Lanthanide‐Doped Upconversion Nanoparticles for Single‐Particle Imaging

Lanthanide‐doped upconversion nanoparticles (UCNPs) have recently demonstrated great promise in single‐particle imaging (SPI) due to their exceptional photostability and minimal background fluorescence. However, their relatively dim brightness has posed a significant barrier to wider adoption in SPI applications. This review highlights recent advances in the application of UCNPs for SPI, focusing on strategies to enhance their brightness and reduce quenching effects in aqueous environments. Additionally, it summarizes the latest progress in employing UCNPs for single‐particle tracking and super‐resolution imaging, underscoring their potential in biomedical research. Finally, the review outlines current challenges and future directions in this field.