Single Tb3+ ion doped ratiometric mechanoluminescence for tunable stress visualization

When a material is stimulated by external stress, the mechanical energy may be converted into light energy calling mechanoluminescent (ML). The unique excitation method makes it promising for a wide range of applications in the field of stress sensing. However, traditional stress sensing methods based on absolute ML intensity have limitations in unpredictable and complex measurement environment. To address this topic, a ratiometric ML intensity-based stress sensing method has been proposed, which significantly improves the reliability and stability of sensing results. In this paper, a single Tb 3+ ion-doped garnet ML compound is designed. The variation of defect concentration in the material was induced by changing the dopant concentration and the local crystal field intensity. Ratiometric ML stress sensing was achieved through external mechanical stimuli, which causes a change in local positional symmetry. The linear relationship between the luminescence intensity asymmetry ratio and stress was investigated, and the excellent stability and reliability of the ML material were demonstrated under multiple stress cycles. The single-activator ratiometric ML intensity strategy presented in this study provides a new approach for improving stress sensing accuracy, which represents an essential step for the application of ML materials in stress sensing.