Photodegradation of luminescence in organic-ligand-capped Eu3+:LaF3 nano-particles

The luminescence from europium doped lanthanum trifluoride (Eu3+:LaF3) nano-crystals can be greatly enhanced by capping with β-diketonate organic ligands. Here, we report on photo-stability measurements for the case of nano-crystals capped with thenoyltrifluroacetone (TTA) and compared with those capped with an inactive ligand, oleic acid. With exposure to UV pump light, we observed significant decrease in fluorescence and change in emission spectrum of the TTA-capped nano-particles whilst the fluorescence lifetime remained approximately constant. After a dose of order 70 kJ cm−2, the luminescence level was similar to that of oleic acid capped nano-crystals. We discuss possible mechanisms.