Synergistic Integration of NB-UVB Persistent Luminescence and Concentration-Dependent Photochromism in a Phosphate Phosphor for Multifunctional Applications

Multifunctional phosphors combining persistent luminescent and photochromic properties have garnered increasing attention, given their capability of absorbing the photon energy and trapping the light-generated charge carriers by defects. To date, extensive efforts have been devoted to achieving reversible photochromism in visible/infrared afterglow materials. However, research on integrating ultraviolet (UV) persistent luminescence and photochromic behavior into a single material is relatively lacking. Herein, multimode luminescence in a Gd 3+ single-doped Sr 3 (PO 4 ) 2 phosphor is demonstrated, featuring narrowband ultraviolet-B (NB-UVB) photoluminescence, NB-UVB afterglow, and multicolor photochromism. The temperature-dependent NB-UVB photoluminescence of the Sr 3 (PO 4 ) 2 :Gd 3+ phosphor reveals its potential as a ratiometric optical thermometer with high relative sensitivity (2.5% K −1 at 110 K). Meanwhile, this phosphor exhibits robust NB-UVB persistent luminescence lasting >24 h upon X-ray irradiation. Besides, the material also displays exceptional concentration-dependent multicolor photochromism (white-to-blue and white-to-brown) under bright-field conditions only in response to X-ray irradiation, coupled with excellent bleaching and recovery capability under thermal treatment or 254 nm UV light stimulation. The synergistic integration of NB-UVB persistent luminescence and concentration-dependent multicolor photochromism positions this phosphor as a promising candidate for versatile applications, including covert optical tagging, optical information storage, and advanced anti-counterfeiting.