Applications of upconversion nanoparticles

The term upconversion refers to a nonlinear optical process in which two or more photons are sequentially absorbed, followed by the emission of a photon with higher energy than the original pumped photons (anti-Stokes emission). Lanthanide-doped upconversion nanoparticles are the most common one and have been recently developed as a new generation of luminescent probes, possessing considerable merits which organic dyes and quantum dots don’t have. For example, lanthanide-doped upconversion nanoparticles offer high penetration depth, low autofluorescence background, large anti-stokes shifts, sharp emission bandwidths, low toxicity, and high photostability.