ABSTRACT
Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted considerable interests due to their unique optical properties by converting near-infrared light to shorter wavelength emissions. Benefiting from the ladder-like energy levels of lanthanide ions, UCNPs with superior features, including the multicolor emissions, tunable emission lifetimes, excellent background suppression, photostability and deep penetration depth through the tissue, are suitable for biological and biomedical applications. This chapter reviewed the recent significant progress made by using UCNPs probes to enable novel approaches in super-resolution microscopy. We illustrate how the nonlinear optical properties of UCNPs can be used to reduce the laser power and improve the optical stability, imaging depth, speed and overall quality toward sub-diffraction imaging in three-dimensional (3D). This chapter further calls for critical research efforts to develop smaller and more efficient UCNPs, as well as surface functionalization strategies for specific labeling of subcellular structures.
