Capping agent-assisted synthesis of nanosized hydroxyapatite: Comparative studies of their physicochemical properties

Nanosized hydroxyapatite [n-HAp, Ca10(PO4)6(OH)2] has been synthesized by a precipitation technique at room temperature using an aqueous solution of calcium nitrate and diammonium hydrogen phosphate as starting materials in presence of various capping agents like triethanolamine (TEA), ethylenediamine tetraacetic acid (EDTA), diethanolamine (DEA) and ethylene glycol (EG) separately. X-ray diffraction (XRD) shows the synthesized HAp powders are nanocrystalline in nature. BET surface area analysis indicates the powders are nonporous in nature with high specific surface area (63.82–97.39 m2/g). Transmission electron microscopy (TEM) shows the formation of smallest particles with 5–8 nm in diameter and 30–56 nm in length using TEA as capping agent, and biggest particles with 12–16 nm in diameter and 80–120 nm in length using EG as capping agent. Particle size distribution (PSD) shows the narrow hydrodynamic particle size distribution of n-HAp powders synthesized using all above mentioned capping agents. A comparative study of particle sizes of n-HAp powders using different capping agents, which have received from various measurements, has been performed. The introduction of capping agents effectively restricts the particle growth during precipitation.