Synthesis and Applications of Lanthanide-Doped Nanocrystals

Lanthanide (Ln3+)-doped nanocrystals continue to receive significant interest due to the large number of applications in display devices, optical communication, solid-state lasers, catalysis, and biological labeling. It is well known that the Ln3+-doped nanocrystals can exhibit unique optical properties such as long fluorescence lifetime, large Stokes shift, single to multicolor emission and good luminescence efficiency combined with high photochemical stability of the hosts. Nano-sized phosphorescent or optoelectronic devices usually exhibit novel properties, depending on their structures, shapes, and sizes, such as tunable wavelengths, rapid responses, and high efficiencies. In terms of the mechanism of luminescence, the 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, which often requires two main components, an inorganic matrix (known as the host) and activated Ln3+ doping ions (activators). Among all the Ln3+-based host materials observed to date including oxides, phosphates, vanadates, oxides, and so on. The optical properties of Ln3+-doped nanocrystals depend critically on the hosts in which the Ln3+ reside, and thus it is important to seek for suitable host matrices to achieve desirable luminescence of Ln3+. In this review, we focus on the most recent advances in the development of the synthesis and applications of Ln3+-doped nanocrystals.