Nanostructured TiO 2 modified by perfluoropolyethers: Gas phase photocatalytic activity
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Giuseppina Cerrato Dipartimento di Chimica IFM & NIS-Interdept. Excellence Centre, Universita` di Torino, via Pietro Giuria, 7, 10125 Torino, Italy
Walter Navarrini and Maurizio Sansotera Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, via Mancinelli 7, 20131, Milano, Italy (Received 14 May 2009; accepted 22 July 2009)
A high-molecular-weight perfluoropolyether (PFPE-YR) and a perfluoropolyether containing ammonium phosphate (PFPE-F10) have been evaluated as fluorinated coating for high-surface-area titanium oxides. Coated nano-TiO2 shows hydrophobic properties and excellent buoyancy on water. In addition to photoactivity toward the degradation of toluene in gas phase, specific trial analyses have been completed to estimate the modified titanium oxide features. Brunauer–Emmett–Teller (BET) analysis for the surface area determination, ultraviolet-visible spectroscopy (UV-Vis) for the material electronic band gap, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) for the morphology, structure, and surface composition, respectively, and water contact angle and infrared (IR) analysis have been performed to estimate the wettability and stability of coated titanium.
I. INTRODUCTION
In the recent years, titanium oxide has caught the interest of engineers and scientists, as a result of its peculiar photocatalytic activity. The photocatalytic processes on a semiconductor material surface originated from the absorption of incident photons, and as consequence an electron can be promoted from valence to conduction band, creating an electronhole couple on the semiconductor surface. Therefore, a species adsorbed on the semiconductor can chemically interact with the just-created electron-hole couple; in particular to directly oxidize the adsorbed species, redox potential of the electron-hole couple must be higher than the redox potential of the adsorbed chemical. Similarly, to reduce the adsorbed species the redox potential of the electron-hole couple must be lower than the redox potential of the adsorbed chemical.1 Two major drawbacks to the applications of titanium oxide in the photodegradation of pollutant are present.
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0008
96
J. Mater. Res., Vol. 25, No. 1, Jan 2010
http://journals.cambridge.org
Downloaded: 19 Mar 2015
These are the complex separation of the titanium oxide from the bulk reaction after degradation of contaminants as well as the stabilization of the active titanium oxide dispersion to assure high kinetic decomposition rate during pollutants degradation. Hydrophobic modification of titania surfaces can solve these inconveniences, and therefore it has been attracting increasing attention. Such interest was also initiated by the fundamental importance of wetting phenomena in various technological applications. The self-cleaning action of hydrophobic TiO2-doped panes is widely used exploiting their
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