Monodisperse Fe3O4 nanocubes have been successfully synthesized by a facile solvothermal method at 260 °C in the presence of oleic acid and oleylamine. Well-defined assembly of uniform Fe3O4 nanocubes with an average size of 12 nm could be obtained without a size-selection process. The shape of as-prepared Fe3O4 nanoparticles could be reversibly interchanged between spheres and cubes by adjusting the reaction parameters. The phase structures, morphologies, and sizes of as-prepared products were investigated in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The magnetic properties of Fe3O4 nanocubes were measured by using a quantum design superconducting quantum interference device (SQUID). The magnetic study reveals that the as-synthesized nanocubes are ferromagnetic at 2 K while they are superparamagnetic at 300 K.
A novel, facile, green and template-free approach was developed for the fabrication of amorphous zinc citrate yolk-shell microspheres and crystalline ZnO yolk-shell nanospheres. In this approach, the amorphous zinc citrate yolk-shell microspheres were prepared through a single chemical reaction at low temperature (90 C) and with room temperature ageing. The zinc citrate yolk-shell microspheres have an average size of about 1.25 mm. The average diameter of the inner cores and the average thickness of the outer shells are 500 nm and 150 nm, respectively. The effect of ageing time on the morphology of the zinc citrate microstructures was analysed. As the ageing time increases from 0 to 12 h, the zinc citrate microstructure transforms from a solid microsphere through a yolk-shell microsphere to a hollow microsphere. The ZnO solid nanospheres, yolk-shell nanospheres and hollow nanospheres can be prepared via the perfect morphology inheritance of the zinc citrate solid microspheres, yolk-shell microspheres and hollow microspheres, by calcination at 600 C for 2 h. The ZnO yolk-shell nanospheres show the largest visible emission and the highest photocatalytic activity.
We demonstrate herein that single-crystalline beta-cobalt hydroxide (beta-Co(OH)(2)) nanosheets can be successfully synthesized in large quantities by a facile hydrothermal synthetic method with aqueous cobalt nitrate as the cobalt source and triethylamine as both an alkaline and a complexing reagent. This synthetic method has good prospects for the future large-scale production of single-crystalline beta-Co(OH)(2) nanosheets owing to its high yield, low cost, and simple reaction apparatus. Single-crystalline porous nanosheets and nanorings of cobalt oxide (Co(3)O(4)) were obtained by a thermal-decomposition method with single-crystalline beta-Co(OH)(2) nanosheets as the precursor. A probable mechanism of formation of beta-Co(OH)(2) nanosheets, porous Co(3)O(4) nanosheets, and Co(3)O(4) nanorings was proposed on the basis of the experimental results.
Uniform CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via the sol–gel method. The samples were characterized using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The surface state analysis by means of X‐ray photoelectron spectroscopy (XPS) shows that the Ti element mainly exists as a chemical state of Ti4+, while the Ce element exists as a mixture of Ce3+ and Ce4+ oxidation states. The photocatalytic degradation of methyl orange (MeO) in CeO2/TiO2 suspension was investigated. The results indicate that the CeO2/TiO2 nanocomposites show higher photocatalytic activity than pure TiO2. Photodegradation of MeO can be improved by increasing the Ce/Ti molar ratio in the initial 15 min.
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