Versatile, Fast, and Easy One-Step Method for the Synthesis of Hydrophilic Lanthanide-Doped Nanoparticles

The preparation of hydrophilic lanthanide-doped nanoparticles (NPs) following a versatile one-step colloidal method at low temperature and short reaction time with different doped lanthanides, capping ligands, and fluoride sources is presented. The photoluminescence of the particles, via both downshifting (DS) and up-conversion (UC), was easily tuned from blue or green by simply changing the lanthanides used. When using the same core type of particles, the size and the photoluminescence intensity were tuned by changing the fluoride source or the capping ligand used: the size of the DSNPs varied from 9 nm (PAA) to 24 nm (PEI) when changing the capping ligand, while if PAA was used as capping ligand, the nanoparticles presented the most intense emission bands. Supramolecular host groups were introduced on the surface of the UCNPs by grafting cyclodextrin (CD) groups onto the capping ligand PiBMA prior to particle synthesis, reaching a CD surface density of 0.28 CD nm-2. In this case, a small particle size (11.7 nm) and strong UC emission bands were observed.