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Abstract: Pure α-MnO2 nanofibers with multiple branches were prepared through a simple refluxing method in the absence of catalysts or surfactants as templates. The synthetic procedure was based on the use of to oxidize under a weak acidic condition. A two-step epitaxial coalescence for the formation of this complex architecture was revealed by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). First of all, the small nanofibers coalesced together through the (110) plane to form larger monocrystalline nanofibers, which then attached one by one through two of (110) and {211} planes, resulting in the final multiple branched architectures. [Copyright &y& Elsevier]

Abstract: The synthesis and shape evolution of α-Fe2O3 nanoparticles through oriented aggregation in solvothermal system were investigated. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) revealed that the three-dimensional (3D) flower-like α-Fe2O3 nanophase was formed by two-step crystallographically oriented aggregations, and then evolved to polyhedral nanoparticles by conventional Ostwald ripening. The organic solvent N, N-dimethylformamide (DMF) played an important role not only in chemical reaction, but also in oriented aggregation-based self-assembly. [Copyright &y& Elsevier]