Figure 12.

Absorption of water in the NIR and the integration scheme of the Nd³⁺→Yb³⁺ energy transfer (ET) process by introducing the Nd³⁺/Yb³⁺ co-doped shell. The resulting Nd³⁺→Yb³⁺→activator ET could extend the effective excitation bands for conventional Yb³⁺-sensitized UCNPs. Featuring lower water absorptions, these alternative excitation bands are expected to minimize the tissue overheating effect caused by NIR laser exposure (the blue line represents the absorption spectrum of water). Adapted with permission from reference [113]. Copyright: American Chemical Society, 2013.