| Nanomaterials with a hierarchical structure have attracted intensive research attention. Their complicated structures are usually concomitant with diverse characteristics, thus having various applications. Recently, nanomaterials with various hierarchical morphologies have been synthesized and successfully used in catalysis and environmental improvement, and as sensors in biological systems.In this paper, a dual iron precursors system in a hydrothermal process was developed for controllable fabrication ofα-Fe2O3 hierarchical structures with different morphologies. Micro-pines, snowflakes and bundles were successfully synthesized simply by tuning the total concentration of the two iron precursors K4[Fe(CN)6] and K3[Fe(CN)6] and their molar ratio. The obtainedα-Fe2O3 hierarchical structures were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and Selected Area Electron Diffraction. The effect of experimental conditions on the morphologies of theα-Fe2O3 crystals was systematically investigated. A possible formation mechanism of differentα-Fe2O3 hierarchical structures was proposed. Good photocatalytic properties were observed for all the hierarchical structures.On the other hand, Prussian blue (PB) and its analogs have attracted intensive research attention due to their unique properties of molecular magnets, electrochemistry, optics, hydrogen storage and biosensors. Prussian blue, the first synthetic coordination compound, is a mixed-valence iron-(III) hexacyanoferrate(II) compound of composition Fe4[Fe(CN)6]3·XH2O with a face-centered-cubic structure, in which Fe3+ in the N-coordinated sites is in the high-spin state and Fe2+ in the C-coordinated sites is in the low-spin state. According to previous reports, two redox processes can take place as to Prussian Blue: chemical reduction of PB produces Prussian white (Fe2II [FeII(CN)6], PW); chemical oxidation of PB yields Prussian yellow (FeIII[FeIII(CN)6], PY). However, to fabricate Prussian blue analog Prussian yellow nanoparticles with different shapes remains a challenge. Here, we have successfully prepared Prussian yellow Fe[Fe(CN)6] colloidal nanospheres (hollow nanospheres and solid nanospheres) by a simple hydrothermal method with the assistance of different phosphate. The obtained Prussian yellow Fe[Fe(CN)6] colloidal nanospheres were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy. A possible formation mechanism of different Prussian yellow Fe[Fe(CN)6] nanostructures was proposed.
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