Group Replacement-Rearrangement-Triggered Linear-Assembly Nonaqueous Precipitation Synthesis of Hydroxyapatite Fibers

A novel method for hydroxyapatite fiber preparation with highly large-scale production prospects is of paramount importance but remains particularly difficult. Here, group replacement-rearrangement-triggered linear-assembly nonaqueous precipitation synthesis has been proposed for hydroxyapatite fibers under mild conditions. Pure hydroxyapatite fibers can be fabricated taking disodium hydrogen phosphate, calcium acetate, and glycerol as the phosphorus source, calcium source, and solvent, respectively. Single hexagonal crystal structures of hydroxyapatite fibers growing along the c-axis and preferential growth of the (002) crystal plane similar to the layered stacking structure of an adult bone have been confirmed by XRD refinement tests and calculation, TEM electron diffraction calibration, and FE-SEM. Highly active carbonate apatite is further demonstrated by EDS, FT-IR, Raman spectroscopy, and XPS. Unsaturated P-O and O-Ca bonds at both ends of the hexagonal-sheet assembly unit in a high-polarity nonaqueous glycerol environment without strongly coordinated OH^- confirm the solution spontaneous linear assembly to form the single hydroxyapatite fibers.