Synthesis of core-shell Au@TiO₂ nanopartides with truncated wedge-shaped morphology and their photocatalytic properties

Core - shell Au@TiO₂ nanoparticles with truncated wedge-shaped TiO₂ morphology have been synthesized successfully by a simple and flexible hydrothermal route. Morphological evolution of TiO₂ shells was investigated by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction technique. It has been revealed that the truncated wedge-shaped TiO₂ shells experience an epitaxially segmented orientation growth. Also, the (101) crystal planes of TiO₂ crystals grow preferentially on the surface of gold nanocrystals stabilizing the heterointerfaces, then faster [001] growth results in the "budding" process occurs, producing growth sites on the initial deposition TiO₂ layers, where the TiO₂ crystals grow up into truncated wedge-shaped morphologies. It is also found that morphological evolution of TiO₂ shells is dependent on the produced F∼ ion concentration from hydrolyzed TiF₄ precursors. The produced F ^- ions not only facilitate the formation of well-defined wedge-like TiO₂ shells, but also contribute to the externally exposed truncated crystal {004} facets. As the representative photocatalyst, the catalytic activities of the resultant core - shell Au@TiO₂ nanoparticles were investigated by photoinitiated oxidation degradation of gaseous acetaldehyde. It has been indicated that the nanostructured core-shell Au@TiO₂ photocatalyst represents high photocatalytic activity when exposed to LTV or visible light irradiation. The high phototocatalytic performance is also largely attributed to the preferentially grown TiO₂ shell structures and metal (Au)-TiO₂ heterointerfaces.