Lanthanide nanoparticles with efficient near-infrared-II emission for biological applications.

The near-infrared II (NIR-II) light (1000-1700 nm) possesses deep penetration capability and high signal-to-noise ratios due to the advances of low autofluorescence and scattering in biological tissues. Differing from the traditional NIR-II-emitting nanoprobes such as carbon nanotubes (CNT), organic dyes, quantum dots (QDs), and polymer dots (PDs), lanthanide-doped NPs feature the characteristic of excellent photo-and-chemical stability, sharp emission peaks, longer lifetime, and larger anti-Stokes shift. These merits have impelled the development of NIR-II-emitting lanthanide NPs in biomedical applications at a terrific speed. In this mini-review, we discuss how to design efficient NIR-II-emitting lanthanide NPs and summarize their recent progress in bioimaging, therapy, and biosensing. Moreover, the limitations and future opportunities of NIR-II-emitting lanthanide NPs are also discussed.