Water-dispersible hydroxyapatite nanorods synthesized by a facile method

A simple and effective method, using calcium nitrate and triammonium phosphate as starting materials, for the preparation of water-dispersible hydroxyapatite nanorods (HAp) was reported. The process primarily involves the preparation of HAp with the addition of sodium citrate (NaC) and the exchange of absorbed ions (NaC) with sodium hexame taphosphate (NaP). The end products were investigated using various means in order to confirm the particles' crystal phase and morphology and to understand how to improve their stability. The results demonstrate that the resulting HAp at 90 °C is rod-like with length of 300-400 nm and width of 40-60 nm. The zeta potential values of pure HAp, HAp-NaC, HAp-NaC/NaP are from −15.20, −30.89 to −44.84 mV. The settling time test shows the HAp-NaC/NaP could keep stable above 7 months without any creaming or visible sedimentation. The amount of NaC and the reaction temperature play significant roles in the whole process due to the formation of Ca containing precipitates.