Block-copolymer-assisted synthesis of hydroxyapatite nanoparticles with high surface area and uniform size

We report the synthesis of hydroxyapatite nanoparticles (HANPs) by the coprecipitation method using calcium D-gluconate and potassium hydrogen phosphate as the sources of calcium and phosphate ions, respectively, and the triblock copolymer F127 as a stabilizer. The HANPs were characterized using scanning electron microscopy, x-ray diffraction, and nitrogen adsorption/desorption isotherms. Removal of F127 by solvent extraction or calcination alters the structure of HANPs. The solvent-extracted HANPs were single crystals with their 〈001〉 axis oriented along the rod axis of the HANP, whereas the calcined HANPs contained two crystal phases that resulted in a spherical morphology. The calcined HANPs had much higher surface area (127 m² g^-1) than the solvent-extracted HANPs (44 m² g^-1).