Lanthanide-doped fluoride nanocrystals have emerged as promising tools in biomedicine, yet their applications are still limited by their low luminescence efficiency. Herein, we developed highly efficient lithium-based core-shell-shell (CSS) nanoprobes (NPs) featuring a rhombic active domain and a spherical inert protective shell. By introducing Yb3+ as an energy transfer bridge and optimizing the CSS design, a remarkable 1643-fold enhancement in visible emission and a 33-fold increase in NIR emission are achieved compared to original nanoparticles. The upconversion quantum yield and brightness are 5-fold and 10-fold higher than those of typical sodium-based NPs, respectively, supported by the finite-difference time-domain simulations revealing stronger light absorption in rhombic LiYF4. Furthermore, the hydrophilic modification enabled the CSS NPs to conjugate with Rose Bengal hexanoic acid, thereby achieving upconversion-activated drug release. Meanwhile, the robust NIR emission of Yb3+ allows for precise lifetime-based thermal mapping and high-resolution imaging, advancing the development of noninvasive clinical diagnostics and targeted cancer therapies.
Keywords: Li-based core−shell engineering; NIR imaging; drug release; enhanced photoluminescence; nanothermometry.