Morphology and Optical Properties of Spatially-Ordered Copper- and Fluorine-Doped Titanium-Dioxide Films
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MORPHOLOGY AND OPTICAL PROPERTIES OF SPATIALLY-ORDERED COPPER- AND FLUORINE-DOPED TITANIUM-DIOXIDE FILMS A. N. Morozov,1, 3 Thant Zin Phyo,1 A. S. Vasil’ev,1 P. I. Ivanov,1 and A. A. Averin2 Translated from Steklo i Keramika, No. 6, pp. 36 – 41, June, 2020.
The results of a study of the morphology and optical properties of copper- and fluorine-doped TiO2 ceramic films synthesized using electrolytic and solvothermal methods are reported. It is shown that the obtained films consist of oriented nanotube arrays possessing the crystalline structure of anatase, a narrow particle-size distribution, and a high degree of hexagonal self-organization. The effect of the conditions of the solvothermal process on the composition, morphology, structure, and optical properties of the obtained materials was determined. Key words: ceramic films, titanium dioxide, nanotubes, anodization, solvothermal synthesis, doping, copper, fluorine.
The photocatalytic properties of thin-film ceramic coatings of nano-crystalline titanium dioxide TiO2 on substrates of different nature have been intensively studied in the last few years [1, 2]. The heightened interest in the photocatalytic properties of TiO2-based oxide ceramic is due to its wide application in deep molecular oxidation of toxic organic substances, viruses, and various pathogenic bacteria under irradiation by light. Methods of obtaining ceramic films by oxidizing metallic preforms are most promising for creating highly efficient photocatalysts. Electrochemical oxidation of titanium makes it possible to obtain a wide range of films from TiO2 nanotubes (NT), which opens up the prospects for creating ceramic materials with specified properties and functions [3]. At the same time the efficiency of photocatalysis depends not only on the morphology of ceramic films but also on the capability of the films to generate electron-hole pairs under exposure to light [4]. Titanium dioxide with anatase structure, showing the greatest photocatalytic activity, possesses a wide bandgap of about 3.2 eV, which limits its intrinsic absorption [5]. In this connection a direction of real research is to expand the spectral range of absorption of films made from TiO2 NT while preserving their ordered porous structure. 1 2 3
Currently, the photocatalytic activity of TiO2 NT in the visible range of the spectrum is improved by creating ceramic composites based on them (for example, Cu2O/TiO2, Fe2O3 /TiO2, NiO/TiO2, and so on) [6 – 8]. Such systems are obtained by using chemical and electrical methods of deposition with firing of the material, which in most cases results in partial closure of pores as well as destruction of the ordered structure of TiO2 films. Moreover, because of their low chemical stability and the weak adhesion of the deposited phase, composite materials possess low operational stability, which strongly limits their application in liquid-phase processes. In this connection, in order to expand the spectral range of sensitivity of TiO2 NT, it is preferable to decrease the
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