Hybridization of silver orthophosphate with a melilite-type phosphor for enhanced energy-harvesting photocatalysis

Abstract

In this study, a silicate-based water-resistant melilite-type (Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺) long-lasting phosphor (LLP) was hybridized with silver orthophosphate (Ag₃PO₄), a typical visible-light active photocatalyst, by a facile solution mixing approach to achieve enhanced energy-harvesting photocatalysis. The structure of the composites was characterized by XRD, FT-IR, XPS and SEM and the effect of hybridization on both solar/visible light and afterglow photocatalysis was examined. Ag₃PO₄ nanocrystals with a size of ∼900 nm were found to be highly dispersed and localized on the surface of the tetragonal melilite crystal in the hybridized material. Photoluminescence and long-lasting luminescence of the LLP were weakened due to the absorption or light filtering effect caused by the deposited Ag₃PO₄. Hybridization of Ag₃PO₄ with the LLP formed a new charge-transfer structure evidenced by the ESR and photocurrent responses, and increased the solar and visible-light photoactivity by 2–2.5 fold. The LLP could absorb and store photon energy ranging from the visible light to ultraviolet region and transform this energy to an afterglow photon emission at 470 nm (∼2.6 eV), which further drove 32% of the retained methyl orange to be degraded after light-off. These results demonstrate that the hybridization of the melilite-type LLP and Ag₃PO₄ can greatly enhance photocatalysis under light illumination and produce a meaningful afterglow photodegradation effect after illumination extinction.