Ultraviolet-B and Near-Infrared Dual-Band Luminescence in Bi3+/Bi2+ Codoped Persistent Phosphor for Optical Storage Application

Abstract

Discovering multifunctional luminescent materials to meet the demands of modern spectroscopy is of great significance. However, it is a standing challenge to enable multiple luminescence properties in a single material system via single metal ion doping. Here, we report the inherently Bi³⁺/Bi²⁺ codoped Ca₃Ga₂Ge₃O₁₂ persistent phosphor where Bi³⁺ is in situ reduced to Bi²⁺. This phosphor can act as an efficient multimodal luminescence material, which simultaneously exhibits long-lasting (>12 h) ultraviolet-B (UVB) and near-infrared (NIR) dual-band persistent luminescence after irradiation by 254 nm ultraviolet (UV) light. UVB and NIR afterglow are ascribed to the distinct Bi³⁺ and Bi²⁺ emitters, respectively, proven by comprehensive spectroscopic investigations including X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. Besides, this phosphor also exhibits exceptional photochromic features, accompanied by a rapid body color transformation from white to brown in response to 254 nm UV light within 60 s and excellent recovery capacity upon thermal or blue/white light stimulation. The combination of UVB persistent luminescence of Bi³⁺ and NIR afterglow of Bi²⁺ coupled with reversible white-to-brown photochromism phenomenon offers one type of promising multifunctional luminescence material, showing potential to be used for optical storage and anti-counterfeiting applications.