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TiO2 Structures (tio2 + structure)

Distribution by Scientific Domains
Polymers and Materials Science66%

Selected Abstracts

Effect of the substrate temperature on the properties of the RF sputtered TiO2 thin films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2010
I. Ben Mbarek
Abstract Titanium dioxide (TiO2) thin films were deposited by RF magnetron sputtering on glass and silicon substrates at different substrate temperatures (20, 100, 200 and 300 °C). The structural and morphological characteristics of the films were investigated by X ray Diffractometry (XRD) and Atomic Force Microscopy (AFM) while the optical properties of the films were studied by optical spectroscopy. It was shown that at room temperature, TiO2 films grown on glass were amorphous following the substrate structure. At higher temperatures, XRD detected only a nanocrystalline rutile TiO2 structure. This indicated that the transition temperature toward the most stable TiO2 phase was obtained from 100 °C and the crystallinity was enhanced at higher growth temperature. For TiO2 films grown on Si substrates, only a nanocrystalline anatase TiO2 structure was obtained at room temperature. At higher temperatures, we noticed the appearance of other secondary phases related to rutile, anatase and brookite structures. From AFM images, we noticed that at room temperature, the films were porous. With increasing the temperature, the structure of the films became crystallized showing a columnar structure. Film growth and structural properties were discussed in terms of the Thornton model. From optical analysis, the films were transparent with an indirect band gap and a refraction index which reached 3.09 eV and 2.7, respectively. The reflectance and transmittance spectra showed, not only that there was a little translation from UVB to UVA and near-visible range, but also a decrease of reflection with a temperature increase indicating that the films could be used as anti-reflection coatings. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Preparation and Characterization of Bi3+ -TiO2 and its Photocatalytic Activity

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 5 2007
H. Zuo
Abstract Bi3+ -TiO2 photocatalysts were prepared by doping bismuth ion into the TiO2 structure in a sol-gel process. The catalyst samples were then characterized by UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Rodamine-B (RhB) was used in this study as a model chemical with the aim of organic pollutants control. The photocatalytic degradation of RhB demonstrated that an optimal loading of bismuth 0.7,at.,% achieved the highest photodegradation rate, with the rate constant increasing by a factor of 3.89 over neat TiO2 (P25) under UV illumination (, , 320,nm). The degradation of p -nitrobenzonic acid (pNBA) was also examined to prevent/preclude/exclude/ the photosensitization pathway. GC-MS results show that pNBA can be effectively degraded and minerized to small molecules, such as quinone, acetic acid and formic acid. [source]

Defect-Related Optical Behavior in Surface Modified TiO2 Nanostructures

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005
M. Prokes
Abstract The surface modification of TiO2 nanostructures to incorporate nitrogen and form visible light absorbing titanium oxynitride centers is studied. Anatase TiO2 structures in the 5,20,nm range, formed by a wet chemical technique, were surface modified and the nitridation of the highly reactive TiO2 nanocolloid surface, as determined by X-ray photoelectron spectroscopy (XPS) studies, is achieved by a quick and simple treatment in alkyl ammonium compounds. The nitriding process was also simultaneously accompanied by metal seeding resulting in a metal coating layer on the TiO2 structures. The structure of the resultant titanium oxynitride nanostructures remains anatase. These freshly prepared samples exhibited a strong emission near 560,nm (2.21,eV), which red-shifted to 660,nm (1.88,eV) and dropped in intensity with aging in the atmosphere. This behavior was also evident in some of the combined nitrogen doped and metal seeded TiO2 nanocolloids. Electron spin resonance (ESR) performed on these samples identified a resonance at g,=,2.0035, which increased significantly with nitridation. The resonance is attributed to an oxygen hole center created near the surface of the nanocolloid, which correlates well with the observed optical activity. [source]

Formation of Highly Efficient Dye-Sensitized Solar Cells by Hierarchical Pore Generation with Nanoporous TiO2 Spheres

ADVANCED MATERIALS, Issue 36 2009
Yong Joo Kim
Nanoporous TiO2 structures were successfully applied for the fabrication of DSC electrodes, providing high surface areas and large pore sizes at the same time. High photocurrent was induced in these DSCs by great adsorption of dye molecules and efficient electrolyte diffusion, caused by the generated hierarchical pore structures in the TiO2 layer. [source]

Well-Defined Crystalline TiO2 Nanoparticles Generated and Immobilized on a Colloidal Nanoreactor

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2009
Yan Lu
Abstract We synthesized well-defined, crystalline TiO2 nanoparticles at room temperature by using spherical polyelectrolyte brush particles as a template. The template particles consist of a polystyrene core from which long chains of poly(styrene sodium sulfonate) are grafted. Tetraethylorthotitanate is hydrolyzed in the presence of brush particles leading to the formation of well-dispersed TiO2 nanoparticles (d,=,4,12 nm). Wide-angle X-ray scattering demonstrates that anatase nanoparticles with high crystallinity have been generated at room temperature. The as-prepared TiO2 nanocomposites present high photocatalytic activity for the degradation of Rhodamine B under UV irradiation. Finally, mesoporous TiO2 structures with defined pore size are formed after calcination. [source]