It is well known that the surface deposition of metallic nanoparticles enhances the photocatalytic efficiency of titania by favouring the charge separation process in the oxide, hence eliminating the electrons-holes recombination. Moreover, both nanodispersed metals and some metal oxides are able to make the titanium oxide active to visible light. In this study, an extensive characterisation by Diffuse Reflectance UV-Vis (DR UV-Vis) Spectrocopy, High Resolution Transmission Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) of differently modified titania powders and films has been carried out. Moreover, zeolitic materials (SBA-15) opportunely functionalised and employed to embed titania and vanadia nanoparticles have been examined. DR UV-Vis Spectroscopy has been employed to evidence the changes on the edge of titania that have been induced by the dispersion of different metals and/or oxides. In particular, it has been observed that when titania (anatase) is modified either by gold nanoparticles (the HRTEM analysis evidenced sizes of 4.1 ± 0.5 nm) or by nanocrystalline ceria, a shift of its fundamental absorption edge towards the low frequencies, hence a gain in photocatalytic terms, is obtained. The simultaneous presence of these modifiers increases furtherly the positive effect. X-ray diffraction measurements performed on the titania films showed only well defined crystalline phases (anatase and rutile). Moreover, a positive effect of gold during the synthesis has been evidenced, since it seems to favour preferentially the formation of anatase (the photoactive phase) rather than rutile. As for the embedded oxide nanoparticles, the presence of elongated crystals with section of exagonal shape has been evidenced by SEM analysis, indicating a strong influence of the zeolitic matrix on the final morphology of the materials. Moreover, HRTEM performed on the sample sections evidenced that the synthesis procedure for the embedding has been effective, since the majority of the oxide particles is inside the channels of SBA-15. These particles are crystalline as evidenced by the analysis of the diffraction fringes. Finally, the presence of extra-framework particles has also been detected and it is related to the order followed during the insertion of either titania or vanadia.

Catalysis and photocatalysis on nanostructured materials based on titania

MANZOLI, Maela;VINDIGNI, FLORIANA;MORANDI, Sara;BOCCUZZI, Flora;CHIORINO, Anna
2006

Abstract

It is well known that the surface deposition of metallic nanoparticles enhances the photocatalytic efficiency of titania by favouring the charge separation process in the oxide, hence eliminating the electrons-holes recombination. Moreover, both nanodispersed metals and some metal oxides are able to make the titanium oxide active to visible light. In this study, an extensive characterisation by Diffuse Reflectance UV-Vis (DR UV-Vis) Spectrocopy, High Resolution Transmission Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) of differently modified titania powders and films has been carried out. Moreover, zeolitic materials (SBA-15) opportunely functionalised and employed to embed titania and vanadia nanoparticles have been examined. DR UV-Vis Spectroscopy has been employed to evidence the changes on the edge of titania that have been induced by the dispersion of different metals and/or oxides. In particular, it has been observed that when titania (anatase) is modified either by gold nanoparticles (the HRTEM analysis evidenced sizes of 4.1 ± 0.5 nm) or by nanocrystalline ceria, a shift of its fundamental absorption edge towards the low frequencies, hence a gain in photocatalytic terms, is obtained. The simultaneous presence of these modifiers increases furtherly the positive effect. X-ray diffraction measurements performed on the titania films showed only well defined crystalline phases (anatase and rutile). Moreover, a positive effect of gold during the synthesis has been evidenced, since it seems to favour preferentially the formation of anatase (the photoactive phase) rather than rutile. As for the embedded oxide nanoparticles, the presence of elongated crystals with section of exagonal shape has been evidenced by SEM analysis, indicating a strong influence of the zeolitic matrix on the final morphology of the materials. Moreover, HRTEM performed on the sample sections evidenced that the synthesis procedure for the embedding has been effective, since the majority of the oxide particles is inside the channels of SBA-15. These particles are crystalline as evidenced by the analysis of the diffraction fringes. Finally, the presence of extra-framework particles has also been detected and it is related to the order followed during the insertion of either titania or vanadia.
VIII Congresso del Consorzio Interuniversitario La Chimica per l’Ambiente (INCA 2006)
Bologna, Italia
23- 24 Marzo 2006
Book of Abstracts
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M. Manzoli; F. Vindigni; S. Morandi; F. Boccuzzi; A. Chiorino
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/112048
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