Surface modification of y₂O₃ nanoparticles

Rare earth ion-doped yttrium oxide (Y₂O₃) nanocrystals are nontoxic and can be prepared as upconversion materials for cellular imaging, but they do not suspend well in water. In contrast to their tendency to dissolve in acidic media, yttria (Y₂O₃) nanoparticles readily react with phosphonic acids to give phosphonate-bonded yttria particles. Through the choice of phosphonic acid, the hydrophilicity of the nanoparticles can be controlled. The synthesis of a novel tetraethylene glycol-derived phosphonic acid is described; yttria treated with the corresponding phosphonate is easily dispersed in aqueous media. The preparation of yttria bonded to a phosphonate that may be used for cross coupling with biomolecules is also described.