Recent Progress on Rare-Earth-Doped Upconversion Nanomaterials for Bioassay Applications

Rare-earth-doped upconversion nanoparticles (UCNPs) have been widely used in biological detection due to their unique anti-Stokes shift, stable chemical properties, tunable emission wavelengths, and low biotoxicity. However, their low fluorescence quantum yield remains a challenge. Constructing a high-performance detection platform based on UCNPs is therefore a critical consideration. Focusing on the biological detection applications of UCNPs, this paper introduces the fundamental principles of upconversion and the design of upconversion fluorescence probes. It then summarizes common strategies for enhancing upconversion luminescence and three biosensing platform formats: solution-based, strip-based, and plate-based. Finally, future directions for UCNPs in biological detection are discussed.