Triple core-shell nanoparticles with Er3+ ultraviolet-blue upconversion emissions via energy regulation

Abstract

So far, existing research on upconversion nanomaterials has concentrated on tuning luminescence properties through the design of core-shell structure and the strategic incorporation of dopant ions, enabling modulation in emission color, intensity, and excitation response. Among them, most of the studies have focused on multilayer (four or more layers) core-shell structures. However, such systems often face challenges related to complex preparation processes and inefficiencies. In this work, we aimed to simplify the system by employing NaErF₄:Nd,Yb,Ce@NaYF₄:Yb@NaYF₄ core-shell-shell nanoparticles and optimizing the doping combination of rare-earth ions for luminescence intensity control. Compared to traditional four-layer designs, this study provides the following significant advantages: (1) ultraviolet-blue upconversion emissions can be achieved without the incorporation of commonly used Tm³⁺ ions, overcoming the concentration quenching problem associated with Tm³⁺, and (2) the luminescence tuning in response to dual-wavelength (980 and 1532 nm) is achieved by a three-layer core-shell structure, significantly reducing system design complexity, fabrication challenges, and improving production efficiency. By validating its fluorescence emission performance, these nanoparticles exhibit unique potential application in photodynamic therapy and real-time fluorescence monitoring.