Novel carbon doped TiO(2) nanotubes, nanowires and nanorods were fabricated by utilizing the nanoconfinement of hollow titanate nanotubes (TNTs). The fabrication process included adsorption of ethanol molecules in the inner space of TNTs and thermal treatment of the complex in inert N(2) atmosphere. The structural morphology of carbon doped TiO(2) nanostructures can be tuned using the calcination temperature. X-ray diffraction, Raman and Brunauer-Emmett-Teller studies proved that the doped carbon promoted the crystallization and phase transition by acting as nucleation seeds. X-ray photoelectron spectroscopy (XPS) showed that O-Ti-C and Ti-O-C bonds were formed in the nanostructures. Additional electronic states from the XPS valence band due to carbon doping were observed. This evidence indicated the electronic origin of the band gap narrowing and visible light absorption. The differences in chemical and electronic states between the surface and bulk of as-prepared samples confirmed that carbon was doped into the lattice of TiO(2) nanostructure through an inner doping process. The as-prepared catalysts exhibited enhanced photocatalytic activity for degradation of toluene in gas phase under both visible and simulated solar light irradiation compared with that of commercial Degussa P25. This novel fabrication approach can valuably contribute to designing nanostructured photocatalytic materials and modifying various nanotube materials.
Alpha calcium sulfate hemihydrate (α-HH) is an important class of cementitious material and exhibits considerable morphology-dependent properties. In the reverse microemulsions of water/n-hexanol/cetyltrimethylammonium bromide (CTAB)/sodium dodecyl sulfonate (SDS), the morphology and aspect ratio of α-HH are successfully controlled by adjusting the mass ratio of CTAB/H(2)O and the concentration of SDS. As the ratio of CTAB/H(2)O is increased from 1.3 to 4.5, the crystal length decreases from 120 to 150 μm to 0.5-1.2 μm with the corresponding aspect ratio reduced sharply from 180 to 250 to 2-7. With increasing SDS concentration, the crystal morphology gradually changes from submicrometer-sized long column to rod, hexagonal plate, and even nanogranule. The preferential adsorption of CTAB on the side facets and SDS on the top facets contributes to the morphology control. This work presents a simple, versatile, highly efficient approach to controlling the morphology of α-HH on a large scale and will offer more opportunities for α-HH multiple applications.
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