Characterization of luminescent hydroxyapatite@terbium complex core-shell composites using chlorobenzoic acid as ligands

Three kinds of novel hydroxyapatite@terbium complex core-shell composites were synthesized with 2-chlorobenzoic acid, 4-chlorobenzoic acid, and 2,4-dichlorobenzoic acid as the ligand, respectively. The XRD, UV/vis absorption and FT-IR results show that terbium ions are coordinated with ligands and the corresponding complexes are successfully included into composites. SEM and EDS results reveal that Tb complexes are fully and homogenously coated on the surface of hydroxyapatite (HAP) microspheres consisting of a large number of nanosized crystals. The strongest luminescence properties are obtained when 2,4-dichlorobenzoic acid is used as ligand. The study on fluorescence lifetime of composites shows that the lifetime is inversely related to emission intensity. TGA-DSC results indicate that the core-shell composites have an excellent thermal stability. Therefore, the current core-shell structure provides a cost-effective route to manufacture of biocompatible and heat-resistant highly luminescent materials.