Self-Recoverable Mechanically Induced Instant Luminescence from Cr3+-Doped LiGa5O8

Currently, most of the mechanoluminescence (ML) phosphors strongly depend on postirradiation stimulation using ultraviolet light (denoted as UV exposure from hereon) to show the ML. However, only a few transition metal cations are proven to be effective luminescence centers, which hinder the development of more ML phosphors. This study reports a self-recoverable deep-red-to-near-infrared ML using Cr3+-doped LiGa5O8 phosphor with fully recoverable ML performance. The ML performance can be further optimized by tuning the trap redistributions by codoping the phosphor with Al3+ and Cr3+ cations. Theoretical calculations reveal the important role of Cr dopants in the modulation of local electronic environments for achieving the ML. Owing to the induced interelectronic levels and shallow electron trap distributions, the electron recombination efficiency is enhanced both through direct tunneling and energy transfer toward the dopant levels. Moreover, the ML of Cr3+-doped LiGa5O8 can penetrate a 2-mm-thick pork slice, showing that it can have wide-ranging in vivo applications, including the optical imaging of intracorporal stress/strain distribution and dynamics. Therefore, this work fabricates a novel ML material with self-recoverable luminescence in an extended wavelength range, increasing the number of potential ML candidates and promoting the fundamental understanding and practical applications of ML materials.

Automated summary

This study reports the development of self-recoverable deep-red-to-near-infrared mechanoluminescence using Cr3+-doped LiGa5O8 phosphor, which exhibits fully recoverable performance and can be further optimized by codoping with other cations. Theoretical calculations reveal the crucial role of Cr dopants in modulating local electronic environments for achieving mechanoluminescence.