Photodegradation of Pollutants in Air: Enhanced Properties of Nano-TiO2Prepared by Ultrasound
1 Department of Physical Chemistry and Electrochemistry, University of Milan, Via Golgi 19, 20133, Milan, Italy
2 Consorzio INSTM, Via Giusti 9, 50121, Florence, Italy
3 Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, 38050, Trento, Italy
Nanoscale Research Letters 2008, 4:97-105 doi:10.1007/s11671-008-9208-3Published: 25 November 2008
Nanocrystalline TiO2samples were prepared by promoting the growth of a sol–gel precursor, in the presence of water, under continuous (CW), or pulsed (PW) ultrasound. All the samples turned out to be made of both anatase and brookite polymorphs. Pulsed US treatments determine an increase in the sample surface area and a decrease of the crystallite size, that is also accompanied by a more ordered crystalline structure and the samples appear to be more regular and can be considered to contain a relatively low concentration of lattice defects. These features result in a lower recombination rate between electrons and holes and, therefore, in a good photocatalytic performance toward the degradation of NOxin air. The continuous mode induces, instead, the formation of surface defects (two components are present in XPS Ti 2p3/2region) and consequently yields the best photocatalyst. The analysis of all the characterization data seems to suggest that the relevant parameter imposing the final features of the oxides is the ultrasound total energypervolume (Etot/V) and not the acoustic intensity or the pulsed/continuous mode.