Microwave-assisted sol-gel synthesis of hydroxyapatite nanoparticles

A rapid sol-gel method for preparing hydroxyapatite nanoparticles (nHAP) has been developed. Three different sets of experimental conditions, in terms of solvents (water and ethanol), synthesis temperatures (25, 40 and 60℃), and microwave irradiation (on and off) were explored. Crystal phase composition, functional groups and morphology of the products were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The solvent and temperature were optimized based on product properties. Most importantly, the microwave-assisted method (with little to no ageing necessary) was much faster than the conventional methods (with slow ageing processes needing from hours to days), while affording pure nHAP with virtually identical morphological and structural properties. This study represents a practical application of the powerful microwave technique in synthesis of nHAP, offering guidance on the selection of optimum experiment conditions.