Anti-Stokes photoluminescence from LiY1-xErxF4 nanocrystals: Proc.SPIE

We have successfully synthesized near-infrared photoluminescent erbium-doped lithium yttrium fluoride nanocrystals using a facile coprecipitation approach. The nanocrystals are capped with oleic acid, enabling dispersion in nonpolar solvents such as toluene and cyclohexane. The relative amounts of yttrium and erbium precursors were adjusted during the synthesis to obtain different concentrations of Er between 1% and 15%. The composition and structure of the nanocrystals were studied via X-ray fluorescence spectroscopy and X-ray powder diffraction. The nanocrystals were optically characterized by extensive photoluminescence studies, including Stokes and anti-Stokes emission. When excited with 1.55-μm light, the nanocrystals displayed strong anti-Stokes emission associated with the ⁴I_13/2 → ⁴I_15/2 transition. These nanocrystals therefore have a high potential to be used in optical cooling applications with telecommunication-wavelength excitation.