Influence of the number of carboxyl groups on the nucleation of hydroxyapatite

This paper reports a novel means of preparing HAp crystals. X-ray diffraction showed that the lactic acid route leads to good crystallinity and pure HAp phases compared to other routes. Impurity phases disappeared with a decrease in the number of carboxyl groups. FTIR indicated the presence of carbonate substitution, which increased as the number of carboxyl groups increased. Scanning electron microscopy observations revealed morphological variation of the particles that occurred when the number of carboxyl groups was changed in the complexing agents. The changes in the morphology with the carboxyl group number were analyzed taking into account the driving force for HAp precipitation and the supersaturation level of Ca ²⁺ and PO ₄ ^3- ions with respect to HAp. The analysis indicated that the supersaturation level of the reactants, especially the number of carboxyl groups in the complexing agent, played a predominant role in the precipitate morphology process of this reaction. Energy-dispersive X-ray spectroscopy (EDX) analysis showed that the Ca/P ratio increased as the number of carboxyl groups decreased.