Figure 2.

Luminescence mechanism of RE nanoparticles. (A) Scheme of emission mechanism of Yb, Er doped RE nanoparticles exited by 980 nm NIR light. Adapted with permission from ⁸³, Copyright 2018, Nature Springer. (B) NIR-spectra of 5% Er³⁺ doped glass ceramics upon 400 nm irradiation. Adapted with permission from ⁸⁴, Copyright 2015, Royal Society of Chemistry. (C) Principal operation scheme for the NIR-to-NIR emission of RE doped nanoparticles. (D) NIR emission bands of Ho³⁺ (1.18 µm), Nd³⁺ (1.34 µm), and Er³⁺ (1.55 µm) ions excited with 806 nm irradiation. Adapted with permission from ⁸⁵, Copyright 2017, Royal Society of Chemistry.