Pore size control in the synthesis of hydroxyapatite nanoparticles: The effect of pore expander content and the synthesis temperature

Porous hydroxyapatite particles were synthesized by a self-assembly method. The process was carried out under a basic pH condition using cetyltrimethylammonium bromide (CTAB) as cationic surfactant and 1-dodecanethiol (RSH) as micelle size expander. The focus of the present work was to investigate the effect of synthesis temperature and pore expander content on the dissociation degree of 1-dodecanethiol and the degree of swelling in the micelle structure. Swelling was related to the electrostatic interaction between the dissociated 1-dodecanethiol molecule (RS−) and the cationic molecules of CTAB (CTA+). The synthesized samples were characterized by low-angle X-ray diffraction (LA-XRD), N2 adsorption–desorption experiments, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The results indicated that pore expander content as well as the synthesis temperature played a significant role in the swelling of the micelle structure. There was a decrease in particle length/diameter ratio with the increase in the synthesis temperature and pore expander concentration. Nanoparticles with pore size in range of 23–40 nm were obtained in this study.