Hydrothermal growth of biomimetic carbonated apatite nanoparticles with tunable size, morphology and ultrastructure

Biomimetic carbonated apatite (CAp) nanoparticles with tunable size, morphology and ultrastructure were synthesized via a facile hydrothermal route. By combining the results of FTIR, XRD, ICP, TGA, TEM and HRTEM, a complete chemical, morphological and structural characterization of the nanoparticles was performed. Based on a systematic examination of the effect of the fundamental factors including pH, carbonate concentration, temperature, and reaction time that control the synthesis of CAp nanocrystals, the nucleation and growth mechanisms were proposed. The results show that CAp nanocrystals can only be synthesized in basic conditions and exhibit a distinct morphology from that of pure hydroxyapatite. Increasing the reaction temperature and time will improve the crystallinity. The resulting CAp nanocrystals have three typical facets: (001), (010) and (1 (1) over bar0). By careful manipulation of the synthesis parameters, CAp nanocrystals mimetic to biological apatite in size and morphology can be obtained. Experimental evidence is given to support the mechanism that the amorphous calcium phosphate phase is a precursor phase that gradually transforms into the mature crystalline apatite mineral. The systematic approach presented in this study provides a helpful guide for the hydrothermal growth of quality CAp nanocrystals and significant implications for understanding the mechanism of biomineralization.