e., dissolution-reprecipitation mechanism (Figure 5d) [58]. The constitutional α-Fe2O3 subcrystals grew into larger NPs, with 1D assembly behavior disappeared largely. Figure 5 Formation mechanism

of the hierarchical mesoporous pod-like hematite nanoarchitectures. https://www.selleckchem.com/products/poziotinib-hm781-36b.html It is notable, however, that the boric acid played a significant role in the formation of the present mesoporous pod-like α-Fe2O3 nanoarchitectures with uniform morphology and size, confirmed by the above experimental results (Figures 1 and 2). Also, as confirmed to improve the uniformity, the amount of boric acid or molar ratio of FeCl3/H3BO3/NaOH should be tuned within a certain composition range. As known, as a weak acid, H3BO3 could form sodium borate (i.e., borax) after the introduction of NaOH, giving rise to the buffer solution. This could tune the release of hydroxyl ions and further control the mild formation of amorphous Fe(OH)3 gel, leading to subsequent β-FeOOH fibrils with relatively uniform size.

This was believed to contribute to the further formation of the peanut-like β-FeOOH/α-Fe2O3 assemblies and ultimate occurrence of the pod-like α-Fe2O3 nanoarchitectures. Optical absorbance analysis Hematite NPs have been widely https://www.selleckchem.com/products/ldk378.html used as ultraviolet absorbents for their broad absorption in the ultraviolet region from the electron transmission of Fe-O. Figure 6 shows the

optical absorbance spectra of the α-Fe2O3 particles with the photon wavelength in the range of 350 to 650 nm. For sample a1, it revealed two absorption edges around 380 to 450 and 540 to 560 nm, which were consistent with the reported hematite NPs [59–61]. When the α-Fe2O3 clustered into samples b1 and c1, the size of α-Fe2O3 agglomerates was around 500 to 800 nm. The absorbance spectra showed two absorption peaks around 520 to 570 and 600 to 640 nm. The change Fossariinae in the degree of transition depended on the shape and size of the particles. When the hematite particles aggregated to pod-like nanoarchitectures, the size became larger, and then the scattering of visible light was superimposed on the absorption of as-prepared architectures. Figure 6 Optical absorbance spectra (a 1 -c 1 ) of the α-Fe 2 O 3 with different morphologies (a 2 -c 2 ). Time (h) = 12.0; Temperature (°C) = 120 (a1, a2, b1, b2), 150 (c1, c2); FeCl3/H3BO3/NaOH = 2:3:6 (a1, a2), 2:3:4 (b1, b2, c1, c2). It was well illustrated that three types of electronic transitions occurred in the optical absorption spectra of Fe3+ substances: (a) the Fe3+ ligand field transition or the d d transitions, (b) the ligand to metal charge-transfer transitions, and (c) the pair excitations resulting from the simultaneous excitations of two neighboring Fe3+ cations that are magnetically coupled.