Spectral properties of Eu3+ doped NaGdF4 nanocrystals

The luminescence properties of Eu3+:NaGdF4 nanocrystalline powders have been investigated as a function of nanoparticle dimensions for three samples characterized by average crystallite sizes of 14, 35 and 60 nm, respectively. It was observed that a structure of luminescence bands, their intensities and lifetimes were significantly different for the smallest nanocrystals compared to the larger ones. The highest emission intensities and the longest lifetimes were recorded for the sample composed of the smallest nanocrystals. The f-f emission transition intensities of Eu3+ in NaGdF4 nanocrystallites were analyzed by means of the Judd-Ofelt model. The spontaneous emission coefficients were calculated and compared to those determined from the experimental lifetimes of the 5DJ (J=0,1,2,3) states.