title: Crystallinity and compositional changes in carbonated apatites: Evidence from31P solid-state NMR, Raman, and AFM analysis.
abstract: Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and31P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse31P NMR linewidth and inverse Raman PO43-ν1bandwidth were both correlated with powder XRDc-axiscrystallinity over the 0.3-10.3 wt% CO32-range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the31P NMR chemical shift frequency and the Raman phosphate ν1band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals.
authors.affiliation: Department of Chemistry and University of Michigan, Ann Arbor, MI 48109-1055.
authors.forename: John-David P
authors.initials: JD
authors.lastname: McElderry
authors.forename: Peizhi
authors.initials: P
authors.lastname: Zhu
authors.forename: Kamal H
authors.initials: KH
authors.lastname: Mroue
authors.forename: Jiadi
authors.initials: J
authors.lastname: Xu
authors.forename: Barbara
authors.initials: B
authors.lastname: Pavan
authors.forename: Ming
authors.initials: M
authors.lastname: Fang
authors.forename: Guisheng
authors.initials: G
authors.lastname: Zhao
authors.forename: Erin
authors.initials: E
authors.lastname: McNerny
authors.forename: David H
authors.initials: DH
authors.lastname: Kohn
authors.forename: Renny T
authors.initials: RT
authors.lastname: Franceschi
authors.forename: Mark M Banaszak
authors.initials: MM
authors.lastname: Holl
authors.forename: Mary M J
authors.initials: MM
authors.lastname: Tecklenburg
authors.forename: Ayyalusamy
authors.initials: A
authors.lastname: Ramamoorthy
authors.forename: Michael D
authors.initials: MD
authors.lastname: Morris
keywords: Bone mineral; Carbonated apatite; Crystallinity; MAS NMR; Raman spectroscopy