Recent advances in responsive lanthanide-doped luminescence nanoprobes in the near-infrared-II window

In recent years, fluorescent probes and their imaging techniques have been widely applied in environmental, biological and medical diagnostic fields. Compared with conventional fluorescent probes, luminescence nanoprobes in the second near-infrared (NIR-II) region are of importance because of their high spatial resolution, deep penetration capability, low invasiveness and autofluorescence. Among the various NIR-II nanoprobes, lanthanide-based NIR-II luminescent sensors exhibit unique advantages, such as narrow emission peaks, large Stokes shifts, longer lifetime and higher photostability. We focus on the recent progress on responsive NIR-II lanthanide nanoprobes in this review. We generalize the design strategies and synthesis methods of lanthanide nanoparticles for luminescent nanoprobe development. Then, we summarize the responsive mechanism of NIR-II lanthanide-based nanoprobes and their applications in biological systems. Finally, the challenges and future developments are discussed.