Upconversion Luminescence Modulation Based on Sandwich Structure with Interlayer Doping

Upconversion nanoparticles (UCNPs) as energy donors in luminescent resonance energy transfer (LRET) technology have shown broad prospects in various applications. To enhance the efficiency of LRET, this study designed and synthesized a sandwich-structured NaYF₄@NaYF₄:Yb^³+/Er³⁺@NaYF₄ upconversion nanoparticle. This core-shell structure places the luminescent ions Er³⁺ in the inner shell, close to the nanoparticle surface, maintaining good proximity to the external energy acceptor. By adjusting the doping concentration in the intermediate layer, we successfully optimized the upconversion luminescence properties, regulating the emission wavelength and intensity. The results show that the luminescence efficiency of the sandwich-structured nanoparticles is significantly superior to that of the single NaYF₄: Yb³⁺/Er³⁺core nanoparticles, effectively improving their signal-to-noise ratio in sensor applications. This study provides stronger support for the application of UCNP-based LRET technology in temperature sensor design.