Facile synthesis, metastable phase induced morphological evolution and crystal ripening, and structure-dependent photocatalytic properties of 3D hierarchical anatase superstructures.

Unique 3D hierarchical anatase TiO2 superstructures with evolvable morphologies and tunable sizes were successfully fabricated through a facile solvothermal route without using any structure-directing additives. A complex assembly process involving nucleation of nascent nanoparticles, agglomeration and ordered attachment of tiny nanocrystals, and regrowth induced by metastable crystal phase was put forward for the formation and morphology evolution of the anatase superstructures. It was revealed the crystalline phase experienced a ripening process from semicrystal to mesocrystal status accompanying the morphologies evolving from peony-like to chrysanthemum-like and eventually to spherical structures. The obtained 3D hierarchical anatase TiO2 superstructures exhibited superior photocatalytic activities for organic pollutant degradation, which could be largely attributed to the more efficient light-harvesting ability and the high specific surface area of the unique structures.