Calcium phosphate synthesized by a wet-mechanochemical reaction between Ca(OH)2 and H3PO4 is identified by X-ray diffractometry as an apparently single phase of hydroxyapatite (HAp). We examined more detail on the local structure of the product by high-resolution 1H and 31P solid-state double nuclear magnetic resonance (NMR) spectroscopy. Adsorbed and structural waters, as well as two kinds of OH groups in HAp, were observed in the inversion recovery 1H magic angle spinning (MAS) spectra. HAp and other calcium phosphate were observed in 1H→31P cross polarization (CP)/MAS spectra. The 31P differential cross polarization (DCP)/MAS and 1H inversion recovery →31P CP/MAS measurements revealed different chemical interactions between 1H and 31P and, hence, could distinguish between ordered and disordered HAp. This micro-inhomogenity results from interiors and near-surface of nanoparticles as well as Ca2+-deficiency.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry