Size-controlled synthesis and characterization of fluorapatite nanocrystals in the presence of gelatin

A biological macromolecule-assisted synthetic route has been developed for the preparation of hexagonal fluorapatite nanocrystals with high crystallinity. In this investigation, we evaluated the resulting mineral habit growth using gelatin as nucleation templates of fluorapatite. Fluorapatite crystals were obtained regardless of the presence of gelatin. The resulting nanocrystals were short (80–150 nm long) and did not grow with time in the absence of gelatin. While in the presence of gelatin, the resulting nanocrystals were shuttle-like and about 400–600 nm long. The dominating microstructures were flower-like and bundle-like arrays consisting of these long fluoraptite nanocrystals. As the reaction time was increased, the shuttle-like fluorapatite nanocrystals grew into hexagonal prisms, which were about 1–3 μm long. The resulted fluorapatite nanocrystals with gelatin were also found to contain trace amounts of sodium and carbonate ions, originating from the reactants during the synthesis. X-ray diffraction patterns and scanning electron microscope images of the fluorapatite crystals strongly indicate that the fluorapatite nanocrystals self-assembled along the c axis under the present experimental conditions.

Graphical AbstractA biomineralization method was developed for the preparation of fluorapatite using gelatin as nucleation templates under mild conditions. Without further thermal treatment, the resulting fluorapatite nanocrystals reacted in the gel matrix at 37 °C for five weeks, showed a typical apatite hexagonal cross section of approximately 60–150 nm in diameter; meanwhile, the crystallinity were higher than that of the fluorapatite soaked for one week.Figure optionsDownload as PowerPoint slideResearch Highlights
► Fluorapatite nanocrystals were synthesized by gelatin-assisted biomimetic process.
► The Ca/P ratio of fluorapatite was preserved in the presence of gelatin.
► The gelatin helped Na+ and CO32- incorporate into the fluorapatite lattice.
► The long reaction time was necessary for the formation of hexagonal structure.
► Combinations of inexpensive gelatin and simple process had commercial significance.