Mn valence state transition via Li+ structure modulation and charge transfer for multi-modal temperature sensing and optical encryption applications

Abstract

Self-reduction phenomena are commonly observed during the synthesis of fluorescent materials, but precise control over the self-reduction behavior of such materials remains challenging. In this study, we effectively suppressed the self-reduction behavior of BaMg_1.072Al_9.928O₁₇:Mn (BMAO:Mn) materials through co-doping with Li⁺ ions. As the concentration of Li ions increases, the self-reduction behavior of the material gets inhibited to varying degrees. The underlying mechanisms responsible for the suppression of self-reduction and the multi-color emission based on varying Li⁺ ion concentrations are investigated in detail. The research demonstrates that Li⁺ ions effectively suppress the self-reduction behavior of Mn through the occupation of interstitial sites or the substitution of tetrahedral Mg²⁺ sites in the BMAO lattice, thereby regulating the Mn valence state. Finally, utilizing the distinct thermally quenched behaviors of Mn²⁺ and Mn⁴⁺ and the resultant temperature-dependent multi-color luminescence, a multi-modal temperature sensor and optical information encryption are achieved.