Rapid formation of mono-dispersed hydroxyapatite nanorods with narrow-size distribution via microwave irradiation

Monodispersed single-crystal hydroxyapatite (HAp) nanorods with nearly uniform diameters and lengths of, respectively, about 25 and 100 nm were rapidly synthesized using a template-free and convenient microwave irradiation method. Precipitation of HAp occurred directly in a calcium-phosphate precursor solution containing ethylenediaminetetraacetic acid (EDTA) as a capping agent and using microwave irradiation of 900 W power and 2.45 GHz frequency as the heating source. Transmission electron microscopy observations revealed that faceted surfaces and narrow-size distribution were two interesting features of the HAp nanorods obtained. The selected area electron diffraction pattern of the nanorods obtained clearly confirmed their single crystalline nature and the growth along the basal (001) planes. Furthermore, the formation mechanism of HAp nanorods was clearly proposed, identifying the influences of EDTA and microwaves in the growth process.