Colloidal synthesis and characterization of monocrystalline apatite nanophosphors

Here, we report the synthesis and characterization of 12 nm long, ultrafine, individualized calcium phosphate nanorods. Synthesis of these nanobuilding blocks involved the preparation of a calcium phosphate hybrid precursor containing an aminophosphate ligand. Colloidal calcium phosphate nanoparticles were achieved through the reorganization of an amorphous hybrid precursor at high temperature during a post-ageing step. These nanoparticles can be described as monocrystalline deficient calcium hydroxyapatite Ca10-x(PO4)6-x(HPO4)x(OH)2-x, with surfaces stabilized by [PO32-O(CH2)2NH3+] groups. A model is proposed in which the [ab] plane of the nanoparticles is formed by 9 unit cells surrounded by a peripheral layer composed of twelve aminoethyl phosphate (AEP)-calcium phosphate (xCa9(PO4)6-yCa-(AEP)2) hybrid units. Our ultrafine individualized calcium phosphate nanophosphors, synthesized in aqueous medium and displaying amino groups on their surface, are good candidates for use as fluorescent probes in biological imaging.