LAUSR

Lanthanide-doped upconversion nanoparticles, converting near infrared light to visible emissions, are promising for a broad spectrum of biological applications spanning from imaging, sensing, to light-activated therapy. However, their brightness are mainly refrained by surface-related quenching, concentration quenching and low lanthanide absorption cross section, hindering their practical performance. Here, we summarize recent advances that address these major challenges, producing about two to four orders of magnitude brighter upconversion luminescence. These brighter nanoparticles substantially improve the imaging, sensing, and therapeutic results, while providing new opportunities for emerging applications such as single nanoparticle imaging, super resolution imaging, and optical imaging in time domain.