Color-Tunable Thermoluminescence From Multi-Shell Nanocrystals via Ultrasound-Induced Heating

Ultrasound-induced luminescence (UL) converts mechanical energy into optical signals and has significant potential applications in multi-parameter sensing, bioimaging, and nondestructive evaluation. However, the mechanisms underlying ultrasound-triggered luminescence vary substantially among different material systems, complicating the rational design of luminescent materials. Herein, we demonstrate color-tunable thermoluminescence from multilayer core-shell fluoride nanocrystals via ultrasound-induced heating. The nanocrystals were designed with spatially separated Tb³⁺ and Pr³⁺ luminescent centers and gradient-distributed trap states. By tuning the ultrasonic electric power generated during ultrasonic excitation, we sequentially release carriers trapped at different depths (0.66, 0.73, 0.96, and 1.20 eV) and direct them to selectively recombine with the spatially isolated Tb³⁺ or Pr³⁺ luminescent centers. This process enables ultrasound-induced, dynamically tunable multicolor evolution, transitioning from pink to white and ultimately to green. The results establish a direct correlation between ultrasound-induced local temperature, trap-carrier release, and emission color, providing a strategy for developing thermally regulated and ultrasound-responsive luminescent systems.