Diethylenediamine-assisted template-free synthesis of a hierarchical TiO2 sphere-in-sphere with enhanced photocatalytic performance.

With the assistance of diethylenediamine (DETA), a template-free solvothermal approach is employed to one-step synthesize a hierarchical TiO2 sphere-in-sphere, which has a unique structure: an interior nanosized sphere is contained in the cavity of another hollow microsphere, and numerous nanosheets of width ca. 20-26 nm vertically distribute on the surface. It is proved that DETA added in solution plays an important inducing role in the formation of both the hollow sphere-in-sphere structure and surface sheet-assembled network. Therefore, a DETA-assisted formation mechanism of the hierarchical TiO2 sphere-in-sphere has been described in detail. The unique hierarchical sphere-in-sphere structure endows the TiO2 product with increasing light-harvesting efficiency and specific surface area, resulting in its enhanced photocatalytic activity for the degradation of various organic pollutants under the illumination of UV light.