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

Nano-crystalline hydroxyapatite (HA), Ca-10(PO4)(6)(OH)(2) has been synthesized by a precipitate conversion technique using hydroxide gel at lower temperatures, e.g. 80 degreesC. HA crystallizes in hexagonal structure (space group: P6(3)/m) having lattice parameters: a = 9.347 Angstrom and c = 6.862 Angstrom and around 17 rim in crystallite-size for the 80 degreesC-heated sample. SEM micrographs show hexagonal crystallites of average particle dimensions approximately 50 x 20 nn for 80 degreesC heated sample. The structure analysis by XRD, FTIR, H-1 and P-31 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. (C) 2002 Elsevier Science Ltd. All rights reserved.