Optical Spectroscopy of Lanthanide-Doped Nanoparticles

Abstract

Lanthanide-doped luminescent inorganic nanoparticles (NPs) of various compositions, albeit most of their bulk counterparts have been well studied previously, have attracted reviving interest and come to the forefront in nanophotonics owing to their potential applications in diverse fields such as biodetection and bioimaging. These lanthanide-doped NPs show superior features including narrow emission bandwidths, long photoluminescence (PL) lifetime, low toxicity, and high resistance to photobleaching, making them highly suitable for use as alternatives to organic fluorescent dyes or quantum dots for various bioapplications such as early cancer theranostics. In this chapter, the most recent progress in the optical spectroscopy of lanthanide-doped NPs is discussed. Particularly, we would like to provide an in-depth overview of the optical properties for lanthanide-doped semiconductor and insulator NPs, with an emphasis on the host-sensitized long-lived downconversion luminescence of Ln3+ exemplified by Eu3+ and Tb3+ and the multicolor upconversion luminescence originating from Er3+, Tm3+, Ho3+, and Yb3+ ions co-doped NPs. Furthermore, the use of Ln3+ ions as a sensitive structural probe to analyze the local structure of dopants will also be highlighted in this chapter, which is crucial to optimizing their optical performance for further biological applications.