Photon upconversion

Optics

Physics

Quenching (fluorescence)

Luminescence

Nanomedicine

Nanoparticle

Nanotechnology

Dopant

Materials science

Optoelectronics

Doping

Fluorescence

Nature Communications

Lanthanide-doped upconversion nanoparticles (UCNPs) are capable of converting near-infra-red excitation into visible and ultraviolet emission. Their unique optical properties have advanced a broad range of applications, such as fluorescent microscopy, deep-tissue bioimaging, nanomedicine, optogenetics, security labelling and volumetric display. However, the constraint of concentration quenching on upconversion luminescence has hampered the nanoscience community to develop bright UCNPs with a large number of dopants. This review surveys recent advances in developing highly doped UCNPs, highlights the strategies that bypass the concentration quenching effect, and discusses new optical properties as well as emerging applications enabled by these nanoparticles.

Advances in highly doped upconversion nanoparticles