Near‐Infrared Mechanoluminescence of Cr 3+ Doped Gallate Spinel and Magnetoplumbite Smart Materials

Mechanoluminescence (ML), as an optical response to deformation stimuli, shows great potential in high‐end stress sensing, ultrasonic field visualization, and multidimensional anti‐counterfeiting. However, processive practical applications in bio‐medicine are constrained by the discovery of near‐infrared (NIR) ML materials. Unlike lanthanides (Ln 3+ ) with sharp multiplets, two kinds of Cr 3+ ‐doped NIR ML materials, gallate spinel (ZnGa 2 O 4 :Cr 3+ , Zn 3 Ga 2 GeO 8 :Cr 3+ ) and gallate magnetoplumbite (SrGa 12 O 19 :Cr 3+ ) are here reported. Owing to the intrinsic cation antisite defects and cation vacancies in the matrix, these materials exhibit bright NIR ML under a relatively low load (20 N). In particular for SrGa 12 O 19 :Cr 3+ (750 nm, peak; 100 nm, FWHM) with low persistent luminescence (PersL) interference, the ML behavior can be further rejuvenated under UV and sunlight irradiation. SrGa 12 O 19 :Cr 3+ also shows bright NIR emission under photo‐ and thermo‐stimulation. Owing to their excellent tissue penetration and concealment capability, NIR ML materials show great potential in the fields of bio‐medicine and anti‐counterfeiting.