Rare-Earth-Ion-Doped Nanophosphors for Advanced Bioimaging Applications

Rare-earth-ion-doped nanophosphors have been shown to be highly promising luminescent materials for advanced bioimaging applications because of their unique optical properties, such as broad emission bands, long luminescence lifetimes, large Stokes/anti-Stokes shifts, high photostability, and low photobleaching. The doping of trivalent rare-earth ions such as Er³⁺, Yb³⁺, Nd³⁺, Eu³⁺, and Tb³⁺ into suitable inorganic host materials enables the generation of upconversion luminescence in the visible to near-infrared (NIR) spectral regions. In particular, NIR-emitting and up conversion nanophosphors provide enhanced tissue penetration depths, reduced auto fluorescence, and enhanced signal-to-noise ratios compared to conventional organic fluorophores and quantum dots. This chapter is in honour of and optical properties for biomedical imaging. Special emphasis is placed on process-structure-property relationships in the control of luminescence efficiency, quantum yield, and biocompatibility. Core-shell nanostructure design, defect passivation, and surface ligand engineering are discussed to enhance emission brightness and physiological stability. Moreover, targeted bio functionalization strategies are introduced to enable selective cellular and tissue imaging. In conclusion, rare-earth-ion-doped nanophosphors are a highly versatile and scalable platform for next-generation precision bioimaging applications.