Visible light photochemical activity of heterostructured PbTiO3–TiO2 core–shell particles

Abstract

Heterostructured powders composed of microcrystalline PbTiO₃ cores coated with nanostructured TiO₂ shells were prepared by a sol–gel method. When exposed to visible light (λ > 420 nm), the heterostructured powder degrades methylene blue at a rate 4.8 times greater than PbTiO₃, TiO₂, or mechanical mixtures of the phases. The rate at which the heterostructured powder degrades methylene blue depends on the processing temperature; samples annealed at 500 °C are the most reactive, even though they do not have the highest surface area. Enhanced degradation rates were not observed for Pb-doped TiO₂, indicating that it is the core–shell architecture and not contamination by lead that increases the reactivity. The improved reactivity of microcrystalline-PbTiO₃/nanostructured-TiO₂ heterostructures in visible light is attributed to visible light absorption in the PbTiO₃ core, charge separation at the buried interface between the ferroelectric PbTiO₃ and the dielectric TiO₂, and dye degradation on the nanostructured TiO₂ shell.