Hierarchical assemblies of bismuth titanate complex architectures and their visible-light photocatalytic activities

Abstract

The shape-controlled synthesis of hierarchically micro- and nanostructured materials has provided new possibilities to improve their physical and chemical properties. In this work, Bi₁₂TiO₂₀ complex architectures, such as nanospheres, nanowires, microflowers and microspheres were prepared through a facile solution-phase hydrothermal process, by controlling the reaction parameters, such as temperature, reagent concentration, and reaction time. Within the hydrothermal temperature range from 150 to 180 °C, the morphology transformed progressively from nanosphere agglomerates to microflowers, nanowires and then to microspheres with increasing time. A possible growth mechanism is proposed to explain the transformation of nanoparticles to microflowers via an Ostwald ripening mechanism followed by self-assembly and then break-up of the microflowers to nanowires and final consolidation into microspheres. Most importantly, these Bi₁₂TiO₂₀ samples dependent on their shape, size, and crystallinity, displayed high photocatalytic activities in comparison with bulk bismuth titanate powders, as demonstrated by the degradation of Rhodamine B under visible-light irradiation. The reasons for the difference in the photocatalytic properties of these Bi₁₂TiO₂₀ architectures are further investigated.