Synthesis and Applications of Lanthanide-Doped Nanocrystals

In recent years, Lanthanide (Ln3+)-doped nanocrystals have become promising alternatives to organic fluorophore because Ln3+ ions can exhibit unique luminescent properties, such as large anti-Stokes shifts, low auto fluorescence background, low toxicity and high penetration depth [1]. In terms of the mechanism of luminescence, luminescence of Ln3+ ions can be divided into down-conversion and up-conversion emission processes. The down-conversion process is the conversion of higher-energy photons into lower-energy photons [2], which often requires two main components, an inorganic matrix (known as the host) and activated Ln3+ doping ions (activators). Hitherto, many types of inorganic compounds, such as oxides, fluorides, phosphates, and vanadates, have been widely used as host materials.