FTIR, XRD, SEM and solid state NMR investigations of carbonate-containing hydroxyapatite nano-particles synthesized by hydroxide-gel technique Original Research Article

Nano-crystalline hydroxyapatite (HA), Ca10(PO4)6(OH)2 has been synthesized by a precipitate conversion technique using hydroxide gel at lower temperatures, e.g. 80 °C. HA crystallizes in hexagonal structure (space group: P63/m) having lattice parameters: and and around 17 nm in crystallite-size for the 80 °C-heated sample. SEM micrographs show hexagonal crystallites of average particle dimensions approximately 50×20 nm for 80 °C heated sample. The structure analysis by XRD, FTIR, 1H and 31P MAS NMR show the existence of structural disorder at the particle surface that either does not form hydrogen bonding due to lack of adequate bonding parameters or forms a very weak dipolar bonding. The structural disorder has been explained as a result of chemical interactions between the phosphate groups either with the surface adsorbed water or the hydroxyl groups at the surface of the nano-particles.