TiO 2 hollow microspheres were successfully synthesized via a controlled hydrolysis reaction, which involved the deposition of an inorganic coating of TiO 2 on the surface of carbon spheres and subsequent removal of carbon spheres by calcination in air. The as-prepared TiO 2 hollow microspheres with an average diameter of 200 nm presented a novel morphology, which was constructed by closely crosslinked TiO 2 nanochains. The morphology of the hollow sphere can be controlled by varying the concentration of TiCl 3 solution. A possible formation mechanism was also proposed. The photo-degradation of rhodamine B (RhB) aqueous solution showed that TiO 2 hollow microspheres exhibited higher photocatalytic activity than that of TiO 2 nanoparticles. The enhanced photocatalytic activity of the as-prepared TiO 2 microspheres here could result from their hollow structures assembled by TiO 2 nanochains and large light-harvesting efficiency.
The ZnO microspheres constructed by porous nanosheets were successfully synthesized by calcinating zinc hydroxide carbonate (ZHC) microspheres obtained by a sample hydrothermal method. The samples were characterized in detail with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric and differential scanning calorimetry (TG-DSC). The results indicated that the prepared ZnO microspheres were well crystalline with wurtzite hexagonal phase. The effects of reaction time, temperature, the amount of trisodium citrate, and urea on the morphology of ZnO microspheres were studied. The formation mechanism of porous ZnO microspheres was discussed. Furthermore, the gas-sensing properties for detection of organic gas of the prepared porous ZnO microspheres were investigated. The results indicated that the prepared porous ZnO microspheres exhibited high gas-sensing properties for detection of ethanol gas.
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