A Mild and Efficient Biomimetic Synthesis of Rodlike Hydroxyapatite Particles with a High Aspect Ratio Using Polyvinylpyrrolidone As Capping Agent

Rodlike hydroxyapatite (HAp) nanoparticles were synthesized at 60 °C through a biomimetic pathway from Ca(NO 3 ) 2 ·4H 2 O, H 3 PO 4, and NH 4 OH. The polymer polyvinylpyrrolidone (PVP) as a capping agent was used to regulate the nucleation and crystal growth of HAp crystal. X-ray diffraction results combined with high-resolution transmission electron microscopy indicated that single phase, nanocrystal HAp powder could be obtained in one-step and the addition of PVP facilitated the preferential growth of nanocrystal HAp along the <002> axis. The formation mechanism of rodlike HAp crystal and the effects of PVP on the crystal nucleation and growth were discussed based on transmission electron microscopy and Fourier transform infrared spectroscopy results.