Emerging applications of rare‐earth fluoride nanocrystals in medicine and biotechnologies

Abstract Inorganic fluoride‐based compounds are present today as decisive components in many advanced technologies, including energy storage and conversion, dye‐sensitized solar cell, microphotonics, medicine, pharmaceuticals, etc. Most of these outstanding behaviors can be correlated to the exceptional electronic properties of the element fluorine: “F 2 .” The role of fluorinated rare‐earth (RE)‐based nanoparticles (NPs), mostly deriving from the fluorite structure, is also crucial in medicine and biotechnologies, where doped photoluminescent rare‐earth fluoride nanoparticles (REFNPs), exhibiting high responsivity, can be used as bi‐ or multi‐modal agents in theranostics, integrating both imaging probes and therapeutics; these materials can thus carry out both diagnosis and therapy within the same nano‐object. Relevant nanotherapeutics also include fluorine‐labeling of NPs, in vivo 19 F magnetic resonance imaging, photodynamic therapy, up‐ and down‐conversion luminescence, ultrafast upconversion superfluorescence, luminescent thermometry, photoacoustic imaging, radiotracers for positron emission tomography. Finally, research aimed at better understanding the toxicity risks of these NPs as well as better knowledge of the type of formulations of the used nano‐sensors should make it possible to improve the correlations between the selected REFNPs and the expected responses.