Figure 5.

(a) Left: The schematic of multi-dye-sensitized UCNPs for a broad range of light absorption. Three dye sensitizers (e.g., BODIPY-FL for blue absorption, Cy 3.5 for green absorption, and IR 806 for red absorption) are immobilized on the nanoparticles. Right: The energy diagram of the three sensitizers and the UCNPs. (b) Left: The schematic of Nd³⁺-doped core/shell UCNPs excited under 800 nm irradiation. Right: The energy diagram of the core/shell UCNPs. (c) NaLuF₄:Yb,Tm@NaGdF₄ (¹⁵³Sm) nanoparticles work as a multimodal imaging agent for upconversion luminescence imaging (Yb³⁺,Tm³⁺), CT (Lu³⁺,Yb³⁺), T₁ MRI (Gd³⁺), and SPECT (¹⁵³Sm³⁺). Reprinted with permission from refs (117, 125), and (139). Copyright 2017 Wiley and 2013 American Chemical Society.