Iron(III) oxide nanoparticles in the thermally induced oxidative decomposition of Prussian Blue, Fe4[Fe(CN)6]3

The thermally induced decomposition of Prussian Blue, Fe-4[Fe(CN)(6)](3) (PB), was studied in air at 250 and 350 C. Amorphous Fe2O3 nanoparticles, cubic bixbyite beta- and cubic spinel gamma-Fe2O3 (maghemite) polymorphs, have been identified as the products of the decomposition under different reaction conditions. Fe-57 Mossbauer spectroscopy, XRD, AFM, TEM, quasielastic light scattering method (QELS) of particle size analysis, BET surface area, and magnetization measurements were used to understand the influence of the PB particle size and oxidation conditions on the decomposition mechanism at 250 and 350 C. At a minimum decomposition temperature of 250 degreesC, amorphous Fe2O3 nanoparticles were formed with the size ranging from 1 to 4 nm and large surface area of 400-200 m(2)/g in dependence on the PB particle size. Such small amorphous Fe2O3 nanoparticles were obtained by the solid-state route for the first time. At 350 degreesC, cubic beta-Fe2O3 and gamma-Fe2O3 polymorphs were identified and their contents were found to be strongly dependent on the initial PB particle size and oxidation-diffusion conditions. Generally, the higher relative content of gamma-Fe2O3 was obtained for larger PB particles and in air-limited conditions.