Near‐Infrared Mechanoluminescence of Gd ₃ Ga ₅ O ₁₂ : Cr ³⁺ , La ³⁺ for Biological Stress Imaging

Abstract Near‐infrared (NIR) mechanoluminescence (ML), capable of visualizing internal biological stress, is crucial for advancing in vivo bioimaging applications. Nonetheless, the scope of its applications is significantly constrained by the scarcity of available ML materials as well as unsatisfied ML efficiency. In this work, a NIR‐ML phosphor of Gd 3 Ga 5 O 12 : Cr 3+ (GGO: Cr 3+ ) is synthesized, which is characterized by a peak at 725 nm and a full width at half maximum (FWHM) of 100 nm. The NIR‐ML phenomenon of GGO: Cr 3+ is demonstrated to stem from contact electrification generated by the interaction between the corresponding oxide powder and the employed elastomer. Accordingly, the NIR‐ML intensity is manipulated to be increased by 340%, attributed to the enhanced surface potential of GGO: Cr 3+ for the incorporation of La 3+ ions. Furthermore, the NIR‐ML of GGO: Cr 3+ /polydimethylsiloxane (PDMS) film performs excellent tissue penetration, which indicates its promising potential for in situ monitoring of biological stress. Hence, it paves the way for novel bioimaging within living organisms.