Ultrastrong Infrared Emission at 1460 nm from Lanthanide-Doped Nanoparticles with Interfacial Sensitization

Fluorescent imaging in the second near-infrared window (NIR-II; 1000-1700 nm) has recently received tremendous attention due to its excellent tissue probing depths and high resolution. Under NIR pumping, lanthanide-doped nanoparticles can emit infrared light covering a wide range of 800-3000 nm which has good potential for NIR-II imaging and detection. However, the low efficiency hinders their application. Here, we report intense infrared emission at 1460 nm from lanthanide-doped core/shell nanoparticles with efficient interfacial sensitization. The emitter Tm³⁺ ion and the sensitizer Yb³⁺ and Nd³⁺ ions are spatially separated in core and shells so that the efficient interfacial energy transfer is established between Tm³⁺ and Yb³⁺/Nd³⁺ ions, while thermal vibration spread of high concentration of Yb³⁺ ions and cross-relaxation among Tm³⁺, Yb³⁺, and Nd³⁺ ions are suppressed. As a result, the ultrastrong NIR-II emission at 1460 nm is achieved, which is more than 100-times that in classic core/shell nanoparticles doped with Tm³⁺ (NaYF₄:20%Yb,0.5%Tm@ NaYF₄).