The composites xTiO2-(1−x)SiO2 (x = 0.1, 0.5, 0.9) were obtained by coprecipitation from solutions of alkoxides: tetraethoxysilane (TEOS) and titanium tetraisopropoxide
(TIPT). Intermolecular interaction of the components of the composite is apparent in the IR absorption spectra in the 928–952
cm−1 region, and is connected with bending vibrations of the Si-O-Ti bond.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 724–728, September–October, 2008. 相似文献
The main drawbacks of anatase titanium dioxide (TiO2) nanoparticles for being used as a photocatalyst are due to the rapid charge recombination of the electron-hole pairs and the wide band gap energy, limiting its photocatalysis application. To enhance photocatalytic activity, structure modification was performed here. Heterogeneous nanostructure of Dy-doped TiO2 nanoparticles hybrid with Monoclinic TiO2 nanobelts (Dy/TNBs) was fabricated via hydrothermal method. Annealing temperature was varied to investigate its effect on phase composition and morphology of the as-prepared TiO2 catalyst. Phase composition and morphology were studied by XRD and SEM, respectively. The effect of amount of catalyst loaded on the degradation efficiency of methylene blue (MB) dye in aqueous solution under UV and fluorescence illumination was investigated. The results showed that pure monoclinic TiO2 nanobelts (TNBs) was achieved at 450 °C. Enhanced photocatalytic activity under both UV and fluorescence irradiation was found on Dy/TNB samples. The optimum Dy dosage providing the highest MB degradation rates under both irradiation sources was 0.1 mol%. 相似文献
The α‐PbO2‐type TiO2 is synthesized under high‐pressure and high‐temperature environment and it shows higher photocatalytic activity as compared to rutile and anatase under UV irradiation. The reduction in α‐PbO2‐type TiO2 induces visible‐light photocatalytic activity. These results indicate that α‐PbO2‐type TiO2 is an important candidate material for use in a photocatalytic matrix.
The photocatalytic activity of thin, nanostructured films of titanium dioxide, synthesized by supersonic cluster beam deposition
(SCBD) from the gas phase, has been investigated employing the photodegradation of salicylic acid as test reaction. Because
of the low deposition energy, the so-deposited highly porous TiO2 films are composed of nanoparticles maintaining their original properties in the film, which can be fully controlled by tuning
the deposition and post-deposition treatment conditions. A systematic investigation on the evolution of light absorption properties
and photoactivity of the films in relation to their morphology, determined by AFM analysis, and phase composition, determined
by Raman spectroscopy, has been performed. The absorption and photocatalytic activity of the nanostructured films in the visible
region could be enhanced either through post-deposition annealing treatment in ammonia containing atmosphere or employing
mild oxidation conditions, followed by annealing in N2 at 600 °C. 相似文献
AbstractPoly(butylene adipate-co-terephthalate) (PBAT) nanocomposite films with various contents of nano-titanium dioxide (TiO2) and titanium dioxide doped silver (Ag-TiO2) were prepared by a solvent casting method. The TiO2 and Ag-TiO2 nanoparticles were surface-modified with silane coupling agents to improve their compatibility and dispersibility in the PBAT matrix. They were denoted as mTiO2 and mAg-TiO2, and were characrterized by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The morphology of the PBAT nanocomposite films was studied by field emission scanning electron microscopy (FE-SEM). The crystallinity of the PBAT film increased upon the introduction of the nano-TiO2/Ag-TiO2. Its mechanical properties and gas barrier properties were also significantly improved. In addition, the PBAT/mTiO2 and PBAT/mAg-TiO2 nanocomposite films showed a strong antibacterial activity against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) food-borne pathogenic bacteria. 相似文献
Three-dimensional networks of Fe(III)-doped TiO2 nanoparticles (2–4 nm) prepared from organic precursors are detected by Cryo-TEM (transmission electron microscopy) in an aqueous environment. High-resolution TEM studies show that the nanoparticles prefer to align along their crystallographic orientation. A novel energy transfer mechanism is suggested in which these three-dimensional networks act as antenna systems thus leading to an enhanced photocatalytic activity of the colloidal preparations. 相似文献
The photocatalytic (PC) performance of titanium dioxide (TiO2) nanoparticles strongly depends on their specific surface, the presence of crystal defects, their crystal phase, and the exposed crystal facets. In order to understand which of these factors contributes most significantly to the PC activity of TiO2 colloids, all of them have to be individually analyzed. This study entails the synthesis of five anatase nanocrystal samples. By maintaining the same reactant ratios as well as hydrothermal sol–gel synthesis route and only varying the autoclaving time or temperature, different crystallite sizes are obtained under comparable experimental conditions. A decrease in PC performance with increase in specific surface area is found. Such an unexpected counterintuitive result establishes the basis for a better understanding of the crucial factors that ultimately determine the PC activity. These are investigated by studying nanocrystals bulk and surface structure and morphology using a selection of complementary analysis methods (X‐ray photoelectron spectroscopy (XPS), X‐ray absorption fine structure (XAFS), X‐ray diffraction (XRD)…). It is found that a change in the nanocrystal morphology from an equilibrium state truncated tetragonal bipyramid to a more elongated rod‐like structure accompanied by an increase in oxygen vacancies is responsible for an augmented PC activity of the TiO2 nanocrystals. 相似文献
TiO2-coated magnetite clusters (nFe3O4@TiO2) were facilely prepared through the sol–gel reaction between Ti alkoxides (TEOT) and magnetite clusters (nFe3O4) with terminated alkoxy groups. The composite particles represented a core–shell nanostructure (nFe3O4@TiO2) consisting of a Fe3O4 cluster core and a TiO2 capsule layer. The capsule layer of nFe3O4@TiO2 was increased with increasing amounts of TEOT (150, 300, 500 μl) in sol–gel reaction. The Fe3O4@TiO2 (150 μl of TEOT) with a thin TiO2 layer (ca. 10 nm) exhibited two kinds of cathodic (0.79 V and 1.61 V) and anodic (1.78 and 2.1 V) peaks attributed to the reduction and oxidation process by Fe3O4 core and TiO2 layer, respectively. The thin nFe3O4@TiO2 (150 μl of TEOT) exhibited the enhanced capacity retention by ca. 40% probably due to the buffering effect of TiO2 capsule layer. However, the thick nFe3O4@TiO2 (300–500 μl of TEOT) exhibited a rapid capacity fading due to the disintegrated core–shell nanostructure, i.e., unfavorable hetero-junction between TiO2 matrix and magnetite clusters. 相似文献
X-ray photoelectron spectroscopy (XPS) was adopted for the analytical characterization of composite titanium dioxide–poly(vinylidenefluoride) (TiO2–PVDF) films developed for applications in the photocatalytic degradation of pollutants.
The composites were deposited on glass substrates by casting or spin coating from TiO2–PVDF suspensions in dimethylformamide (DMF). XPS data on the TiO2–PVDF surface composition were used to optimize preparation conditions (composition of the TiO2/PVDF suspension, deposition technique) in terms of titanium dioxide surface amount and film stability.
The use of spin-coating deposition and the increase of TiO2 amount in the DMF suspensions were found to improve the titanium surface content, although high TiO2/PVDF ratios led to film instability. PVDF–TiO2 films were also used in preliminary photocatalytic degradation tests on isoproturon, a phenylurea herbicide, under solar UV irradiation; the results were compared to direct photolysis to evaluate the catalytic efficiency of immobilized TiO2 and the role played by the PVDF film during the degradation process. 相似文献
The influence of Al(III)/Sb(III)-doping on the properties of tris(thiourea)zinc(II) sulphate (ZTS) crystals grown by slow evaporation solution growth technique is reported. The as-grown crystals belong to orthorhombic system and cell parameters are, a = 7.77 Å, b = 11.13 Å, c = 15.47 Å, V = 1338 Å3 (Al(III)-doped) and a = 11.1996 Å, b = 7.770 Å, c = 15.5598 Å, V = 1368.3 Å3 (Sb(III)-doped). The structure and the crystallinity of the materials are further confirmed by powder X-ray diffraction analysis. The modes of vibrations of different functional groups present are identified by Fourier transform infrared studies. Thermogravimetric/differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. Surface morphological changes due to doping are observed by scanning electron microscopy. Microhardness study was carried out to elucidate the mechanistic behavior microhardness studies were carried out to elucidate the mechanistic behavior. Second harmonic generation activity is much better in the case of Sb(III)-doping. The specimen is also characterized by dielectric studies. 相似文献
The state of Pd in Pd/TiO2 and Pd/TiO2(Nb2O) systems is investigated by means of electron diffuse reflection spectroscopy, x-ray electron spectroscopy, and IR spectroscopy
of adsorbed CO as a function of thermal and reduction treatments. Modification of titanium dioxide TiO2 leads to intensification of metal-support interaction, which manifests itself as an increase in the content of surface complexes
of Pd strongly bound to TiO2. As a result of electron density transfer from TiO2 with electron-excess Ti3+ ions to the metal deposited, the latter acquires an enhanced reduction ability.
Institute of Physical and Organic Chemistry, National Academy of Sciences of Belarus, 13, Surganov St., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 84–88 January–February, 1999. 相似文献
The electrical conductivity and photoconductivity of films of composites based on electrically neutral poly(vinyl butyral) with additions of Cu(II)/Cr(III) heteropolynuclear complexes introduced in the form of solutions or mechanically ground polycrystalline powders are studied. Photocurrents in samples prepared in different ways differ no more than tenfold. The photoconductivity of the composite films increases with decreasing distance between the metal centers in the complexes. A phenomenological model of carrier photogeneration and transport in films of polymer composites with embedded particles of heteropolynuclear complexes prepared from a solution or by grinding is proposed. The slight difference in photocurrents between samples containing the same complexes but prepared by different methods can be accounted for by the close geometric sizes of particles of the complexes. 相似文献
Multi-walled carbon nanotube (MWCNT)-supported tungsten trioxide (WO3) composite catalysts were prepared by liquid-phase process. WO3 nanoparticles grew on the inner and outer surface of MWCNTs. Their photocatalytic activities in the degradation of the Rhodamine B Dye were studied. The effects of mass ratio of MWCNTs to WO3 were discussed. X-ray diffraction, field emission transmission electron microscopy, thermogravimetric-differential thermal analysis and ultraviolet-visible light absorption spectra were carried out to characterize the composite catalysts. The results indicated that the optimum mass ratio of MWCNTs to WO3 is 5:100. 相似文献