Facile one-pot synthesis of hydrophilic NaYF 4 :Yb,Er@NaYF 4 :Yb active-core/active-shell nanoparticles with enhanced upconversion luminescence

Abstract We report a facile one-pot synthesis strategy for hydrophilic NaYF 4 :Yb,Er@NaYF 4 :Yb active-core/active-shell nanoparticles by two-step injection of ethylene glycol (EG) solution containing different rare earth ions, BF 4 − , Na + and Poly(vinylpyrrolidone) (PVP) into EG at 180 °C. NaYF 4 :Yb,Er@NaYF 4 :Yb nanoparticles have the size of about 100 nm and cubic-phase structure. The presence of PVP ligands on their surface confers high solubility in water. The aqueous dispersion of these NaYF 4 :Yb,Er@NaYF 4 :Yb nanoparticles exhibits greatly enhanced up-converting luminescence, compared with that of NaYF 4 :Yb,Er core-only nanoparticles and NaYF 4 :Yb,Er@NaYF 4 active-core/inert-shell nanoparticles. Therefore, these hydrophilic NaYF 4 :Yb,Er@NaYF 4 :Yb nanoparticles have great superiority as luminescent labeling materials for biological applications.