Preparation of Au@TiO2 yolk-shell nanocomposites for solar-light degradation of methylene blue

A novel synthetic approach has been developed to prepare Au@TiO2 yolk-shell (Au@TiO2-YS) structures using silica as a template with controllable size, shape, crystal phase. This approach shows a few unique features, including tunable TiO2 shell thickness, high repeatability, low cost, and easy operation. The morphology, composition and the corresponding properties were characterized by several advanced techniques, such as TEM, XRD, and UV-vis spectroscopy. The Au@TiO2-YS structures consist of Au NPs as cores and TiO2 hollow spheres as shells. The Au NPs can be controlled in various diameters (e.g., 100 nm, 50nm, and 30 nm), while the TiO2 shell can form cavities with diameters of 255 nm and the thickness of similar to 45 nm. The absorption peak of the product can be changed by adjusting the size of Au cores. In addition, the photocatalytic activities of the synthesized composites were systematically measured by degrading methylene blue (MB) under simulated solar light irradiation. The photocatalytic performance test reveals that the reaction kinetic constants of the Au@TiO2-YS structures with different Au core sizes are superior to that of the TiO2 hollow spheres (0.00521 min(-1)). Among the yolk-shell structures, the YS-50 show highest kinetic constant (0.00704 min(-1)), which is 1.35 times higher than that of pure TiO2 hollow spheres. These findings provide an effective way for design and construction of TiO2-based photocatalysts for solar-light degradation of organic pollutant.