Regulating Broadband Near‐Infrared Mechanoluminescence via Energy‐Level Engineering for Potential Biomechanical Imaging

Abstract Near‐infrared mechanoluminescent (NIR ML) materials have attracted attention due to their advantages, such as in situ and real‐time monitoring of biomechanical information in vivo. However, most ML materials are focused on the UV–vis light range, which limits their potential applications in the biological field. In this work, a broadband NIR ML material Ca 2 YGa 3 Ge 2 O 12 : 0.10Cr 3+ (CYGGG: 0.10Cr 3+ ) is successfully prepared by chemical co‐substitution and Cr 3+ heavy doping. Density functional theory (DFT) calculations are used to determine the type of defects in the material, and the composite defects formed by interstitial oxygen (i O ′′) and antisite defects (Ca Y ′ ‐ Y Ca °) mostly dominate NIR ML. Cr 3+ ions act as electronic bridges to regulate energy levels, becoming the key to turning on the Nd 3+ ion's NIR ML. Finally, based on the excellent ML properties of CYGGG: 0.10Cr 3+ and CYGGG: 0.10Cr 3+ , 0.01Nd 3+ , the ML composites can penetrate pork tissues of different compositions/thicknesses under stress loads. Potentially, this work tries to realize biological tissue stress imaging, providing a new way for the biological application of NIR ML materials.