10 to 0.31 using the multipoint Brunauer-Emmett-Teller (BET) method, and the pore size distribution was evaluated LGX818 from the N2 desorption isotherm using the Barrett-Joyner-Halenda method. The optical properties were examined using a UV–vis spectrophotometer (Cary 300, Varian, Palo Alto, CA, USA), with absolute alcohol as the dispersive medium. Results and discussion Hematite structures obtained at different molar ratios of the reactants Figure 1 shows the influences of the molar ratio of FeCl3/H3BO3/NaOH on the compositions and morphologies of the hydrothermal products obtained at 150°C for 12.0 h. When changing the molar ratio of FeCl3/H3BO3/NaOH within the range of 2:(0–3):(2–6), all products

were composed of pure-phase hematite (α-Fe2O3, JCPDS No. 33–0664), with a detectable slight difference of the crystallinity (Figure 1a). With the molar ratio of FeCl3/H3BO3/NaOH changed from 2:0:6 to 2:0:4 and to 2:0:2, the crystallinity of hematite decreased slightly (Figure 1a 1,a2,a3). In contrast, the morphologies of the obtained products varied significantly with the change of the molar ratio of reactants. Quasi-spherical hematite NPs with a diameter of 30 to 150 nm were obtained

when the molar ratio of FeCl3/H3BO3/NaOH was 2:0:6 (Figure 1b,b1), similar to the so-called α-Fe2O3 nanopolyhedra synthesized in the ammonia-water system at 180°C for 8.0 h [23]. With the molar ratio decreased to 2:0:4 and 2:0:2, hierarchical pod-like (with elliptical ends and relatively uniform cAMP diameter along the long axial direction, Figure 1c) and peanut-type nanoarchitectures Selonsertib (with relatively sharp elliptical ends and saddle-shaped middle part, Figure 1d,d1) were acquired, respectively. The pod-like architectures contained

1D or linear chain-like assemblies of smaller nanoparticles or rod-like subcrystals within the body (as shown in red dotted elliptical and rectangular regions in Figure 1c), with distinct cavities on the surfaces (Figure 1c). The peanut-type nanoarchitectures (Figure 1d,d1) also comprised small nanoparticles within the body whereas with not so distinct cavities on the surfaces owing to the relatively compact assembly. Similar 1D assemblies, such as rod-like subcrystals and linear chains of interconnected primary particles, have also been found to exist as the subunits of peanut-type [45] and double-cupola [46] hematite, respectively. Obviously, the molar ratio of 2:0:6 (FeCl3/H3BO3/NaOH) led to nearly monodisperse hematite NPs, whereas the molar ratio of 2:0:4 and 2:0:2 resulted in porous hierarchical architectures with different morphologies. According to Sugimoto’s research [45, 47, 48], size control is generally performed by controlling the number of nuclei during the nucleation stage, and nucleation occurs during the addition of NaOH solution into FeCl3 solution.