Boosting near-infrared mechanoluminescence from activated gallate solids by Ga₂O₃ heterojunction engineering for intelligent sensing

Long-wavelength mechanoluminescent (ML) materials that convert mechanical stimuli into light hold promise for biomedical imaging and wireless sensing but are often restricted by low brightness and shallow tissue penetration. Here, a heterojunction engineering strategy is employed to enhance near-infrared ML emission in LiGa₅O₈/Ga₂O₃:Cr³⁺ composites, achieving a 416% intensity increase compared with the single-phase LiGa₅O₈. Incorporation of Ga₂O₃ introduces deeper electron traps and strengthens the crystal field around Cr³⁺ centers, thereby boosting emission efficiency in the 700–750 nm range. Density functional theory calculations reveal that orbital hybridization at the interface lowers recombination barriers and promotes radiative transitions. The optimized composite shows excellent aqueous stability over 240 h, while the flexible films fabricated with polydimethylsiloxane enable effective ML imaging through biological tissue, as verified using chicken joints. These findings demonstrate a promising pathway toward high-performance near-infrared ML materials for in vivo monitoring, biomedical imaging, wireless sensing, and intelligent sensing applications.