Sound, Force and Light Induced Emissions from Er3+-Mn2+ doped ZnS/CaZnOS Heterostructure for Remote Temperature Monitoring via Photo- and Mechanoluminescence

Mechanoluminescence (ML) is a powerful phenomenon that enables light generation induced with mechanical or acoustic waves, and remote temperature sensing via luminescence thermometry techniques. In this work, the multi-functional, ML-active materials based on Er³⁺ and Mn²⁺ co-doped ZnS/CaZnOS heterostructure are developed for remote temperature monitoring and visual sensing of force and sound. The material exhibits characteristic photoluminescence (PL) under UV and NIR (up-conversion) excitation, with energy transfer from Er³⁺ to Mn²⁺ influencing the emission color. The effects of force-to-light conversion are studied in detail by measuring the ML intensity vs. the applied power for Er³⁺ and Mn²⁺ emission in the single-doped and co-doped materials. Temperature-dependent PL is utilized to calibrate luminescence thermometry response, with Er³⁺ thermally-coupled levels and non-thermally-coupled levels of Er³⁺/Mn^2+, providing temperature sensing capabilities. The unique combination of sound-induced ML with luminescence thermometry allowed optical temperature detection, alike during the drilling process, and in the externally heated system, using pulsed sonications. Whereas, applying continuous excitation, the sound-to-heat conversion is studied and visualized using the developed ML-based optical thermometers. This approach demonstrates the excellent application potential of sound-to-light conversion for remote monitoring and, more importantly, for excitation-light-free temperature probing of different systems and working devices.