Awakening dumb Mn2+ mechanoluminescence site to achieve force, temperature and time-domain induced color tuning via trap-assisted energy transfer

Mn2+ is a vital mechanoluminescent (ML) center with the properties of wide and color tunable spectrum. However, it is arduously to generate ML in asymmetric polyhedra, except in tetrahedral or octahedral coordination, which immensely impede the development and application of new-type Mn2+ doped ML materials. In this paper, a trap-assisted energy transfer model is proposed, successfully awakening dumb Mn2+ ML within the asymmetric [SrO9] polyhedron in Sr5(PO4)3Cl structure. Via this model, Sr5(PO4)3Cl:Eu2+,Mn2+ ML powder exhibits remarkable ML discoloration under variational force and temperature stimulation. Significantly, millisecond level of time domain change induced ML discoloration is observed for the first time, enabling force, temperature and time-domain triple-mode stress sensing. Finally, basing on the ML intensity ratio method (MLIR), 1.02 %·K−1 of relative sensitivity for self-powered temperature sensing and a distinguishable stress distribution imaging are presented. This work not only broadens the substitution site of Mn2+ ML, but also offers a new insight for the development of multi-mode ML sensing technology.