ABSTRACT
Pure and Ni-doped ZnO nanostructures have been synthesized by a solvothermal process. The structure, morphology and properties of as-synthesized samples have been investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), selected-area electron diffraction (SAED), UV-vis spectrometer as well as by vibrating sample magnetometer (VSM). XRD and EDS studies indicated that the as-prepared products were well-crystallized wurtzite hexagonal structure. The SEM and TEM images show that the individual Zn0.96Ni0.04O nanostructure is composed of several nanorods with average diameter of 200 nm and lengths of 500 nm. The structure and morphology analyses show that Ni doping can influence the nanostructures morphology, but cannot change the crystal structures of ZnO samples. The UV-vis spectra showed that Ni dopant can result in an appreciable blue-shift for the absorption edge of the Ni-doped ZnO samples. The band gap energy of the Zn0.96Ni0.04O nanostructure was about 3.23 eV. By magnetic measurements, it was observed that the pure ZnO nanostructure exhibits diamagnetic property while the sample of 4% Ni shows an obvious ferromagnetic behavior at room temperature due to the formation of solid solution Zn0.96Ni0.04O, sp-d and d-d carrier exchange interactions, and the presence of abundant defects and oxygen vacancies.
ABSTRACT
Porous fluorine-doped maghemite(γ-Fe2O3) hollow spheres have been prepared by facile route based on solvothermal reaction and sequential calcinations. The composition and morphology of the as-prepared samples were characterized by various techniques. The SEM and TEM results showed that the as-synthesized products exhibited a spherical morphology with porous hollow structures. Ultraviolet-visible (UV-vis) diffuse reflectance spectra display that the optical performance of γ-Fe2O3 products are related to their structure and the fluorine concentrations. The porous hollow structured fluorine-doped γ-Fe2O3 spheres exhibit ferromagnetic properties with relatively high saturation magnetization at room temperature. According to the experimental results, a formation mechanism of the fluorine-doped γ-Fe2O3 hollow spheres has been presented. Under UV light irradiation, the photocatalytic degradation activities of the as-synthesized fluorine-doped γ-Fe2O3 samples for RhB dye were 2-5 times higher than that of the undoped sample. The prepared fluorine-doped γ-Fe2O3 hollow spheres will also aroused great interest for their application in catalysis, separation technology, sensors, nanotechnology, and biomedical fields.
ABSTRACT
In this work, a facile route using a simple solvothermal reaction to synthesize 3D porous flowerlike hierarchical nanostructures (HNs) of α-Fe(2)O(3) without employing templates or matrices for self-assembly is presented. The morphology and compositional characteristics of the 3D HNs were investigated by various techniques. The 3D HNs composed of 2D nanopetals, were intercrossed with each other and constructed from nanobricks with a length of about 100 nm and a diameter of about 30 nm. Influencing factors such as the reaction time, dosage of reactants and the solvents are systematically investigated. A possible formation mechanism for the 3D HNs is proposed. On the basis of characterization results, the growth of such 3D HNs has been proposed as a self-assembly followed by Ostwald ripening process. The specific surface area of the 3D HNs also was investigated by using nitrogen adsorption and desorption isotherms. The as-prepared α-Fe(2)O(3) HNs have a comparatively large Brunauer-Emmett-Teller (BET) surface area of about 52.51 m(2) g(-1). The photocatalytic properties of the as-obtained α-Fe(2)O(3) 3D HNs are systematically investigated, which was evaluated by the degradation of RhB dye under ultraviolet light irradiation. The result shows that photocatalytic activity is greatly affected by the hierarchical and porous structure.
