Intense green mechanoluminescence from rare-earth doped gallium gehlenite for multimode anti-counterfeiting

Mechanoluminescence (ML) materials, for the advantages of stress visualization and real-time dynamic response, are expected to have broad application in stress sensing, lighting and nondestructive stress detection. However, the application of ML material is still limited due to weak ML intensity, deficient ML repeatability and stability especially when composed with elastic matrix. It is urgent to explore new materials to realize their potential in various fields. In this work, a novel rare-earth ion doped phosphor Ca2Ga2SiO7:Tb3+, Li+ is prepared and its Photoluminescence (PL) and ML properties were investigated. A significant enhancement of the PL intensity is successfully achieved by introducing Ce3+ into the Tb3+ doped samples, for the effective energy transfer from Ce3+ to Tb3+. ML is created by compositing the phosphor into flexible Polydimethylsiloxane (PDMS). The elastomer exhibits intense green ML under mechanics stimuli without pre-irradiation. In addition, the ML intensity was correlated with the strain of the elastomer, the tension, and the stretch velocity. The ML intensity increased simultaneously with increasing the variables. Based on the research, a multi-mode luminescence barcode label was designed and fabricated demonstrating a potential for anti-counterfeiting.