Upconverting NIR Photons for Bioimaging.

Lanthanide-doped upconverting nanoparticles (UCNPs) possess uniqueanti-Stokes optical properties, in which low energy near-infrared (NIR) photons can beconverted into high energy UV, visible, shorter NIR emission via multiphoton upconversionprocesses. Due to the rapid development of synthesis chemistry, lanthanide-doped UCNPscan be fabricated with narrow distribution and tunable multi-color optical properties. Theseunique attributes grant them unique NIR-driven imaging/drug delivery/therapeuticapplications, especially in the cases of deep tissue environments. In this brief review, weintroduce both the basic concepts of and recent progress with UCNPs in material engineeringand theranostic applications in imaging, molecular delivery, and tumor therapeutics. The aimof this brief review is to address the most typical progress in basic mechanism, materialdesign as bioimaging tools.