Luminescence and energy transfer in water soluble CeF ₃ and CeF ₃:Tb ³⁺ nanoparticles

CeF ₃ and CeF ₃:Tb ³⁺ 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 CeF ₃ and CeF ₃:Tb ³⁺ NPs have a hexagonal structure with the P 6 ₃/mcm space group. The average size of CeF ₃ NPs is about 10 nm, and that of CeF ₃:Tb ³⁺ NPs is about 5.5 nm as measured from transmission electron microscope (TEM). The aqueous solution sample of CeF ₃ NPs has an emission peaking at 325.5 nm, which is from the 5d → 4f transition of Ce ³⁺, and CeF ₃:Tb ³⁺ NPs have a broad emission at 355.5 nm, which is from the 5d → 4f transition of Ce ³⁺ (325.5 nm), and several sharp emissions in the visible ranges that are from the ⁵D ₄ → ⁷F _J transition of Tb ³⁺. As the concentration of Tb ³⁺ increases, the emission intensity of Ce ³⁺ decreases gradually, while the emission intensity of Tb ³⁺ first increases and then decreases. Our observations indicate that there is an energy transfer from Ce ³⁺ to Tb ³⁺ in the CeF ₃:Tb ³⁺ nanoparticles, and the maximal energy transfer rate is estimated to be 93.2% at the Tb ³⁺ concentration of 25%.