Multicolour PEI/NaGdF4:Ce3+,Ln3+nanocrystals by single-wavelength excitation

Multicolour colloidal PEI/NaGdF4:Ce3+,Ln3+ (Ln = Tb, Eu, Sm or Dy) nanocrystals were synthesized using a simple one-pot hydrothermal procedure. The nanocrystals consist of well crystallized hexagonal phase and have an elongated spherical shape, with diameters between 25 and 45 nm. Under single-wavelength excitation at 254 nm in the ultraviolet (UV) region, the nanocrystals doped with different lanthanide ions show intense visible (VIS) emissions of different colours. The characteristic luminescence property of the nanocrystals can be attributed to strong absorption of the UV irradiation by the Ce3+, followed by energy transfer to (via Gd3+ sublattice) and emission from the luminescent centres.