Impact of doping on mechanoluminescence

Mechanoluminescence (ML) is the form of luminescence arising from mechanical stimuli. Currently, mechanoluminescent materials have become an inherent part of our daily lives because of their pervasive applications in mechano-optical devices like stress sensors, sensors for damage and crack propagation, and sensors for examining impact and fracture in addition to safety management surveillance systems. Mechanoluminescence is exceptionally receptive to the purity of the material and can also be utilized for morphological analysis of the constituents. Any mechanoluminescent material is principally composed of a host lattice and a dopant. Sometimes, it may also contain codopants for the enhancement of the mechanoluminescence performance. The nature of the dopant/codopant and host–dopant interactions fundamentally determines the efficiency of mechanoluminescence because the dopant acts as the primary luminescent center. When doped with suitable ions, mechanoluminescent materials generally emit light over a broad spectrum, that is, from ultraviolet (UV) to near-infrared (NIR) region. Moreover, enhancement in the luminescence and color tunability 33(either blue shift or red shift) can be achieved by selecting a range of dopants and varying the chemical composition of the host. Modification of synthesis method, choice of lanthanide or transition metal ions for doping and codoping into the host lattice will definitely enhance the properties of the trap centers to give desired mechanoluminescence. The increase in mechanoluminescence properties may be attributed to better responsiveness of the local electronic structure to the additional foreign pressure when doped with a higher concentration of dopant.