Self-recoverable broadband near infrared mechanoluminescence from BaGa12O19:Cr3+ using a multi-site occupation strategy.

Near infrared mechanoluminescence (NIR-ML) materials have attracted the attention of researchers due to their unique advantages, such as high resistance to bright-field interference and higher penetration depth into biological tissues. However, the reported NIR-ML materials are mainly rare-ion-activated narrow-band emitters. In this work, we report a NIR-ML material of BaGa₁₂O₁₉:Cr³⁺ by a solid state reaction method. Broad NIR ML (650-1000 nm) is observed at lower force loads (12 N), which is based on the Cr³⁺ ion's multi-lattice site occupation. After heat treatment at 573 K for 20 min, BaGa₁₂O₁₉:Cr³⁺ still maintains 84.4% of its ML intensity. Furthermore, the ML intensity of BaGa₁₂O₁₉:Cr³⁺ is also significantly improved after UV pre-irradiation. Due to the defective piezoelectric photonic effect, BaGa₁₂O₁₉:Cr³⁺ has great self-recoverable properties even in the absence of UV and sunlight irradiation. Finally, the ML penetration rate of BaGa₁₂O₁₉:Cr³⁺ has reached as high as 66.97% in biological tissues, which suggests potential prospects for biostress detection towards bio-imaging applications.