TiO₂ Nanoflakes Modified with Gold Nanoparticles as Photocatalysts with High Activity and Durability under near UV Irradiation

Titania nanoflakes modified with gold nanoparticles (NPs) were successfully prepared by depositing of Au NPs onto TiO2 nanoflakes using a direct “green” process in the absence of organic capping agents. The photocatalyst has been characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and UV−vis diffuse reflectance spectroscopy. Results of these analyses revealed that the Au NPs (∼1 nm) are homogeneously dispersed on the surface of highly crystalline TiO2 (anatase) nanoflakes with a narrow size distribution. Further, XPS studies indicate a strong electronic interaction between Au (in metallic state) and TiO2. Inspiringly, the photocatalyst showed high-efficiency and ultrastability for the degradation of the nonbiodegradable azo dye brilliant red X-3B under near UV irradiation with activity 4.3 times higher than that exhibited by the commercial Degussa P25. Durability tests established that the catalyst remains intact even after 15 consecutive experiments. The ultrafine metal particle size and strong metal−support interaction were considered as the key factors for the overall photocatalytic activity of the metal-semiconductor composite system.