Towards core-shell engineering for efficient luminescence and temperature sensing.

Research on the core-shell design of rare earth-doped nanoparticles has recently gained significant attention, particularly in exploring the synergistic effects of combining active and inert shell layers. In this study, we successfully synthesized 8 types of spherical core-shell Na-based nanoparticles to enhance the efficiency of core-shell design in upconversion luminescence and temperature sensing through the strategic arrangement of inert and active layers. The most effective upconversion luminescence was observed under 980 nm and 808 nm laser excitation using NaYF inert shell NaYF:Yb, Er@ NaYF and NaYF@ NaYF4:Yb, Nd core-shell nanostructures. Moreover, the incorporation of the NaYbF active shell structure led to a significant increase in relative sensitivity in ratio luminescence thermometry. Notably, the NaYF:Yb, Nd, Er@ NaYbF core-shell structure demonstrated the highest relative sensitivity of 1.12 %K. This research underscores the crucial role of inert shell layers in enhancing upconversion luminescence in core-shell structure design, while active layers play a key role in achieving high-sensitivity temperature detection capabilities.