Bright Er <sup>3+</sup> ‐Activated Multi‐Band Luminescence in Yb <sup>3+</sup> ‐Rich Eulytite Phosphate for Bio‐Imaging and Dynamic Authentication
Jiaqi Zhao, Kejie Li, Dongxu Guo, Zuoling Fu
Abstract
ABSTRACT The integration of the second nearinfrared window (NIR‐II, 1000–1700 nm) with visible light (400–700 nm) offers a powerful route for bioimaging, optical communication, and advanced security. However, realizing bright and polymorphic multiband emission within a single material remains challenging. Herein, Er 3+ doped eulytitetype Ba 3 Yb(PO 4 ) 3 phosphors have been rationally designed and synthesized to harness the rich energy level architecture of Er 3+ ions, yielding simultaneous bright blue (450 nm), green (525 and 550 nm), and NIR‐II (1550 nm) emissions. Tailored Yb 3+ →Er 3+ energy transfer delivers an exceptional NIR‐II quantum yield of 80%, enabling 12 mm tissue penetration in bovine tissue, roughly twice that of conventional NIR‐II probes. The Ba 3 Yb(PO 4 ) 3 : Er 3+ /polydimethylsiloxane (PDMS) elastomer film exhibits both mechano‐ and radioluminescence, featuring an atypical blue emission centered at ∼ 450 nm. This behavior is attributed to a strong triboelectric field arising from the high dielectric constant of the Yb 3+ rich eulytite host (ε ≈ 13‐14) under ultralow excitation, which suppresses the 4 F 5/2 → 2 H 11/2 pathway and promotes the 4 F 5/2 → 4 I 15/2 transition. These breakthroughs in bright, stimuli‐responsive, multi‐band emissions define a new paradigm for the design of versatile optical materials, offering broad opportunities in non‐contact sensing, dynamic authentication, and next‐generation photonic communication.