Iron(III) Oxide Nanoparticles in the Thermally Induced Oxidative Decomposition of Prussian Blue, Fe₄[Fe(CN)₆]₃

Abstract

The thermally induced decomposition of Prussian Blue, Fe 4 [Fe(CN) 6 ] 3 (PB), was studied in air at 250 and 350 °C. Amorphous Fe 2 O 3 nanoparticles, cubic bixbyite β-and cubic spinel γ-Fe 2 O 3 (maghemite) polymorphs, have been identified as the products of the decomposition under different reaction conditions. 57 Fe Mo ¨ssbauer 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 °C, amorphous Fe 2 O 3 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 Fe 2 O 3 nanoparticles were obtained by the solid-state route for the first time. At 350 °C, cubic β-Fe 2 O 3 and γ-Fe 2 O 3 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 γ-Fe 2 O 3 was obtained for larger PB particles and in air-limited conditions.

Photocatalytic Degradation of Direct Violet 4-Azodye in Aqueous Solution Using Α-Fe2o3thin Films

“…This is similar to amorphous Fe 2 O 3 powders, prepared by thermal induced oxidative decomposition at 250˚C of the same precursor [16]. …”

On determination of the Curie point from thermomagnetic curves

“…Approximation of Curie points of Cr-substituted hematite [Grygar et al, 2003], determined from temperature dependence of magnetic susceptibility (y axis) using the two-tangent method (open squares, gray fit line), using the paramagnetic test of inverse susceptibility (diamonds, black fit line), and as temperature of the susceptibility peak (gray circles, dashed gray fit line, peak for the sample with 40% Cr substitution is not pronounced), with reference values determined using the two-tangent method from temperature dependence of induced magnetization (x axis). [Zbořil et al, 2004]. Decrease of the latter parameter to zero at 55 K reflects that the onset of paramagnetic behavior (absence of the minor hysteresis loop area) corresponds well with the onset of hyperbolic decay on the in-phase susceptibility.…”

“…However, at low temperatures, for instance, Quantum Design MPMS can be used. One such example is shown in Figure 8, depicting temperature dependence of in-phase and out-of-phase susceptibility of amorphous Fe 2 O 3 , prepared by thermal decomposition of Prussian Blue [Zbořil et al, 2004]. It is obvious that the two-tangent method cannot be applied here at all, because the curve does not show suitable linear sections on its descending section, which is hyperbolic after the maximum at 50 K. The minor hysteresis loop reduces to a straight line at 55 K, as evident from the decay of out-of-phase susceptibility to zero.…”

Carbon Electrodes Modified by Nanoscopic Iron(III) Oxides to Assemble Chemical Sensors for the Hydrogen Peroxide Amperometric Detection

“…Amorphous iron(III)-oxide nanopowder (2 -4 nm) was synthesized according to the procedure described in [25]. Prussian blue nanoparticles (15 -30 nm) were obtained by controlled solid-state oxidative decomposition of ammonium ferrocyanide at 160 8C [26]. Poorly crystalline ferrihydrite (2 -3 nm) was prepared by fast hydrolysis of Fe(NO 3 ) 3 solution followed by immediate filtration and vacuum evaporation of the solvent at room temperature [27].…”