Hydrothermal synthesis of hexagonal lanthanide-dopedLaF3 nanoplates with bright upconversion luminescence

Abstract

Hexagonal Yb/Er or Yb/Ho co-dopedLaF3 nanoplates with uniform morphology have been synthesized with an average diameter of∼15 nm. It was found that the coating reagent, hydrothermal temperature and time play criticalroles in the control of the shape of the final products. A possible growth mechanismincluding ion exchange, ‘burst-nucleation’, and ‘heat-up’ growth is proposed.1H NMR spectra and Fourier transform infrared (FTIR) spectra indicate that thesurface of the nanoplates is coated with oleic acid ligands. Those hexagonalnanoplates display the capability of forming self-assembled two-dimensionalnanoarrays. Moreover, under continuous-wave excitation at 980 nm, theLaF3:12%Yb,3%Er nanoplates exhibited bright orange emission (a combination of greenbetween 515 and 556 nm and red between 640 and 675 nm) and theLaF3:20%Yb,1%Ho nanoplates had nearly pure green upconversion luminescence between 530 and 554 nm. Theintensity of upconversion luminescence increased with time and increase of thehydrothermal temperature. For the bright upconversion luminescence, the as-preparedsamples show potential applications in color displays, the building of nanodevices and asbiolabels.