Mechanically Charged and Self-Recoverable Green-Emitting Long-Persistent Mechanoluminescence in Ca₉NaMg(PO₄)₇:Tb³

Mechanoluminescent (ML) materials have shown promising applications in visualized mechanical sensing, imaging, and real-time monitoring because of their unique mechanics-optics conversion. However, the short emission lifetime of transient ML presents challenges in overcoming temporal and spatial constraints in practical applications. In this work, a mechanically charged persistent ML material was created by compositing the Ca₉NaMg(PO₄)₇:Tb³⁺ and flexible poly(dimethylsiloxane) (PDMS) matrix. Without preirradiation, the composite film emits self-activating and persistent ML (Pers-ML), simultaneously responding to the rubbing or stretching stimuli. Mechanical stimulation not only generates transient ML but also effectively fills traps through excitation of the interface triboelectric field during the process. Once the mechanical stimulus is removed, the release of trapped carriers leads to Pers-ML. In addition, the Ca₉NaMg(PO₄)₇:Tb³⁺/PDMS also exhibits self-recoverable ML and good thermal stability in the range of 298-573 K. Compared to traditional ultraviolet (UV)-charged long-persistent luminescent materials, the self-charging Pers-ML proposed in this work overcomes the temporal and spatial challenges of transient ML, further expanding the application scope of ML materials.