Highly luminescent lanthanide fluoride nanoparticles functionalized by aromatic carboxylate acids

Abstract

Highly dispersible LaF₃:x% Tb³⁺ (x = 1, 3, 5, 8, 10) nanoparticles capped with citrate ligands have been prepared and functionalized by salicylate and 5-sulfosalicylate, respectively. The structure, morphology, photoluminescence properties, fluorescence dynamics and ligand sensitization mechanism have been studied systemically. Monitoring the characteristic emission of the Tb^{3+ 5}D₄–⁷F₅ transition, the broad absorption bands in the UV domain are obtained with the functionalized nanoparticles. Under excitation of the π–π* electron transition absorption of salicylate (or 5-sulfosalicylate), the enhanced luminescence of Tb³⁺ ions is achieved in the functionalized nanoparticles. The ligand sensitization is potentially interpreted by a dipole–dipole sensitization mechanism. The luminescence lifetimes of Tb³⁺ ions in the nanoparticles functionalized by aromatic carboxylate acids are longer than the ones in LaF₃:Tb³⁺ nanoparticles capped with citrate ligands.