Nanocomposites and nanomaterials

Photocatalytic Activity of TiO2 and TiO2:S Nanopowders Under Visible Light
Bulavinets T.O.1, Yaremchuk I.Ya.1, Bobitski Ya.V.1,2
1 Department of Photonics, Lviv Polytechnic National University,
12, S. Bandera Str., Lviv 79013, Ukraine 
E-mail: tetiana.o.bulavinets@lpnu.ua 
2 Faculty of Mathematics and Natural Sciences University of Rzeszow 
Rzeszow, Poland.

Currently, titanium dioxide is one of the most promising photocatalysts. Many studies in nanotechnology are devoted to the research of TiO2 properties, synthesis methods and applications. Due to unique photocatalytic, optical and physico-chemical properties titanium dioxide is extensively used in various fields of science. This is semiconductor material which characterized by insolubility in acids and high chemical resistance, biological inertness, low toxicity and relatively low cost. However, its photochemical activity is in the UV spectral region and this is one of the main drawbacks of TiO2 as a photocatalyst. This limits a lot the possible fields and prospects for its application. 
One of the promising ways to increase TiO2 photocatalytic activity and shift its absorption spectrum into the visible region is the doping TiO2 by the impurities of different materials. In particular, the modification of titanium dioxide with sulfur allows one to shift absorption sprectra into the visible range, significantly improve its photocatalytic properties and expand the range of possible practical applications.
In present research the photocatalytic properties of TiO2 and TiO2:S nanopowders have been investigated during the process of photodegradation of the Rodamin G dye. The activation of the process was carried out by semiconductor laser with wavelength λ=450 nm. During the experiment, gel-like paste was prepared on the basis of polyvinyl alcohol aqueous solution (PVA) containing 6% hydrogen peroxide, Rodamine G dye and different amounts of TiO2 and TiO2:S nanopowders. For each material, its optimal concentration for the dye photocatalytic decomposition has been determined. It is shown that sulfur-modified titanium dioxide exhibits considerably higher photocatalytic properties in the visible spectral range and significantly reduces the half-reaction duration which is an important characteristic for the wide practical application of the nanoscale catalyst.