Synthesis of Au/TiO 2 Thin Films for Photocatalytic Degradation of Methylene Blue
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Synthesis of Au/TiO2 Thin Films for Photocatalytic Degradation of Methylene Blue F. Palomar1, I. Gómez1*, Patricia Zambrano2 Laboratorio de Materiales I, Facultad de Ciencias Químicas, UANL, San Nicolás de los Garza, N.L. México 2 Departamento de Mecánica, Facultad de Ingeniería Mecánica y Eléctrica, UANL, San Nicolás de los Garza, N.L. México. *[email protected]
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ABSTRACT Au/TiO2 thin films have been prepared from Titanium Tetrabuthoxide-acetylacetone solution and buthanol as solvent by sol-gel and dip-coating technique. Au nanoparticles were prepared from HAuCl4 solution. The deposition of Au nanoparticles was by spray pyrolysis method. The films from the sol gel solution were heat treated at 450°C for 1 hour. The surface structures, morphology, composition and optical properties on the films were investigated by atomic force microscopy (AFM), optical microscopy (OM), X-ray Diffraction (XRD) and UVVis spectrometer. It was found the film consisted of anatase phase (TiO2), Au nanoparticles in the range of 50 to 100 nm, and few cracks on the surface remaining attached to the glass substrate. In this study, we measured the photocatalytic degradation of a methylene blue (MB) aqueous solution by a film prepared by the sol-gel and dip-coating methods TiO2 and Au/TiO2 films prepared by spray pyrolysis method. We found that Au nanoparticles deposited on the TiO2 films improved the photocatalytic activity and minor degradation time that TiO2 films. INTRODUCTION Titanium dioxide (TiO2) is a well-know photocatalyst material. When titanium oxides are irradiated with UV light that is greater than the band gap energy of the catalyst (about λ=380 nm), electrons (e-) and holes (h+) are produced in the conduction and valence bands, respectively. These electrons and holes have a high reductive potential and oxidative potential, respectively, which, together, cause catalytic reaction on the surfaces; namely photocatalytic reactions are induced. In the presence of O2 and H2O, the photo-formed e- and h+ react with these molecules on the titanium oxide surfaces to produces O2- and OH radicals, respectively. These O2- and OH radicals have a very high oxidation potential, inducing the complete oxidation reaction of various organic compounds [1]. TiO2 under anatase form is usually as an efficient photocatalyst. Several attempts, for example, ion doping [2], noble metal deposition [3] and adding a coadsorbent [4] are mostly used to enhance the activity. Ion doping and noble metal deposition can separate photogenerated electrons and the holes; while the function of coadsorbent is to improve the absorption of the catalyst. The approach of establishing a semiconductor-metal composite system is usually considered as an effective way to reduce the recombination of electrons and holes and improve quantum efficiency of the photocatalytic process [5]. Metal particles such as Au and Ag have been reported to enhance the photocatalytic performance of TiO2, because the photogenerated electrons are trapped by these particles leading to high efficien
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