The synthesis and luminescent properties of novel water-soluble CaF₂:Tb³⁺ nanoparticles

Novel water-soluble CaF₂:Tb³⁺ nanoparticles were synthesized using benzoimidazole-5-carboxylic acid (Ligand) as surfactant. The particle size of the nanoparticles is below 10 nm. The investigation of fluorescence properties showed that there exists energy transfer from the surface coating of nanoparticles to Tb³⁺ leading to the sensitized fluorescence emission of Tb³⁺. The luminescence lifetimes of Tb³⁺ were 937.56 μs (37.41%) and 2.78 ms (62.59%). It is more important that Cu²⁺ and Fe³⁺ can give rise to emission quenching to the Tb³⁺ of nanoparticles, especially Cu²⁺. In the region of 2.5×10⁻⁵–5×10⁻⁴ M, the higher the concentration of Cu²⁺ or Fe³⁺ is, the stronger fluorescence quenching to the Tb³⁺ is. Additionally, the possible mechanisms of the luminescence quenching were also discussed.