To meet the growing demand for stable dual-emission phosphors for use in optoelectronic applications, this study investigated a self-reduction strategy with Mn-doped Li₂ZnGe₃O₈ (LZGO) phosphors. The spinel-structured LZGO lattice enables the coexistence of Mn²⁺ and Mn⁴⁺ via oxygen vacancies and lattice defects, achieving visible (Vis) and near-infrared (NIR) dual emission without the need for external reducing agents. Spectroscopic analyses, including X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS), confirmed the presence of heterovalent Mn states, with lifetimes of 3.63 ms (Mn²⁺) and 0.32 ms (Mn⁴⁺) under selective excitation. The LZGO:xMn system thus demonstrates excitation-tunable Vis-NIR luminescence and high stability, making it a cost-effective and environmentally friendly candidate for anticounterfeiting and bioimaging applications. This work presents a defect engineering-driven design concept for developing multifunctional redox-active phosphors with broad application prospects.

Novel scheelite structures of Li₂Ca(WO₄)₂, Li₂Ca₂(WO₄)(SiO₄), and LiCa₂(WO₄)(PO₄) fluorescent materials were successfully prepared using a high-temperature solid-phase process. The compounds were characterized by X-ray diffraction and energy dispersive spectroscopy. The tests revealed that the substitution of [WO₄]^2- by [SiO₄]^4- or [PO₄]^3- tetrahedron in tungstate had no significant influence on the crystal structure of the Li₂Ca(WO₄)₂. When Dy³⁺ ions were introduced as an activator at an optimum doping concentration of 0.08 mol%, all of the as-prepared phosphors generated yellow light emissions, and the emission peak was located close to 576 nm. Replacing [WO₄]^2- with [SiO₄]^4- or [PO₄]^3- tetrahedron significantly increased the luminescence of the Li₂Ca(WO₄)₂ phosphors. Among them, the LiCa₂(WO₄)(PO₄):0.08Dy³⁺ phosphor had the best luminescence properties, decay life (τ = 0.049 ms), and thermal stability (87.8%). In addition, the as-prepared yellow Li₂Ca(WO₄)₂:0.08Dy³⁺, Li₂Ca₂(WO₄)(SiO₄):0.08Dy³⁺, and LiCa₂(WO₄)(PO₄):0.08Dy³⁺ phosphor can be used to fabricate white light emitting diode (LED) devices.