Cooperative Doping in Ultrasmall BaF₂ Nanocrystals for Multimodal ¹⁹F-MRI and CT Applications

Nanostructured metal fluorides (nanofluorides) are an emerging type of inorganic nanocrystals (NCs) with unique physiochemical properties for advanced applications. One recent demonstration used water-dispersed ultrasmall CaF2 nanofluorides as imaging agents that combined the advantages NCs benefit background-free 19F-magnetic resonance (19F-MRI). Nevertheless, obtaining small a face-centered cubic crystal structure, where all magnetically equivalent to result in single 19F NMR signal, is challenging other types nanofluorides, preventing their use 19F-MRI. Here, we show development ultrasmall, water-dispersed, barium fluoride (BaF2) bioimaging By doping BaF2 two lanthanides, diamagnetic-La3+ and paramagnetic-Sm3+, were able control morphology 19F-MR final La,Sm:BaF2 (termed LaSamBa) formulation. The fine-tuning La3+ content enabled us obtain monodispersed 4.5 nm NCs, over Sm3+ provided LaSamBa very short T1 relaxation (ca. 100 ms) needed enhanced 19F-MRI sensitivity. This was examined different modalities (i.e., CT), benefiting from 19F-NMR signal high atomic number atoms, respectively. As chemical shift significantly differs (e.g., SrF2), expanded nanofluoride library future multitarget studies.