Near-ultraviolet and deep red dual-band mechanoluminescence for color manipulation and biomechanics detection

In this work, an efficient mechanoluminescent composite elastomer, Ca9Bi(PO4)7:Ce3+/polydimethylsiloxane, is reported. Because of the crystal restriction of Ca9Bi(PO4)7, Bi3+ and Bi2+ ions with luminescent characteristics co-exist in the structure. The doping of Ce3+ further shows effective energy transfer to the Bi ions, and hence the Ca9Bi(PO4)7:Ce3+/polydimethylsiloxane exhibits the unique and enhanced near-ultraviolet and deep red dual-band emissions under mechanics stimuli. Further studies on the thermoluminescence, cathodoluminescence, triboelectricity properties as well as the matrix effects suggest that the interfacial triboelectrification-induced electron bombardment model should be responsible for the mechanics excitation/activation processes. The mechanoluminescence of the Ca9Bi(PO4)7:Ce3+/polydimethylsiloxane is further utilized for two types of applications. By employing the emitted near-ultraviolet mechanoluminescence as the excitation source, a large variety of materials that only have photoluminescence can also exhibit mechanoluminescence. By demonstrating the penetration and sensing abilities of the long-wavelength deep red mechanoluminescence in the simulated tissues, this work also suggests that the Ca9Bi(PO4)7:Ce3+/polydimethylsiloxane is promising for the in-situ detection of biomechanics.