Intense visible multicolored luminescence from lanthanide ion-pair codoped NaGdF₄ nanocrystals

Lanthanide ion-pair (Eu(3+)/Tb(3+), Dy(3+)/Tb(3+), Sm(3+)/Tb(3+) and Eu(3+)/Dy(3+)) codoped NaGdF(4) nanocrystals using Ce(3+) as the sensitizer were prepared via the polyol method. The nanocrystals with different codoped lanthanide ion-pairs retain their individual optical properties and the combined spectra can be detected using single-wavelength excitation at about 251 nm. The combined spectra intensity ratios can be adjusted through control of the doping ions molar ratios. Excited with a UV lamp at 254 nm, the as-prepared nanocrystals in aqueous solution emit intense visible emissions of different colors. The nanocrystals were coated with SiO(2), to make them biocompatible.