Investigation of site-selective luminescence on core-shell persistent phosphors using synchrotron radiation

Abstract

With the growing interest in the development of multifunctional luminescent nanomaterials for applications in energy conversion and storage, several new methods have been studied for the fabrication of efficient core-shell persistent phosphors with long-lasting persistent luminescence in the visible and near-infrared range. Such materials often exhibit particular optical properties that may be precisely tuned via the modification of structural parameters and surface functionalization. [1-3] Hence, in this work, site-selective luminescence of core-shell green-emitting rare-earth-doped strontium aluminate persistent phosphors functionalized with europium β-diketonate (tta, dbm) complexes were investigated utilizing a combination of synchrotron-based techniques at the CARNAÚBA beamline of Sirius, such as X-ray absorption near edge structure (XANES), X-ray Excited Optical Luminescence (XEOL), and X-ray fluorescence (XRF). X-ray excited luminescence spectroscopy revealed that single-shell materials exhibit distinct emission profiles associated with energy-transfer mechanisms via the “antenna effect” for the different β-diketonate ligands, while double-shell materials showed that the ratio between Eu2+ (green) and Eu3+ (red) emission is intrinsically different for the edge and the bulk of the studied particles. Promising results also revealed the influence of shell thickness and distance in potential energy-transfer processes, outlining an important framework for the development of multifunctional persistent phosphors utilizing rare-earth complexes as luminescent sensitizers.