A facile template-free and one-pot thermal decomposition approach was used for the mass preparation of submicrometer-sized NiO octahedra. Ni octahedra with tailored crystallization and texture characteristics are easily achieved through H₂-annealing of NiO octahedra at various temperatures. The good morphology retention of Ni octahedra is due to the principle of minimum surface free energy as well as the similar crystallographic system to that of NiO. Studies on static magnetic and microwave electromagnetic properties reveal the relationships among the reactivity, shape, and resultant properties of the nanomaterials. Because of their high BET specific surface area and favorable crystal size, porous Ni octahedra produced at 300 °C exhibit excellent matching and absorbing properties with a minimum R_L value of −37.93 dB at 12.80 GHz and 11.60 GHz bandwidth (below −20 dB). Thus the Ni octahedra described here are believed to have a wide range of applications, including catalysis, electromagnetic shielding, and absorption.

Complex ZnO architectures with tunable morphologies and structures were obtained by modulating only the base type and molar ratio of base to Zn²⁺ (α) using an easy one-pot hydrothermal approach without any template or organic additive. Characterizations by X-ray diffraction, Fourier-transform infrared spectrometry, scanning electron microscopy, transmission electron microscopy, and surface area analysis were performed. The effect of the base type and base/Zn²⁺ molar ratio on the morphology and corresponding mechanism were determined. The correlations between the microstructure and properties were established. The antibacterial effect of the ZnO samples was probably due to a combination of variable factors. Better antibacterial activity is derived from more effective antibacterial surfaces, which are mainly associated with the specific surface area and Zn-polar plane. Thus, flower-like architectures with larger specific surface areas and more highly exposed (0001) Zn-polar surfaces outwards are promising structures for ZnO antibacterial agents. This work provides a guide for devising and synthesizing highly efficient antibacterial materials.

The morphological modulation and phase conversion of α- and β-Ni(OH)₂ complex architectures with varying subunits from nanopetals, nanocolumns, nanocones, and nanoflakes were investigated using a facile coordination homogeneous precipitation method in the Ni(NO₃)₂+ urea system. Slow growth and nucleation rates due to relatively low reaction temperatures and molar ratios of CO(NH₂)₂ to Ni(NO₃)₂ induced the formation of uniform flower-like α-Ni(OH)₂ architectures. Such flower-like architectures originated from subordinate nanopetals that grow perpendicular to the primordial nanopetal surface and are driven by minimum surface free energy effects. At relatively high reaction temperatures, flower-like α-Ni(OH)₂ can transform into β-Ni(OH)₂ microspheres assembled from nanocolumns, nanocones, and even nanoflakes by varying the reaction time. These processes could be related to the synergetic effect of the anisotropic growth and continuous increase in mass transportation along the [001] direction. Flower-like α-Ni(OH)₂ exhibited better electrochemical activity for glucose oxidation compared with β-Ni(OH)₂ microspheres consisting of nanocones because of its special flower-like morphology with high specific surface areas, well-ordered pores, and layered structures intercalated by water and anions. The approach in this study can be used to fabricate other metal hydroxide nanostructures. Flower-like Ni(OH)₂ nanoarchitectures have potential applications in rechargeable batteries, photonic catalysis, and non-enzymatic sensors for glucose.