Luminescence and energy transfer in water soluble CeF3 and CeF3:Tb3+ nanoparticles.

CeF3 and CeF3:Tb3+ water soluble nanoparticles (NPs) were prepared by wet chemistry, and their structure and luminescence properties were studied systematically. The results of XRD indicate that the obtained CeF3 and CeF3:Tb3+ NPs have a hexagonal structure with the P 6(3)/mcm space group. The average size of CeF3 NPs is about 10 nm, and that of CeF3:Tb3+ NPs is about 5.5 nm as measured from transmission electron microscope (TEM). The aqueous solution sample of CeF3 NPs has an emission peaking at 325.5 nm, which is from the 5d-->4f transition of Ce3+, and CeF3:Tb3+ NPs have a broad emission at 355.5 nm, which is from the 5d--4f transition of Ce3+ (325.5 nm), and several sharp emissions in the visible ranges that are from the (5)D4-->7F(J) transition of Tb3+. As the concentration of Tb3+ increases, the emission intensity of Ce3+ decreases gradually, while the emission intensity of Tb3+ first increases and then decreases. Our observations indicate that there is an energy transfer from Ce3+ to Tb3+ in the CeF3:Tb3+ nanoparticles, and the maximal energy transfer rate is estimated to be 93.2% at the Tb3+ concentration of 25%.