Local field effect on Nd3+-doped α-NaYF4 nanocrystals in liquids

The oleate-capped α-NaYF4:Nd3+ nanocrystals (NCs) were synthesized via solvothermal method. By a ligand exchange method, the oleate-capped NCs could be changed to citrate-capped samples which can be dispersed in polar solvents. By the relation between the measured emission lifetime and effective refractive indices of the composites containing NCs, the local field effect was investigated. It was found that the preferable model would change from the real cavity model to virtual cavity model when the particle size reduced to 6 nm in nonpolar solvent system, but the preferable model kept being real cavity model in polar solvent system.