magnetic behaviour of final sample is also studied. This work confirms that the ferritin cores contain more than one phase.