Pure TiO2
and S-doped TiO2 sol–gel nanopowders were prepared
by controlled hydrolysis-condensation of titanium alkoxides. The influence
of different Ti-alkoxides (tetraethyl-, tetraisopropyl- and tetrabutyl-orthotitanate)
used in obtaining TiO2 porous materials in similar
conditions (water/alkoxide ratio, solvent/alkoxide ratio, pH and temperature
of reaction) has been investigated. The relationship between the synthesis
conditions and the properties of titania nanosized powders, such as thermal
stability, phase composition, crystallinity, morphology and size of particles,
BET surface area and the influence of dopant was investigated. The nature
of the alkyl group strongly influences the main characteristics of the obtained
oxide powders, fact which is pointed out by thermal analysis, X-ray diffraction,
TEM and BET surface area measurements. 相似文献
Among the great number of sol–gel prepared nanomaterials, TiO2 has attracted significant interest due to its high photocatalytic activity, excellent functionality, thermal stability and
non-toxicity. The photocatalytic degradation of pollutants using un-doped and doped TiO2 nanopowders or thin films is very attractive for applications in environmental protection, as a possible solution for water
purification. The present work describes a comparative structural and chemical study of un-doped TiO2 and the corresponding S- and Ag-doped materials. The photocatalytic activity was established by testing the degradation of
organic chloride compounds from aqueous solutions. Sol–gel Ag-doped TiO2 coatings, prepared by co-gelation and sol–gel Ag-doped TiO2 coatings obtained from nanopowders were also compared. Their structural evolution and crystallization behaviour (lattice
parameters, crystallite sizes, internal strains) with thermal treatment were followed by thermal analysis, X-ray diffraction,
transmission electron microscopy, atomic force microscopy and specific surface areas measurements. X-ray photoelectron spectroscopy
analyses were performed to characterize the surface composition and S or Ag speciation, which was used to interpret the catalytic
data. 相似文献
S-doped TiO2 (S-TiO2) photocatalyst was synthesized by sol–gel method with tetrabutyl titanate and thiourea as precursor. S-TiO2 was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis absorption spectroscopy, transmission electron microscopy (TEM) and the photocatalytic activity was evaluated by 1-naphthol-5-sulfonic acid (L-acid) under UV, visible light and solar light radiation. The results showed that doped S could improve photoabsorption property of TiO2 in the visible region, leading the increase in the photocatalytical activity of TiO2.
The average particle size of the S-TiO2 photocatalyst is about 10 nm. The S-TiO2-4 photocatalyst contains 100% anatase crystalline phase of TiO2. In the S-TiO2-4 photocatalyst, S does not exist independently, but is incorporated into the crystal lattice of TiO2. In the inner crystal lattice of the S-TiO2-4 photocatalyst, S as S2− replaces O in TiO2, while on the surface of crystal lattice, S exists as S4+ and S6+.
The photocatalytical activity of S-TiO2-4 photocatalyst for the photodegradation of L-acid is better than that of pure TiO2. Under the same conditions, the photodegradation efficiency of L-acid for the S-TiO2-4 photocatalyst and the solar light irradiation is 85.1%, while it is only 26.4% for pure TiO2. In addition, the final products of the photocatalysis of L-acid using the S-TiO2-4 photocatalyst are not organic compounds with low molecular weight, but the inorganic compounds. 相似文献
In this study, the optical properties of S- and Sn-doped ZnO nanobelts, grown by thermal evaporation, were investigated. The sulfur and tin contents in the nanobelts were about 12% and 8% (atomic), respectively. The average widths of the S- and Sn-doped ZnO nanobelts were 73 and 121 nm, respectively. Room temperature photoluminescence (PL) spectroscopy exhibits significantly different optical properties for the two types of nanobelts. The PL result of the S-doped ZnO nanobelts shows the broad visible emission with no detectable ultraviolet (UV) peak, while the PL result of the Sn-doped sample shows two emission bands, one related to UV emission with a strong peak at 376 nm that is blue-shifted by 4 nm in comparison to pure ZnO nanobelts, and another related to green emission with a weak peak. A weak peak in the UV region at 383 nm appeared after annealing the S-doped ZnO nanobelts at 600 °C. Additionally, the annealed S-doped nanobelts show a stronger peak in the visible emission region in comparison to that observed prior to annealing. The Sn-doped ZnO nanobelts are also affected by annealing, as the UV emission peak is blue-shifted to 372 nm after annealing. 相似文献