Defect-Induced Self-Reduction of Manganese in Zn₂SiO₄ via Nonequivalent Doping of Yb³⁺ and B³⁺ for Dynamic Multimode Optical Information Storage and Information Encryption

A series of long-persistent luminescence (LPL) phosphors Zn₂SiO₄ (ZSO) codoped with Mn²⁺, Yb³⁺, and B³⁺ were prepared by the traditional high-temperature solid phase method in air. By using Mn₂CO₃ or MnO₂ as the manganese source, a complete self-reduction behavior of Mn⁴⁺ to Mn²⁺ was observed in the ZSO host, yielding intense green LPL, thermoluminescence (TL), and photostimulated luminescence (PSL) emission from Mn²⁺. The spontaneous reduction behavior originates from the intrinsic defect of the Zn vacancy (V_Zn) caused by Yb³⁺ and B³⁺ occupying the Zn²⁺ and Si⁴⁺ sites. The influence of synthetic conditions, including Mn sources and doping concentrations, on the crystal structure and optical (photoluminescence (PL), LPL, PSL, TL) properties was systematically investigated. By analyzing the TL spectra at different temperatures and heating rates, the trap depth and distribution of ZSO:Mn²⁺,Yb³⁺,B³⁺ were characterized. With the incorporation of Yb³⁺ and B³⁺, the intensity of LPL and PSL and the decay time of ZSO:Mn²⁺ improved significantly under ultraviolet (UV) irradiation and near-infrared (NIR) stimulation. Utilizing the LPL, TL, and PSL properties of ZSO:Mn²⁺,Yb³⁺,B³⁺ phosphors, an intelligent LPL pattern was realized under various stimulations, which provides a quick-response approach for information encryption and optical information storage.